Magnetoencephalography Study of Right Parietal Lobe Dysfunction of the Evoked Mirror Neuron System in Antipsychotic-Free Schizophrenia

PubMed Central

Kato, Yutaka; Muramatsu, Taro; Kato, Motoichiro; Shibukawa, Yoshiyuki; Shintani, Masuro; Mimura, Masaru

2011-01-01

Introduction Patients with schizophrenia commonly exhibit deficits of non-verbal communication in social contexts, which may be related to cognitive dysfunction that impairs recognition of biological motion. Although perception of biological motion is known to be mediated by the mirror neuron system, there have been few empirical studies of this system in patients with schizophrenia. Methods Using magnetoencephalography, we examined whether antipsychotic-free schizophrenia patients displayed mirror neuron system dysfunction during observation of biological motion (jaw movement of another individual). Results Compared with normal controls, the patients with schizophrenia had fewer components of both the waveform and equivalent current dipole, suggesting aberrant brain activity resulting from dysfunction of the right inferior parietal cortex. They also lacked the changes of alpha band and gamma band oscillation seen in normal controls, and had weaker phase-locking factors and gamma-synchronization predominantly in right parietal cortex. Conclusions Our findings demonstrate that untreated patients with schizophrenia exhibit aberrant mirror neuron system function based on the right inferior parietal cortex, which is characterized by dysfunction of gamma-synchronization in the right parietal lobe during observation of biological motion. PMID:22132217

Mirror neuron system: basic findings and clinical applications.

PubMed

Iacoboni, Marco; Mazziotta, John C

2007-09-01

In primates, ventral premotor and rostral inferior parietal neurons fire during the execution of hand and mouth actions. Some cells (called mirror neurons) also fire when hand and mouth actions are just observed. Mirror neurons provide a simple neural mechanism for understanding the actions of others. In humans, posterior inferior frontal and rostral inferior parietal areas have mirror properties. These human areas are relevant to imitative learning and social behavior. Indeed, the socially isolating condition of autism is associated with a deficit in mirror neuron areas. Strategies inspired by mirror neuron research recently have been used in the treatment of autism and in motor rehabilitation after stroke.

Reward Size Informs Repeat-Switch Decisions and Strongly Modulates the Activity of Neurons in Parietal Cortex

PubMed Central

Kubanek, Jan; Snyder, Lawrence H.

2017-01-01

Abstract Behavior is guided by previous experience. Good, positive outcomes drive a repetition of a previous behavior or choice, whereas poor or bad outcomes lead to an avoidance. How these basic drives are implemented by the brain has been of primary interest to psychology and neuroscience. We engaged animals in a choice task in which the size of a reward outcome strongly governed the animals' subsequent decision whether to repeat or switch the previous choice. We recorded the discharge activity of neurons implicated in reward-based choice in 2 regions of parietal cortex. We found that the tendency to retain previous choice following a large (small) reward was paralleled by a marked decrease (increase) in the activity of parietal neurons. This neural effect is independent of, and of sign opposite to, value-based modulations reported in parietal cortex previously. This effect shares the same basic properties with signals previously reported in the limbic system that detect the size of the recently obtained reward to mediate proper repeat-switch decisions. We conclude that the size of the obtained reward is a decision variable that guides the decision between retaining a choice or switching, and neurons in parietal cortex strongly respond to this novel decision variable. PMID:26491065

Mapping human temporal and parietal neuronal population activity and functional coupling during mathematical cognition

PubMed Central

Daitch, Amy L.; Foster, Brett L.; Schrouff, Jessica; Rangarajan, Vinitha; Kaşikçi, Itır; Gattas, Sandra; Parvizi, Josef

2016-01-01

Brain areas within the lateral parietal cortex (LPC) and ventral temporal cortex (VTC) have been shown to code for abstract quantity representations and for symbolic numerical representations, respectively. To explore the fast dynamics of activity within each region and the interaction between them, we used electrocorticography recordings from 16 neurosurgical subjects implanted with grids of electrodes over these two regions and tracked the activity within and between the regions as subjects performed three different numerical tasks. Although our results reconfirm the presence of math-selective hubs within the VTC and LPC, we report here a remarkable heterogeneity of neural responses within each region at both millimeter and millisecond scales. Moreover, we show that the heterogeneity of response profiles within each hub mirrors the distinct patterns of functional coupling between them. Our results support the existence of multiple bidirectional functional loops operating between discrete populations of neurons within the VTC and LPC during the visual processing of numerals and the performance of arithmetic functions. These findings reveal information about the dynamics of numerical processing in the brain and also provide insight into the fine-grained functional architecture and connectivity within the human brain. PMID:27821758

Representation of numerosity in posterior parietal cortex

PubMed Central

Roitman, Jamie D.; Brannon, Elizabeth M.; Platt, Michael L.

2012-01-01

Humans and animals appear to share a similar representation of number as an analog magnitude on an internal, subjective scale. Neurological and neurophysiological data suggest that posterior parietal cortex (PPC) is a critical component of the circuits that form the basis of numerical abilities in humans. Patients with parietal lesions are impaired in their ability to access the deep meaning of numbers. Acalculiac patients with inferior parietal damage often have difficulty performing arithmetic (2 + 4?) or number bisection (what is between 3 and 5?) tasks, but are able to recite multiplication tables and read or write numerals. Functional imaging studies of neurologically intact humans performing subtraction, number comparison, and non-verbal magnitude comparison tasks show activity in areas within the intraparietal sulcus (IPS). Taken together, clinical cases and imaging studies support a critical role for parietal cortex in the mental manipulation of numerical quantities. Further, responses of single PPC neurons in non-human primates are sensitive to the numerosity of visual stimuli independent of low-level stimulus qualities. When monkeys are trained to make explicit judgments about the numerical value of such stimuli, PPC neurons encode their cardinal numerical value; without such training PPC neurons appear to encode numerical magnitude in an analog fashion. Here we suggest that the spatial and integrative properties of PPC neurons contribute to their critical role in numerical cognition. PMID:22666194

Dynamic Divisive Normalization Predicts Time-Varying Value Coding in Decision-Related Circuits

PubMed Central

LoFaro, Thomas; Webb, Ryan; Glimcher, Paul W.

2014-01-01

Normalization is a widespread neural computation, mediating divisive gain control in sensory processing and implementing a context-dependent value code in decision-related frontal and parietal cortices. Although decision-making is a dynamic process with complex temporal characteristics, most models of normalization are time-independent and little is known about the dynamic interaction of normalization and choice. Here, we show that a simple differential equation model of normalization explains the characteristic phasic-sustained pattern of cortical decision activity and predicts specific normalization dynamics: value coding during initial transients, time-varying value modulation, and delayed onset of contextual information. Empirically, we observe these predicted dynamics in saccade-related neurons in monkey lateral intraparietal cortex. Furthermore, such models naturally incorporate a time-weighted average of past activity, implementing an intrinsic reference-dependence in value coding. These results suggest that a single network mechanism can explain both transient and sustained decision activity, emphasizing the importance of a dynamic view of normalization in neural coding. PMID:25429145

Investigating common coding of observed and executed actions in the monkey brain using cross-modal multi-variate fMRI classification.

PubMed

Fiave, Prosper Agbesi; Sharma, Saloni; Jastorff, Jan; Nelissen, Koen

2018-05-19

Mirror neurons are generally described as a neural substrate hosting shared representations of actions, by simulating or 'mirroring' the actions of others onto the observer's own motor system. Since single neuron recordings are rarely feasible in humans, it has been argued that cross-modal multi-variate pattern analysis (MVPA) of non-invasive fMRI data is a suitable technique to investigate common coding of observed and executed actions, allowing researchers to infer the presence of mirror neurons in the human brain. In an effort to close the gap between monkey electrophysiology and human fMRI data with respect to the mirror neuron system, here we tested this proposal for the first time in the monkey. Rhesus monkeys either performed reach-and-grasp or reach-and-touch motor acts with their right hand in the dark or observed videos of human actors performing similar motor acts. Unimodal decoding showed that both executed or observed motor acts could be decoded from numerous brain regions. Specific portions of rostral parietal, premotor and motor cortices, previously shown to house mirror neurons, in addition to somatosensory regions, yielded significant asymmetric action-specific cross-modal decoding. These results validate the use of cross-modal multi-variate fMRI analyses to probe the representations of own and others' actions in the primate brain and support the proposed mapping of others' actions onto the observer's own motor cortices. Copyright © 2018 Elsevier Inc. All rights reserved.

Interlaminar differences in the pyramidal cell phenotype in parietal cortex of an Indian bat, cynopterus sphinx.

PubMed

Srivastava, U C; Pathak, S V

2010-10-30

To study interlaminar phenotypic variations in the pyramidal neurons of parietal isocortex in bat (Cynopterus sphinx), Golgi and Nissl methods have been employed. The parietal isocortex is relatively thin in the bat as compared to prototheria with layer III, V and VI accounting for more than two—thirds of total cortical thickness. Thick cell free layer I and thinnest accentuated layer II are quite in connotation with other chiropterids. Poor demarcation of layer III/IV in the present study is also in connotation with primitive eutherian mammal (i.e. prototherian) and other chiropterids. Most of the pyramidal cells in the different layers of the parietal isocortex are of typical type as seen in other eutherians but differ significantly in terms of soma shape and size, extent of dendritic arbor, diameter of dendrites and spine density. Percentage of pyramidal neurons, diameter of apical dendrite and spine density on apical dendrite appear to follow an increasing trend from primitive to advanced mammals; but extent of dendrites are probably governed by the specific life patterns of these mammals. It is thus concluded that 'typical' pyramidal neurons in parietal isocortex are similar in therians but different from those in prototherians. It is possible that these cells might have arisen among early eutherians after divergence from prototherian stock.

Representation of the Numerosity ‘zero’ in the Parietal Cortex of the Monkey

PubMed Central

Okuyama, Sumito; Kuki, Toshinobu; Mushiake, Hajime

2015-01-01

Zero is a fundamental concept in mathematics and modern science. Empty sets are considered a precursor of the concept of numerosity zero and a part of numerical continuum. How is numerosity zero (the absence of visual items) represented in the primate cortex? To address this question, we trained monkeys to perform numerical operations including numerosity zero. Here we show a group of neurons in the posterior parietal cortex of the monkey activated in response to numerosity ‘zero’. ‘Zero’ neurons are classified into exclusive and continuous types; the exclusive type discretely encodes numerical absence and the continuous type encodes numerical absence as a part of a numerical continuum. “Numerosity-zero” neurons enhance behavioral discrimination of not only zero numerosity but also non-zero numerosities. Representation of numerosity zero in the parietal cortex may be a precursor of non-verbal concept of zero in primates. PMID:25989598

Representation of the Numerosity 'zero' in the Parietal Cortex of the Monkey.

PubMed

Okuyama, Sumito; Kuki, Toshinobu; Mushiake, Hajime

2015-05-22

Zero is a fundamental concept in mathematics and modern science. Empty sets are considered a precursor of the concept of numerosity zero and a part of numerical continuum. How is numerosity zero (the absence of visual items) represented in the primate cortex? To address this question, we trained monkeys to perform numerical operations including numerosity zero. Here we show a group of neurons in the posterior parietal cortex of the monkey activated in response to numerosity 'zero'. 'Zero' neurons are classified into exclusive and continuous types; the exclusive type discretely encodes numerical absence and the continuous type encodes numerical absence as a part of a numerical continuum. "Numerosity-zero" neurons enhance behavioral discrimination of not only zero numerosity but also non-zero numerosities. Representation of numerosity zero in the parietal cortex may be a precursor of non-verbal concept of zero in primates.

Dynamic divisive normalization predicts time-varying value coding in decision-related circuits.

PubMed

Louie, Kenway; LoFaro, Thomas; Webb, Ryan; Glimcher, Paul W

2014-11-26

Normalization is a widespread neural computation, mediating divisive gain control in sensory processing and implementing a context-dependent value code in decision-related frontal and parietal cortices. Although decision-making is a dynamic process with complex temporal characteristics, most models of normalization are time-independent and little is known about the dynamic interaction of normalization and choice. Here, we show that a simple differential equation model of normalization explains the characteristic phasic-sustained pattern of cortical decision activity and predicts specific normalization dynamics: value coding during initial transients, time-varying value modulation, and delayed onset of contextual information. Empirically, we observe these predicted dynamics in saccade-related neurons in monkey lateral intraparietal cortex. Furthermore, such models naturally incorporate a time-weighted average of past activity, implementing an intrinsic reference-dependence in value coding. These results suggest that a single network mechanism can explain both transient and sustained decision activity, emphasizing the importance of a dynamic view of normalization in neural coding. Copyright © 2014 the authors 0270-6474/14/3416046-12$15.00/0.

Role of medio-dorsal frontal and posterior parietal neurons during auditory detection performance in rats.

PubMed

Bohon, Kaitlin S; Wiest, Michael C

2014-01-01

To further characterize the role of frontal and parietal cortices in rat cognition, we recorded action potentials simultaneously from multiple sites in the medio-dorsal frontal cortex and posterior parietal cortex of rats while they performed a two-choice auditory detection task. We quantified neural correlates of task performance, including response movements, perception of a target tone, and the differentiation between stimuli with distinct features (different pitches or durations). A minority of units--15% in frontal cortex, 23% in parietal cortex--significantly distinguished hit trials (successful detections, response movement to the right) from correct rejection trials (correct leftward response to the absence of the target tone). Estimating the contribution of movement-related activity to these responses suggested that more than half of these units were likely signaling correct perception of the auditory target, rather than merely movement direction. In addition, we found a smaller and mostly not overlapping population of units that differentiated stimuli based on task-irrelevant details. The detection-related spiking responses we observed suggest that correlates of perception in the rat are sparsely represented among neurons in the rat's frontal-parietal network, without being concentrated preferentially in frontal or parietal areas.

Uniting functional network topology and oscillations in the fronto-parietal single unit network of behaving primates.

PubMed

Dann, Benjamin; Michaels, Jonathan A; Schaffelhofer, Stefan; Scherberger, Hansjörg

2016-08-15

The functional communication of neurons in cortical networks underlies higher cognitive processes. Yet, little is known about the organization of the single neuron network or its relationship to the synchronization processes that are essential for its formation. Here, we show that the functional single neuron network of three fronto-parietal areas during active behavior of macaque monkeys is highly complex. The network was closely connected (small-world) and consisted of functional modules spanning these areas. Surprisingly, the importance of different neurons to the network was highly heterogeneous with a small number of neurons contributing strongly to the network function (hubs), which were in turn strongly inter-connected (rich-club). Examination of the network synchronization revealed that the identified rich-club consisted of neurons that were synchronized in the beta or low frequency range, whereas other neurons were mostly non-oscillatory synchronized. Therefore, oscillatory synchrony may be a central communication mechanism for highly organized functional spiking networks.

Modeling the Development of Goal-Specificity in Mirror Neurons.

PubMed

Thill, Serge; Svensson, Henrik; Ziemke, Tom

2011-12-01

Neurophysiological studies have shown that parietal mirror neurons encode not only actions but also the goal of these actions. Although some mirror neurons will fire whenever a certain action is perceived (goal-independently), most will only fire if the motion is perceived as part of an action with a specific goal. This result is important for the action-understanding hypothesis as it provides a potential neurological basis for such a cognitive ability. It is also relevant for the design of artificial cognitive systems, in particular robotic systems that rely on computational models of the mirror system in their interaction with other agents. Yet, to date, no computational model has explicitly addressed the mechanisms that give rise to both goal-specific and goal-independent parietal mirror neurons. In the present paper, we present a computational model based on a self-organizing map, which receives artificial inputs representing information about both the observed or executed actions and the context in which they were executed. We show that the map develops a biologically plausible organization in which goal-specific mirror neurons emerge. We further show that the fundamental cause for both the appearance and the number of goal-specific neurons can be found in geometric relationships between the different inputs to the map. The results are important to the action-understanding hypothesis as they provide a mechanism for the emergence of goal-specific parietal mirror neurons and lead to a number of predictions: (1) Learning of new goals may mostly reassign existing goal-specific neurons rather than recruit new ones; (2) input differences between executed and observed actions can explain observed corresponding differences in the number of goal-specific neurons; and (3) the percentage of goal-specific neurons may differ between motion primitives.

Sensitivity to perception level differentiates two subnetworks within the mirror neuron system.

PubMed

Simon, Shiri; Mukamel, Roy

2017-05-01

Mirror neurons are a subset of brain cells that discharge during action execution and passive observation of similar actions. An open question concerns the functional role of their ability to match observed and executed actions. Since understanding of goals requires conscious perception of actions, we expect that mirror neurons potentially involved in action goal coding, will be modulated by changes in action perception level. Here, we manipulated perception level of action videos depicting short hand movements and measured the corresponding fMRI BOLD responses in mirror regions. Our results show that activity levels within a network of regions, including the sensorimotor cortex, primary motor cortex, dorsal premotor cortex and posterior superior temporal sulcus, are sensitive to changes in action perception level, whereas activity levels in the inferior frontal gyrus, ventral premotor cortex, supplementary motor area and superior parietal lobule are invariant to such changes. In addition, this parcellation to two sub-networks manifest as smaller functional distances within each group of regions during task and resting state. Our results point to functional differences between regions within the mirror neurons system which may have implications with respect to their possible role in action understanding. © The Author (2017). Published by Oxford University Press.

Comparison of visual receptive fields in the dorsolateral prefrontal cortex and ventral intraparietal area in macaques.

PubMed

Viswanathan, Pooja; Nieder, Andreas

2017-12-01

The concept of receptive field (RF) describes the responsiveness of neurons to sensory space. Neurons in the primate association cortices have long been known to be spatially selective but a detailed characterisation and direct comparison of RFs between frontal and parietal association cortices are missing. We sampled the RFs of a large number of neurons from two interconnected areas of the frontal and parietal lobes, the dorsolateral prefrontal cortex (dlPFC) and ventral intraparietal area (VIP), of rhesus monkeys by systematically presenting a moving bar during passive fixation. We found that more than half of neurons in both areas showed spatial selectivity. Single neurons in both areas could be assigned to five classes according to the spatial response patterns: few non-uniform RFs with multiple discrete response maxima could be dissociated from the vast majority of uniform RFs showing a single maximum; the latter were further classified into full-field and confined foveal, contralateral and ipsilateral RFs. Neurons in dlPFC showed a preference for the contralateral visual space and collectively encoded the contralateral visual hemi-field. In contrast, VIP neurons preferred central locations, predominantly covering the foveal visual space. Putative pyramidal cells with broad-spiking waveforms in PFC had smaller RFs than putative interneurons showing narrow-spiking waveforms, but distributed similarly across the visual field. In VIP, however, both putative pyramidal cells and interneurons had similar RFs at similar eccentricities. We provide a first, thorough characterisation of visual RFs in two reciprocally connected areas of a fronto-parietal cortical network. © 2017 Federation of European Neuroscience Societies and John Wiley & Sons Ltd.

Uniting functional network topology and oscillations in the fronto-parietal single unit network of behaving primates

PubMed Central

Dann, Benjamin; Michaels, Jonathan A; Schaffelhofer, Stefan; Scherberger, Hansjörg

2016-01-01

The functional communication of neurons in cortical networks underlies higher cognitive processes. Yet, little is known about the organization of the single neuron network or its relationship to the synchronization processes that are essential for its formation. Here, we show that the functional single neuron network of three fronto-parietal areas during active behavior of macaque monkeys is highly complex. The network was closely connected (small-world) and consisted of functional modules spanning these areas. Surprisingly, the importance of different neurons to the network was highly heterogeneous with a small number of neurons contributing strongly to the network function (hubs), which were in turn strongly inter-connected (rich-club). Examination of the network synchronization revealed that the identified rich-club consisted of neurons that were synchronized in the beta or low frequency range, whereas other neurons were mostly non-oscillatory synchronized. Therefore, oscillatory synchrony may be a central communication mechanism for highly organized functional spiking networks. DOI: http://dx.doi.org/10.7554/eLife.15719.001 PMID:27525488

Spatial effects of shifting prisms on properties of posterior parietal cortex neurons

PubMed Central

Karkhanis, Anushree N; Heider, Barbara; Silva, Fabian Muñoz; Siegel, Ralph M

2014-01-01

The posterior parietal cortex contains neurons that respond to visual stimulation and motor behaviour. The objective of the current study was to test short-term adaptation in neurons in macaque area 7a and the dorsal prelunate during visually guided reaching using Fresnel prisms that displaced the visual field. The visual perturbation shifted the eye position and created a mismatch between perceived and actual reach location. Two non-human primates were trained to reach to visual targets before, during and after prism exposure while fixating the reach target in different locations. They were required to reach to the physical location of the reach target and not the perceived, displaced location. While behavioural adaptation to the prisms occurred within a few trials, the majority of neurons responded to the distortion either with substantial changes in spatial eye position tuning or changes in overall firing rate. These changes persisted even after prism removal. The spatial changes were not correlated with the direction of induced prism shift. The transformation of gain fields between conditions was estimated by calculating the translation and rotation in Euler angles. Rotations and translations of the horizontal and vertical spatial components occurred in a systematic manner for the population of neurons suggesting that the posterior parietal cortex retains a constant representation of the visual field remapping between experimental conditions. PMID:24928956

Neuronal responses to target onset in oculomotor and somatomotor parietal circuits differ markedly in a choice task.

PubMed

Kubanek, J; Wang, C; Snyder, L H

2013-11-01

We often look at and sometimes reach for visible targets. Looking at a target is fast and relatively easy. By comparison, reaching for an object is slower and is associated with a larger cost. We hypothesized that, as a result of these differences, abrupt visual onsets may drive the circuits involved in saccade planning more directly and with less intermediate regulation than the circuits involved in reach planning. To test this hypothesis, we recorded discharge activity of neurons in the parietal oculomotor system (area LIP) and in the parietal somatomotor system (area PRR) while monkeys performed a visually guided movement task and a choice task. We found that in the visually guided movement task LIP neurons show a prominent transient response to target onset. PRR neurons also show a transient response, although this response is reduced in amplitude, is delayed, and has a slower rise time compared with LIP. A more striking difference is observed in the choice task. The transient response of PRR neurons is almost completely abolished and replaced with a slow buildup of activity, while the LIP response is merely delayed and reduced in amplitude. Our findings suggest that the oculomotor system is more closely and obligatorily coupled to the visual system, whereas the somatomotor system operates in a more discriminating manner.

Sign language processing and the mirror neuron system.

PubMed

Corina, David P; Knapp, Heather

2006-05-01

In this paper we review evidence for frontal and parietal lobe involvement in sign language comprehension and production, and evaluate the extent to which these data can be interpreted within the context of a mirror neuron system for human action observation and execution. We present data from three literatures--aphasia, cortical stimulation, and functional neuroimaging. Generally, we find support for the idea that sign language comprehension and production can be viewed in the context of a broadly-construed frontal-parietal human action observation/execution system. However, sign language data cannot be fully accounted for under a strict interpretation of the mirror neuron system. Additionally, we raise a number of issues concerning the lack of specificity in current accounts of the human action observation/execution system.

Putative pyramidal neurons and interneurons in the monkey parietal cortex make different contributions to the performance of a visual grouping task.

PubMed

Yokoi, Isao; Komatsu, Hidehiko

2010-09-01

Visual grouping of discrete elements is an important function for object recognition. We recently conducted an experiment to study neural correlates of visual grouping. We recorded neuronal activities while monkeys performed a grouping detection task in which they discriminated visual patterns composed of discrete dots arranged in a cross and detected targets in which dots with the same contrast were aligned horizontally or vertically. We found that some neurons in the lateral bank of the intraparietal sulcus exhibit activity related to visual grouping. In the present study, we analyzed how different types of neurons contribute to visual grouping. We classified the recorded neurons as putative pyramidal neurons or putative interneurons, depending on the duration of their action potentials. We found that putative pyramidal neurons exhibited selectivity for the orientation of the target, and this selectivity was enhanced by attention to a particular target orientation. By contrast, putative interneurons responded more strongly to the target stimuli than to the nontargets, regardless of the orientation of the target. These results suggest that different classes of parietal neurons contribute differently to the grouping of discrete elements.

Choice-specific sequences in parietal cortex during a virtual-navigation decision task

PubMed Central

Harvey, Christopher D.; Coen, Philip; Tank, David W.

2012-01-01

The posterior parietal cortex (PPC) plays an important role in many cognitive behaviors; however, the neural circuit dynamics underlying PPC function are not well understood. Here we optically imaged the spatial and temporal activity patterns of neuronal populations in mice performing a PPC-dependent task that combined a perceptual decision and memory-guided navigation in a virtual environment. Individual neurons had transient activation staggered relative to one another in time, forming a sequence of neuronal activation spanning the entire length of a task trial. Distinct sequences of neurons were triggered on trials with opposite behavioral choices and defined divergent, choice-specific trajectories through a state space of neuronal population activity. Cells participating in the different sequences and at distinct time points in the task were anatomically intermixed over microcircuit length scales (< 100 micrometers). During working memory decision tasks the PPC may therefore perform computations through sequence-based circuit dynamics, rather than long-lived stable states, implemented using anatomically intermingled microcircuits. PMID:22419153

Temporal coding of reward-guided choice in the posterior parietal cortex

PubMed Central

Hawellek, David J.; Wong, Yan T.; Pesaran, Bijan

2016-01-01

Making a decision involves computations across distributed cortical and subcortical networks. How such distributed processing is performed remains unclear. We test how the encoding of choice in a key decision-making node, the posterior parietal cortex (PPC), depends on the temporal structure of the surrounding population activity. We recorded spiking and local field potential (LFP) activity in the PPC while two rhesus macaques performed a decision-making task. We quantified the mutual information that neurons carried about an upcoming choice and its dependence on LFP activity. The spiking of PPC neurons was correlated with LFP phases at three distinct time scales in the theta, beta, and gamma frequency bands. Importantly, activity at these time scales encoded upcoming decisions differently. Choice information contained in neural firing varied with the phase of beta and gamma activity. For gamma activity, maximum choice information occurred at the same phase as the maximum spike count. However, for beta activity, choice information and spike count were greatest at different phases. In contrast, theta activity did not modulate the encoding properties of PPC units directly but was correlated with beta and gamma activity through cross-frequency coupling. We propose that the relative timing of local spiking and choice information reveals temporal reference frames for computations in either local or large-scale decision networks. Differences between the timing of task information and activity patterns may be a general signature of distributed processing across large-scale networks. PMID:27821752

Neural mechanisms of imitation and 'mirror neuron' functioning in autistic spectrum disorder.

PubMed

Williams, Justin H G; Waiter, Gordon D; Gilchrist, Anne; Perrett, David I; Murray, Alison D; Whiten, Andrew

2006-01-01

An association between autistic spectrum disorder and imitative impairment might result from dysfunction in mirror neurons (MNs) that serve to relate observed actions to motor codings. To explore this hypothesis, we employed a functional magnetic resonance imaging (fMRI) protocol previously used to identify the neural substrate of imitation, and human MN function, to compare 16 adolescent males of normal intelligence with autistic spectrum disorder (ASD) and age, sex and IQ matched controls. In the control group, in accord with previous findings, we identified activity attributable to MNs in areas of the right parietal lobe. Activity in this area was less extensive in the ASD group and was absent during non-imitative action execution. Broca's area was minimally active during imitation in controls. Differential patterns of activity during imitation and action observation in ASD and controls were most evident in an area at the right temporo-parietal junction also associated with a 'theory of mind' (ToM) function. ASD participants also failed to show modulation of left amygdala activity during imitation that was evident in the controls. This may have implications for understanding the imitation of emotional stimuli in ASD. Overall, we suggest that ASD is associated with altered patterns of brain activity during imitation, which could stem from poor integration between areas serving visual, motor, proprioceptive and emotional functions. Such poor integration is likely to adversely affect the development of ToM through imitation as well as other aspects of social cognitive function in ASD.

Influences of Long-Term Memory-Guided Attention and Stimulus-Guided Attention on Visuospatial Representations within Human Intraparietal Sulcus.

PubMed

Rosen, Maya L; Stern, Chantal E; Michalka, Samantha W; Devaney, Kathryn J; Somers, David C

2015-08-12

Human parietal cortex plays a central role in encoding visuospatial information and multiple visual maps exist within the intraparietal sulcus (IPS), with each hemisphere symmetrically representing contralateral visual space. Two forms of hemispheric asymmetries have been identified in parietal cortex ventrolateral to visuotopic IPS. Key attentional processes are localized to right lateral parietal cortex in the temporoparietal junction and long-term memory (LTM) retrieval processes are localized to the left lateral parietal cortex in the angular gyrus. Here, using fMRI, we investigate how spatial representations of visuotopic IPS are influenced by stimulus-guided visuospatial attention and by LTM-guided visuospatial attention. We replicate prior findings that a hemispheric asymmetry emerges under stimulus-guided attention: in the right hemisphere (RH), visual maps IPS0, IPS1, and IPS2 code attentional targets across the visual field; in the left hemisphere (LH), IPS0-2 codes primarily contralateral targets. We report the novel finding that, under LTM-guided attention, both RH and LH IPS0-2 exhibit bilateral responses and hemispheric symmetry re-emerges. Therefore, we demonstrate that both hemispheres of IPS0-2 are independently capable of dynamically changing spatial coding properties as attentional task demands change. These findings have important implications for understanding visuospatial and memory-retrieval deficits in patients with parietal lobe damage. The human parietal lobe contains multiple maps of the external world that spatially guide perception, action, and cognition. Maps in each cerebral hemisphere code information from the opposite side of space, not from the same side, and the two hemispheres are symmetric. Paradoxically, damage to specific parietal regions that lack spatial maps can cause patients to ignore half of space (hemispatial neglect syndrome), but only for right (not left) hemisphere damage. Conversely, the left parietal cortex has been linked to retrieval of vivid memories regardless of space. Here, we investigate possible underlying mechanisms in healthy individuals. We demonstrate two forms of dynamic changes in parietal spatial representations: an asymmetric one for stimulus-guided attention and a symmetric one for long-term memory-guided attention. Copyright © 2015 the authors 0270-6474/15/3511358-06$15.00/0.

Impairment of actions chains in autism and its possible role in intention understanding

PubMed Central

Cattaneo, Luigi; Fabbri-Destro, Maddalena; Boria, Sonia; Pieraccini, Cinzia; Monti, Annalisa; Cossu, Giuseppe; Rizzolatti, Giacomo

2007-01-01

Experiments in monkeys demonstrated that many parietal and premotor neurons coding a specific motor act (e.g., grasping) show a markedly different activation when this act is part of actions that have different goals (e.g., grasping for eating vs. grasping for placing). Many of these “action-constrained” neurons have mirror properties firing selectively to the observation of the initial motor act of the actions to which they belong motorically. By activating a specific action chain from its very outset, this mechanism allows the observers to have an internal copy of the whole action before its execution, thus enabling them to understand directly the agent's intention. Using electromyographic recordings, we show that a similar chained organization exists in typically developing children, whereas it is impaired in children with autism. We propose that, as a consequence of this functional impairment, high-functioning autistic children may understand the intentions of others cognitively but lack the mechanism for understanding them experientially. PMID:17965234

Impairment of actions chains in autism and its possible role in intention understanding.

PubMed

Cattaneo, Luigi; Fabbri-Destro, Maddalena; Boria, Sonia; Pieraccini, Cinzia; Monti, Annalisa; Cossu, Giuseppe; Rizzolatti, Giacomo

2007-11-06

Experiments in monkeys demonstrated that many parietal and premotor neurons coding a specific motor act (e.g., grasping) show a markedly different activation when this act is part of actions that have different goals (e.g., grasping for eating vs. grasping for placing). Many of these "action-constrained" neurons have mirror properties firing selectively to the observation of the initial motor act of the actions to which they belong motorically. By activating a specific action chain from its very outset, this mechanism allows the observers to have an internal copy of the whole action before its execution, thus enabling them to understand directly the agent's intention. Using electromyographic recordings, we show that a similar chained organization exists in typically developing children, whereas it is impaired in children with autism. We propose that, as a consequence of this functional impairment, high-functioning autistic children may understand the intentions of others cognitively but lack the mechanism for understanding them experientially.

High-alpha band synchronization across frontal, parietal and visual cortex mediates behavioral and neuronal effects of visuospatial attention.

PubMed

Lobier, Muriel; Palva, J Matias; Palva, Satu

2018-01-15

Visuospatial attention prioritizes processing of attended visual stimuli. It is characterized by lateralized alpha-band (8-14 Hz) amplitude suppression in visual cortex and increased neuronal activity in a network of frontal and parietal areas. It has remained unknown what mechanisms coordinate neuronal processing among frontoparietal network and visual cortices and implement the attention-related modulations of alpha-band amplitudes and behavior. We investigated whether large-scale network synchronization could be such a mechanism. We recorded human cortical activity with magnetoencephalography (MEG) during a visuospatial attention task. We then identified the frequencies and anatomical networks of inter-areal phase synchronization from source localized MEG data. We found that visuospatial attention is associated with robust and sustained long-range synchronization of cortical oscillations exclusively in the high-alpha (10-14 Hz) frequency band. This synchronization connected frontal, parietal and visual regions and was observed concurrently with amplitude suppression of low-alpha (6-9 Hz) band oscillations in visual cortex. Furthermore, stronger high-alpha phase synchronization was associated with decreased reaction times to attended stimuli and larger suppression of alpha-band amplitudes. These results thus show that high-alpha band phase synchronization is functionally significant and could coordinate the neuronal communication underlying the implementation of visuospatial attention. Copyright © 2017 Elsevier Inc. All rights reserved.

[Dynamics of the dominance of identified cardioregulatory neurons in the snail Achatina fulica] .

PubMed

Zhuravlev, V L; Bugaĭ, V V; Safronova, T A

2000-08-01

9 cardioregulating neurones belonging to 5 different functional groups were studied in visceral and right parietal ganglia of the Giant African snail Achatina fulica. The neuronal network included multimodal and multifunctional cells exerting short- or long-lasting chronoionotropic effects on the cardiac electro- and mechanograms. Mechanisms of the differences in the cardioregulating effectiveness of these groups were discussed.

Posterior parietal cortex contains a command apparatus for hand movements.

PubMed

Rathelot, Jean-Alban; Dum, Richard P; Strick, Peter L

2017-04-18

Mountcastle and colleagues proposed that the posterior parietal cortex contains a "command apparatus" for the operation of the hand in immediate extrapersonal space [Mountcastle et al. (1975) J Neurophysiol 38(4):871-908]. Here we provide three lines of converging evidence that a lateral region within area 5 has corticospinal neurons that are directly linked to the control of hand movements. First, electrical stimulation in a lateral region of area 5 evokes finger and wrist movements. Second, corticospinal neurons in the same region of area 5 terminate at spinal locations that contain last-order interneurons that innervate hand motoneurons. Third, this lateral region of area 5 contains many neurons that make disynaptic connections with hand motoneurons. The disynaptic input to motoneurons from this portion of area 5 is as direct and prominent as that from any of the premotor areas in the frontal lobe. Thus, our results establish that a region within area 5 contains a motor area with corticospinal neurons that could function as a command apparatus for operation of the hand.

A Model of Self-Organizing Head-Centered Visual Responses in Primate Parietal Areas

PubMed Central

Mender, Bedeho M. W.; Stringer, Simon M.

2013-01-01

We present a hypothesis for how head-centered visual representations in primate parietal areas could self-organize through visually-guided learning, and test this hypothesis using a neural network model. The model consists of a competitive output layer of neurons that receives afferent synaptic connections from a population of input neurons with eye position gain modulated retinal receptive fields. The synaptic connections in the model are trained with an associative trace learning rule which has the effect of encouraging output neurons to learn to respond to subsets of input patterns that tend to occur close together in time. This network architecture and synaptic learning rule is hypothesized to promote the development of head-centered output neurons during periods of time when the head remains fixed while the eyes move. This hypothesis is demonstrated to be feasible, and each of the core model components described is tested and found to be individually necessary for successful self-organization. PMID:24349064

Learning of spatial relationships between observed and imitated actions allows invariant inverse computation in the frontal mirror neuron system.

PubMed

Oh, Hyuk; Gentili, Rodolphe J; Reggia, James A; Contreras-Vidal, José L

2011-01-01

It has been suggested that the human mirror neuron system can facilitate learning by imitation through coupling of observation and action execution. During imitation of observed actions, the functional relationship between and within the inferior frontal cortex, the posterior parietal cortex, and the superior temporal sulcus can be modeled within the internal model framework. The proposed biologically plausible mirror neuron system model extends currently available models by explicitly modeling the intraparietal sulcus and the superior parietal lobule in implementing the function of a frame of reference transformation during imitation. Moreover, the model posits the ventral premotor cortex as performing an inverse computation. The simulations reveal that: i) the transformation system can learn and represent the changes in extrinsic to intrinsic coordinates when an imitator observes a demonstrator; ii) the inverse model of the imitator's frontal mirror neuron system can be trained to provide the motor plans for the imitated actions.

Spatial updating in human parietal cortex

NASA Technical Reports Server (NTRS)

Merriam, Elisha P.; Genovese, Christopher R.; Colby, Carol L.

2003-01-01

Single neurons in monkey parietal cortex update visual information in conjunction with eye movements. This remapping of stimulus representations is thought to contribute to spatial constancy. We hypothesized that a similar process occurs in human parietal cortex and that we could visualize it with functional MRI. We scanned subjects during a task that involved remapping of visual signals across hemifields. We observed an initial response in the hemisphere contralateral to the visual stimulus, followed by a remapped response in the hemisphere ipsilateral to the stimulus. We ruled out the possibility that this remapped response resulted from either eye movements or visual stimuli alone. Our results demonstrate that updating of visual information occurs in human parietal cortex.

Distinct cortical codes and temporal dynamics for conscious and unconscious percepts

PubMed Central

Salti, Moti; Monto, Simo; Charles, Lucie; King, Jean-Remi; Parkkonen, Lauri; Dehaene, Stanislas

2015-01-01

The neural correlates of consciousness are typically sought by comparing the overall brain responses to perceived and unperceived stimuli. However, this comparison may be contaminated by non-specific attention, alerting, performance, and reporting confounds. Here, we pursue a novel approach, tracking the neuronal coding of consciously and unconsciously perceived contents while keeping behavior identical (blindsight). EEG and MEG were recorded while participants reported the spatial location and visibility of a briefly presented target. Multivariate pattern analysis demonstrated that considerable information about spatial location traverses the cortex on blindsight trials, but that starting ≈270 ms post-onset, information unique to consciously perceived stimuli, emerges in superior parietal and superior frontal regions. Conscious access appears characterized by the entry of the perceived stimulus into a series of additional brain processes, each restricted in time, while the failure of conscious access results in the breaking of this chain and a subsequent slow decay of the lingering unconscious activity. DOI: http://dx.doi.org/10.7554/eLife.05652.001 PMID:25997100

Multiscale neural connectivity during human sensory processing in the brain

NASA Astrophysics Data System (ADS)

Maksimenko, Vladimir A.; Runnova, Anastasia E.; Frolov, Nikita S.; Makarov, Vladimir V.; Nedaivozov, Vladimir; Koronovskii, Alexey A.; Pisarchik, Alexander; Hramov, Alexander E.

2018-05-01

Stimulus-related brain activity is considered using wavelet-based analysis of neural interactions between occipital and parietal brain areas in alpha (8-12 Hz) and beta (15-30 Hz) frequency bands. We show that human sensory processing related to the visual stimuli perception induces brain response resulted in different ways of parieto-occipital interactions in these bands. In the alpha frequency band the parieto-occipital neuronal network is characterized by homogeneous increase of the interaction between all interconnected areas both within occipital and parietal lobes and between them. In the beta frequency band the occipital lobe starts to play a leading role in the dynamics of the occipital-parietal network: The perception of visual stimuli excites the visual center in the occipital area and then, due to the increase of parieto-occipital interactions, such excitation is transferred to the parietal area, where the attentional center takes place. In the case when stimuli are characterized by a high degree of ambiguity, we find greater increase of the interaction between interconnected areas in the parietal lobe due to the increase of human attention. Based on revealed mechanisms, we describe the complex response of the parieto-occipital brain neuronal network during the perception and primary processing of the visual stimuli. The results can serve as an essential complement to the existing theory of neural aspects of visual stimuli processing.

The Role of Architectural and Learning Constraints in Neural Network Models: A Case Study on Visual Space Coding.

PubMed

Testolin, Alberto; De Filippo De Grazia, Michele; Zorzi, Marco

2017-01-01

The recent "deep learning revolution" in artificial neural networks had strong impact and widespread deployment for engineering applications, but the use of deep learning for neurocomputational modeling has been so far limited. In this article we argue that unsupervised deep learning represents an important step forward for improving neurocomputational models of perception and cognition, because it emphasizes the role of generative learning as opposed to discriminative (supervised) learning. As a case study, we present a series of simulations investigating the emergence of neural coding of visual space for sensorimotor transformations. We compare different network architectures commonly used as building blocks for unsupervised deep learning by systematically testing the type of receptive fields and gain modulation developed by the hidden neurons. In particular, we compare Restricted Boltzmann Machines (RBMs), which are stochastic, generative networks with bidirectional connections trained using contrastive divergence, with autoencoders, which are deterministic networks trained using error backpropagation. For both learning architectures we also explore the role of sparse coding, which has been identified as a fundamental principle of neural computation. The unsupervised models are then compared with supervised, feed-forward networks that learn an explicit mapping between different spatial reference frames. Our simulations show that both architectural and learning constraints strongly influenced the emergent coding of visual space in terms of distribution of tuning functions at the level of single neurons. Unsupervised models, and particularly RBMs, were found to more closely adhere to neurophysiological data from single-cell recordings in the primate parietal cortex. These results provide new insights into how basic properties of artificial neural networks might be relevant for modeling neural information processing in biological systems.

The Role of Architectural and Learning Constraints in Neural Network Models: A Case Study on Visual Space Coding

PubMed Central

Testolin, Alberto; De Filippo De Grazia, Michele; Zorzi, Marco

2017-01-01

The recent “deep learning revolution” in artificial neural networks had strong impact and widespread deployment for engineering applications, but the use of deep learning for neurocomputational modeling has been so far limited. In this article we argue that unsupervised deep learning represents an important step forward for improving neurocomputational models of perception and cognition, because it emphasizes the role of generative learning as opposed to discriminative (supervised) learning. As a case study, we present a series of simulations investigating the emergence of neural coding of visual space for sensorimotor transformations. We compare different network architectures commonly used as building blocks for unsupervised deep learning by systematically testing the type of receptive fields and gain modulation developed by the hidden neurons. In particular, we compare Restricted Boltzmann Machines (RBMs), which are stochastic, generative networks with bidirectional connections trained using contrastive divergence, with autoencoders, which are deterministic networks trained using error backpropagation. For both learning architectures we also explore the role of sparse coding, which has been identified as a fundamental principle of neural computation. The unsupervised models are then compared with supervised, feed-forward networks that learn an explicit mapping between different spatial reference frames. Our simulations show that both architectural and learning constraints strongly influenced the emergent coding of visual space in terms of distribution of tuning functions at the level of single neurons. Unsupervised models, and particularly RBMs, were found to more closely adhere to neurophysiological data from single-cell recordings in the primate parietal cortex. These results provide new insights into how basic properties of artificial neural networks might be relevant for modeling neural information processing in biological systems. PMID:28377709

Binocular disparity tuning and visual-vestibular congruency of multisensory neurons in macaque parietal cortex

PubMed Central

Yang, Yun; Liu, Sheng; Chowdhury, Syed A.; DeAngelis, Gregory C.; Angelaki, Dora E.

2012-01-01

Many neurons in the dorsal medial superior temporal (MSTd) and ventral intraparietal (VIP) areas of the macaque brain are multisensory, responding to both optic flow and vestibular cues to self-motion. The heading tuning of visual and vestibular responses can be either congruent or opposite, but only congruent cells have been implicated in cue integration for heading perception. Because of the geometric properties of motion parallax, however, both congruent and opposite cells could be involved in coding self-motion when observers fixate a world-fixed target during translation, if congruent cells prefer near disparities and opposite cells prefer far disparities. We characterized the binocular disparity selectivity and heading tuning of MSTd and VIP cells using random-dot stimuli. Most (70%) MSTd neurons were disparity-selective with monotonic tuning, and there was no consistent relationship between depth preference and congruency of visual and vestibular heading tuning. One-third of disparity-selective MSTd cells reversed their depth preference for opposite directions of motion (direction-dependent disparity tuning, DDD), but most of these cells were unisensory with no tuning for vestibular stimuli. Inconsistent with previous reports, the direction preferences of most DDD neurons do not reverse with disparity. By comparison to MSTd, VIP contains fewer disparity-selective neurons (41%) and very few DDD cells. On average, VIP neurons also preferred higher speeds and nearer disparities than MSTd cells. Our findings are inconsistent with the hypothesis that visual/vestibular congruency is linked to depth preference, and also suggest that DDD cells are not involved in multisensory integration for heading perception. PMID:22159105

Correlates of stimulus-response congruence in the posterior parietal cortex.

PubMed

Stoet, Gijsbert; Snyder, Lawrence H

2007-02-01

Primate behavior is flexible: The response to a stimulus often depends on the task in which it occurs. Here we study how single neurons in the posterior parietal cortex (PPC) respond to stimuli which are associated with different responses in different tasks. Two rhesus monkeys performed a task-switching paradigm. Each trial started with a task cue instructing which of two tasks to perform, followed by a stimulus requiring a left or right button press. For half the stimuli, the associated responses were different in the two tasks, meaning that the task context was necessary to disambiguate the incongruent stimuli. The other half of stimuli required the same response irrespective of task context (congruent). Using this paradigm, we previously showed that behavioral responses to incongruent stimuli are significantly slower than to congruent stimuli. We now demonstrate a neural correlate in the PPC of the additional processing time required for incongruent stimuli. Furthermore, we previously found that 29% of parietal neurons encode the task being performed (task-selective cells). We now report differences in neuronal timing related to congruency in task-selective versus task nonselective cells. These differences in timing suggest that the activity in task nonselective cells reflects a motor command, whereas activity in task-selective cells reflects a decision process.

Altered Brain Activation During Action Imitation and Observation in Schizophrenia: A Translational Approach to Investigating Social Dysfunction in Schizophrenia

PubMed Central

Thakkar, Katharine N.; Peterman, Joel S.; Park, Sohee

2015-01-01

Objective Social impairments are a key feature of schizophrenia, but their underlying mechanisms are poorly understood. Imitation, a process through which we understand the minds of others, involves the so-called mirror neuron system, a network comprising the inferior parietal lobe, inferior frontal gyrus, and posterior superior temporal sulcus. The authors examined mirror neuron system function in schizophrenia. Method Sixteen medicated schizophrenia patients and 16 healthy comparison subjects performed an action imitation/ observation task during functional MRI. Participants saw a video of a moving hand or spatial cue and were instructed to either execute finger movements associated with the stimulus or simply observe. Activation in the mirror neuron system was measured during imitative versus nonimitative actions and observation of a moving hand versus a moving spatial cue. These contrasts were compared across groups. Results Activation in the mirror neuron system was less specific for imitation in schizophrenia. Relative to healthy subjects, patients had reduced activity in the posterior superior temporal sulcus during imitation and greater activity in the posterior superior temporal sulcus and inferior parietal lobe during nonimitative action. Patients also showed reduced activity in these regions during action observation. Mirror neuron system activation was related to symptom severity and social functioning in patients and to schizotypal syndrome in comparison subjects. Conclusions Given the role of the inferior parietal lobe and posterior superior temporal sulcus in imitation and social cognition, impaired imitative ability in schizophrenia may stem from faulty perception of biological motion and transformations from perception to action. These findings extend our understanding of social dysfunction in schizophrenia. PMID:24626638

The Visual Representation of 3D Object Orientation in Parietal Cortex

PubMed Central

Cowan, Noah J.; Angelaki, Dora E.

2013-01-01

An accurate representation of three-dimensional (3D) object orientation is essential for interacting with the environment. Where and how the brain visually encodes 3D object orientation remains unknown, but prior studies suggest the caudal intraparietal area (CIP) may be involved. Here, we develop rigorous analytical methods for quantifying 3D orientation tuning curves, and use these tools to the study the neural coding of surface orientation. Specifically, we show that single neurons in area CIP of the rhesus macaque jointly encode the slant and tilt of a planar surface, and that across the population, the distribution of preferred slant-tilts is not statistically different from uniform. This suggests that all slant-tilt combinations are equally represented in area CIP. Furthermore, some CIP neurons are found to also represent the third rotational degree of freedom that determines the orientation of the image pattern on the planar surface. Together, the present results suggest that CIP is a critical neural locus for the encoding of all three rotational degrees of freedom specifying an object's 3D spatial orientation. PMID:24305830

The mirror neuron system and the consequences of its dysfunction.

PubMed

Iacoboni, Marco; Dapretto, Mirella

2006-12-01

The discovery of premotor and parietal cells known as mirror neurons in the macaque brain that fire not only when the animal is in action, but also when it observes others carrying out the same actions provides a plausible neurophysiological mechanism for a variety of important social behaviours, from imitation to empathy. Recent data also show that dysfunction of the mirror neuron system in humans might be a core deficit in autism, a socially isolating condition. Here, we review the neurophysiology of the mirror neuron system and its role in social cognition and discuss the clinical implications of mirror neuron dysfunction.

Mirror Neurons in Humans: Consisting or Confounding Evidence?

ERIC Educational Resources Information Center

Turella, Luca; Pierno, Andrea C.; Tubaldi, Federico; Castiello, Umberto

2009-01-01

The widely known discovery of mirror neurons in macaques shows that premotor and parietal cortical areas are not only involved in executing one's own movement, but are also active when observing the action of others. The goal of this essay is to critically evaluate the substance of functional magnetic resonance imaging (fMRI) and positron emission…

Functional versus effector-specific organization of the human posterior parietal cortex: revisited

PubMed Central

Leone, Frank T. M.; Medendorp, W. Pieter

2016-01-01

It has been proposed that the posterior parietal cortex (PPC) is characterized by an effector-specific organization. However, strikingly similar functional MRI (fMRI) activation patterns have been found in the PPC for hand and foot movements. Because the fMRI signal is related to average neuronal activity, similar activation levels may result either from effector-unspecific neurons or from intermingled subsets of effector-specific neurons within a voxel. We distinguished between these possibilities using fMRI repetition suppression (RS). Participants made delayed, goal-directed eye, hand, and foot movements to visual targets. In each trial, the instructed effector was identical or different to that of the previous trial. RS effects indicated an attenuation of the fMRI signal in repeat trials. The caudal PPC was active during the delay but did not show RS, suggesting that its planning activity was effector independent. Hand and foot-specific RS effects were evident in the anterior superior parietal lobule (SPL), extending to the premotor cortex, with limb overlap in the anterior SPL. Connectivity analysis suggested information flow between the caudal PPC to limb-specific anterior SPL regions and between the limb-unspecific anterior SPL toward limb-specific motor regions. These results underline that both function and effector specificity should be integrated into a concept of PPC action representation not only on a regional but also on a fine-grained, subvoxel level. PMID:27466132

Neuronal oscillations reveal the processes underlying intentional compared to incidental learning in children and young adults.

PubMed

Köster, Moritz; Haese, André; Czernochowski, Daniela

2017-01-01

This EEG study investigated the neuronal processes during intentional compared to incidental learning in young adults and two groups of children aged 10 and 7 years. Theta (3-8 Hz) and alpha (10-16 Hz) neuronal oscillations were analyzed to compare encoding processes during an intentional and an incidental encoding task. In all three age groups, both encoding conditions were associated with an increase in event-related theta activity. Encoding-related alpha suppression increased with age. Memory performance was higher in the intentional compared to the incidental task in all age groups. Furthermore, intentional learning was associated with an improved encoding of perceptual features, which were relevant for the retrieval phase. Theta activity increased from incidental to intentional encoding. Specifically, frontal theta increased in all age groups, while parietal theta increased only in adults and older children. In younger children, parietal theta was similarly high in both encoding phases. While alpha suppression may reflect semantic processes during encoding, increased theta activity during intentional encoding may indicate perceptual binding processes, in accordance with the demands of the encoding task. Higher encoding-related alpha suppression in the older age groups, together with age differences in parietal theta activity during incidental learning in young children, is in line with recent theoretical accounts, emphasizing the role of perceptual processes in mnemonic processing in young children, whereas semantic encoding processes continue to mature throughout middle childhood.

Parietal neurons encode expected gains in instrumental information

PubMed Central

Foley, Nicholas C.; Kelly, Simon P.; Mhatre, Himanshu; Gottlieb, Jacqueline

2017-01-01

In natural behavior, animals have access to multiple sources of information, but only a few of these sources are relevant for learning and actions. Beyond choosing an appropriate action, making good decisions entails the ability to choose the relevant information, but fundamental questions remain about the brain’s information sampling policies. Recent studies described the neural correlates of seeking information about a reward, but it remains unknown whether, and how, neurons encode choices of instrumental information, in contexts in which the information guides subsequent actions. Here we show that parietal cortical neurons involved in oculomotor decisions encode, before an information sampling saccade, the reduction in uncertainty that the saccade is expected to bring for a subsequent action. These responses were distinct from the neurons’ visual and saccadic modulations and from signals of expected reward or reward prediction errors. Therefore, even in an instrumental context when information and reward gains are closely correlated, individual cells encode decision variables that are based on informational factors and can guide the active sampling of action-relevant cues. PMID:28373569

Body representations in the human brain revealed by kinesthetic illusions and their essential contributions to motor control and corporeal awareness.

PubMed

Naito, Eiichi; Morita, Tomoyo; Amemiya, Kaoru

2016-03-01

The human brain can generate a continuously changing postural model of our body. Somatic (proprioceptive) signals from skeletal muscles and joints contribute to the formation of the body representation. Recent neuroimaging studies of proprioceptive bodily illusions have elucidated the importance of three brain systems (motor network, specialized parietal systems, right inferior fronto-parietal network) in the formation of the human body representation. The motor network, especially the primary motor cortex, processes afferent input from skeletal muscles. Such information may contribute to the formation of kinematic/dynamic postural models of limbs, thereby enabling fast online feedback control. Distinct parietal regions appear to play specialized roles in the transformation/integration of information across different coordinate systems, which may subserve the adaptability and flexibility of the body representation. Finally, the right inferior fronto-parietal network, connected by the inferior branch of the superior longitudinal fasciculus, is consistently recruited when an individual experiences various types of bodily illusions and its possible roles relate to corporeal awareness, which is likely elicited through a series of neuronal processes of monitoring and accumulating bodily information and updating the body representation. Because this network is also recruited when identifying one's own features, the network activity could be a neuronal basis for self-consciousness. Copyright © 2015 Elsevier Ireland Ltd and the Japan Neuroscience Society. All rights reserved.

A role for the anterior insular cortex in the global neuronal workspace model of consciousness.

PubMed

Michel, Matthias

2017-03-01

According to the global neuronal workspace model of consciousness, consciousness results from the global broadcast of information throughout the brain. The global neuronal workspace is mainly constituted by a fronto-parietal network. The anterior insular cortex is part of this global neuronal workspace, but the function of this region has not yet been defined within the global neuronal workspace model of consciousness. In this review, I hypothesize that the anterior insular cortex implements a cross-modal priority map, the function of which is to determine priorities for the processing of information and subsequent entrance in the global neuronal workspace. Copyright © 2017 Elsevier Inc. All rights reserved.

[Neuroeffector connections of multimodal neurons in the African snail (Achatina fulica)].

PubMed

Bugaĭ, V V; Zhuravlev, V L; Safonova, T A

2004-02-01

Using a new method of animal preparation, the efferent connections of giant paired neurons on the dorsal surface of visceral and right parietal ganglia of snail, Achatina fulica, were examined. It was found that spikes in giant neurons d-VLN and d-RPLN evoke postjunctional potentials in different points of the snail body and viscerae (in the heart, in pericardium, in lung cavity and kidney walls, in mantle and body wall muscles, in tentacle retractors and in cephalic artery). The preliminary analysis of synaptic latency and facilitation suggests a direct connections between giant neurons and investigated efferents.

Implicit representations of space after bilateral parietal lobe damage.

PubMed

Kim, M S; Robertson, L C

2001-11-15

There is substantial evidence that the primate cortex is grossly divided into two functional streams, an occipital-parietal-frontal pathway that processes "where" and an occipital-temporal-frontal pathway that processes "what" (Ungerleider and Mishkin, 1982). In humans, bilateral occipital-parietal damage results in severe spatial deficits and a neuropsychological disorder known as Balint's syndrome in which a single object can be perceived (simultanagnosia) but its location is unknown (Balint, 1995). The data reported here demonstrate that spatial information for visual features that cannot be explicitly located is represented normally below the level of spatial awareness even with large occipital-parietal lesions. They also demonstrate that parietal damage does not affect preattentive spatial coding of feature locations or complex spatial relationships between parts of a stimulus despite explicit spatial deficits and simultanagnosia.

Widespread heterogeneous neuronal loss across the cerebral cortex in Huntington's disease.

PubMed

Nana, Alissa L; Kim, Eric H; Thu, Doris C V; Oorschot, Dorothy E; Tippett, Lynette J; Hogg, Virginia M; Synek, Beth J; Roxburgh, Richard; Waldvogel, Henry J; Faull, Richard L M

2014-01-01

Huntington's disease is an autosomal dominant neurodegenerative disease characterized by neuronal degeneration in the basal ganglia and cerebral cortex, and a variable symptom profile. Although progressive striatal degeneration is known to occur and is related to symptom profile, little is known about the cellular basis of symptom heterogeneity across the entire cerebral cortex. To investigate this, we have undertaken a double blind study using unbiased stereological cell counting techniques to determine the pattern of cell loss in six representative cortical regions from the frontal, parietal, temporal, and occipital lobes in the brains of 14 Huntington's disease cases and 15 controls. The results clearly demonstrate a widespread loss of total neurons and pyramidal cells across all cortical regions studied, except for the primary visual cortex. Importantly, the results show that cell loss is remarkably variable both within and between Huntington's disease cases. The results also show that neuronal loss in the primary sensory and secondary visual cortices relate to Huntington's disease motor symptom profiles, and neuronal loss across the associational cortices in the frontal, parietal and temporal lobes is related to both Huntington's disease motor and to mood symptom profiles. This finding considerably extends a previous study (Thu et al., Brain, 2010; 133:1094-1110) which showed that neuronal loss in the primary motor cortex was related specifically to the motor symptom profiles while neuronal loss in the anterior cingulate cortex was related specifically to mood symptom profiles. The extent of cortical cell loss in the current study was generally related to the striatal neuropathological grade, but not to CAG repeat length on the HTT gene. Overall our findings show that Huntington's disease is characterized by a heterogeneous pattern of neuronal cell loss across the entire cerebrum which varies with symptom profile.

Neurochemical phenotype of corticocortical connections in the macaque monkey: quantitative analysis of a subset of neurofilament protein-immunoreactive projection neurons in frontal, parietal, temporal, and cingulate cortices

NASA Technical Reports Server (NTRS)

Hof, P. R.; Nimchinsky, E. A.; Morrison, J. H.; Bloom, F. E. (Principal Investigator)

1995-01-01

The neurochemical characteristics of the neuronal subsets that furnish different types of corticocortical connections have been only partially determined. In recent years, several cytoskeletal proteins have emerged as reliable markers to distinguish subsets of pyramidal neurons in the cerebral cortex of primates. In particular, previous studies using an antibody to nonphosphorylated neurofilament protein (SMI-32) have revealed a consistent degree of regional and laminar specificity in the distribution of a subpopulation of pyramidal cells in the primate cerebral cortex. The density of neurofilament protein-immunoreactive neurons was shown to vary across corticocortical pathways in macaque monkeys. In the present study, we have used the antibody SMI-32 to examine further and to quantify the distribution of a subset of corticocortically projecting neurons in a series of long ipsilateral corticocortical pathways in comparison to short corticocortical, commissural, and limbic connections. The results demonstrate that the long association pathways interconnecting the frontal, parietal, and temporal neocortex have a high representation of neurofilament protein-enriched pyramidal neurons (45-90%), whereas short corticocortical, callosal, and limbic pathways are characterized by much lower numbers of such neurons (4-35%). These data suggest that different types of corticocortical connections have differential representation of highly specific neuronal subsets that share common neurochemical characteristics, thereby determining regional and laminar cortical patterns of morphological and molecular heterogeneity. These differences in neuronal neurochemical phenotype among corticocortical circuits may have considerable influence on cortical processing and may be directly related to the type of integrative function subserved by each cortical pathway. Finally, it is worth noting that neurofilament protein-immunoreactive neurons are dramatically affected in the course of Alzheimer's disease. The present results support the hypothesis that neurofilament protein may be crucially linked to the development of selective neuronal vulnerability and subsequent disruption of corticocortical pathways that lead to the severe impairment of cognitive function commonly observed in age-related dementing disorders.

The brain's dress code: How The Dress allows to decode the neuronal pathway of an optical illusion.

PubMed

Schlaffke, Lara; Golisch, Anne; Haag, Lauren M; Lenz, Melanie; Heba, Stefanie; Lissek, Silke; Schmidt-Wilcke, Tobias; Eysel, Ulf T; Tegenthoff, Martin

2015-12-01

Optical illusions have broadened our understanding of the brain's role in visual perception. A modern day optical illusion emerged from a posted photo of a striped dress, which some perceived as white and gold and others as blue and black. Here we show, using functional magnetic resonance imaging (fMRI), that those who perceive The Dress as white/gold have higher activation in response to the image of The Dress in brain regions critically involved in higher cognition (frontal and parietal brain areas). These results are consistent with theories of top-down modulation and present a neural signature associated with the differences in perceiving The Dress as white/gold or blue/black. Furthermore the results support recent psychophysiological data on this phenomenon and provide a fundamental building block to study interindividual differences in visual processing. Copyright © 2015 Elsevier Ltd. All rights reserved.

Neural representations of social status hierarchy in human inferior parietal cortex.

PubMed

Chiao, Joan Y; Harada, Tokiko; Oby, Emily R; Li, Zhang; Parrish, Todd; Bridge, Donna J

2009-01-01

Mental representations of social status hierarchy share properties with that of numbers. Previous neuroimaging studies have shown that the neural representation of numerical magnitude lies within a network of regions within inferior parietal cortex. However the neural basis of social status hierarchy remains unknown. Using fMRI, we studied subjects while they compared social status magnitude of people, objects and symbols, as well as numerical magnitude. Both social status and number comparisons recruited bilateral intraparietal sulci. We also observed a semantic distance effect whereby neural activity within bilateral intraparietal sulci increased for semantically close relative to far numerical and social status comparisons. These results demonstrate that social status and number comparisons recruit distinct and overlapping neuronal representations within human inferior parietal cortex.

Regional distribution of neuropeptide Y mRNA in postmortem human brain.

PubMed

Brené, S; Lindefors, N; Kopp, J; Sedvall, G; Persson, H

1989-12-01

The distribution of messenger RNA encoding neuropeptide Y (NPY) was studied in 11 different postmortem human brain regions using in situ hybridization histochemistry, and RNA blot analysis. In situ hybridization data revealed that the highest numerical density of labeled cells corresponded to neurons in accumbens area, caudate nucleus, putamen, and substantia innominata. Significantly fewer NPY mRNA-containing neurons were found in frontal and parietal cortex, amygdaloid body and dentate gyrus. No NPY mRNA-containing cells were found in substantia nigra. NPY mRNA-positive neurons from all regions studied showed relatively similar labeling, as revealed by computerized image analysis. Blot analysis showed an approximately 0.8 kb NPY mRNA in all brain regions studied, except in substantia nigra and cerebellum. Densitometric scanning of the autoradiograms revealed levels of NPY mRNA in the following order: putamen greater than caudate nucleus greater than frontal cortex (Brodmann areas 4 and 6) greater than temporal cortex (Brodmann area 38) greater than parietal cortex (Brodmann areas 5 and 7) greater than frontal cortex (Brodmann area 11). Hence, although NPY mRNA is widely distributed in neurons of the human brain large regional variation exists, with the highest expression in accumbens area and parts of the basal ganglia.

Converging levels of analysis in the cognitive neuroscience of visual attention.

PubMed Central

Duncan, J

1998-01-01

Experiments using behavioural, lesion, functional imaging and single neuron methods are considered in the context of a neuropsychological model of visual attention. According to this model, inputs compete for representation in multiple visually responsive brain systems, sensory and motor, cortical and subcortical. Competition is biased by advance priming of neurons responsive to current behavioural targets. Across systems competition is integrated such that the same, selected object tends to become dominant throughout. The behavioural studies reviewed concern divided attention within and between modalities. They implicate within-modality competition as one main restriction on concurrent stimulus identification. In contrast to the conventional association of lateral attentional focus with parietal lobe function, the lesion studies show attentional bias to be a widespread consequence of unilateral cortical damage. Although the clinical syndrome of unilateral neglect may indeed be associated with parietal lesions, this probably reflects an assortment of further deficits accompanying a simple attentional imbalance. The functional imaging studies show joint involvement of lateral prefrontal and occipital cortex in lateral attentional focus and competition. The single unit studies suggest how competition in several regions of extrastriate cortex is biased by advance priming of neurons responsive to current behavioural targets. Together, the concepts of competition, priming and integration allow a unified theoretical approach to findings from behavioural to single neuron levels. PMID:9770224

The mirror neuron system is more active during complementary compared with imitative action.

PubMed

Newman-Norlund, Roger D; van Schie, Hein T; van Zuijlen, Alexander M J; Bekkering, Harold

2007-07-01

We assessed the role of the human mirror neuron system (MNS) in complementary actions using functional magnetic resonance imaging while participants prepared to execute imitative or complementary actions. The BOLD signal in the right inferior frontal gyrus and bilateral inferior parietal lobes was greater during preparation of complementary than during imitative actions, suggesting that the MNS may be essential in dynamically coupling action observation to action execution.

Brain-Machine Interface Enables Bimanual Arm Movements in Monkeys

PubMed Central

Ifft, Peter J.; Shokur, Solaiman; Li, Zheng; Lebedev, Mikhail A.; Nicolelis, Miguel A. L.

2014-01-01

Brain-machine interfaces (BMIs) are artificial systems that aim to restore sensation and movement to severely paralyzed patients. However, previous BMIs enabled only single arm functionality, and control of bimanual movements was a major challenge. Here, we developed and tested a bimanual BMI that enabled rhesus monkeys to control two avatar arms simultaneously. The bimanual BMI was based on the extracellular activity of 374–497 neurons recorded from several frontal and parietal cortical areas of both cerebral hemispheres. Cortical activity was transformed into movements of the two arms with a decoding algorithm called a 5th order unscented Kalman filter (UKF). The UKF is well-suited for BMI decoding because it accounts for both characteristics of reaching movements and their representation by cortical neurons. The UKF was trained either during a manual task performed with two joysticks or by having the monkeys passively observe the movements of avatar arms. Most cortical neurons changed their modulation patterns when both arms were engaged simultaneously. Representing the two arms jointly in a single UKF decoder resulted in improved decoding performance compared with using separate decoders for each arm. As the animals’ performance in bimanual BMI control improved over time, we observed widespread plasticity in frontal and parietal cortical areas. Neuronal representation of the avatar and reach targets was enhanced with learning, whereas pairwise correlations between neurons initially increased and then decreased. These results suggest that cortical networks may assimilate the two avatar arms through BMI control. PMID:24197735

Two different mirror neuron networks: The sensorimotor (hand) and limbic (face) pathways.

PubMed

Ferrari, P F; Gerbella, M; Coudé, G; Rozzi, S

2017-09-01

The vast majority of functional studies investigating mirror neurons (MNs) explored their properties in relation to hand actions, and very few investigated how MNs respond to mouth actions or communicative gestures. Since hand and mouth MNs were recorded in two partially overlapping sectors of the ventral precentral cortex of the macaque monkey, there is a general assumption that they share a same neuroanatomical network, with the parietal cortex as a main source of visual information. In the current review, we challenge this perspective and describe the connectivity pattern of mouth MN sector. The mouth MNs F5/opercular region is connected with premotor, parietal areas mostly related to the somatosensory and motor representation of the face/mouth, and with area PrCO, involved in processing gustatory and somatosensory intraoral input. Unlike hand MNs, mouth MNs do not receive their visual input from parietal regions. Such information related to face/communicative behaviors could come from the ventrolateral prefrontal cortex. Further strong connections derive from limbic structures involved in encoding emotional facial expressions and motivational/reward processing. These brain structures include the anterior cingulate cortex, the anterior and mid-dorsal insula, orbitofrontal cortex and the basolateral amygdala. The mirror mechanism is therefore composed and supported by at least two different anatomical pathways: one is concerned with sensorimotor transformation in relation to reaching and hand grasping within the traditional parietal-premotor circuits; the second one is linked to the mouth/face motor control and is connected with limbic structures, involved in communication/emotions and reward processing. Copyright © 2017. Published by Elsevier Ltd.

Multiple forebrain systems converge on motor neurons innervating the thyroarytenoid muscle

PubMed Central

Van Daele, Douglas J.; Cassell, Martin D.

2009-01-01

The present study investigated the central connections of motor neurons innervating the thyroarytenoid laryngeal muscle that is active in swallowing, respiration and vocalization. In both intact and sympathectomized rats, the pseudorabies virus (PRV) was inoculated into the muscle. After initial infection of laryngomotor neurons in the ipsilateral loose division of the nucleus ambiguous (NA) by 3 days post-inoculation., PRV spread to the ipsilateral compact portion of the NA, the central and intermediate divisions of the nucleus tractus solitarii (NTS), the Botzinger complex, and the parvocellular reticular formation by 4 days. Infection was subsequently expanded to include the ipsilateral granular and dysgranular parietal insular cortex, the ipsilateral medial division of the central nucleus of the amygdala, the lateral, paraventricular, ventrolateral and medial preoptic nuclei of the hypothalamus (generally bilaterally), the lateral periaqueductal gray, the A7 and oral and caudal pontine nuclei. At the latest time points sampled post-inoculation (5 days), infected neurons were identified in the ipsilateral agranular insular cortex, the caudal parietal insular cortex, the anterior cingulate cortex, and the contralateral motor cortex. In the amygdala, infection had spread to the lateral central nucleus and the parvocellular portion of the basolateral nucleus. Hypothalamic infection was largely characterized by an increase in the number of infected cells in earlier infected regions though the posterior, dorsomedial, tuberomammillary and mammillary nuclei contained infected cells. Comparison with previous connectional data suggest PRV followed three interconnected systems originating in the forebrain; a bilateral system including the ventral anterior cingulate cortex, periaqueductal gray and ventral respiratory group; an ipsilateral system involving the parietal insular cortex, central nucleus of the amygdala and parvicellular reticular formation, and a minor contralateral system originating in motor cortex. Hypothalamic innervation involved several functionally specific nuclei. Overall, the data imply complex central nervous system control over the multi-functional thyroarytenoid muscle.[297 words] PMID:19426785

The mirror neuron system: a neural substrate for methods in stroke rehabilitation.

PubMed

Garrison, Kathleen A; Winstein, Carolee J; Aziz-Zadeh, Lisa

2010-06-01

Mirror neurons found in the premotor and parietal cortex respond not only during action execution, but also during observation of actions being performed by others. Thus, the motor system may be activated without overt movement. Rehabilitation of motor function after stroke is often challenging due to severity of impairment and poor to absent voluntary movement ability. Methods in stroke rehabilitation based on the mirror neuron system--action observation, motor imagery, and imitation--take advantage of this opportunity to rebuild motor function despite impairments, as an alternative or complement to physical therapy. Here the authors review research into each condition of practice, and discuss the relevance of the mirror neuron system to stroke recovery.

Sensory Afferents Use Different Coding Strategies for Heat and Cold.

PubMed

Wang, Feng; Bélanger, Erik; Côté, Sylvain L; Desrosiers, Patrick; Prescott, Steven A; Côté, Daniel C; De Koninck, Yves

2018-05-15

Primary afferents transduce environmental stimuli into electrical activity that is transmitted centrally to be decoded into corresponding sensations. However, it remains unknown how afferent populations encode different somatosensory inputs. To address this, we performed two-photon Ca 2+ imaging from thousands of dorsal root ganglion (DRG) neurons in anesthetized mice while applying mechanical and thermal stimuli to hind paws. We found that approximately half of all neurons are polymodal and that heat and cold are encoded very differently. As temperature increases, more heating-sensitive neurons are activated, and most individual neurons respond more strongly, consistent with graded coding at population and single-neuron levels, respectively. In contrast, most cooling-sensitive neurons respond in an ungraded fashion, inconsistent with graded coding and suggesting combinatorial coding, based on which neurons are co-activated. Although individual neurons may respond to multiple stimuli, our results show that different stimuli activate distinct combinations of diversely tuned neurons, enabling rich population-level coding. Copyright © 2018 The Author(s). Published by Elsevier Inc. All rights reserved.

Are mirror neurons the basis of speech perception? Evidence from five cases with damage to the purported human mirror system

PubMed Central

Rogalsky, Corianne; Love, Tracy; Driscoll, David; Anderson, Steven W.; Hickok, Gregory

2013-01-01

The discovery of mirror neurons in macaque has led to a resurrection of motor theories of speech perception. Although the majority of lesion and functional imaging studies have associated perception with the temporal lobes, it has also been proposed that the ‘human mirror system’, which prominently includes Broca’s area, is the neurophysiological substrate of speech perception. Although numerous studies have demonstrated a tight link between sensory and motor speech processes, few have directly assessed the critical prediction of mirror neuron theories of speech perception, namely that damage to the human mirror system should cause severe deficits in speech perception. The present study measured speech perception abilities of patients with lesions involving motor regions in the left posterior frontal lobe and/or inferior parietal lobule (i.e., the proposed human ‘mirror system’). Performance was at or near ceiling in patients with fronto-parietal lesions. It is only when the lesion encroaches on auditory regions in the temporal lobe that perceptual deficits are evident. This suggests that ‘mirror system’ damage does not disrupt speech perception, but rather that auditory systems are the primary substrate for speech perception. PMID:21207313

Solvent inhalation (toluene and n-hexane) during the brain growth spurt impairs the maturation of frontal, parietal and occipital cerebrocortical neurons in rats.

PubMed

Pascual, Rodrigo; Aedo, Luz; Meneses, Juan Carlos; Vergara, Daniela; Reyes, Alvaro; Bustamante, Carlos

2010-10-01

Solvent abuse during pregnancy may cause "fetal solvent syndrome", which is characterized by mild brain atrophy and associated with behavioral, cognitive, and emotional abnormalities. The present study investigated whether solvent inhalation during the preweaning period (P2-P21) alters the morphological maturation of frontal, parietal, and occipital cortical neurons. Twelve hours after delivery (postnatal day 0, P0), litters were cross-fostered, culled to 8 pups/dam and housed together with a dam in standard laboratory cages. Litters were randomly assigned to the "air-only" group (n=64, 8 litters) and to the "solvent-sniffer" group (n=72, 9 litters). During P2-P21, each animal was exposed daily to either organic solvent vapors (75% toluene and 18% n-hexane, a solvent mixture commonly found in glues and adhesives) or clean air. To determine the impact of early solvent inhalation on cortical neuronal differentiation, brains were stained using the Golgi-Cox-Sholl procedure to quantitatively assess neocortical pyramidal cell dendrogenesis. Preweaning, solvent-exposed animals displayed dramatic impairments in dendritic growth as well as significant reductions in brain weight and size. Copyright 2010 ISDN. Published by Elsevier Ltd. All rights reserved.

A systems neurophysiology approach to voluntary event coding.

PubMed

Petruo, Vanessa A; Stock, Ann-Kathrin; Münchau, Alexander; Beste, Christian

2016-07-15

Mechanisms responsible for the integration of perceptual events and appropriate actions (sensorimotor processes) have been subject to intense research. Different theoretical frameworks have been put forward with the "Theory of Event Coding (TEC)" being one of the most influential. In the current study, we focus on the concept of 'event files' within TEC and examine what sub-processes being dissociable by means of cognitive-neurophysiological methods are involved in voluntary event coding. This was combined with EEG source localization. We also introduce reward manipulations to delineate the neurophysiological sub-processes most relevant for performance variations during event coding. The results show that processes involved in voluntary event coding included predominantly stimulus categorization, feature unbinding and response selection, which were reflected by distinct neurophysiological processes (the P1, N2 and P3 ERPs). On a system's neurophysiological level, voluntary event-file coding is thus related to widely distributed parietal-medial frontal networks. Attentional selection processes (N1 ERP) turned out to be less important. Reward modulated stimulus categorization in parietal regions likely reflecting aspects of perceptual decision making but not in other processes. The perceptual categorization stage appears central for voluntary event-file coding. Copyright © 2016 Elsevier Inc. All rights reserved.

Reversible deactivation of higher-order posterior parietal areas. II. Alterations in response properties of neurons in areas 1 and 2

PubMed Central

Goldring, Adam B.; Cooke, Dylan F.; Baldwin, Mary K. L.; Recanzone, Gregg H.; Gordon, Adam G.; Pan, Tingrui; Simon, Scott I.

2014-01-01

The role that posterior parietal (PPC) and motor cortices play in modulating neural responses in somatosensory areas 1 and 2 was examined with reversible deactivation by transient cooling. Multiunit recordings from neurons in areas 1 and 2 were collected from six anesthetized adult monkeys (Macaca mulatta) before, during, and after reversible deactivation of areas 5L or 7b or motor cortex (M1/PM), while select locations on the hand and forelimb were stimulated. Response changes were quantified as increases and decreases to stimulus-driven activity relative to baseline and analyzed during three recording epochs: during deactivation (“cool”) and at two time points after deactivation (“rewarm 1,” “rewarm 2”). Although the type of response change observed was variable, for neurons at the recording sites tested >90% exhibited a significant change in response during cooling of 7b while cooling area 5L or M1/PM produced a change in 75% and 64% of sites, respectively. These results suggest that regions in the PPC, and to a lesser extent motor cortex, shape the response characteristics of neurons in areas 1 and 2 and that this kind of feedback modulation is necessary for normal somatosensory processing. Furthermore, this modulation appears to happen on a minute-by-minute basis and may serve as the substrate for phenomena such as somatosensory attention. PMID:25143537

Phase synchronization motion and neural coding in dynamic transmission of neural information.

PubMed

Wang, Rubin; Zhang, Zhikang; Qu, Jingyi; Cao, Jianting

2011-07-01

In order to explore the dynamic characteristics of neural coding in the transmission of neural information in the brain, a model of neural network consisting of three neuronal populations is proposed in this paper using the theory of stochastic phase dynamics. Based on the model established, the neural phase synchronization motion and neural coding under spontaneous activity and stimulation are examined, for the case of varying network structure. Our analysis shows that, under the condition of spontaneous activity, the characteristics of phase neural coding are unrelated to the number of neurons participated in neural firing within the neuronal populations. The result of numerical simulation supports the existence of sparse coding within the brain, and verifies the crucial importance of the magnitudes of the coupling coefficients in neural information processing as well as the completely different information processing capability of neural information transmission in both serial and parallel couplings. The result also testifies that under external stimulation, the bigger the number of neurons in a neuronal population, the more the stimulation influences the phase synchronization motion and neural coding evolution in other neuronal populations. We verify numerically the experimental result in neurobiology that the reduction of the coupling coefficient between neuronal populations implies the enhancement of lateral inhibition function in neural networks, with the enhancement equivalent to depressing neuronal excitability threshold. Thus, the neuronal populations tend to have a stronger reaction under the same stimulation, and more neurons get excited, leading to more neurons participating in neural coding and phase synchronization motion.

Spatial eye–hand coordination during bimanual reaching is not systematically coded in either LIP or PRR

PubMed Central

Snyder, Lawrence H.

2018-01-01

We often orient to where we are about to reach. Spatial and temporal correlations in eye and arm movements may depend on the posterior parietal cortex (PPC). Spatial representations of saccade and reach goals preferentially activate cells in the lateral intraparietal area (LIP) and the parietal reach region (PRR), respectively. With unimanual reaches, eye and arm movement patterns are highly stereotyped. This makes it difficult to study the neural circuits involved in coordination. Here, we employ bimanual reaching to two different targets. Animals naturally make a saccade first to one target and then the other, resulting in different patterns of limb–gaze coordination on different trials. Remarkably, neither LIP nor PRR cells code which target the eyes will move to first. These results suggest that the parietal cortex plays at best only a permissive role in some aspects of eye–hand coordination and makes the role of LIP in saccade generation unclear. PMID:29610356

Time has come.

PubMed

Gallistel, C R

2003-04-24

The ramp-like rise and fall of activity in neurons of the LIP area of the posterior parietal cortex of alert behaving monkeys performing a duration discrimination task tracks the changing relative likelihoods that the stimulus in their response field will become the target of a saccade.

Population interactions between parietal and primary motor cortices during reach

PubMed Central

Rao, Naveen G.; Bondy, Adrian; Truccolo, Wilson; Donoghue, John P.

2014-01-01

Neural interactions between parietal area 2/5 and primary motor cortex (M1) were examined to determine the timing and behavioral correlates of cortico-cortical interactions. Neural activity in areas 2/5 and M1 was simultaneously recorded with 96-channel microelectrode arrays in three rhesus monkeys performing a center-out reach task. We introduce a new method to reveal parietal-motor interactions at a population level using partial spike-field coherence (PSFC) between ensembles of neurons in one area and a local field potential (LFP) in another. PSFC reflects the extent of phase locking between spike times and LFP, after removing the coherence between LFPs in the two areas. Spectral analysis of M1 LFP revealed three bands: low, medium, and high, differing in power between movement preparation and performance. We focus on PSFC in the 1–10 Hz band, in which coherence was strongest. PSFC was also present in the 10–40 Hz band during movement preparation in many channels but generally nonsignificant in the 60–200 Hz band. Ensemble PSFC revealed stronger interactions than single cell-LFP pairings. PSFC of area 2/5 ensembles with M1 LFP typically rose around movement onset and peaked ∼500 ms afterward. PSFC was typically stronger for subsets of area 2/5 neurons and M1 LFPs with similar directional bias than for those with opposite bias, indicating that area 2/5 contributes movement direction information. Together with linear prediction of M1 LFP by area 2/5 spiking, the ensemble-LFP pairing approach reveals interactions missed by single neuron-LFP pairing, demonstrating that cortico-cortical communication can be more readily observed at the ensemble level. PMID:25210154

Interactive Exploration for Continuously Expanding Neuron Databases.

PubMed

Li, Zhongyu; Metaxas, Dimitris N; Lu, Aidong; Zhang, Shaoting

2017-02-15

This paper proposes a novel framework to help biologists explore and analyze neurons based on retrieval of data from neuron morphological databases. In recent years, the continuously expanding neuron databases provide a rich source of information to associate neuronal morphologies with their functional properties. We design a coarse-to-fine framework for efficient and effective data retrieval from large-scale neuron databases. In the coarse-level, for efficiency in large-scale, we employ a binary coding method to compress morphological features into binary codes of tens of bits. Short binary codes allow for real-time similarity searching in Hamming space. Because the neuron databases are continuously expanding, it is inefficient to re-train the binary coding model from scratch when adding new neurons. To solve this problem, we extend binary coding with online updating schemes, which only considers the newly added neurons and update the model on-the-fly, without accessing the whole neuron databases. In the fine-grained level, we introduce domain experts/users in the framework, which can give relevance feedback for the binary coding based retrieval results. This interactive strategy can improve the retrieval performance through re-ranking the above coarse results, where we design a new similarity measure and take the feedback into account. Our framework is validated on more than 17,000 neuron cells, showing promising retrieval accuracy and efficiency. Moreover, we demonstrate its use case in assisting biologists to identify and explore unknown neurons. Copyright © 2017 Elsevier Inc. All rights reserved.

Distributed task-specific processing of somatosensory feedback for voluntary motor control

PubMed Central

Omrani, Mohsen; Murnaghan, Chantelle D; Pruszynski, J Andrew; Scott, Stephen H

2016-01-01

Corrective responses to limb disturbances are surprisingly complex, but the neural basis of these goal-directed responses is poorly understood. Here we show that somatosensory feedback is transmitted to many sensory and motor cortical regions within 25 ms of a mechanical disturbance applied to the monkey’s arm. When limb feedback was salient to an ongoing motor action (task engagement), neurons in parietal area 5 immediately (~25 ms) increased their response to limb disturbances, whereas neurons in other regions did not alter their response until 15 to 40 ms later. In contrast, initiation of a motor action elicited by a limb disturbance (target selection) altered neural responses in primary motor cortex ~65 ms after the limb disturbance, and then in dorsal premotor cortex, with no effect in parietal regions until 150 ms post-perturbation. Our findings highlight broad parietofrontal circuits that provide the neural substrate for goal-directed corrections, an essential aspect of highly skilled motor behaviors. DOI: http://dx.doi.org/10.7554/eLife.13141.001 PMID:27077949

Sequential sensory and decision processing in posterior parietal cortex

PubMed Central

Ibos, Guilhem; Freedman, David J

2017-01-01

Decisions about the behavioral significance of sensory stimuli often require comparing sensory inference of what we are looking at to internal models of what we are looking for. Here, we test how neuronal selectivity for visual features is transformed into decision-related signals in posterior parietal cortex (area LIP). Monkeys performed a visual matching task that required them to detect target stimuli composed of conjunctions of color and motion-direction. Neuronal recordings from area LIP revealed two main findings. First, the sequential processing of visual features and the selection of target-stimuli suggest that LIP is involved in transforming sensory information into decision-related signals. Second, the patterns of color and motion selectivity and their impact on decision-related encoding suggest that LIP plays a role in detecting target stimuli by comparing bottom-up sensory inputs (what the monkeys were looking at) and top-down cognitive encoding inputs (what the monkeys were looking for). DOI: http://dx.doi.org/10.7554/eLife.23743.001 PMID:28418332

Simulation of Code Spectrum and Code Flow of Cultured Neuronal Networks.

PubMed

Tamura, Shinichi; Nishitani, Yoshi; Hosokawa, Chie; Miyoshi, Tomomitsu; Sawai, Hajime

2016-01-01

It has been shown that, in cultured neuronal networks on a multielectrode, pseudorandom-like sequences (codes) are detected, and they flow with some spatial decay constant. Each cultured neuronal network is characterized by a specific spectrum curve. That is, we may consider the spectrum curve as a "signature" of its associated neuronal network that is dependent on the characteristics of neurons and network configuration, including the weight distribution. In the present study, we used an integrate-and-fire model of neurons with intrinsic and instantaneous fluctuations of characteristics for performing a simulation of a code spectrum from multielectrodes on a 2D mesh neural network. We showed that it is possible to estimate the characteristics of neurons such as the distribution of number of neurons around each electrode and their refractory periods. Although this process is a reverse problem and theoretically the solutions are not sufficiently guaranteed, the parameters seem to be consistent with those of neurons. That is, the proposed neural network model may adequately reflect the behavior of a cultured neuronal network. Furthermore, such prospect is discussed that code analysis will provide a base of communication within a neural network that will also create a base of natural intelligence.

Joining forces: Motor control meets mirror neurons. Comment on "Grasping synergies: A motor-control approach to the mirror neuron mechanism" by D'Ausilio, Bartoli, and Maffongelli

NASA Astrophysics Data System (ADS)

Casile, Antonino

2015-03-01

Several consistent and compelling experimental findings suggest that in primates the observation of actions or movements activates the observer's motor cortex (for a recent and very thorough review see [1]). One important piece of evidence was the discovery of mirror neurons, that are neurons in the macaque ventral pre-motor (area F5), motor and parietal cortices (area PFG) that respond both when the monkey executes a goal-directed motor act (e.g. breaking a peanut) or when it sees a similar action executed by others [2-5]. A similar system has been later reported also in humans ([6-8] but see also [9,10] for negative results).

Correlated variability modifies working memory fidelity in primate prefrontal neuronal ensembles

PubMed Central

Leavitt, Matthew L.; Pieper, Florian; Sachs, Adam J.; Martinez-Trujillo, Julio C.

2017-01-01

Neurons in the primate lateral prefrontal cortex (LPFC) encode working memory (WM) representations via sustained firing, a phenomenon hypothesized to arise from recurrent dynamics within ensembles of interconnected neurons. Here, we tested this hypothesis by using microelectrode arrays to examine spike count correlations (rsc) in LPFC neuronal ensembles during a spatial WM task. We found a pattern of pairwise rsc during WM maintenance indicative of stronger coupling between similarly tuned neurons and increased inhibition between dissimilarly tuned neurons. We then used a linear decoder to quantify the effects of the high-dimensional rsc structure on information coding in the neuronal ensembles. We found that the rsc structure could facilitate or impair coding, depending on the size of the ensemble and tuning properties of its constituent neurons. A simple optimization procedure demonstrated that near-maximum decoding performance could be achieved using a relatively small number of neurons. These WM-optimized subensembles were more signal correlation (rsignal)-diverse and anatomically dispersed than predicted by the statistics of the full recorded population of neurons, and they often contained neurons that were poorly WM-selective, yet enhanced coding fidelity by shaping the ensemble’s rsc structure. We observed a pattern of rsc between LPFC neurons indicative of recurrent dynamics as a mechanism for WM-related activity and that the rsc structure can increase the fidelity of WM representations. Thus, WM coding in LPFC neuronal ensembles arises from a complex synergy between single neuron coding properties and multidimensional, ensemble-level phenomena. PMID:28275096

Reward value-based gain control: divisive normalization in parietal cortex.

PubMed

Louie, Kenway; Grattan, Lauren E; Glimcher, Paul W

2011-07-20

The representation of value is a critical component of decision making. Rational choice theory assumes that options are assigned absolute values, independent of the value or existence of other alternatives. However, context-dependent choice behavior in both animals and humans violates this assumption, suggesting that biological decision processes rely on comparative evaluation. Here we show that neurons in the monkey lateral intraparietal cortex encode a relative form of saccadic value, explicitly dependent on the values of the other available alternatives. Analogous to extra-classical receptive field effects in visual cortex, this relative representation incorporates target values outside the response field and is observed in both stimulus-driven activity and baseline firing rates. This context-dependent modulation is precisely described by divisive normalization, indicating that this standard form of sensory gain control may be a general mechanism of cortical computation. Such normalization in decision circuits effectively implements an adaptive gain control for value coding and provides a possible mechanistic basis for behavioral context-dependent violations of rationality.

On the Origin of Cortical Dopamine: Is it a Co-Transmitter in Noradrenergic Neurons?

PubMed Central

Devoto, Paola; Flore, Giovanna

2006-01-01

Dopamine (DA) and noradrenaline (NA) in the prefrontal cortex (PFC) modulate superior cognitive functions, and are involved in the aetiology of depressive and psychotic symptoms. Moreover, microdialysis studies in rats have shown how pharmacological treatments that induce modifications of extracellular NA in the medial PFC (mPFC), also produce parallel changes in extracellular DA. To explain the coupling of NA and DA changes, this article reviews the evidence supporting the hypothesis that extracellular DA in the cerebral cortex originates not only from dopaminergic terminals but also from noradrenergic ones, where it acts both as precursor for NA and as a co-transmitter. Accordingly, extracellular DA concentration in the occipital, parietal and cerebellar cortex was found to be much higher than expected in view of the scarce dopaminergic innervation in these areas. Systemic administration or intra-cortical perfusion of α2-adrenoceptor agonists and antagonists, consistent with their action on noradrenergic neuronal activity, produced concomitant changes not only in extracellular NA but also in DA in the mPFC, occipital and parietal cortex. Chemical modulation of the locus coeruleus by locally applied carbachol, kainate, NMDA or clonidine modified both NA and DA in the mPFC. Electrical stimulation of the locus coeruleus led to an increased efflux of both NA and DA in mPFC, parietal and occipital cortex, while in the striatum, NA efflux alone was enhanced. Atypical antipsychotics, such as clozapine and olanzapine, or antidepressants, including mirtazapine and mianserine, have been found to increase both NA and DA throughout the cerebral cortex, likely through blockade of α2-adrenoceptors. On the other hand, drugs selectively acting on dopaminergic transmission produced modest changes in extracellular DA in mPFC, and had no effect on the occipital or parietal cortex. Acute administration of morphine did not increase DA levels in the PFC (where NA is diminished), in contrast with augmented dopaminergic neuronal activity; moreover, during morphine withdrawal both DA and NA levels increased, in spite of a diminished dopaminergic activity, both increases being antagonised by clonidine but not quinpirole administration. Extensive 6-hydroxy dopamine lesion of the ventral tegmental area (VTA) decreases below 95% of control both intra- and extracellular DA and DOPAC in the nucleus accumbens, but only partially or not significantly in the mPFC and parietal cortex. The above evidence points to a common origin for NA and DA in the cerebral cortex and suggests the possible utility of noradrenergic system modulation as a target for drugs with potential clinical efficacy on cognitive functions. PMID:18615131

On the origin of cortical dopamine: is it a co-transmitter in noradrenergic neurons?

PubMed

Devoto, Paola; Flore, Giovanna

2006-04-01

Dopamine (DA) and noradrenaline (NA) in the prefrontal cortex (PFC) modulate superior cognitive functions, and are involved in the aetiology of depressive and psychotic symptoms. Moreover, microdialysis studies in rats have shown how pharmacological treatments that induce modifications of extracellular NA in the medial PFC (mPFC), also produce parallel changes in extracellular DA.To explain the coupling of NA and DA changes, this article reviews the evidence supporting the hypothesis that extracellular DA in the cerebral cortex originates not only from dopaminergic terminals but also from noradrenergic ones, where it acts both as precursor for NA and as a co-transmitter.Accordingly, extracellular DA concentration in the occipital, parietal and cerebellar cortex was found to be much higher than expected in view of the scarce dopaminergic innervation in these areas.Systemic administration or intra-cortical perfusion of alpha(2)-adrenoceptor agonists and antagonists, consistent with their action on noradrenergic neuronal activity, produced concomitant changes not only in extracellular NA but also in DA in the mPFC, occipital and parietal cortex.Chemical modulation of the locus coeruleus by locally applied carbachol, kainate, NMDA or clonidine modified both NA and DA in the mPFC.Electrical stimulation of the locus coeruleus led to an increased efflux of both NA and DA in mPFC, parietal and occipital cortex, while in the striatum, NA efflux alone was enhanced.Atypical antipsychotics, such as clozapine and olanzapine, or antidepressants, including mirtazapine and mianserine, have been found to increase both NA and DA throughout the cerebral cortex, likely through blockade of alpha(2)-adrenoceptors. On the other hand, drugs selectively acting on dopaminergic transmission produced modest changes in extracellular DA in mPFC, and had no effect on the occipital or parietal cortex.Acute administration of morphine did not increase DA levels in the PFC (where NA is diminished), in contrast with augmented dopaminergic neuronal activity; moreover, during morphine withdrawal both DA and NA levels increased, in spite of a diminished dopaminergic activity, both increases being antagonised by clonidine but not quinpirole administration.Extensive 6-hydroxy dopamine lesion of the ventral tegmental area (VTA) decreases below 95% of control both intra- and extracellular DA and DOPAC in the nucleus accumbens, but only partially or not significantly in the mPFC and parietal cortex.The above evidence points to a common origin for NA and DA in the cerebral cortex and suggests the possible utility of noradrenergic system modulation as a target for drugs with potential clinical efficacy on cognitive functions.

Inactivation of the Parietal Reach Region Causes Optic Ataxia, Impairing Reaches but Not Saccades

PubMed Central

Hwang, Eun Jung; Hauschild, Markus; Wilke, Melanie; Andersen, Richard A.

2013-01-01

SUMMARY Lesions in human posterior parietal cortex can cause optic ataxia (OA), in which reaches but not saccades to visual objects are impaired, suggesting separate visuomotor pathways for the two effectors. In monkeys, one potentially crucial area for reach control is the parietal reach region (PRR), in which neurons respond preferentially during reach planning as compared to saccade planning. However, direct causal evidence linking the monkey PRR to the deficits observed in OA is missing. We thus inactivated part of the macaque PRR, in the medial wall of the intraparietal sulcus, and produced the hallmarks of OA, misreaching for peripheral targets but unimpaired saccades. Furthermore, reach errors were larger for the targets preferred by the neural population local to the injection site. These results demonstrate that PRR is causally involved in reach-specific visuomotor pathways, and reach goal disruption in PRR can be a neural basis of OA. PMID:23217749

Temporal and Motor Representation of Rhythm in Fronto-Parietal Cortical Areas: An fMRI Study

PubMed Central

Konoike, Naho; Kotozaki, Yuka; Jeong, Hyeonjeong; Miyazaki, Atsuko; Sakaki, Kohei; Shinada, Takamitsu; Sugiura, Motoaki; Kawashima, Ryuta; Nakamura, Katsuki

2015-01-01

When sounds occur with temporally structured patterns, we can feel a rhythm. To memorize a rhythm, perception of its temporal patterns and organization of them into a hierarchically structured sequence are necessary. On the other hand, rhythm perception can often cause unintentional body movements. Thus, we hypothesized that rhythm information can be manifested in two different ways; temporal and motor representations. The motor representation depends on effectors, such as the finger or foot, whereas the temporal representation is effector-independent. We tested our hypothesis with a working memory paradigm to elucidate neuronal correlates of temporal or motor representation of rhythm and to reveal the neural networks associated with these representations. We measured brain activity by fMRI while participants memorized rhythms and reproduced them by tapping with the right finger, left finger, or foot, or by articulation. The right inferior frontal gyrus and the inferior parietal lobule exhibited significant effector-independent activations during encoding and retrieval of rhythm information, whereas the left inferior parietal lobule and supplementary motor area (SMA) showed effector-dependent activations during retrieval. These results suggest that temporal sequences of rhythm are probably represented in the right fronto-parietal network, whereas motor sequences of rhythm can be represented in the SMA-parietal network. PMID:26076024

Parietal cortex mediates perceptual Gestalt grouping independent of stimulus size.

PubMed

Grassi, Pablo R; Zaretskaya, Natalia; Bartels, Andreas

2016-06-01

The integration of local moving elements into a unified gestalt percept has previously been linked to the posterior parietal cortex. There are two possible interpretations for the lack of involvement of other occipital regions. The first is that parietal cortex is indeed uniquely functionally specialized to perform grouping. Another possibility is that other visual regions can perform grouping as well, but that the large spatial separation of the local elements used previously exceeded their neurons' receptive field (RF) sizes, preventing their involvement. In this study we distinguished between these two alternatives. We measured whole-brain activity using fMRI in response to a bistable motion illusion that induced mutually exclusive percepts of either an illusory global Gestalt or of local elements. The stimulus was presented in two sizes, a large version known to activate IPS only, and a version sufficiently small to fit into the RFs of mid-level dorsal regions such as V5/MT. We found that none of the separately localized motion regions apart from parietal cortex showed a preference for global Gestalt perception, even for the smaller version of the stimulus. This outcome suggests that grouping-by-motion is mediated by a specialized size-invariant mechanism with parietal cortex as its anatomical substrate. Copyright © 2016 Elsevier Inc. All rights reserved.

Reversible deactivation of higher-order posterior parietal areas. I. Alterations of receptive field characteristics in early stages of neocortical processing

PubMed Central

Cooke, Dylan F.; Goldring, Adam B.; Baldwin, Mary K. L.; Recanzone, Gregg H.; Chen, Arnold; Pan, Tingrui; Simon, Scott I.

2014-01-01

Somatosensory processing in the anesthetized macaque monkey was examined by reversibly deactivating posterior parietal areas 5L and 7b and motor/premotor cortex (M1/PM) with microfluidic thermal regulators developed by our laboratories. We examined changes in receptive field size and configuration for neurons in areas 1 and 2 that occurred during and after cooling deactivation. Together the deactivated fields and areas 1 and 2 form part of a network for reaching and grasping in human and nonhuman primates. Cooling area 7b had a dramatic effect on receptive field size for neurons in areas 1 and 2, while cooling area 5 had moderate effects and cooling M1/PM had little effect. Specifically, cooling discrete locations in 7b resulted in expansions of the receptive fields for neurons in areas 1 and 2 that were greater in magnitude and occurred in a higher proportion of sites than similar changes evoked by cooling the other fields. At some sites, the neural receptive field returned to the precooling configuration within 5–22 min of rewarming, but at other sites changes in receptive fields persisted. These results indicate that there are profound top-down influences on sensory processing of early cortical areas in the somatosensory cortex. PMID:25143546

Joint representation of translational and rotational components of optic flow in parietal cortex

PubMed Central

Sunkara, Adhira; DeAngelis, Gregory C.; Angelaki, Dora E.

2016-01-01

Terrestrial navigation naturally involves translations within the horizontal plane and eye rotations about a vertical (yaw) axis to track and fixate targets of interest. Neurons in the macaque ventral intraparietal (VIP) area are known to represent heading (the direction of self-translation) from optic flow in a manner that is tolerant to rotational visual cues generated during pursuit eye movements. Previous studies have also reported that eye rotations modulate the response gain of heading tuning curves in VIP neurons. We tested the hypothesis that VIP neurons simultaneously represent both heading and horizontal (yaw) eye rotation velocity by measuring heading tuning curves for a range of rotational velocities of either real or simulated eye movements. Three findings support the hypothesis of a joint representation. First, we show that rotation velocity selectivity based on gain modulations of visual heading tuning is similar to that measured during pure rotations. Second, gain modulations of heading tuning are similar for self-generated eye rotations and visually simulated rotations, indicating that the representation of rotation velocity in VIP is multimodal, driven by both visual and extraretinal signals. Third, we show that roughly one-half of VIP neurons jointly represent heading and rotation velocity in a multiplicatively separable manner. These results provide the first evidence, to our knowledge, for a joint representation of translation direction and rotation velocity in parietal cortex and show that rotation velocity can be represented based on visual cues, even in the absence of efference copy signals. PMID:27095846

Exploiting the gain-modulation mechanism in parieto-motor neurons: application to visuomotor transformations and embodied simulation.

PubMed

Mahé, Sylvain; Braud, Raphaël; Gaussier, Philippe; Quoy, Mathias; Pitti, Alexandre

2015-02-01

The so-called self-other correspondence problem in imitation demands to find the transformation that maps the motor dynamics of one partner to our own. This requires a general purpose sensorimotor mechanism that transforms an external fixation-point (partner's shoulder) reference frame to one's own body-centered reference frame. We propose that the mechanism of gain-modulation observed in parietal neurons may generally serve these types of transformations by binding the sensory signals across the modalities with radial basis functions (tensor products) on the one hand and by permitting the learning of contextual reference frames on the other hand. In a shoulder-elbow robotic experiment, gain-field neurons (GF) intertwine the visuo-motor variables so that their amplitude depends on them all. In situations of modification of the body-centered reference frame, the error detected in the visuo-motor mapping can serve then to learn the transformation between the robot's current sensorimotor space and the new one. These situations occur for instance when we turn the head on its axis (visual transformation), when we use a tool (body modification), or when we interact with a partner (embodied simulation). Our results defend the idea that the biologically-inspired mechanism of gain modulation found in parietal neurons can serve as a basic structure for achieving nonlinear mapping in spatial tasks as well as in cooperative and social functions. Copyright © 2014 Elsevier Ltd. All rights reserved.

Functional connectivity in the resting brain as biological correlate of the Affective Neuroscience Personality Scales.

PubMed

Deris, Nadja; Montag, Christian; Reuter, Martin; Weber, Bernd; Markett, Sebastian

2017-02-15

According to Jaak Panksepp's Affective Neuroscience Theory and the derived self-report measure, the Affective Neuroscience Personality Scales (ANPS), differences in the responsiveness of primary emotional systems form the basis of human personality. In order to investigate neuronal correlates of personality, the underlying neuronal circuits of the primary emotional systems were analyzed in the present fMRI-study by associating the ANPS to functional connectivity in the resting brain. N=120 healthy participants were invited for the present study. The results were reinvestigated in an independent, smaller sample of N=52 participants. A seed-based whole brain approach was conducted with seed-regions bilaterally in the basolateral and superficial amygdalae. The selection of seed-regions was based on meta-analytic data on affective processing and the Juelich histological atlas. Multiple regression analyses on the functional connectivity maps revealed associations with the SADNESS-scale in both samples. Functional resting-state connectivity between the left basolateral amygdala and a cluster in the postcentral gyrus, and between the right basolateral amygdala and clusters in the superior parietal lobe and subgyral in the parietal lobe was associated with SADNESS. No other ANPS-scale revealed replicable results. The present findings give first insights into the neuronal basis of the SADNESS-scale of the ANPS and support the idea of underlying neuronal circuits. In combination with previous research on genetic associations of the ANPS functional resting-state connectivity is discussed as a possible endophenotype of personality. Copyright © 2016 Elsevier Inc. All rights reserved.

A brain-machine interface enables bimanual arm movements in monkeys.

PubMed

Ifft, Peter J; Shokur, Solaiman; Li, Zheng; Lebedev, Mikhail A; Nicolelis, Miguel A L

2013-11-06

Brain-machine interfaces (BMIs) are artificial systems that aim to restore sensation and movement to paralyzed patients. So far, BMIs have enabled only one arm to be moved at a time. Control of bimanual arm movements remains a major challenge. We have developed and tested a bimanual BMI that enables rhesus monkeys to control two avatar arms simultaneously. The bimanual BMI was based on the extracellular activity of 374 to 497 neurons recorded from several frontal and parietal cortical areas of both cerebral hemispheres. Cortical activity was transformed into movements of the two arms with a decoding algorithm called a fifth-order unscented Kalman filter (UKF). The UKF was trained either during a manual task performed with two joysticks or by having the monkeys passively observe the movements of avatar arms. Most cortical neurons changed their modulation patterns when both arms were engaged simultaneously. Representing the two arms jointly in a single UKF decoder resulted in improved decoding performance compared with using separate decoders for each arm. As the animals' performance in bimanual BMI control improved over time, we observed widespread plasticity in frontal and parietal cortical areas. Neuronal representation of the avatar and reach targets was enhanced with learning, whereas pairwise correlations between neurons initially increased and then decreased. These results suggest that cortical networks may assimilate the two avatar arms through BMI control. These findings should help in the design of more sophisticated BMIs capable of enabling bimanual motor control in human patients.

Neuronal foundations of human numerical representations.

PubMed

Eger, E

2016-01-01

The human species has developed complex mathematical skills which likely emerge from a combination of multiple foundational abilities. One of them seems to be a preverbal capacity to extract and manipulate the numerosity of sets of objects which is shared with other species and in humans is thought to be integrated with symbolic knowledge to result in a more abstract representation of numerical concepts. For what concerns the functional neuroanatomy of this capacity, neuropsychology and functional imaging have localized key substrates of numerical processing in parietal and frontal cortex. However, traditional fMRI mapping relying on a simple subtraction approach to compare numerical and nonnumerical conditions is limited to tackle with sufficient precision and detail the issue of the underlying code for number, a question which more easily lends itself to investigation by methods with higher spatial resolution, such as neurophysiology. In recent years, progress has been made through the introduction of approaches sensitive to within-category discrimination in combination with fMRI (adaptation and multivariate pattern recognition), and the present review summarizes what these have revealed so far about the neural coding of individual numbers in the human brain, the format of these representations and parallels between human and monkey neurophysiology findings. © 2016 Elsevier B.V. All rights reserved.

Single neuron firing properties impact correlation-based population coding

PubMed Central

Hong, Sungho; Ratté, Stéphanie; Prescott, Steven A.; De Schutter, Erik

2012-01-01

Correlated spiking has been widely observed but its impact on neural coding remains controversial. Correlation arising from co-modulation of rates across neurons has been shown to vary with the firing rates of individual neurons. This translates into rate and correlation being equivalently tuned to the stimulus; under those conditions, correlated spiking does not provide information beyond that already available from individual neuron firing rates. Such correlations are irrelevant and can reduce coding efficiency by introducing redundancy. Using simulations and experiments in rat hippocampal neurons, we show here that pairs of neurons receiving correlated input also exhibit correlations arising from precise spike-time synchronization. Contrary to rate co-modulation, spike-time synchronization is unaffected by firing rate, thus enabling synchrony- and rate-based coding to operate independently. The type of output correlation depends on whether intrinsic neuron properties promote integration or coincidence detection: “ideal” integrators (with spike generation sensitive to stimulus mean) exhibit rate co-modulation whereas “ideal” coincidence detectors (with spike generation sensitive to stimulus variance) exhibit precise spike-time synchronization. Pyramidal neurons are sensitive to both stimulus mean and variance, and thus exhibit both types of output correlation proportioned according to which operating mode is dominant. Our results explain how different types of correlations arise based on how individual neurons generate spikes, and why spike-time synchronization and rate co-modulation can encode different stimulus properties. Our results also highlight the importance of neuronal properties for population-level coding insofar as neural networks can employ different coding schemes depending on the dominant operating mode of their constituent neurons. PMID:22279226

Cognitive and metacognitive activity in mathematical problem solving: prefrontal and parietal patterns.

PubMed

Anderson, John R; Betts, Shawn; Ferris, Jennifer L; Fincham, Jon M

2011-03-01

Students were taught an algorithm for solving a new class of mathematical problems. Occasionally in the sequence of problems, they encountered exception problems that required that they extend the algorithm. Regular and exception problems were associated with different patterns of brain activation. Some regions showed a Cognitive pattern of being active only until the problem was solved and no difference between regular or exception problems. Other regions showed a Metacognitive pattern of greater activity for exception problems and activity that extended into the post-solution period, particularly when an error was made. The Cognitive regions included some of parietal and prefrontal regions associated with the triple-code theory of (Dehaene, S., Piazza, M., Pinel, P., & Cohen, L. (2003). Three parietal circuits for number processing. Cognitive Neuropsychology, 20, 487-506) and associated with algebra equation solving in the ACT-R theory (Anderson, J. R. (2005). Human symbol manipulation within an 911 integrated cognitive architecture. Cognitive science, 29, 313-342. Metacognitive regions included the superior prefrontal gyrus, the angular gyrus of the triple-code theory, and frontopolar regions.

Neural foundations and functional specificity of number representations.

PubMed

Piazza, Manuela; Eger, Evelyn

2016-03-01

Number is a complex category, as with the word "number" we may refer to different entities. First, it is a perceptual property that characterizes any set of individual items, namely its cardinality. The ability to extract the (approximate) cardinality of sets is almost universal in the animal domain and present in humans since birth. In primates, posterior parietal cortex seems to be a crucial site for this ability, even if the degree of selectivity of numerical representations in parietal cortex reported to date appears much lower compared to that of other semantic categories in the ventral stream. Number can also be intended as a mathematical object, which we humans use to count, measure, and order: a (verbal or visual) symbol that stands for the cardinality of a set, the intensity of a continuous quantity or the position of an item on a list. Evidence points to a convergence towards parietal cortex for the semantic coding of numerical symbols and to the bilateral occipitotemporal cortex for the shape coding of Arabic digits and other number symbols. Copyright © 2015 Elsevier Ltd. All rights reserved.

Mirror neurons: functions, mechanisms and models.

PubMed

Oztop, Erhan; Kawato, Mitsuo; Arbib, Michael A

2013-04-12

Mirror neurons for manipulation fire both when the animal manipulates an object in a specific way and when it sees another animal (or the experimenter) perform an action that is more or less similar. Such neurons were originally found in macaque monkeys, in the ventral premotor cortex, area F5 and later also in the inferior parietal lobule. Recent neuroimaging data indicate that the adult human brain is endowed with a "mirror neuron system," putatively containing mirror neurons and other neurons, for matching the observation and execution of actions. Mirror neurons may serve action recognition in monkeys as well as humans, whereas their putative role in imitation and language may be realized in human but not in monkey. This article shows the important role of computational models in providing sufficient and causal explanations for the observed phenomena involving mirror systems and the learning processes which form them, and underlines the need for additional circuitry to lift up the monkey mirror neuron circuit to sustain the posited cognitive functions attributed to the human mirror neuron system. Copyright © 2012 Elsevier Ireland Ltd. All rights reserved.

"What" and "where" in word reading: ventral coding of written words revealed by parietal atrophy.

PubMed

Vinckier, Fabien; Naccache, Lionel; Papeix, Caroline; Forget, Joaquim; Hahn-Barma, Valerie; Dehaene, Stanislas; Cohen, Laurent

2006-12-01

The visual system of literate adults develops a remarkable perceptual expertise for printed words. To delineate the aspects of this competence intrinsic to the occipitotemporal "what" pathway, we studied a patient with bilateral lesions of the occipitoparietal "where" pathway. Depending on critical geometric features of the display (rotation angle, letter spacing, mirror reversal, etc.), she switched from a good performance, when her intact ventral pathway was sufficient to encode words, to severely impaired reading, when her parietal lesions prevented the use of alternative reading strategies as a result of spatial and attentional impairments. In particular, reading was disrupted (a) by rotating word by more than 50 degrees , providing an approximation of the invariance range for words encoding in the ventral pathway; (b) by separating letters with double spaces, revealing the limits of letter grouping into perceptual wholes; (c) by mirror-reversing words, showing that words escape the default mirror-invariant representation of visual objects in the ventral pathway. Moreover, because of her parietal lesions, she was unable to discriminate mirror images of common objects, although she was excellent with reversible pseudowords, confirming that the breaking of mirror symmetry was intrinsic to the occipitotemporal cortex. Thus, charting the display conditions associated with preserved or impaired performance allowed us to infer properties of word coding in the normal ventral pathway and to delineate the roles of the parietal lobes in single-word recognition.

[Unconscious sexual desire: fMRI and EEG evidences from self-expansion theory to mirror neurons].

PubMed

Ortigue, Stephanie; Bianchi-Demicheli, Francesco

2010-03-24

Recent advances in cognitive-social neuroscience allow a better understanding of the mechanisms underlying dyadic relationships. From a neuronal viewpoint, desire in dyadic relationships involves a specific fronto-temporo-parietal network and also a subcortical network that mediates conscious and unconscious mechanisms of reward, satisfaction, attention, self representation and self-expansion. The integration of this neuroscientific knowledge on the unconscious neurobiological activation for sexual desire in the human brain will provide physicians with new therapeutical and neuroscientific tools to apprehend sexual disorders in couple.

Coding stimulus amplitude by correlated neural activity

NASA Astrophysics Data System (ADS)

Metzen, Michael G.; Ávila-Åkerberg, Oscar; Chacron, Maurice J.

2015-04-01

While correlated activity is observed ubiquitously in the brain, its role in neural coding has remained controversial. Recent experimental results have demonstrated that correlated but not single-neuron activity can encode the detailed time course of the instantaneous amplitude (i.e., envelope) of a stimulus. These have furthermore demonstrated that such coding required and was optimal for a nonzero level of neural variability. However, a theoretical understanding of these results is still lacking. Here we provide a comprehensive theoretical framework explaining these experimental findings. Specifically, we use linear response theory to derive an expression relating the correlation coefficient to the instantaneous stimulus amplitude, which takes into account key single-neuron properties such as firing rate and variability as quantified by the coefficient of variation. The theoretical prediction was in excellent agreement with numerical simulations of various integrate-and-fire type neuron models for various parameter values. Further, we demonstrate a form of stochastic resonance as optimal coding of stimulus variance by correlated activity occurs for a nonzero value of noise intensity. Thus, our results provide a theoretical explanation of the phenomenon by which correlated but not single-neuron activity can code for stimulus amplitude and how key single-neuron properties such as firing rate and variability influence such coding. Correlation coding by correlated but not single-neuron activity is thus predicted to be a ubiquitous feature of sensory processing for neurons responding to weak input.

Polarized skylight navigation in insects: model and electrophysiology of e-vector coding by neurons in the central complex.

PubMed

Sakura, Midori; Lambrinos, Dimitrios; Labhart, Thomas

2008-02-01

Many insects exploit skylight polarization for visual compass orientation or course control. As found in crickets, the peripheral visual system (optic lobe) contains three types of polarization-sensitive neurons (POL neurons), which are tuned to different ( approximately 60 degrees diverging) e-vector orientations. Thus each e-vector orientation elicits a specific combination of activities among the POL neurons coding any e-vector orientation by just three neural signals. In this study, we hypothesize that in the presumed orientation center of the brain (central complex) e-vector orientation is population-coded by a set of "compass neurons." Using computer modeling, we present a neural network model transforming the signal triplet provided by the POL neurons to compass neuron activities coding e-vector orientation by a population code. Using intracellular electrophysiology and cell marking, we present evidence that neurons with the response profile of the presumed compass neurons do indeed exist in the insect brain: each of these compass neuron-like (CNL) cells is activated by a specific e-vector orientation only and otherwise remains silent. Morphologically, CNL cells are tangential neurons extending from the lateral accessory lobe to the lower division of the central body. Surpassing the modeled compass neurons in performance, CNL cells are insensitive to the degree of polarization of the stimulus between 99% and at least down to 18% polarization and thus largely disregard variations of skylight polarization due to changing solar elevations or atmospheric conditions. This suggests that the polarization vision system includes a gain control circuit keeping the output activity at a constant level.

Population coding in sparsely connected networks of noisy neurons.

PubMed

Tripp, Bryan P; Orchard, Jeff

2012-01-01

This study examines the relationship between population coding and spatial connection statistics in networks of noisy neurons. Encoding of sensory information in the neocortex is thought to require coordinated neural populations, because individual cortical neurons respond to a wide range of stimuli, and exhibit highly variable spiking in response to repeated stimuli. Population coding is rooted in network structure, because cortical neurons receive information only from other neurons, and because the information they encode must be decoded by other neurons, if it is to affect behavior. However, population coding theory has often ignored network structure, or assumed discrete, fully connected populations (in contrast with the sparsely connected, continuous sheet of the cortex). In this study, we modeled a sheet of cortical neurons with sparse, primarily local connections, and found that a network with this structure could encode multiple internal state variables with high signal-to-noise ratio. However, we were unable to create high-fidelity networks by instantiating connections at random according to spatial connection probabilities. In our models, high-fidelity networks required additional structure, with higher cluster factors and correlations between the inputs to nearby neurons.

Decoding the neural mechanisms of human tool use

PubMed Central

Gallivan, Jason P; McLean, D Adam; Valyear, Kenneth F; Culham, Jody C

2013-01-01

Sophisticated tool use is a defining characteristic of the primate species but how is it supported by the brain, particularly the human brain? Here we show, using functional MRI and pattern classification methods, that tool use is subserved by multiple distributed action-centred neural representations that are both shared with and distinct from those of the hand. In areas of frontoparietal cortex we found a common representation for planned hand- and tool-related actions. In contrast, in parietal and occipitotemporal regions implicated in hand actions and body perception we found that coding remained selectively linked to upcoming actions of the hand whereas in parietal and occipitotemporal regions implicated in tool-related processing the coding remained selectively linked to upcoming actions of the tool. The highly specialized and hierarchical nature of this coding suggests that hand- and tool-related actions are represented separately at earlier levels of sensorimotor processing before becoming integrated in frontoparietal cortex. DOI: http://dx.doi.org/10.7554/eLife.00425.001 PMID:23741616

Decreased NAA in gray matter is correlated with decreased availability of acetate in white matter in postmortem multiple sclerosis cortex.

PubMed

Li, S; Clements, R; Sulak, M; Gregory, R; Freeman, E; McDonough, J

2013-11-01

Multiple sclerosis (MS) is an inflammatory neurodegenerative disease of the central nervous system (CNS) which leads to progressive neurological disability. Our previous studies have demonstrated mitochondrial involvement in MS cortical pathology and others have documented decreased levels of the neuronal mitochondrial metabolite N-acetyl aspartate (NAA) in the MS brain. While NAA is synthesized in neurons, it is broken down in oligodendrocytes into aspartate and acetate. The resulting acetate is incorporated into myelin lipids, linking neuronal mitochondrial function to oligodendrocyte-mediated elaboration of myelin lipids in the CNS. In the present study we show that treating human SH-SY5Y neuroblastoma cells with the electron transport chain inhibitor antimycin A decreased levels of NAA as measured by HPLC. To better understand the significance of the relationship between mitochondrial function and levels of NAA and its breakdown product acetate on MS pathology we then quantitated the levels of NAA and acetate in MS and control postmortem tissue blocks. Regardless of lesion status, we observed that levels of NAA were decreased 25 and 32 % in gray matter from parietal and motor cortex in MS, respectively, compared to controls. Acetate levels in adjacent white matter mirrored these decreases as evidenced by the 36 and 45 % reduction in acetate obtained from parietal and motor cortices. These data suggest a novel mechanism whereby mitochondrial dysfunction and reduced NAA levels in neurons may result in compromised myelination by oligodendrocytes due to decreased availability of acetate necessary for the synthesis of myelin lipids.

Decreased NAA in Gray Matter is Correlated with Decreased Availability of Acetate in White Matter in Postmortem Multiple Sclerosis Cortex

PubMed Central

Li, S.; Clements, R.; Sulak, M.; Gregory, R.; Freeman, E.; McDonough, J.

2013-01-01

Multiple sclerosis (MS) is an inflammatory neurodegenerative disease of the central nervous system (CNS) which leads to progressive neurological disability. Our previous studies have demonstrated mitochondrial involvement in MS cortical pathology and others have documented decreased levels of the neuronal mitochondrial metabolite N-acetyl aspartate (NAA) in the MS brain. While NAA is synthesized in neurons, it is broken down in oligodendrocytes into aspartate and acetate. The resulting acetate is incorporated into myelin lipids, linking neuronal mitochondrial function to oligodendrocyte-mediated elaboration of myelin lipids in the CNS. In the present study we show that treating human SH-SY5Y neuroblastoma cells with the electron transport chain inhibitor antimycin A decreased levels of NAA as measured by HPLC. To better understand the significance of the relationship between mitochondrial function and levels of NAA and its breakdown product acetate on MS pathology we then quantitated the levels of NAA and acetate in MS and control postmortem tissue blocks. Regardless of lesion status, we observed that levels of NAA were decreased 25 and 32 % in gray matter from parietal and motor cortex in MS, respectively, compared to controls. Acetate levels in adjacent white matter mirrored these decreases as evidenced by the 36 and 45 % reduction in acetate obtained from parietal and motor cortices. These data suggest a novel mechanism whereby mitochondrial dysfunction and reduced NAA levels in neurons may result in compromised myelination by oligodendrocytes due to decreased availability of acetate necessary for the synthesis of myelin lipids. PMID:24078261

Activating Developmental Reserve Capacity Via Cognitive Training or Non-invasive Brain Stimulation: Potentials for Promoting Fronto-Parietal and Hippocampal-Striatal Network Functions in Old Age

PubMed Central

Passow, Susanne; Thurm, Franka; Li, Shu-Chen

2017-01-01

Existing neurocomputational and empirical data link deficient neuromodulation of the fronto-parietal and hippocampal-striatal circuitries with aging-related increase in processing noise and declines in various cognitive functions. Specifically, the theory of aging neuronal gain control postulates that aging-related suboptimal neuromodulation may attenuate neuronal gain control, which yields computational consequences on reducing the signal-to-noise-ratio of synaptic signal transmission and hampering information processing within and between cortical networks. Intervention methods such as cognitive training and non-invasive brain stimulation, e.g., transcranial direct current stimulation (tDCS), have been considered as means to buffer cognitive functions or delay cognitive decline in old age. However, to date the reported effect sizes of immediate training gains and maintenance effects of a variety of cognitive trainings are small to moderate at best; moreover, training-related transfer effects to non-trained but closely related (i.e., near-transfer) or other (i.e., far-transfer) cognitive functions are inconsistent or lacking. Similarly, although applying different tDCS protocols to reduce aging-related cognitive impairments by inducing temporary changes in cortical excitability seem somewhat promising, evidence of effects on short- and long-term plasticity is still equivocal. In this article, we will review and critically discuss existing findings of cognitive training- and stimulation-related behavioral and neural plasticity effects in the context of cognitive aging, focusing specifically on working memory and episodic memory functions, which are subserved by the fronto-parietal and hippocampal-striatal networks, respectively. Furthermore, in line with the theory of aging neuronal gain control we will highlight that developing age-specific brain stimulation protocols and the concurrent applications of tDCS during cognitive training may potentially facilitate short- and long-term cognitive and brain plasticity in old age. PMID:28280465

Neural Basis of Action Understanding: Evidence from Sign Language Aphasia.

PubMed

Rogalsky, Corianne; Raphel, Kristin; Tomkovicz, Vivian; O'Grady, Lucinda; Damasio, Hanna; Bellugi, Ursula; Hickok, Gregory

2013-01-01

The neural basis of action understanding is a hotly debated issue. The mirror neuron account holds that motor simulation in fronto-parietal circuits is critical to action understanding including speech comprehension, while others emphasize the ventral stream in the temporal lobe. Evidence from speech strongly supports the ventral stream account, but on the other hand, evidence from manual gesture comprehension (e.g., in limb apraxia) has led to contradictory findings. Here we present a lesion analysis of sign language comprehension. Sign language is an excellent model for studying mirror system function in that it bridges the gap between the visual-manual system in which mirror neurons are best characterized and language systems which have represented a theoretical target of mirror neuron research. Twenty-one life long deaf signers with focal cortical lesions performed two tasks: one involving the comprehension of individual signs and the other involving comprehension of signed sentences (commands). Participants' lesions, as indicated on MRI or CT scans, were mapped onto a template brain to explore the relationship between lesion location and sign comprehension measures. Single sign comprehension was not significantly affected by left hemisphere damage. Sentence sign comprehension impairments were associated with left temporal-parietal damage. We found that damage to mirror system related regions in the left frontal lobe were not associated with deficits on either of these comprehension tasks. We conclude that the mirror system is not critically involved in action understanding.

Anticipation of somatosensory and motor events increases centro-parietal functional coupling: an EEG coherence study.

PubMed

Babiloni, Claudio; Brancucci, Alfredo; Vecchio, Fabrizio; Arendt-Nielsen, Lars; Chen, Andrew C N; Rossini, Paolo M

2006-05-01

Does functional coupling of centro-parietal EEG rhythms selectively increase during the anticipation of sensorimotor events composed by somatosensory stimulation and visuomotor task? EEG data were recorded in (1) 'simultaneous' condition in which the subjects waited for somatosensory stimulation at left hand concomitant with a Go (or NoGo) visual stimulus triggering (50%) right hand movements and in (2) 'sequential' condition where the somatosensory stimulation was followed (+1.5 s) by a visuomotor Go/NoGo task. Centro-parietal functional coupling was modeled by spectral coherence. Spectral coherence was computed from Laplacian-transformed EEG data at delta-theta (2-7 Hz), alpha (8-14 Hz), beta 1 (15-21 Hz), beta 2 (22-33 Hz), and gamma (34-45 Hz) rhythms. Before 'simultaneous' sensorimotor events, centro-parietal coherence regions increased in both hemispheres and at all rhythms. In the 'sequential' condition, right centro-parietal coherence increased before somatosensory event (left hand), whereas left centro-parietal coherence increased before subsequent Go/NoGo event (right hand). Anticipation of somatosensory and visuomotor events enhances contralateral centro-parietal coupling of slow and fast EEG rhythms. Predictable somatosensory and visuomotor events are anticipated not only by synchronization of cortical pyramidal neurons generating EEG power in parietal and primary sensorimotor cortical areas (Babiloni C, Brancucci A, Capotosto P, Arendt-Nielsen L, Chen ACN, Rossini PM. Expectancy of pain is influenced by motor preparation: a high-resolution EEG study of cortical alpha rhythms. Behav. Neurosci. 2005a;119(2):503-511; Babiloni C, Brancucci A, Pizzella V, Romani G.L, Tecchio F, Torquati K, Zappasodi F, Arendt-Nielsen L, Chen ACN, Rossini PM. Contingent negative variation in the parasylvian cortex increases during expectancy of painful sensorimotor events: a magnetoencephalographic study. Behav. Neurosci. 2005b;119(2):491-502) but also by functional coordination of these areas.

Temporal order processing of syllables in the left parietal lobe.

PubMed

Moser, Dana; Baker, Julie M; Sanchez, Carmen E; Rorden, Chris; Fridriksson, Julius

2009-10-07

Speech processing requires the temporal parsing of syllable order. Individuals suffering from posterior left hemisphere brain injury often exhibit temporal processing deficits as well as language deficits. Although the right posterior inferior parietal lobe has been implicated in temporal order judgments (TOJs) of visual information, there is limited evidence to support the role of the left inferior parietal lobe (IPL) in processing syllable order. The purpose of this study was to examine whether the left inferior parietal lobe is recruited during temporal order judgments of speech stimuli. Functional magnetic resonance imaging data were collected on 14 normal participants while they completed the following forced-choice tasks: (1) syllable order of multisyllabic pseudowords, (2) syllable identification of single syllables, and (3) gender identification of both multisyllabic and monosyllabic speech stimuli. Results revealed increased neural recruitment in the left inferior parietal lobe when participants made judgments about syllable order compared with both syllable identification and gender identification. These findings suggest that the left inferior parietal lobe plays an important role in processing syllable order and support the hypothesized role of this region as an interface between auditory speech and the articulatory code. Furthermore, a breakdown in this interface may explain some components of the speech deficits observed after posterior damage to the left hemisphere.

Temporal Order Processing of Syllables in the Left Parietal Lobe

PubMed Central

Baker, Julie M.; Sanchez, Carmen E.; Rorden, Chris; Fridriksson, Julius

2009-01-01

Speech processing requires the temporal parsing of syllable order. Individuals suffering from posterior left hemisphere brain injury often exhibit temporal processing deficits as well as language deficits. Although the right posterior inferior parietal lobe has been implicated in temporal order judgments (TOJs) of visual information, there is limited evidence to support the role of the left inferior parietal lobe (IPL) in processing syllable order. The purpose of this study was to examine whether the left inferior parietal lobe is recruited during temporal order judgments of speech stimuli. Functional magnetic resonance imaging data were collected on 14 normal participants while they completed the following forced-choice tasks: (1) syllable order of multisyllabic pseudowords, (2) syllable identification of single syllables, and (3) gender identification of both multisyllabic and monosyllabic speech stimuli. Results revealed increased neural recruitment in the left inferior parietal lobe when participants made judgments about syllable order compared with both syllable identification and gender identification. These findings suggest that the left inferior parietal lobe plays an important role in processing syllable order and support the hypothesized role of this region as an interface between auditory speech and the articulatory code. Furthermore, a breakdown in this interface may explain some components of the speech deficits observed after posterior damage to the left hemisphere. PMID:19812331

Spike-timing-dependent plasticity in the human dorso-lateral prefrontal cortex.

PubMed

Casula, Elias Paolo; Pellicciari, Maria Concetta; Picazio, Silvia; Caltagirone, Carlo; Koch, Giacomo

2016-12-01

Changes in the synaptic strength of neural connections are induced by repeated coupling of activity of interconnected neurons with precise timing, a phenomenon known as spike-timing-dependent plasticity (STDP). It is debated if this mechanism exists in large-scale cortical networks in humans. We combined transcranial magnetic stimulation (TMS) with concurrent electroencephalography (EEG) to directly investigate the effects of two paired associative stimulation (PAS) protocols (fronto-parietal and parieto-frontal) of pre and post-synaptic inputs within the human fronto-parietal network. We found evidence that the dorsolateral prefrontal cortex (DLPFC) has the potential to form robust STDP. Long-term potentiation/depression of TMS-evoked cortical activity is prompted after that DLPFC stimulation is followed/preceded by posterior parietal stimulation. Such bidirectional changes are paralleled by sustained increase/decrease of high-frequency oscillatory activity, likely reflecting STDP responsivity. The current findings could be important to drive plasticity of damaged cortical circuits in patients with cognitive or psychiatric disorders. Copyright © 2016 Elsevier Inc. All rights reserved.

Decoding emotional valence from electroencephalographic rhythmic activity.

PubMed

Celikkanat, Hande; Moriya, Hiroki; Ogawa, Takeshi; Kauppi, Jukka-Pekka; Kawanabe, Motoaki; Hyvarinen, Aapo

2017-07-01

We attempt to decode emotional valence from electroencephalographic rhythmic activity in a naturalistic setting. We employ a data-driven method developed in a previous study, Spectral Linear Discriminant Analysis, to discover the relationships between the classification task and independent neuronal sources, optimally utilizing multiple frequency bands. A detailed investigation of the classifier provides insight into the neuronal sources related with emotional valence, and the individual differences of the subjects in processing emotions. Our findings show: (1) sources whose locations are similar across subjects are consistently involved in emotional responses, with the involvement of parietal sources being especially significant, and (2) even though the locations of the involved neuronal sources are consistent, subjects can display highly varying degrees of valence-related EEG activity in the sources.

M-type potassium conductance controls the emergence of neural phase codes: a combined experimental and neuron modelling study

PubMed Central

Kwag, Jeehyun; Jang, Hyun Jae; Kim, Mincheol; Lee, Sujeong

2014-01-01

Rate and phase codes are believed to be important in neural information processing. Hippocampal place cells provide a good example where both coding schemes coexist during spatial information processing. Spike rate increases in the place field, whereas spike phase precesses relative to the ongoing theta oscillation. However, what intrinsic mechanism allows for a single neuron to generate spike output patterns that contain both neural codes is unknown. Using dynamic clamp, we simulate an in vivo-like subthreshold dynamics of place cells to in vitro CA1 pyramidal neurons to establish an in vitro model of spike phase precession. Using this in vitro model, we show that membrane potential oscillation (MPO) dynamics is important in the emergence of spike phase codes: blocking the slowly activating, non-inactivating K+ current (IM), which is known to control subthreshold MPO, disrupts MPO and abolishes spike phase precession. We verify the importance of adaptive IM in the generation of phase codes using both an adaptive integrate-and-fire and a Hodgkin–Huxley (HH) neuron model. Especially, using the HH model, we further show that it is the perisomatically located IM with slow activation kinetics that is crucial for the generation of phase codes. These results suggest an important functional role of IM in single neuron computation, where IM serves as an intrinsic mechanism allowing for dual rate and phase coding in single neurons. PMID:25100320

Coding of spatial attention priorities and object features in the macaque lateral intraparietal cortex.

PubMed

Levichkina, Ekaterina; Saalmann, Yuri B; Vidyasagar, Trichur R

2017-03-01

Primate posterior parietal cortex (PPC) is known to be involved in controlling spatial attention. Neurons in one part of the PPC, the lateral intraparietal area (LIP), show enhanced responses to objects at attended locations. Although many are selective for object features, such as the orientation of a visual stimulus, it is not clear how LIP circuits integrate feature-selective information when providing attentional feedback about behaviorally relevant locations to the visual cortex. We studied the relationship between object feature and spatial attention properties of LIP cells in two macaques by measuring the cells' orientation selectivity and the degree of attentional enhancement while performing a delayed match-to-sample task. Monkeys had to match both the location and orientation of two visual gratings presented separately in time. We found a wide range in orientation selectivity and degree of attentional enhancement among LIP neurons. However, cells with significant attentional enhancement had much less orientation selectivity in their response than cells which showed no significant modulation by attention. Additionally, orientation-selective cells showed working memory activity for their preferred orientation, whereas cells showing attentional enhancement also synchronized with local neuronal activity. These results are consistent with models of selective attention incorporating two stages, where an initial feature-selective process guides a second stage of focal spatial attention. We suggest that LIP contributes to both stages, where the first stage involves orientation-selective LIP cells that support working memory of the relevant feature, and the second stage involves attention-enhanced LIP cells that synchronize to provide feedback on spatial priorities. © 2017 The Authors. Physiological Reports published by Wiley Periodicals, Inc. on behalf of The Physiological Society and the American Physiological Society.

Neurofilament protein defines regional patterns of cortical organization in the macaque monkey visual system: a quantitative immunohistochemical analysis

NASA Technical Reports Server (NTRS)

Hof, P. R.; Morrison, J. H.; Bloom, F. E. (Principal Investigator)

1995-01-01

Visual function in monkeys is subserved at the cortical level by a large number of areas defined by their specific physiological properties and connectivity patterns. For most of these cortical fields, a precise index of their degree of anatomical specialization has not yet been defined, although many regional patterns have been described using Nissl or myelin stains. In the present study, an attempt has been made to elucidate the regional characteristics, and to varying degrees boundaries, of several visual cortical areas in the macaque monkey using an antibody to neurofilament protein (SMI32). This antibody labels a subset of pyramidal neurons with highly specific regional and laminar distribution patterns in the cerebral cortex. Based on the staining patterns and regional quantitative analysis, as many as 28 cortical fields were reliably identified. Each field had a homogeneous distribution of labeled neurons, except area V1, where increases in layer IVB cell and in Meynert cell counts paralleled the increase in the degree of eccentricity in the visual field representation. Within the occipitotemporal pathway, areas V3 and V4 and fields in the inferior temporal cortex were characterized by a distinct population of neurofilament-rich neurons in layers II-IIIa, whereas areas located in the parietal cortex and part of the occipitoparietal pathway had a consistent population of large labeled neurons in layer Va. The mediotemporal areas MT and MST displayed a distinct population of densely labeled neurons in layer VI. Quantitative analysis of the laminar distribution of the labeled neurons demonstrated that the visual cortical areas could be grouped in four hierarchical levels based on the ratio of neuron counts between infragranular and supragranular layers, with the first (areas V1, V2, V3, and V3A) and third (temporal and parietal regions) levels characterized by low ratios and the second (areas MT, MST, and V4) and fourth (frontal regions) levels characterized by high to very high ratios. Such density trends may correspond to differential representation of corticocortically (and corticosubcortically) projecting neurons at several functional steps in the integration of the visual stimuli. In this context, it is possible that neurofilament protein is crucial for the unique capacity of certain subsets of neurons to perform the highly precise mapping functions of the monkey visual system.

A Corticocortical Circuit Directly Links Retrosplenial Cortex to M2 in the Mouse

PubMed Central

Radulovic, Jelena

2016-01-01

Retrosplenial cortex (RSC) is a dorsomedial parietal area involved in a range of cognitive functions, including episodic memory, navigation, and spatial memory. Anatomically, the RSC receives inputs from dorsal hippocampal networks and in turn projects to medial neocortical areas. A particularly prominent projection extends rostrally to the posterior secondary motor cortex (M2), suggesting a functional corticocortical link from the RSC to M2 and thus a bridge between hippocampal and neocortical networks involved in mnemonic and sensorimotor aspects of navigation. We investigated the cellular connectivity in this RSC→M2 projection in the mouse using optogenetic photostimulation, retrograde labeling, and electrophysiology. Axons from RSC formed monosynaptic excitatory connections onto M2 pyramidal neurons across layers and projection classes, including corticocortical/intratelencephalic neurons (reciprocally and callosally projecting) in layers 2–6, pyramidal tract neurons (corticocollicular, corticopontine) in layer 5B, and, to a lesser extent, corticothalamic neurons in layer 6. In addition to these direct connections, disynaptic connections were made via posterior parietal cortex (RSC→PPC→M2) and anteromedial thalamus (RSC→AM→M2). In the reverse direction, axons from M2 monosynaptically excited M2-projecting corticocortical neurons in the RSC, especially in the superficial layers of the dysgranular region. These findings establish an excitatory RSC→M2 corticocortical circuit that engages diverse types of excitatory projection neurons in the downstream area, suggesting a basis for direct communication from dorsal hippocampal networks involved in spatial memory and navigation to neocortical networks involved in diverse aspects of sensorimotor integration and motor control. SIGNIFICANCE STATEMENT Corticocortical pathways interconnect cortical areas extensively, but the cellular connectivity in these pathways remains largely uncharacterized. Here, we show that a posterior part of secondary motor cortex receives corticocortical axons from the rostral retrosplenial cortex (RSC) and these form monosynaptic excitatory connections onto a wide spectrum of excitatory projection neurons in this area. Our results define a cellular basis for direct communication from RSC to this medial frontal area, suggesting a direct link from dorsal hippocampal networks involved in spatial cognition and navigation (the “map”) to sensorimotor networks involved the control of movement (the “motor”). PMID:27605612

Mirror Neurons of Ventral Premotor Cortex Are Modulated by Social Cues Provided by Others' Gaze.

PubMed

Coudé, Gino; Festante, Fabrizia; Cilia, Adriana; Loiacono, Veronica; Bimbi, Marco; Fogassi, Leonardo; Ferrari, Pier Francesco

2016-03-16

Mirror neurons (MNs) in the inferior parietal lobule and ventral premotor cortex (PMv) can code the intentions of other individuals using contextual cues. Gaze direction is an important social cue that can be used for understanding the meaning of actions made by other individuals. Here we addressed the issue of whether PMv MNs are influenced by the gaze direction of another individual. We recorded single-unit activity in macaque PMv while the monkey was observing an experimenter performing a grasping action and orienting his gaze either toward (congruent gaze condition) or away (incongruent gaze condition) from a target object. The results showed that one-half of the recorded MNs were modulated by the gaze direction of the human agent. These gaze-modulated neurons were evenly distributed between those preferring a gaze direction congruent with the direction where the grasping action was performed and the others that preferred an incongruent gaze. Whereas the presence of congruent responses is in line with the usual coupling of hand and gaze in both executed and observed actions, the incongruent responses can be explained by the long exposure of the monkeys to this condition. Our results reveal that the representation of observed actions in PMv is influenced by contextual information not only extracted from physical cues, but also from cues endowed with biological or social value. In this study, we present the first evidence showing that social cues modulate MNs in the monkey ventral premotor cortex. These data suggest that there is an integrated representation of other's hand actions and gaze direction at the single neuron level in the ventral premotor cortex, and support the hypothesis of a functional role of MNs in decoding actions and understanding motor intentions. Copyright © 2016 the authors 0270-6474/16/363145-12$15.00/0.

Coding of Velocity Storage in the Vestibular Nuclei.

PubMed

Yakushin, Sergei B; Raphan, Theodore; Cohen, Bernard

2017-01-01

Semicircular canal afferents sense angular acceleration and output angular velocity with a short time constant of ≈4.5 s. This output is prolonged by a central integrative network, velocity storage that lengthens the time constants of eye velocity. This mechanism utilizes canal, otolith, and visual (optokinetic) information to align the axis of eye velocity toward the spatial vertical when head orientation is off-vertical axis. Previous studies indicated that vestibular-only (VO) and vestibular-pause-saccade (VPS) neurons located in the medial and superior vestibular nucleus could code all aspects of velocity storage. A recently developed technique enabled prolonged recording while animals were rotated and received optokinetic stimulation about a spatial vertical axis while upright, side-down, prone, and supine. Firing rates of 33 VO and 8 VPS neurons were studied in alert cynomolgus monkeys. Majority VO neurons were closely correlated with the horizontal component of velocity storage in head coordinates, regardless of head orientation in space. Approximately, half of all tested neurons (46%) code horizontal component of velocity in head coordinates, while the other half (54%) changed their firing rates as the head was oriented relative to the spatial vertical, coding the horizontal component of eye velocity in spatial coordinates. Some VO neurons only coded the cross-coupled pitch or roll components that move the axis of eye rotation toward the spatial vertical. Sixty-five percent of these VO and VPS neurons were more sensitive to rotation in one direction (predominantly contralateral), providing directional orientation for the subset of VO neurons on either side of the brainstem. This indicates that the three-dimensional velocity storage integrator is composed of directional subsets of neurons that are likely to be the bases for the spatial characteristics of velocity storage. Most VPS neurons ceased firing during drowsiness, but the firing rates of VO neurons were unaffected by states of alertness and declined with the time constant of velocity storage. Thus, the VO neurons are the prime components of the mechanism of coding for velocity storage, whereas the VPS neurons are likely to provide the path from the vestibular to the oculomotor system for the VO neurons.

Coding of Velocity Storage in the Vestibular Nuclei

PubMed Central

Yakushin, Sergei B.; Raphan, Theodore; Cohen, Bernard

2017-01-01

Semicircular canal afferents sense angular acceleration and output angular velocity with a short time constant of ≈4.5 s. This output is prolonged by a central integrative network, velocity storage that lengthens the time constants of eye velocity. This mechanism utilizes canal, otolith, and visual (optokinetic) information to align the axis of eye velocity toward the spatial vertical when head orientation is off-vertical axis. Previous studies indicated that vestibular-only (VO) and vestibular-pause-saccade (VPS) neurons located in the medial and superior vestibular nucleus could code all aspects of velocity storage. A recently developed technique enabled prolonged recording while animals were rotated and received optokinetic stimulation about a spatial vertical axis while upright, side-down, prone, and supine. Firing rates of 33 VO and 8 VPS neurons were studied in alert cynomolgus monkeys. Majority VO neurons were closely correlated with the horizontal component of velocity storage in head coordinates, regardless of head orientation in space. Approximately, half of all tested neurons (46%) code horizontal component of velocity in head coordinates, while the other half (54%) changed their firing rates as the head was oriented relative to the spatial vertical, coding the horizontal component of eye velocity in spatial coordinates. Some VO neurons only coded the cross-coupled pitch or roll components that move the axis of eye rotation toward the spatial vertical. Sixty-five percent of these VO and VPS neurons were more sensitive to rotation in one direction (predominantly contralateral), providing directional orientation for the subset of VO neurons on either side of the brainstem. This indicates that the three-dimensional velocity storage integrator is composed of directional subsets of neurons that are likely to be the bases for the spatial characteristics of velocity storage. Most VPS neurons ceased firing during drowsiness, but the firing rates of VO neurons were unaffected by states of alertness and declined with the time constant of velocity storage. Thus, the VO neurons are the prime components of the mechanism of coding for velocity storage, whereas the VPS neurons are likely to provide the path from the vestibular to the oculomotor system for the VO neurons. PMID:28861030

Stimulus features coded by single neurons of a macaque body category selective patch.

PubMed

Popivanov, Ivo D; Schyns, Philippe G; Vogels, Rufin

2016-04-26

Body category-selective regions of the primate temporal cortex respond to images of bodies, but it is unclear which fragments of such images drive single neurons' responses in these regions. Here we applied the Bubbles technique to the responses of single macaque middle superior temporal sulcus (midSTS) body patch neurons to reveal the image fragments the neurons respond to. We found that local image fragments such as extremities (limbs), curved boundaries, and parts of the torso drove the large majority of neurons. Bubbles revealed the whole body in only a few neurons. Neurons coded the features in a manner that was tolerant to translation and scale changes. Most image fragments were excitatory but for a few neurons both inhibitory and excitatory fragments (opponent coding) were present in the same image. The fragments we reveal here in the body patch with Bubbles differ from those suggested in previous studies of face-selective neurons in face patches. Together, our data indicate that the majority of body patch neurons respond to local image fragments that occur frequently, but not exclusively, in bodies, with a coding that is tolerant to translation and scale. Overall, the data suggest that the body category selectivity of the midSTS body patch depends more on the feature statistics of bodies (e.g., extensions occur more frequently in bodies) than on semantics (bodies as an abstract category).

Noise-enhanced coding in phasic neuron spike trains.

PubMed

Ly, Cheng; Doiron, Brent

2017-01-01

The stochastic nature of neuronal response has lead to conjectures about the impact of input fluctuations on the neural coding. For the most part, low pass membrane integration and spike threshold dynamics have been the primary features assumed in the transfer from synaptic input to output spiking. Phasic neurons are a common, but understudied, neuron class that are characterized by a subthreshold negative feedback that suppresses spike train responses to low frequency signals. Past work has shown that when a low frequency signal is accompanied by moderate intensity broadband noise, phasic neurons spike trains are well locked to the signal. We extend these results with a simple, reduced model of phasic activity that demonstrates that a non-Markovian spike train structure caused by the negative feedback produces a noise-enhanced coding. Further, this enhancement is sensitive to the timescales, as opposed to the intensity, of a driving signal. Reduced hazard function models show that noise-enhanced phasic codes are both novel and separate from classical stochastic resonance reported in non-phasic neurons. The general features of our theory suggest that noise-enhanced codes in excitable systems with subthreshold negative feedback are a particularly rich framework to study.

A reservoir of time constants for memory traces in cortical neurons

PubMed Central

Bernacchia, Alberto; Seo, Hyojung; Lee, Daeyeol; Wang, Xiao-Jing

2011-01-01

According to reinforcement learning theory of decision making, reward expectation is computed by integrating past rewards with a fixed timescale. By contrast, we found that a wide range of time constants is available across cortical neurons recorded from monkeys performing a competitive game task. By recognizing that reward modulates neural activity multiplicatively, we found that one or two time constants of reward memory can be extracted for each neuron in prefrontal, cingulate, and parietal cortex. These timescales ranged from hundreds of milliseconds to tens of seconds, according to a power-law distribution, which is consistent across areas and reproduced by a “reservoir” neural network model. These neuronal memory timescales were weakly but significantly correlated with those of monkey's decisions. Our findings suggest a flexible memory system, where neural subpopulations with distinct sets of long or short memory timescales may be selectively deployed according to the task demands. PMID:21317906

Spike Code Flow in Cultured Neuronal Networks.

PubMed

Tamura, Shinichi; Nishitani, Yoshi; Hosokawa, Chie; Miyoshi, Tomomitsu; Sawai, Hajime; Kamimura, Takuya; Yagi, Yasushi; Mizuno-Matsumoto, Yuko; Chen, Yen-Wei

2016-01-01

We observed spike trains produced by one-shot electrical stimulation with 8 × 8 multielectrodes in cultured neuronal networks. Each electrode accepted spikes from several neurons. We extracted the short codes from spike trains and obtained a code spectrum with a nominal time accuracy of 1%. We then constructed code flow maps as movies of the electrode array to observe the code flow of "1101" and "1011," which are typical pseudorandom sequence such as that we often encountered in a literature and our experiments. They seemed to flow from one electrode to the neighboring one and maintained their shape to some extent. To quantify the flow, we calculated the "maximum cross-correlations" among neighboring electrodes, to find the direction of maximum flow of the codes with lengths less than 8. Normalized maximum cross-correlations were almost constant irrespective of code. Furthermore, if the spike trains were shuffled in interval orders or in electrodes, they became significantly small. Thus, the analysis suggested that local codes of approximately constant shape propagated and conveyed information across the network. Hence, the codes can serve as visible and trackable marks of propagating spike waves as well as evaluating information flow in the neuronal network.

Callosally projecting neurons in the macaque monkey V1/V2 border are enriched in nonphosphorylated neurofilament protein

NASA Technical Reports Server (NTRS)

Hof, P. R.; Ungerleider, L. G.; Adams, M. M.; Webster, M. J.; Gattass, R.; Blumberg, D. M.; Morrison, J. H.; Bloom, F. E. (Principal Investigator)

1997-01-01

Previous immunohistochemical studies combined with retrograde tracing in macaque monkeys have demonstrated that corticocortical projections can be differentiated by their content of neurofilament protein. The present study analyzed the distribution of nonphosphorylated neurofilament protein in callosally projecting neurons located at the V1/V2 border. All of the retrogradely labeled neurons were located in layer III at the V1/V2 border and at an immediately adjacent zone of area V2. A quantitative analysis showed that the vast majority (almost 95%) of these interhemispheric projection neurons contain neurofilament protein immunoreactivity. This observation differs from data obtained in other sets of callosal connections, including homotypical interhemispheric projections in the prefrontal, temporal, and parietal association cortices, that were found to contain uniformly low proportions of neurofilament protein-immunoreactive neurons. Comparably, highly variable proportions of neurofilament protein-containing neurons have been reported in intrahemispheric corticocortical pathways, including feedforward and feedback visual connections. These results indicate that neurofilament protein is a prominent neurochemical feature that identifies a particular population of interhemispheric projection neurons at the V1/V2 border and suggest that this biochemical attribute may be critical for the function of this subset of callosal neurons.

Toll-Like Receptor-4 Mediates Neuronal Apoptosis Induced by Amyloid β-Peptide and the Membrane Lipid Peroxidation Product 4-Hydroxynonenal

PubMed Central

Tang, Sung-Chun; Lathia, Justin D.; Selvaraj, Pradeep K.; Jo, Dong-Gyu; Mughal, Mohamed R.; Cheng, Aiwu; Siler, Dominic A.; Markesbery, William R.; Arumugam, Thiruma V.; Mattson, Mark. P.

2008-01-01

The innate immune system senses the invasion of pathogenic microorganisms and tissue injury through Toll-like receptors (TLR), a mechanism thought to be limited to immune cells. We recently found that neurons express several TLRs, and that the levels of TLR2 and TLR4 are increased in neurons in response to energy deprivation. Here we report that TLR4 expression increases in neurons when exposed to amyloid β-peptide (Aβ1-42) or the lipid peroxidation product 4-hydroxynonenal (HNE). Neuronal apoptosis triggered by Aβ and HNE was mediated by jun N-terminal kinase (JNK); neurons from TLR4 mutant mice exhibited reduced JNK and caspase-3 activation and were protected against apoptosis induced by Aβ and HNE. Levels of TLR4 were decreased in inferior parietal cortex tissue specimens from end-stage AD patients compared to aged-matched control subjects, possibly as the result of loss of neurons expressing TLR4. Our findings suggest that TLR4 signaling increases the vulnerability of neurons to Aβ and oxidative stress in AD, and identify TLR4 as a potential therapeutic target for AD. PMID:18586243

Sensory and Working Memory Representations of Small and Large Numerosities in the Crow Endbrain.

PubMed

Ditz, Helen M; Nieder, Andreas

2016-11-23

Neurons in the avian nidopallium caudolaterale (NCL), an endbrain structure that originated independently from the mammalian neocortex, process visual numerosities. To clarify the code for number in this anatomically distinct endbrain area in birds, neuronal responses to a broad range of numerosities were analyzed. We recorded single-neuron activity from the NCL of crows performing a delayed match-to-sample task with visual numerosities as discriminanda. The responses of >20% of randomly selected neurons were modulated significantly by numerosities ranging from one to 30 items. Numerosity-selective neurons showed bell-shaped tuning curves with one of the presented numerosities as preferred numerosity regardless of the physical appearance of the items. The resulting labeled-line code exhibited logarithmic compression obeying the Weber-Fechner law for magnitudes. Comparable proportions of selective neurons were found, not only during stimulus presentation, but also in the delay phase, indicating a dominant role of the NCL in numerical working memory. Both during sensory encoding and memorization of numerosities in working memory, NCL activity predicted the crows' number discrimination performance. These neuronal data reveal striking similarities across vertebrate taxa in their code for number despite convergently evolved and anatomically distinct endbrain structures. Birds are known for their capabilities to process numerical quantity. However, birds lack a six-layered neocortex that enables primates with numerical competence. We aimed to decipher the neuronal code for numerical quantity in the independently and distinctly evolved endbrain of birds. We recorded the activity of neurons in an endbrain association area termed nidopallium caudolaterale (NCL) from crows that assessed and briefly memorized numerosities from one to 30 dots. We report a neuronal code for sensory representation and working memory of numerosities in the crow NCL exhibiting several characteristics that are surprisingly similar to the ones found in primates. Our data suggest a common code for number in two different vertebrate taxa that has evolved based on convergent evolution. Copyright © 2016 the authors 0270-6474/16/3612044-09$15.00/0.

Development of rostral inferior parietal lobule area functional connectivity from late childhood to early adulthood.

PubMed

Wang, Mengxing; Zhang, Jilei; Dong, Guangheng; Zhang, Hui; Lu, Haifeng; Du, Xiaoxia

2017-06-01

Although the mirror neuron system (MNS) has been extensively studied in monkeys and adult humans, very little is known about its development. Previous studies suggest that the MNS is present by infancy and that the brain and MNS-related cognitive abilities (such as language, empathy, and imitation learning) continue to develop after childhood. In humans, the PFt area of the inferior parietal lobule (IPL) seems to particularly correlate with the functional properties of the PF area in primates, which contains mirror neurons. However, little is known about the functional connectivity (FC) of the PFt area with other brain areas and whether these networks change over time. Here, we investigated the FC development of the PFt area-based network in 59 healthy subjects aged 7-26 years at resting-state to study brain development from late childhood through adolescence to early adulthood. The bilateral PFt showed similar core FC networks, which included the frontal lobe, the cingulate gyri, the insula, the somatosensory cortex, the precuneus, the superior and inferior parietal lobules, the temporal lobe, and the cerebellum posterior lobes. Furthermore, the FC between the left PFt and the left IPL exhibited a significantly positive correlation with age, and the FC between the left PFt and the right postcentral gyrus exhibited a significantly negative correlation with age. In addition, the FC between the right PFt and the right putamen exhibited a significantly negative correlation with age. Our findings suggest that the PFt area-based network develops and is reorganized with age. Copyright © 2017 ISDN. Published by Elsevier Ltd. All rights reserved.

CNS activation and regional connectivity during pantomime observation: no engagement of the mirror neuron system for deaf signers.

PubMed

Emmorey, Karen; Xu, Jiang; Gannon, Patrick; Goldin-Meadow, Susan; Braun, Allen

2010-01-01

Deaf signers have extensive experience using their hands to communicate. Using fMRI, we examined the neural systems engaged during the perception of manual communication in 14 deaf signers and 14 hearing non-signers. Participants passively viewed blocked video clips of pantomimes (e.g., peeling an imaginary banana) and action verbs in American Sign Language (ASL) that were rated as meaningless by non-signers (e.g., TO-DANCE). In contrast to visual fixation, pantomimes strongly activated fronto-parietal regions (the mirror neuron system, MNS) in hearing non-signers, but only bilateral middle temporal regions in deaf signers. When contrasted with ASL verbs, pantomimes selectively engaged inferior and superior parietal regions in hearing non-signers, but right superior temporal cortex in deaf signers. The perception of ASL verbs recruited similar regions as pantomimes for deaf signers, with some evidence of greater involvement of left inferior frontal gyrus for ASL verbs. Functional connectivity analyses with left hemisphere seed voxels (ventral premotor, inferior parietal lobule, fusiform gyrus) revealed robust connectivity with the MNS for the hearing non-signers. Deaf signers exhibited functional connectivity with the right hemisphere that was not observed for the hearing group for the fusiform gyrus seed voxel. We suggest that life-long experience with manual communication, and/or auditory deprivation, may alter regional connectivity and brain activation when viewing pantomimes. We conclude that the lack of activation within the MNS for deaf signers does not support an account of human communication that depends upon automatic sensorimotor resonance between perception and action.

Neural noise and movement-related codes in the macaque supplementary motor area.

PubMed

Averbeck, Bruno B; Lee, Daeyeol

2003-08-20

We analyzed the variability of spike counts and the coding capacity of simultaneously recorded pairs of neurons in the macaque supplementary motor area (SMA). We analyzed the mean-variance functions for single neurons, as well as signal and noise correlations between pairs of neurons. All three statistics showed a strong dependence on the bin width chosen for analysis. Changes in the correlation structure of single neuron spike trains over different bin sizes affected the mean-variance function, and signal and noise correlations between pairs of neurons were much smaller at small bin widths, increasing monotonically with the width of the bin. Analyses in the frequency domain showed that the noise between pairs of neurons, on average, was most strongly correlated at low frequencies, which explained the increase in noise correlation with increasing bin width. The coding performance was analyzed to determine whether the temporal precision of spike arrival times and the interactions within and between neurons could improve the prediction of the upcoming movement. We found that in approximately 62% of neuron pairs, the arrival times of spikes at a resolution between 66 and 40 msec carried more information than spike counts in a 200 msec bin. In addition, in 19% of neuron pairs, inclusion of within (11%)- or between-neuron (8%) correlations in spike trains improved decoding accuracy. These results suggest that in some SMA neurons elements of the spatiotemporal pattern of activity may be relevant for neural coding.

Transfer of Cognitive Training across Magnitude Dimensions Achieved with Concurrent Brain Stimulation of the Parietal Lobe

PubMed Central

Gessaroli, Erica; Hithersay, Rosalyn; Mitolo, Micaela; Didino, Daniele; Kanai, Ryota; Cohen Kadosh, Roi; Walsh, Vincent

2013-01-01

Improvement in performance following cognitive training is known to be further enhanced when coupled with brain stimulation. Here we ask whether training-induced changes can be maintained long term and, crucially, whether they can extend to other related but untrained skills. We trained overall 40 human participants on a simple and well established paradigm assessing the ability to discriminate numerosity–or the number of items in a set–which is thought to rely on an “approximate number sense” (ANS) associated with parietal lobes. We coupled training with parietal stimulation in the form of transcranial random noise stimulation (tRNS), a noninvasive technique that modulates neural activity. This yielded significantly better and longer lasting improvement (up to 16 weeks post-training) of the precision of the ANS compared with cognitive training in absence of stimulation, stimulation in absence of cognitive training, and cognitive training coupled to stimulation to a control site (motor areas). Critically, only ANS improvement induced by parietal tRNS + Training transferred to proficiency in other parietal lobe-based quantity judgment, i.e., time and space discrimination, but not to quantity-unrelated tasks measuring attention, executive functions, and visual pattern recognition. These results indicate that coupling intensive cognitive training with tRNS to critical brain regions resulted not only in the greatest and longer lasting improvement of numerosity discrimination, but importantly in this enhancement being transferable when trained and untrained abilities are carefully chosen to share common cognitive and neuronal components. PMID:24027289

Transfer of cognitive training across magnitude dimensions achieved with concurrent brain stimulation of the parietal lobe.

PubMed

Cappelletti, Marinella; Gessaroli, Erica; Hithersay, Rosalyn; Mitolo, Micaela; Didino, Daniele; Kanai, Ryota; Cohen Kadosh, Roi; Walsh, Vincent

2013-09-11

Improvement in performance following cognitive training is known to be further enhanced when coupled with brain stimulation. Here we ask whether training-induced changes can be maintained long term and, crucially, whether they can extend to other related but untrained skills. We trained overall 40 human participants on a simple and well established paradigm assessing the ability to discriminate numerosity--or the number of items in a set--which is thought to rely on an "approximate number sense" (ANS) associated with parietal lobes. We coupled training with parietal stimulation in the form of transcranial random noise stimulation (tRNS), a noninvasive technique that modulates neural activity. This yielded significantly better and longer lasting improvement (up to 16 weeks post-training) of the precision of the ANS compared with cognitive training in absence of stimulation, stimulation in absence of cognitive training, and cognitive training coupled to stimulation to a control site (motor areas). Critically, only ANS improvement induced by parietal tRNS + Training transferred to proficiency in other parietal lobe-based quantity judgment, i.e., time and space discrimination, but not to quantity-unrelated tasks measuring attention, executive functions, and visual pattern recognition. These results indicate that coupling intensive cognitive training with tRNS to critical brain regions resulted not only in the greatest and longer lasting improvement of numerosity discrimination, but importantly in this enhancement being transferable when trained and untrained abilities are carefully chosen to share common cognitive and neuronal components.

A dynamic code for economic object valuation in prefrontal cortex neurons

PubMed Central

Tsutsui, Ken-Ichiro; Grabenhorst, Fabian; Kobayashi, Shunsuke; Schultz, Wolfram

2016-01-01

Neuronal reward valuations provide the physiological basis for economic behaviour. Yet, how such valuations are converted to economic decisions remains unclear. Here we show that the dorsolateral prefrontal cortex (DLPFC) implements a flexible value code based on object-specific valuations by single neurons. As monkeys perform a reward-based foraging task, individual DLPFC neurons signal the value of specific choice objects derived from recent experience. These neuronal object values satisfy principles of competitive choice mechanisms, track performance fluctuations and follow predictions of a classical behavioural model (Herrnstein’s matching law). Individual neurons dynamically encode both, the updating of object values from recently experienced rewards, and their subsequent conversion to object choices during decision-making. Decoding from unselected populations enables a read-out of motivational and decision variables not emphasized by individual neurons. These findings suggest a dynamic single-neuron and population value code in DLPFC that advances from reward experiences to economic object values and future choices. PMID:27618960

Neuroimaging and Neuromodulation: Complementary Approaches for Identifying the Neuronal Correlates of Tinnitus

PubMed Central

Langguth, Berthold; Schecklmann, Martin; Lehner, Astrid; Landgrebe, Michael; Poeppl, Timm Benjamin; Kreuzer, Peter Michal; Schlee, Winfried; Weisz, Nathan; Vanneste, Sven; De Ridder, Dirk

2012-01-01

An inherent limitation of functional imaging studies is their correlational approach. More information about critical contributions of specific brain regions can be gained by focal transient perturbation of neural activity in specific regions with non-invasive focal brain stimulation methods. Functional imaging studies have revealed that tinnitus is related to alterations in neuronal activity of central auditory pathways. Modulation of neuronal activity in auditory cortical areas by repetitive transcranial magnetic stimulation (rTMS) can reduce tinnitus loudness and, if applied repeatedly, exerts therapeutic effects, confirming the relevance of auditory cortex activation for tinnitus generation and persistence. Measurements of oscillatory brain activity before and after rTMS demonstrate that the same stimulation protocol has different effects on brain activity in different patients, presumably related to interindividual differences in baseline activity in the clinically heterogeneous study cohort. In addition to alterations in auditory pathways, imaging techniques also indicate the involvement of non-auditory brain areas, such as the fronto-parietal “awareness” network and the non-tinnitus-specific distress network consisting of the anterior cingulate cortex, anterior insula, and amygdale. Involvement of the hippocampus and the parahippocampal region putatively reflects the relevance of memory mechanisms in the persistence of the phantom percept and the associated distress. Preliminary studies targeting the dorsolateral prefrontal cortex, the dorsal anterior cingulate cortex, and the parietal cortex with rTMS and with transcranial direct current stimulation confirm the relevance of the mentioned non-auditory networks. Available data indicate the important value added by brain stimulation as a complementary approach to neuroimaging for identifying the neuronal correlates of the various clinical aspects of tinnitus. PMID:22509155

Absence of Cerebrospinal Fluid Signs of Neuronal Injury Before and After Immediate Antiretroviral Therapy in Acute HIV Infection

PubMed Central

Peluso, Michael J.; Valcour, Victor; Ananworanich, Jintanat; Sithinamsuwan, Pasiri; Chalermchai, Thep; Fletcher, James L. K.; Lerdlum, Sukalya; Chomchey, Nitiya; Slike, Bonnie; Sailasuta, Napapon; Gisslén, Magnus; Zetterberg, Henrik; Spudich, Serena

2015-01-01

Background. It is unknown whether neuronal injury begins during acute human immunodeficiency virus (HIV) infection, and whether immediate initiation of combination antiretroviral therapy (cART) prevents neuronal injury. Methods. Cerebrospinal fluid (CSF) neurofilament light chain (NFL), a measure of axonal injury, was assessed before and after cART initiation in individuals starting treatment during acute or chronic HIV infection. Nonparametric statistics examined relationships between NFL and disease progression, neuroinflammation, and cognitive performance. Results. Before treatment, subjects with acute infection had lower CSF NFL levels, with elevations for their age in 1 of 32 subjects with acute infection (3.1%) and 10 of 32 with chronic infection (31%) (P = .006). This persisted after cART initiation, with 1 of 25 acute (4%) and 4 of 9 chronic subjects (44%) showing elevated NFL levels (P = .01). In acute infection, pre-cART NFL levels were inversely correlated with proton magnetic resonance spectroscopic findings of N-acetylaspartate/creatine in frontal gray matter (r = −0.40; P = .03), frontal white matter (r = −0.46; P = .01), and parietal gray matter (r = −0.47; P = .01); correlations persisted after treatment in the frontal white matter (r = −0.51; P = .02) and parietal gray matter (r = −0.46; P = .04). Conclusions. CSF NFL levels are not elevated in untreated acute HIV infection or after 6 months of immediately initiated cART but are abnormal in chronic HIV infection before and after treatment. In acute HIV infection, CSF NFL levels are inversely associated with neuroimaging markers of neuronal health. PMID:25995196

Absence of Cerebrospinal Fluid Signs of Neuronal Injury Before and After Immediate Antiretroviral Therapy in Acute HIV Infection.

PubMed

Peluso, Michael J; Valcour, Victor; Ananworanich, Jintanat; Sithinamsuwan, Pasiri; Chalermchai, Thep; Fletcher, James L K; Lerdlum, Sukalya; Chomchey, Nitiya; Slike, Bonnie; Sailasuta, Napapon; Gisslén, Magnus; Zetterberg, Henrik; Spudich, Serena

2015-12-01

It is unknown whether neuronal injury begins during acute human immunodeficiency virus (HIV) infection, and whether immediate initiation of combination antiretroviral therapy (cART) prevents neuronal injury. Cerebrospinal fluid (CSF) neurofilament light chain (NFL), a measure of axonal injury, was assessed before and after cART initiation in individuals starting treatment during acute or chronic HIV infection. Nonparametric statistics examined relationships between NFL and disease progression, neuroinflammation, and cognitive performance. Before treatment, subjects with acute infection had lower CSF NFL levels, with elevations for their age in 1 of 32 subjects with acute infection (3.1%) and 10 of 32 with chronic infection (31%) (P = .006). This persisted after cART initiation, with 1 of 25 acute (4%) and 4 of 9 chronic subjects (44%) showing elevated NFL levels (P = .01). In acute infection, pre-cART NFL levels were inversely correlated with proton magnetic resonance spectroscopic findings of N-acetylaspartate/creatine in frontal gray matter (r = -0.40; P = .03), frontal white matter (r = -0.46; P = .01), and parietal gray matter (r = -0.47; P = .01); correlations persisted after treatment in the frontal white matter (r = -0.51; P = .02) and parietal gray matter (r = -0.46; P = .04). CSF NFL levels are not elevated in untreated acute HIV infection or after 6 months of immediately initiated cART but are abnormal in chronic HIV infection before and after treatment. In acute HIV infection, CSF NFL levels are inversely associated with neuroimaging markers of neuronal health. © The Author 2015. Published by Oxford University Press on behalf of the Infectious Diseases Society of America. All rights reserved. For Permissions, please e-mail: journals.permissions@oup.com.

Coding of auditory temporal and pitch information by hippocampal individual cells and cell assemblies in the rat.

PubMed

Sakurai, Y

2002-01-01

This study reports how hippocampal individual cells and cell assemblies cooperate for neural coding of pitch and temporal information in memory processes for auditory stimuli. Each rat performed two tasks, one requiring discrimination of auditory pitch (high or low) and the other requiring discrimination of their duration (long or short). Some CA1 and CA3 complex-spike neurons showed task-related differential activity between the high and low tones in only the pitch-discrimination task. However, without exception, neurons which showed task-related differential activity between the long and short tones in the duration-discrimination task were always task-related neurons in the pitch-discrimination task. These results suggest that temporal information (long or short), in contrast to pitch information (high or low), cannot be coded independently by specific neurons. The results also indicate that the two different behavioral tasks cannot be fully differentiated by the task-related single neurons alone and suggest a model of cell-assembly coding of the tasks. Cross-correlation analysis among activities of simultaneously recorded multiple neurons supported the suggested cell-assembly model.Considering those results, this study concludes that dual coding by hippocampal single neurons and cell assemblies is working in memory processing of pitch and temporal information of auditory stimuli. The single neurons encode both auditory pitches and their temporal lengths and the cell assemblies encode types of tasks (contexts or situations) in which the pitch and the temporal information are processed.

Fine-Tuning of Neurogenesis is Essential for the Evolutionary Expansion of the Cerebral Cortex

PubMed Central

Poluch, Sylvie; Juliano, Sharon L.

2015-01-01

We used several animal models to study global and regional cortical surface expansion: The lissencephalic mouse, gyrencephalic normal ferrets, in which the parietal cortex expands more than the temporal cortex, and moderately lissencephalic ferrets, showing a similar degree of temporal and parietal expansion. We found that overall cortical surface expansion is achieved when specific events occur prior to surpragranular layer formation. (1) The subventricular zone (SVZ) shows substantial growth, (2) the inner SVZ contains an increased number of outer radial glia and intermediate progenitor cells expressing Pax6, and (3) the outer SVZ contains a progenitor cell composition similar to the combined VZ and inner SVZ. A greater parietal expansion is also achieved by eliminating the latero-dorsal neurogenic gradient, so that neurogenesis displays a similar developmental degree between parietal and temporal regions. In contrast, mice or lissencephalic ferrets show more advanced neurogenesis in the temporal region. In conclusion, we propose that global and regional cortical surface expansion rely on similar strategies consisting in altering the timing of neurogenic events prior to the surpragranular layer formation, so that more progenitor cells, and ultimately more neurons, are produced. This hypothesis is supported by findings from a ferret model of lissencephaly obtained by transiently blocking neurogenesis during the formation of layer IV. PMID:23968831

[Mirror neurons--novel data on the neurobiology of intersubjectivity].

PubMed

Simon, Mária; Herold, Róbert; Fekete, Sándor; Tényi, Tamás

2007-01-01

Social experiences are largely intersubjective in nature, offering an abundance of pre-reflective, simulative knowledge of others' subjective experiences. In the last decades, special mirror neurons have been found in the premotor area and in the posterior parietal cortex. They directly link perception to action: the perception of actions activates the relevant parts of the observer's motor system. Emotional expressions evoke resonance states inside the observer in a similar way. Besides underscoring the prereflective and implicit nature of intersubjectivity, this can provide an access to the neuronal basis of empathy and intuition. Moreover, a new integration of psychoanalysis and neuroscience seems to be possible, which shifts the psychoanalytic technique toward non-verbal and non-interpretative methods, and can explain psychoanalytic phenomena, such as introjection, projection, transference, counter-transference, and the very complex enactments.

The neuronal encoding of information in the brain.

PubMed

Rolls, Edmund T; Treves, Alessandro

2011-11-01

We describe the results of quantitative information theoretic analyses of neural encoding, particularly in the primate visual, olfactory, taste, hippocampal, and orbitofrontal cortex. Most of the information turns out to be encoded by the firing rates of the neurons, that is by the number of spikes in a short time window. This has been shown to be a robust code, for the firing rate representations of different neurons are close to independent for small populations of neurons. Moreover, the information can be read fast from such encoding, in as little as 20 ms. In quantitative information theoretic studies, only a little additional information is available in temporal encoding involving stimulus-dependent synchronization of different neurons, or the timing of spikes within the spike train of a single neuron. Feature binding appears to be solved by feature combination neurons rather than by temporal synchrony. The code is sparse distributed, with the spike firing rate distributions close to exponential or gamma. A feature of the code is that it can be read by neurons that take a synaptically weighted sum of their inputs. This dot product decoding is biologically plausible. Understanding the neural code is fundamental to understanding not only how the cortex represents, but also processes, information. Copyright © 2011 Elsevier Ltd. All rights reserved.

Modulation of spike coding by subthreshold extracellular electric fields and neuronal morphology

NASA Astrophysics Data System (ADS)

Wei, Xile; Li, Bingjie; Lu, Meili; Yi, Guosheng; Wang, Jiang

2015-07-01

We use a two-compartment model, which includes soma and dendrite, to explore how extracellular subthreshold sinusoidal electric fields (EFs) influence the spike coding of an active neuron. By changing the intensity and the frequency of subthreshold EFs, we find that subthreshold EFs indeed affect neuronal coding remarkably within several stimulus frequency windows where the field effects on spike timing are stronger than that on spiking rate. The field effects are maximized at several harmonics of the intrinsic spiking frequency of an active neuron. Our findings implicate the potential resonance mechanism underlying subthreshold field effects. We also discuss how neuronal morphologic properties constrain subthreshold EF effects on spike timing. The morphologic properties are represented by two parameters, gc and p, where gc is the internal conductance between soma and dendrite and geometric factor p characterizes the proportion of area occupied by soma. We find that the contribution to field effects from the variation of p is stronger than that from gc, which suggests that neuronal geometric features play a crucial role in subthreshold field effects. Theoretically, these insights into how subthreshold sinusoidal EFs modulate ongoing neuron behaviors could contribute to uncovering the relevant mechanism of subthreshold sinusoidal EFs effects on neuronal coding. Furthermore, they are useful in rationally designing noninvasive brain stimulation strategies and developing electromagnetic stimulus techniques.

Neural representation of hand kinematics during prehension in posterior parietal cortex of the macaque monkey.

PubMed

Chen, Jessie; Reitzen, Shari D; Kohlenstein, Jane B; Gardner, Esther P

2009-12-01

Studies of hand manipulation neurons in posterior parietal cortex of monkeys suggest that their spike trains represent objects by the hand postures needed for grasping or by the underlying patterns of muscle activation. To analyze the role of hand kinematics and object properties in a trained prehension task, we correlated the firing rates of neurons in anterior area 5 with hand behaviors as monkeys grasped and lifted knobs of different shapes and locations in the workspace. Trials were divided into four classes depending on the approach trajectory: forward, lateral, and local approaches, and regrasps. The task factors controlled by the animal-how and when he used the hand-appeared to play the principal roles in modulating firing rates of area 5 neurons. In all, 77% of neurons studied (58/75) showed significant effects of approach style on firing rates; 80% of the population responded at higher rates and for longer durations on forward or lateral approaches that included reaching, wrist rotation, and hand preshaping prior to contact, but only 13% distinguished the direction of reach. The higher firing rates in reach trials reflected not only the arm movements needed to direct the hand to the target before contact, but persisted through the contact, grasp, and lift stages. Moreover, the approach style exerted a stronger effect on firing rates than object features, such as shape and location, which were distinguished by half of the population. Forty-three percent of the neurons signaled both the object properties and the hand actions used to acquire them. However, the spread in firing rates evoked by each knob on reach and no-reach trials was greater than distinctions between different objects grasped with the same approach style. Our data provide clear evidence for synergies between reaching and grasping that may facilitate smooth, coordinated actions of the arm and hand.

Stimulus features coded by single neurons of a macaque body category selective patch

PubMed Central

Popivanov, Ivo D.; Schyns, Philippe G.; Vogels, Rufin

2016-01-01

Body category-selective regions of the primate temporal cortex respond to images of bodies, but it is unclear which fragments of such images drive single neurons’ responses in these regions. Here we applied the Bubbles technique to the responses of single macaque middle superior temporal sulcus (midSTS) body patch neurons to reveal the image fragments the neurons respond to. We found that local image fragments such as extremities (limbs), curved boundaries, and parts of the torso drove the large majority of neurons. Bubbles revealed the whole body in only a few neurons. Neurons coded the features in a manner that was tolerant to translation and scale changes. Most image fragments were excitatory but for a few neurons both inhibitory and excitatory fragments (opponent coding) were present in the same image. The fragments we reveal here in the body patch with Bubbles differ from those suggested in previous studies of face-selective neurons in face patches. Together, our data indicate that the majority of body patch neurons respond to local image fragments that occur frequently, but not exclusively, in bodies, with a coding that is tolerant to translation and scale. Overall, the data suggest that the body category selectivity of the midSTS body patch depends more on the feature statistics of bodies (e.g., extensions occur more frequently in bodies) than on semantics (bodies as an abstract category). PMID:27071095

Neuronal substrates of Corsi Block span: Lesion symptom mapping analyses in relation to attentional competition and spatial bias.

PubMed

Chechlacz, Magdalena; Rotshtein, Pia; Humphreys, Glyn W

2014-11-01

Spatial working memory problems are frequently reported following brain damage within both left and right hemispheres but with the severity often being grater in individuals with right hemisphere lesions. Clinically, deficits in spatial working memory have also been noted in patients with visuospatial disorders such as unilateral neglect. Here, we examined neural substrates of short-term memory for spatial locations based on the Corsi Block tapping task and the relationship with the visuospatial deficits of neglect and extinction in a group of chronic neuropsychological patients. Principal Component Analysis (PCA) was used to distinguish shared and dissociate functional components. The neural substrates of spatial short-term memory deficits and the components identified by PCA were examined using whole brain voxel-based morphometry and tract-wise lesion deficits analyses. We found that bilateral lesions within occipital cortex (middle occipital gyrus) and right posterior parietal cortex, along with disconnection of the right parieto-temporal segment of arcuate fasciculus, were associated with low spatial memory span. A single component revealed by PCA accounted for over half of the variance and was linked to damage to right posterior brain regions (temporo-parietal junction, the inferior parietal lobule and middle temporal gyrus extending into middle occipital gyrus). We also found link to disconnections within several association pathways including the superior longitudinal fasciculus, arcuate fasciculus, inferior fronto-occipital fasciculus and inferior longitudinal fasciculus. These results indicate that different visuospatial deficits converge into a single component mapped within posterior parietal areas and fronto-parietal white matter pathways. Furthermore, the data presented here fit with the role of posterior parietal cortex/temporo-parietal junction in maintaining a map of salient locations in space, with Corsi Block performance being impaired when the spatial map is damaged. Copyright © 2014 Elsevier Ltd. All rights reserved.

Electrophysiological evidence for differential processing of numerical quantity and order in humans.

PubMed

Turconi, Eva; Jemel, Boutheina; Rossion, Bruno; Seron, Xavier

2004-09-01

It is yet unclear whether the processing of number magnitude and order rely on common or different functional processes and neural substrates. On the one hand, recent neuroimaging studies show that quantity and order coding activate the same areas in the parietal and prefrontal cortices. On the other hand, evidence from developmental and neuropsychological studies suggest dissociated mechanisms for processing quantity and order information. To clarify this issue, the present study investigated the spatio-temporal course of quantity and order coding operations using event-related potentials (ERPs). Twenty-four subjects performed a quantity task (classifying numbers as smaller or larger than 15) and an order task on the same material (classifying numbers as coming before or after 15), as well as a control order task on letters (classifying letters as coming before or after M). Behavioral results showed a classical distance effect (decreasing reaction times [RTs] with increasing distance from the standard) for all tasks. In agreement with previous electrophysiological evidence, this effect was significant on a P2 parietal component for numerical material. However, the difference between processing numbers close or far from the target appeared earlier and was larger on the left hemisphere for quantity processing, while it was delayed and bilateral for order processing. There was also a significant distance effect in all tasks on parietal sites for the following P3 component elicited by numbers, but this effect was larger on prefrontal areas for the order judgment. In conclusion, both quantity and order show similar behavioral effects, but they are associated with different spatio-temporal courses in parietal and prefrontal cortices.

The mirror neuron system and treatment of stroke.

PubMed

Small, Steven L; Buccino, Giovanni; Solodkin, Ana

2012-04-01

Mirror neurons discharge during the execution of ecological goal-directed manual and oral actions, as well as during the observation of the same actions done by other individuals. These neurons were first identified in the ventral premotor cortex (PMv; area F5) and later on in the inferior parietal lobule (areas PF and PFG) of monkey brain, constituting a "mirror neuron" system. Several pieces of experimental data suggest that a mirror neuron system devoted to hand, mouth, and foot actions might also be present in humans. In the present paper, we review the experimental evidence on the role of the mirror neuron system in action understanding and imitation, both in hand motor function and speech. Based on the features of the mirror neuron system and its role in action understanding and imitation, we discuss the use of action observation and imitation as an approach for systematic training in the rehabilitation of patients with motor impairment of the upper limb and aphasia following stroke. We present the results of some preliminary studies to test this concept, and a discussion of network models as a measure of neurobiological change. Copyright © 2010 Wiley Periodicals, Inc.

Modality-independent representations of small quantities based on brain activation patterns.

PubMed

Damarla, Saudamini Roy; Cherkassky, Vladimir L; Just, Marcel Adam

2016-04-01

Machine learning or MVPA (Multi Voxel Pattern Analysis) studies have shown that the neural representation of quantities of objects can be decoded from fMRI patterns, in cases where the quantities were visually displayed. Here we apply these techniques to investigate whether neural representations of quantities depicted in one modality (say, visual) can be decoded from brain activation patterns evoked by quantities depicted in the other modality (say, auditory). The main finding demonstrated, for the first time, that quantities of dots were decodable by a classifier that was trained on the neural patterns evoked by quantities of auditory tones, and vice-versa. The representations that were common across modalities were mainly right-lateralized in frontal and parietal regions. A second finding was that the neural patterns in parietal cortex that represent quantities were common across participants. These findings demonstrate a common neuronal foundation for the representation of quantities across sensory modalities and participants and provide insight into the role of parietal cortex in the representation of quantity information. © 2016 Wiley Periodicals, Inc.

Cerebral (1)H MRS alterations in recreational 3, 4-methylenedioxymethamphetamine (MDMA, "ecstasy") users.

PubMed

Chang, L; Ernst, T; Grob, C S; Poland, R E

1999-10-01

3,4-methylenedioxymethamphetamine (MDMA) is an illicit drug that has been associated with serotonergic axonal degeneration in animals. This study evaluates neurochemical abnormalities in recreational MDMA users. Twenty-two MDMA users and 37 normal subjects were evaluated with magnetic resonance imaging (MRI) and proton magnetic resonance spectroscopy ((1)H MRS) in the mid-frontal, mid-occipital, and parietal brain regions. (1)H MRS showed normal N-acetyl (NA) compounds in all brain regions. The myo-inositol (MI) concentration (+16.3%, P = 0.04) and the MI to creatine (CR) ratio (+14.1%, P = 0. 01) were increased in the parietal white matter of MDMA users. The cumulative lifetime MDMA dose showed significant effects on [MI] in the parietal white matter and the occipital cortex. The normal NA concentration suggests a lack of significant neuronal injury in recreational MDMA users. However, the usage-related increase in MI suggests that exposure to MDMA, even at recreational doses, may cause increased glial content. J. Magn. Reson. Imaging 1999;10:521-526. Copyright 1999 Wiley-Liss, Inc.

Cell-assembly coding in several memory processes.

PubMed

Sakurai, Y

1998-01-01

The present paper discusses why the cell assembly, i.e., an ensemble population of neurons with flexible functional connections, is a tenable view of the basic code for information processes in the brain. The main properties indicating the reality of cell-assembly coding are neurons overlaps among different assemblies and connection dynamics within and among the assemblies. The former can be detected as multiple functions of individual neurons in processing different kinds of information. Individual neurons appear to be involved in multiple information processes. The latter can be detected as changes of functional synaptic connections in processing different kinds of information. Correlations of activity among some of the recorded neurons appear to change in multiple information processes. Recent experiments have compared several different memory processes (tasks) and detected these two main properties, indicating cell-assembly coding of memory in the working brain. The first experiment compared different types of processing of identical stimuli, i.e., working memory and reference memory of auditory stimuli. The second experiment compared identical processes of different types of stimuli, i.e., discriminations of simple auditory, simple visual, and configural auditory-visual stimuli. The third experiment compared identical processes of different types of stimuli with or without temporal processing of stimuli, i.e., discriminations of elemental auditory, configural auditory-visual, and sequential auditory-visual stimuli. Some possible features of the cell-assembly coding, especially "dual coding" by individual neurons and cell assemblies, are discussed for future experimental approaches. Copyright 1998 Academic Press.

Brain activation during mental rotation in school children and adults.

PubMed

Kucian, K; von Aster, M; Loenneker, T; Dietrich, T; Mast, F W; Martin, E

2007-01-01

Mental rotation is a complex cognitive skill depending on the manipulation of mental representations. We aimed to investigate the maturing neuronal network for mental rotation by measuring brain activation in 20 children and 20 adults using functional magnetic resonance imaging. Our results indicate that brain activation patterns are very similar between children and adults. However, adults exhibit stronger activation in the left intraparietal sulcus compared to children. This finding suggests a shift of activation from a predominantly right parietal activation in children to a bilateral activation pattern in adults. Furthermore, adults show a deactivation of the posterior cingulate gyrus and precuneus, which is not observed in children. In conclusion, developmental changes of brain activation during mental rotation are leading to a bilateral parietal activation pattern and faster performance.

Incorporating spike-rate adaptation into a rate code in mathematical and biological neurons

PubMed Central

Ralston, Bridget N.; Flagg, Lucas Q.; Faggin, Eric

2016-01-01

For a slowly varying stimulus, the simplest relationship between a neuron's input and output is a rate code, in which the spike rate is a unique function of the stimulus at that instant. In the case of spike-rate adaptation, there is no unique relationship between input and output, because the spike rate at any time depends both on the instantaneous stimulus and on prior spiking (the “history”). To improve the decoding of spike trains produced by neurons that show spike-rate adaptation, we developed a simple scheme that incorporates “history” into a rate code. We utilized this rate-history code successfully to decode spike trains produced by 1) mathematical models of a neuron in which the mechanism for adaptation (IAHP) is specified, and 2) the gastropyloric receptor (GPR2), a stretch-sensitive neuron in the stomatogastric nervous system of the crab Cancer borealis, that exhibits long-lasting adaptation of unknown origin. Moreover, when we modified the spike rate either mathematically in a model system or by applying neuromodulatory agents to the experimental system, we found that changes in the rate-history code could be related to the biophysical mechanisms responsible for altering the spiking. PMID:26888106

Neurocognitive Predictions of Performance.

DTIC Science & Technology

1987-09-25

feedback (see Section 1V.A). Many of these results, along with pilot analyses of intracerebral recordings using a. primate model, cannot be explained by...are subject to considerable distortion by the intervening media of cerebrum, cerebro -spinal fluid, skull, and scalp. The result is a smeaxing or...parietal component is consistent with evidence from primates and humans for neuronal firing in motor and somatost.nsory cortices prior to motor responses

The Mirror Neurons Network in Aging, Mild Cognitive Impairment, and Alzheimer Disease: A functional MRI Study

PubMed Central

Farina, Elisabetta; Baglio, Francesca; Pomati, Simone; D'Amico, Alessandra; Campini, Isabella C.; Di Tella, Sonia; Belloni, Giulia; Pozzo, Thierry

2017-01-01

The aim of the current study is to investigate the integrity of the Mirror Neurons (MN) network in normal aging, Mild Cognitive Impairment (MCI), and Alzheimer disease (AD). Although AD and MCI are considered “cognitive” diseases, there has been increasing recognition of a link between motor function and AD. More recently the embodied cognition hypothesis has also been developed: it postulates that a part of cognition results from the coupling between action and perception representations. MN represent a neuronal population which links perception, action, and cognition, therefore we decided to characterize MN functioning in neurodegenerative cognitive decline. Three matched groups of 16 subjects (normal elderly-NE, amnesic MCI with hippocampal atrophy and AD) were evaluated with a focused neuropsychological battery and an fMRI task specifically created to test MN: that comprised of an observation run, where subjects were shown movies of a right hand grasping different objects, and of a motor run, where subjects observed visual pictures of objects oriented to be grasped with the right hand. In NE subjects, the conjunction analysis (comparing fMRI activation during observation and execution), showed the activation of a bilateral fronto-parietal network in “classical” MN areas, and of the superior temporal gyrus (STG). The MCI group showed the activation of areas belonging to the same network, however, parietal areas were activated to a lesser extent and the STG was not activated, while the opposite was true for the right Broca's area. We did not observe any activation of the fronto-parietal network in AD participants. They did not perform as well as the NE subjects in all the neuropsychological tests (including tests of functions attributed to MN) whereas the MCI subjects were significantly different from the NE subjects only in episodic memory and semantic fluency. Here we show that the MN network is largely preserved in aging, while it appears involved following an anterior-posterior gradient in neurodegenerative decline. In AD, task performance decays and the MN network appears clearly deficient. The preservation of the anterior part of the MN network in MCI could possibly supplement the initial decay of the posterior part, preserving cognitive performance. PMID:29249956

Architecture and Chemical Coding of the Inner and Outer Submucous Plexus in the Colon of Piglets

PubMed Central

Petto, Carola; Gäbel, Gotthold; Pfannkuche, Helga

2015-01-01

In the porcine colon, the submucous plexus is divided into an inner submucous plexus (ISP) on the epithelial side and an outer submucous plexus (OSP) on the circular muscle side. Although both plexuses are probably involved in the regulation of epithelial functions, they might differ in function and neurochemical coding according to their localization. Therefore, we examined expression and co-localization of different neurotransmitters and neuronal markers in both plexuses as well as in neuronal fibres. Immunohistochemical staining was performed on wholemount preparations of ISP and OSP and on cryostat sections. Antibodies against choline acetyltransferase (ChAT), substance P (SP), somatostatin (SOM), neuropeptide Y (NPY), vasoactive intestinal peptide (VIP), neuronal nitric oxide synthase (nNOS) and the pan-neuronal markers Hu C/D and neuron specific enolase (NSE) were used. The ISP contained 1,380 ± 131 ganglia per cm2 and 122 ± 12 neurons per ganglion. In contrast, the OSP showed a wider meshwork (215 ± 33 ganglia per cm2) and smaller ganglia (57 ± 3 neurons per ganglion). In the ISP, 42% of all neurons expressed ChAT. About 66% of ChAT-positive neurons co-localized SP. A small number of ISP neurons expressed SOM. Chemical coding in the OSP was more complex. Besides the ChAT/±SP subpopulation (32% of all neurons), a nNOS-immunoreactive population (31%) was detected. Most nitrergic neurons were only immunoreactive for nNOS; 10% co-localized with VIP. A small subpopulation of OSP neurons was immunoreactive for ChAT/nNOS/±VIP. All types of neurotransmitters found in the ISP or OSP were also detected in neuronal fibres within the mucosa. We suppose that the cholinergic population in the ISP is involved in the control of epithelial functions. Regarding neurochemical coding, the OSP shares some similarities with the myenteric plexus. Because of its location and neurochemical characteristics, the OSP may be involved in controlling both the mucosa and circular muscle. PMID:26230272

Olfactory coding: giant inhibitory neuron governs sparse odor codes.

PubMed

Gupta, Nitin; Stopfer, Mark

2011-07-12

Electrophysiological investigations in locusts have revealed that the sparseness of odor representations, in the brain region expected to mediate olfactory learning, is shaped by a unique inhibitory neuron. Copyright © 2011 Elsevier Ltd. All rights reserved.

Hearing sounds, understanding actions: action representation in mirror neurons.

PubMed

Kohler, Evelyne; Keysers, Christian; Umiltà, M Alessandra; Fogassi, Leonardo; Gallese, Vittorio; Rizzolatti, Giacomo

2002-08-02

Many object-related actions can be recognized by their sound. We found neurons in monkey premotor cortex that discharge when the animal performs a specific action and when it hears the related sound. Most of the neurons also discharge when the monkey observes the same action. These audiovisual mirror neurons code actions independently of whether these actions are performed, heard, or seen. This discovery in the monkey homolog of Broca's area might shed light on the origin of language: audiovisual mirror neurons code abstract contents-the meaning of actions-and have the auditory access typical of human language to these contents.

SPATIAL NEGLECT AND ATTENTION NETWORKS

PubMed Central

Corbetta, Maurizio; Shulman, Gordon L.

2013-01-01

Unilateral spatial neglect is a common neurological syndrome following predominantly right hemisphere injuries to ventral fronto-parietal cortex. We propose that neglect reflects deficits in the coding of saliency, control of spatial attention, and representation within an egocentric frame of reference, in conjunction with non-spatial deficits of reorienting, target detection, and arousal/vigilance. In contrast to theories that link spatial neglect to structural damage of specific brain regions, we argue that neglect is better explained by the physiological dysfunction of distributed cortical networks. The ventral lesions in right parietal, temporal, and frontal cortex that cause neglect directly impair non-spatial functions and hypoactivate the right hemisphere, inducing abnormalities in task-evoked activity and functional connectivity of a dorsal frontal-parietal network that controls spatial attention. The anatomy and right hemisphere dominance of neglect follows from the anatomy and laterality of the ventral regions that interact with the dorsal attention network. PMID:21692662

Interaction Between Spatial and Feature Attention in Posterior Parietal Cortex

PubMed Central

Ibos, Guilhem; Freedman, David J.

2016-01-01

Summary Lateral intraparietal (LIP) neurons encode a vast array of sensory and cognitive variables. Recently, we proposed that the flexibility of feature representations in LIP reflect the bottom-up integration of sensory signals, modulated by feature-based attention (FBA), from upstream feature-selective cortical neurons. Moreover, LIP activity is also strongly modulated by the position of space-based attention (SBA). However, the mechanisms by which SBA and FBA interact to facilitate the representation of task-relevant spatial and non-spatial features in LIP remain unclear. We recorded from LIP neurons during performance of a task which required monkeys to detect specific conjunctions of color, motion-direction, and stimulus position. Here we show that FBA and SBA potentiate each other’s effect in a manner consistent with attention gating the flow of visual information along the cortical visual pathway. Our results suggest that linear bottom-up integrative mechanisms allow LIP neurons to emphasize task-relevant spatial and non-spatial features. PMID:27499082

Real-time prediction of hand trajectory by ensembles of cortical neurons in primates

NASA Astrophysics Data System (ADS)

Wessberg, Johan; Stambaugh, Christopher R.; Kralik, Jerald D.; Beck, Pamela D.; Laubach, Mark; Chapin, John K.; Kim, Jung; Biggs, S. James; Srinivasan, Mandayam A.; Nicolelis, Miguel A. L.

2000-11-01

Signals derived from the rat motor cortex can be used for controlling one-dimensional movements of a robot arm. It remains unknown, however, whether real-time processing of cortical signals can be employed to reproduce, in a robotic device, the kind of complex arm movements used by primates to reach objects in space. Here we recorded the simultaneous activity of large populations of neurons, distributed in the premotor, primary motor and posterior parietal cortical areas, as non-human primates performed two distinct motor tasks. Accurate real-time predictions of one- and three-dimensional arm movement trajectories were obtained by applying both linear and nonlinear algorithms to cortical neuronal ensemble activity recorded from each animal. In addition, cortically derived signals were successfully used for real-time control of robotic devices, both locally and through the Internet. These results suggest that long-term control of complex prosthetic robot arm movements can be achieved by simple real-time transformations of neuronal population signals derived from multiple cortical areas in primates.

Independent controls for neocortical neuron production and histogenetic cell death

NASA Technical Reports Server (NTRS)

Verney, C.; Takahashi, T.; Bhide, P. G.; Nowakowski, R. S.; Caviness, V. S. Jr

2000-01-01

We estimated the proportion of cells eliminated by histogenetic cell death during the first 2 postnatal weeks in areas 1, 3 and 40 of the mouse parietal neocortex. For each layer and for the subcortical white matter in each neocortical area, the number of dying cells per mm(2) was calculated and the proportionate cell death for each day of the 2-week interval was estimated. The data show that cell death proceeds essentially uniformly across the neocortical areas and layers and that it does not follow either the spatiotemporal gradient of cell cycle progression in the pseudostratified ventricular epithelium of the cerebral wall, the source of neocortical neurons, or the 'inside-out' neocortical neuronogenetic sequence. Therefore, we infer that the control mechanisms of neocortical histogenetic cell death are independent of mechanisms controlling neuronogenesis or neuronal migration but may be associated with the ingrowth, expansion and a system-wide matching of neuronal connectivity. Copyright 2000 S. Karger AG, Basel.

Interaction between Spatial and Feature Attention in Posterior Parietal Cortex.

PubMed

Ibos, Guilhem; Freedman, David J

2016-08-17

Lateral intraparietal (LIP) neurons encode a vast array of sensory and cognitive variables. Recently, we proposed that the flexibility of feature representations in LIP reflect the bottom-up integration of sensory signals, modulated by feature-based attention (FBA), from upstream feature-selective cortical neurons. Moreover, LIP activity is also strongly modulated by the position of space-based attention (SBA). However, the mechanisms by which SBA and FBA interact to facilitate the representation of task-relevant spatial and non-spatial features in LIP remain unclear. We recorded from LIP neurons during performance of a task that required monkeys to detect specific conjunctions of color, motion direction, and stimulus position. Here we show that FBA and SBA potentiate each other's effect in a manner consistent with attention gating the flow of visual information along the cortical visual pathway. Our results suggest that linear bottom-up integrative mechanisms allow LIP neurons to emphasize task-relevant spatial and non-spatial features. Copyright © 2016 Elsevier Inc. All rights reserved.

Spatial Correlations in Natural Scenes Modulate Response Reliability in Mouse Visual Cortex

PubMed Central

Rikhye, Rajeev V.

2015-01-01

Intrinsic neuronal variability significantly limits information encoding in the primary visual cortex (V1). Certain stimuli can suppress this intertrial variability to increase the reliability of neuronal responses. In particular, responses to natural scenes, which have broadband spatiotemporal statistics, are more reliable than responses to stimuli such as gratings. However, very little is known about which stimulus statistics modulate reliable coding and how this occurs at the neural ensemble level. Here, we sought to elucidate the role that spatial correlations in natural scenes play in reliable coding. We developed a novel noise-masking method to systematically alter spatial correlations in natural movies, without altering their edge structure. Using high-speed two-photon calcium imaging in vivo, we found that responses in mouse V1 were much less reliable at both the single neuron and population level when spatial correlations were removed from the image. This change in reliability was due to a reorganization of between-neuron correlations. Strongly correlated neurons formed ensembles that reliably and accurately encoded visual stimuli, whereas reducing spatial correlations reduced the activation of these ensembles, leading to an unreliable code. Together with an ensemble-specific normalization model, these results suggest that the coordinated activation of specific subsets of neurons underlies the reliable coding of natural scenes. SIGNIFICANCE STATEMENT The natural environment is rich with information. To process this information with high fidelity, V1 neurons have to be robust to noise and, consequentially, must generate responses that are reliable from trial to trial. While several studies have hinted that both stimulus attributes and population coding may reduce noise, the details remain unclear. Specifically, what features of natural scenes are important and how do they modulate reliability? This study is the first to investigate the role of spatial correlations, which are a fundamental attribute of natural scenes, in shaping stimulus coding by V1 neurons. Our results provide new insights into how stimulus spatial correlations reorganize the correlated activation of specific ensembles of neurons to ensure accurate information processing in V1. PMID:26511254

Large-scale Exploration of Neuronal Morphologies Using Deep Learning and Augmented Reality.

PubMed

Li, Zhongyu; Butler, Erik; Li, Kang; Lu, Aidong; Ji, Shuiwang; Zhang, Shaoting

2018-02-12

Recently released large-scale neuron morphological data has greatly facilitated the research in neuroinformatics. However, the sheer volume and complexity of these data pose significant challenges for efficient and accurate neuron exploration. In this paper, we propose an effective retrieval framework to address these problems, based on frontier techniques of deep learning and binary coding. For the first time, we develop a deep learning based feature representation method for the neuron morphological data, where the 3D neurons are first projected into binary images and then learned features using an unsupervised deep neural network, i.e., stacked convolutional autoencoders (SCAEs). The deep features are subsequently fused with the hand-crafted features for more accurate representation. Considering the exhaustive search is usually very time-consuming in large-scale databases, we employ a novel binary coding method to compress feature vectors into short binary codes. Our framework is validated on a public data set including 58,000 neurons, showing promising retrieval precision and efficiency compared with state-of-the-art methods. In addition, we develop a novel neuron visualization program based on the techniques of augmented reality (AR), which can help users take a deep exploration of neuron morphologies in an interactive and immersive manner.

Decoupled choice-driven and stimulus-related activity in parietal neurons may be misrepresented by choice probabilities.

PubMed

Zaidel, Adam; DeAngelis, Gregory C; Angelaki, Dora E

2017-09-28

Trial-by-trial correlations between neural responses and choices (choice probabilities) are often interpreted to reflect a causal contribution of neurons to task performance. However, choice probabilities may arise from top-down, rather than bottom-up, signals. We isolated distinct sensory and decision contributions to single-unit activity recorded from the dorsal medial superior temporal (MSTd) and ventral intraparietal (VIP) areas of monkeys during perception of self-motion. Superficially, neurons in both areas show similar tuning curves during task performance. However, tuning in MSTd neurons primarily reflects sensory inputs, whereas choice-related signals dominate tuning in VIP neurons. Importantly, the choice-related activity of VIP neurons is not predictable from their stimulus tuning, and these factors are often confounded in choice probability measurements. This finding was confirmed in a subset of neurons for which stimulus tuning was measured during passive fixation. Our findings reveal decoupled stimulus and choice signals in the VIP area, and challenge our understanding of choice signals in the brain.Choice-related signals in neuronal activity may reflect bottom-up sensory processes, top-down decision-related influences, or a combination of the two. Here the authors report that choice-related activity in VIP neurons is not predictable from their stimulus tuning, and that dominant choice signals can bias the standard metric of choice preference (choice probability).

Reduced N-acetylaspartate levels in the frontal cortex of 3,4-methylenedioxymethamphetamine (Ecstasy) users: preliminary results.

PubMed

Reneman, Liesbeth; Majoie, Charles B L M; Flick, Herman; den Heeten, Gerard J

2002-02-01

The perceived safety of the recreational drug methylenedioxymethamphetamine (MDMA), or Ecstasy, conflicts with animal evidence indicating that MDMA damages cortical serotonin (5-HT) neurons at doses similar to those used by humans. Few data are available about the effects of MDMA on the human brain. This study was designed to evaluate MDMA-related alterations in metabolite ratios with single-voxel proton ((1)H) MR spectroscopy. Fifteen male MDMA users (mean lifetime exposure, 723 tablets; mean time since last tablet, 12.0 weeks) and 12 age-matched control subjects underwent single-voxel (1)H MR spectroscopy. N-Acetylaspartate (NAA)/creatine (Cr), NAA/Choline (Cho), and myoinositol (MI)/Cr ratios were measured in midfrontal gray matter, midoccipital gray matter, and right parietal white matter. Data were analyzed with linear model-based multivariate analysis of variance. NAA/Cr (P =.04) and NAA/Cho (P =.03) ratios, markers associated with neuronal loss or dysfunction, were reduced in the frontal cortex of MDMA users. Neither NAA/Cr (P =.72) nor NAA/Cho (P =.12) ratios were different between both groups in occipital gray matter and parietal white matter (P =.18). Extent of previous MDMA use and frontal cortical NAA/Cr (rho = -.50, P =.012) or NAA/Cho (rho = -.550, P <.01) ratios were significantly associated. Reduced NAA/Cr and NAA/Cho ratios at (1)H MR spectroscopy provide evidence for neuronal abnormality in the frontal cortex of MDMA users; these are correlated with the degree of MDMA exposure. These data suggest that MDMA may be a neurotoxin in humans, as it is in animals.

Neurochemical coding of enteric neurons in the guinea pig stomach.

PubMed

Schemann, M; Schaaf, C; Mäder, M

1995-03-06

The aim of this study was to investigate the neurochemical coding of myenteric neurons in the guinea pig gastric corpus by using immunohistochemical methods. Antibodies and antisera against calbindin (CALB), calretinin (CALRET), choline acetyltransferase (ChAT), calcitonin gene-related peptide (CGRP), dopamine beta-hydroxylase (DBH), beta-endorphin (ENK), neuropeptide Y (NPY), neuron-specific enolase (NSE), nitric oxide synthase (NOS), protein gene product 9.5 (PGP), parvalbumin (PARV), serotonin (5-HT), somatostatin (SOM), substance P (SP), tyrosine hydroxylase (TH), and vasoactive intestinal peptide (VIP) were used. Double- and triple-labeling studies revealed colocalization of certain transmitters and enabled the identification of distinct subpopulations of gastric enteric neurons. NPY/VIP/NOS/ENK were present in 28% of all neurons, whereas 11% had NPY/VIP/DBH/ChAT; NOS-only neurons made up 2% of the population. The combination SP/ChAT/ENK occurred in 21% of the population, whereas SP/ChAT/ENK/CALRET and SP/CHAT/SOM/ +/- CALRET was identified in 5% and 6% of all cells, respectively. 5-HT-containing neurons comprised 2% of all cells and could be further classified by the presence of additional antigens as 5-HT/SP/(ChAT) or 5-HT/VIP/(ChAT). Approximately 21% of all neurons contained only ChAT with no additional antigen present and are referred to as ChAT/-. Gastric myenteric ganglion cells were not immunoreactive for CALB, PARV, CGRP, or TH. The results of this study indicate that gastric myenteric neurons can be characterized on the basis of different chemical coding. Neurochemical coding of corpus myenteric neurons revealed some similarities and significant differences in comparison with other regions of the gut. These differences might reflect adaptation of enteric nerves according to regional specialization and the distinct functions of the proximal stomach as a gastric reservoir.

Mind the gap: Neural coding of species identity in birdsong prosody.

PubMed

Araki, Makoto; Bandi, M M; Yazaki-Sugiyama, Yoko

2016-12-09

Juvenile songbirds learn vocal communication from adult tutors of the same species but not from adults of other species. How species-specific learning emerges from the basic features of song prosody remains unknown. In the zebra finch auditory cortex, we discovered a class of neurons that register the silent temporal gaps between song syllables and are distinct from neurons encoding syllable morphology. Behavioral learning and neuronal coding of temporal gap structure resisted song tutoring from other species: Zebra finches fostered by Bengalese finch parents learned Bengalese finch song morphology transposed onto zebra finch temporal gaps. During the vocal learning period, temporal gap neurons fired selectively to zebra finch song. The innate temporal coding of intersyllable silent gaps suggests a neuronal barcode for conspecific vocal learning and social communication in acoustically diverse environments. Copyright © 2016, American Association for the Advancement of Science.

Spatial Navigation in Complex and Radial Mazes in APP23 Animals and Neurotrophin Signaling as a Biological Marker of Early Impairment

ERIC Educational Resources Information Center

Hellweg, Rainer; Huber, Roman; Kuhl, Alexander; Riepe, Matthias W.; Lohmann, Peter

2006-01-01

Impairment of hippocampal function precedes frontal and parietal cortex impairment in human Alzheimer's disease(AD). Neurotrophins are critical for behavioral performance and neuronal survival in AD. We used complex and radial mazes to assess spatial orientation and learning in wild-type and B6-Tg(ThylAPP)23Sdz (APP23) animals, a transgenic mouse…

Retention of identity versus expression of emotional faces differs in the recruitment of limbic areas.

PubMed

Röder, Christian H; Mohr, Harald; Linden, David E J

2011-02-01

Faces are multidimensional stimuli that convey information for complex social and emotional functions. Separate neural systems have been implicated in the recognition of facial identity (mainly extrastriate visual cortex) and emotional expression (limbic areas and the superior temporal sulcus). Working-memory (WM) studies with faces have shown different but partly overlapping activation patterns in comparison to spatial WM in parietal and prefrontal areas. However, little is known about the neural representations of the different facial dimensions during WM. In the present study 22 subjects performed a face-identity or face-emotion WM task at different load levels during functional magnetic resonance imaging. We found a fronto-parietal-visual WM-network for both tasks during maintenance, including fusiform gyrus. Limbic areas in the amygdala and parahippocampal gyrus demonstrated a stronger activation for the identity than the emotion condition. One explanation for this finding is that the repetitive presentation of faces with different identities but the same emotional expression during the identity-task is responsible for the stronger increase in BOLD signal in the amygdala. These results raise the question how different emotional expressions are coded in WM. Our findings suggest that emotional expressions are re-coded in an abstract representation that is supported at the neural level by the canonical fronto-parietal WM network. Copyright © 2010 Elsevier Ltd. All rights reserved.

Effects of isoflurane anesthesia on ensemble patterns of Ca2+ activity in mouse v1: reduced direction selectivity independent of increased correlations in cellular activity.

PubMed

Goltstein, Pieter M; Montijn, Jorrit S; Pennartz, Cyriel M A

2015-01-01

Anesthesia affects brain activity at the molecular, neuronal and network level, but it is not well-understood how tuning properties of sensory neurons and network connectivity change under its influence. Using in vivo two-photon calcium imaging we matched neuron identity across episodes of wakefulness and anesthesia in the same mouse and recorded spontaneous and visually evoked activity patterns of neuronal ensembles in these two states. Correlations in spontaneous patterns of calcium activity between pairs of neurons were increased under anesthesia. While orientation selectivity remained unaffected by anesthesia, this treatment reduced direction selectivity, which was attributable to an increased response to the null-direction. As compared to anesthesia, populations of V1 neurons coded more mutual information on opposite stimulus directions during wakefulness, whereas information on stimulus orientation differences was lower. Increases in correlations of calcium activity during visual stimulation were correlated with poorer population coding, which raised the hypothesis that the anesthesia-induced increase in correlations may be causal to degrading directional coding. Visual stimulation under anesthesia, however, decorrelated ongoing activity patterns to a level comparable to wakefulness. Because visual stimulation thus appears to 'break' the strength of pairwise correlations normally found in spontaneous activity under anesthesia, the changes in correlational structure cannot explain the awake-anesthesia difference in direction coding. The population-wide decrease in coding for stimulus direction thus occurs independently of anesthesia-induced increments in correlations of spontaneous activity.

Effects of Isoflurane Anesthesia on Ensemble Patterns of Ca2+ Activity in Mouse V1: Reduced Direction Selectivity Independent of Increased Correlations in Cellular Activity

PubMed Central

Goltstein, Pieter M.; Montijn, Jorrit S.; Pennartz, Cyriel M. A.

2015-01-01

Anesthesia affects brain activity at the molecular, neuronal and network level, but it is not well-understood how tuning properties of sensory neurons and network connectivity change under its influence. Using in vivo two-photon calcium imaging we matched neuron identity across episodes of wakefulness and anesthesia in the same mouse and recorded spontaneous and visually evoked activity patterns of neuronal ensembles in these two states. Correlations in spontaneous patterns of calcium activity between pairs of neurons were increased under anesthesia. While orientation selectivity remained unaffected by anesthesia, this treatment reduced direction selectivity, which was attributable to an increased response to the null-direction. As compared to anesthesia, populations of V1 neurons coded more mutual information on opposite stimulus directions during wakefulness, whereas information on stimulus orientation differences was lower. Increases in correlations of calcium activity during visual stimulation were correlated with poorer population coding, which raised the hypothesis that the anesthesia-induced increase in correlations may be causal to degrading directional coding. Visual stimulation under anesthesia, however, decorrelated ongoing activity patterns to a level comparable to wakefulness. Because visual stimulation thus appears to ‘break’ the strength of pairwise correlations normally found in spontaneous activity under anesthesia, the changes in correlational structure cannot explain the awake-anesthesia difference in direction coding. The population-wide decrease in coding for stimulus direction thus occurs independently of anesthesia-induced increments in correlations of spontaneous activity. PMID:25706867

Olfactory bulb dysgenesis, mirror neuron system dysfunction, and autonomic dysregulation as the neural basis for autism.

PubMed

Brang, David; Ramachandran, V S

2010-05-01

Autism is a disorder characterized by social withdrawal, impoverished language and empathy, and a profound inability to adopt another's viewpoint - a failure to construct a "theory of mind" for interpreting another person's thoughts and intentions. We previously showed that these symptoms might be explained, in part, by a paucity of mirror neurons. Prompted by an MRI report of an individual with autism, we now suggest that there may be, in addition, a congenital aplasia/dysplasia of the olfactory bulbs with consequent reduction of vasopressin and oxytocin receptor binding. There may also be sub-clinical temporal lobe epilepsy affecting the recently discovered third visual system that is rich in "empathy" related mirror neurons (MNS) and projects (via the TOP junction - just below the inferior parietal lobule) to limbic structures that regulate autonomic outflow. This causes deranged autonomic feedback, resulting in additional deficiencies in MNS with loss of emotional empathy and introspection.

Superior colliculus neurons encode a visual saliency map during free viewing of natural dynamic video

NASA Astrophysics Data System (ADS)

White, Brian J.; Berg, David J.; Kan, Janis Y.; Marino, Robert A.; Itti, Laurent; Munoz, Douglas P.

2017-01-01

Models of visual attention postulate the existence of a saliency map whose function is to guide attention and gaze to the most conspicuous regions in a visual scene. Although cortical representations of saliency have been reported, there is mounting evidence for a subcortical saliency mechanism, which pre-dates the evolution of neocortex. Here, we conduct a strong test of the saliency hypothesis by comparing the output of a well-established computational saliency model with the activation of neurons in the primate superior colliculus (SC), a midbrain structure associated with attention and gaze, while monkeys watched video of natural scenes. We find that the activity of SC superficial visual-layer neurons (SCs), specifically, is well-predicted by the model. This saliency representation is unlikely to be inherited from fronto-parietal cortices, which do not project to SCs, but may be computed in SCs and relayed to other areas via tectothalamic pathways.

Correlated neuronal discharges that increase coding efficiency during perceptual discrimination.

PubMed

Romo, Ranulfo; Hernández, Adrián; Zainos, Antonio; Salinas, Emilio

2003-05-22

During a sensory discrimination task, the responses of multiple sensory neurons must be combined to generate a choice. The optimal combination of responses is determined both by their dependence on the sensory stimulus and by their cofluctuations across trials-that is, the noise correlations. Positively correlated noise is considered deleterious, because it limits the coding accuracy of populations of similarly tuned neurons. However, positively correlated fluctuations between differently tuned neurons actually increase coding accuracy, because they allow the common noise to be subtracted without signal loss. This is demonstrated with data recorded from the secondary somatosensory cortex of monkeys performing a vibrotactile discrimination task. The results indicate that positive correlations are not always harmful and may be exploited by cortical networks to enhance the neural representation of features to be discriminated.

Efficient transformation of an auditory population code in a small sensory system.

PubMed

Clemens, Jan; Kutzki, Olaf; Ronacher, Bernhard; Schreiber, Susanne; Wohlgemuth, Sandra

2011-08-16

Optimal coding principles are implemented in many large sensory systems. They include the systematic transformation of external stimuli into a sparse and decorrelated neuronal representation, enabling a flexible readout of stimulus properties. Are these principles also applicable to size-constrained systems, which have to rely on a limited number of neurons and may only have to fulfill specific and restricted tasks? We studied this question in an insect system--the early auditory pathway of grasshoppers. Grasshoppers use genetically fixed songs to recognize mates. The first steps of neural processing of songs take place in a small three-layer feed-forward network comprising only a few dozen neurons. We analyzed the transformation of the neural code within this network. Indeed, grasshoppers create a decorrelated and sparse representation, in accordance with optimal coding theory. Whereas the neuronal input layer is best read out as a summed population, a labeled-line population code for temporal features of the song is established after only two processing steps. At this stage, information about song identity is maximal for a population decoder that preserves neuronal identity. We conclude that optimal coding principles do apply to the early auditory system of the grasshopper, despite its size constraints. The inputs, however, are not encoded in a systematic, map-like fashion as in many larger sensory systems. Already at its periphery, part of the grasshopper auditory system seems to focus on behaviorally relevant features, and is in this property more reminiscent of higher sensory areas in vertebrates.

In-situ recording of ionic currents in projection neurons and Kenyon cells in the olfactory pathway of the honeybee

PubMed Central

Rössler, Wolfgang

2018-01-01

The honeybee olfactory pathway comprises an intriguing pattern of convergence and divergence: ~60.000 olfactory sensory neurons (OSN) convey olfactory information on ~900 projection neurons (PN) in the antennal lobe (AL). To transmit this information reliably, PNs employ relatively high spiking frequencies with complex patterns. PNs project via a dual olfactory pathway to the mushroom bodies (MB). This pathway comprises the medial (m-ALT) and the lateral antennal lobe tract (l-ALT). PNs from both tracts transmit information from a wide range of similar odors, but with distinct differences in coding properties. In the MBs, PNs form synapses with many Kenyon cells (KC) that encode odors in a spatially and temporally sparse way. The transformation from complex information coding to sparse coding is a well-known phenomenon in insect olfactory coding. Intrinsic neuronal properties as well as GABAergic inhibition are thought to contribute to this change in odor representation. In the present study, we identified intrinsic neuronal properties promoting coding differences between PNs and KCs using in-situ patch-clamp recordings in the intact brain. We found very prominent K+ currents in KCs clearly differing from the PN currents. This suggests that odor coding differences between PNs and KCs may be caused by differences in their specific ion channel properties. Comparison of ionic currents of m- and l-ALT PNs did not reveal any differences at a qualitative level. PMID:29351552

Leaky gate model: intensity-dependent coding of pain and itch in the spinal cord

PubMed Central

Sun, Shuohao; Xu, Qian; Guo, Changxiong; Guan, Yun; Liu, Qin; Dong, Xinzhong

2017-01-01

SUMMARY Coding of itch versus pain has been heatedly debated for decades. However, the current coding theories (labeled line, intensity and selectivity theory) cannot accommodate all experimental observations. Here we identified a subset of spinal interneurons, labeled by gastrin releasing peptide (Grp), that receive direct synaptic input from both pain and itch primary sensory neurons. When activated, these Grp+ neurons generated rarely-seen simultaneous robust pain and itch responses that were intensity-dependent. Accordingly, we propose a “leaky gate” model, in which Grp+ neurons transmit both itch and weak pain signals, however upon strong painful stimuli the recruitment of endogenous opioids works to close this gate, reducing overwhelming pain generated by parallel pathways. Consistent with our model, loss of these Grp+ neurons increased pain responses while itch was decreased. Our new model serves as an example of non-monotonic coding in the spinal cord and better explains observations in human psychophysical studies. PMID:28231466

Mathematically gifted adolescents mobilize enhanced workspace configuration of theta cortical network during deductive reasoning.

PubMed

Zhang, L; Gan, J Q; Wang, H

2015-03-19

Previous studies have established the importance of the fronto-parietal brain network in the information processing of reasoning. At the level of cortical source analysis, this eletroencepalogram (EEG) study investigates the functional reorganization of the theta-band (4-8Hz) neurocognitive network of mathematically gifted adolescents during deductive reasoning. Depending on the dense increase of long-range phase synchronizations in the reasoning process, math-gifted adolescents show more significant adaptive reorganization and enhanced "workspace" configuration in the theta network as compared with average-ability control subjects. The salient areas are mainly located in the anterior cortical vertices of the fronto-parietal network. Further correlation analyses have shown that the enhanced workspace configuration with respect to the global topological metrics of the theta network in math-gifted subjects is correlated with the intensive frontal midline theta (fm theta) response that is related to strong neural effort for cognitive events. These results suggest that by investing more cognitive resources math-gifted adolescents temporally mobilize an enhanced task-related global neuronal workspace, which is manifested as a highly integrated fronto-parietal information processing network during the reasoning process. Copyright © 2015 IBRO. Published by Elsevier Ltd. All rights reserved.

Remembering the past and imagining the future

PubMed Central

Byrne, Patrick; Becker, Suzanna; Burgess, Neil

2009-01-01

The neural mechanisms underlying spatial cognition are modelled, integrating neuronal, systems and behavioural data, and addressing the relationships between long-term memory, short-term memory and imagery, and between egocentric and allocentric and visual and idiothetic representations. Long-term spatial memory is modeled as attractor dynamics within medial-temporal allocentric representations, and short-term memory as egocentric parietal representations driven by perception, retrieval and imagery, and modulated by directed attention. Both encoding and retrieval/ imagery require translation between egocentric and allocentric representations, mediated by posterior parietal and retrosplenial areas and utilizing head direction representations in Papez’s circuit. Thus hippocampus effectively indexes information by real or imagined location, while Papez’s circuit translates to imagery or from perception according to the direction of view. Modulation of this translation by motor efference allows “spatial updating” of representations, while prefrontal simulated motor efference allows mental exploration. The alternating temporo-parietal flows of information are organized by the theta rhythm. Simulations demonstrate the retrieval and updating of familiar spatial scenes, hemispatial neglect in memory, and the effects on hippocampal place cell firing of lesioned head direction representations and of conflicting visual and ideothetic inputs. PMID:17500630

Decoding the ubiquitous role of microRNAs in neurogenesis.

PubMed

Nampoothiri, Sreekala S; Rajanikant, G K

2017-04-01

Neurogenesis generates fledgling neurons that mature to form an intricate neuronal circuitry. The delusion on adult neurogenesis was far resolved in the past decade and became one of the largely explored domains to identify multifaceted mechanisms bridging neurodevelopment and neuropathology. Neurogenesis encompasses multiple processes including neural stem cell proliferation, neuronal differentiation, and cell fate determination. Each neurogenic process is specifically governed by manifold signaling pathways, several growth factors, coding, and non-coding RNAs. A class of small non-coding RNAs, microRNAs (miRNAs), is ubiquitously expressed in the brain and has emerged to be potent regulators of neurogenesis. It functions by fine-tuning the expression of specific neurogenic gene targets at the post-transcriptional level and modulates the development of mature neurons from neural progenitor cells. Besides the commonly discussed intrinsic factors, the neuronal morphogenesis is also under the control of several extrinsic temporal cues, which in turn are regulated by miRNAs. This review enlightens on dicer controlled switch from neurogenesis to gliogenesis, miRNA regulation of neuronal maturation and the differential expression of miRNAs in response to various extrinsic cues affecting neurogenesis.

Energy-efficient neural information processing in individual neurons and neuronal networks.

PubMed

Yu, Lianchun; Yu, Yuguo

2017-11-01

Brains are composed of networks of an enormous number of neurons interconnected with synapses. Neural information is carried by the electrical signals within neurons and the chemical signals among neurons. Generating these electrical and chemical signals is metabolically expensive. The fundamental issue raised here is whether brains have evolved efficient ways of developing an energy-efficient neural code from the molecular level to the circuit level. Here, we summarize the factors and biophysical mechanisms that could contribute to the energy-efficient neural code for processing input signals. The factors range from ion channel kinetics, body temperature, axonal propagation of action potentials, low-probability release of synaptic neurotransmitters, optimal input and noise, the size of neurons and neuronal clusters, excitation/inhibition balance, coding strategy, cortical wiring, and the organization of functional connectivity. Both experimental and computational evidence suggests that neural systems may use these factors to maximize the efficiency of energy consumption in processing neural signals. Studies indicate that efficient energy utilization may be universal in neuronal systems as an evolutionary consequence of the pressure of limited energy. As a result, neuronal connections may be wired in a highly economical manner to lower energy costs and space. Individual neurons within a network may encode independent stimulus components to allow a minimal number of neurons to represent whole stimulus characteristics efficiently. This basic principle may fundamentally change our view of how billions of neurons organize themselves into complex circuits to operate and generate the most powerful intelligent cognition in nature. © 2017 Wiley Periodicals, Inc. © 2017 Wiley Periodicals, Inc.

Thalamic neuron models encode stimulus information by burst-size modulation

PubMed Central

Elijah, Daniel H.; Samengo, Inés; Montemurro, Marcelo A.

2015-01-01

Thalamic neurons have been long assumed to fire in tonic mode during perceptive states, and in burst mode during sleep and unconsciousness. However, recent evidence suggests that bursts may also be relevant in the encoding of sensory information. Here, we explore the neural code of such thalamic bursts. In order to assess whether the burst code is generic or whether it depends on the detailed properties of each bursting neuron, we analyzed two neuron models incorporating different levels of biological detail. One of the models contained no information of the biophysical processes entailed in spike generation, and described neuron activity at a phenomenological level. The second model represented the evolution of the individual ionic conductances involved in spiking and bursting, and required a large number of parameters. We analyzed the models' input selectivity using reverse correlation methods and information theory. We found that n-spike bursts from both models transmit information by modulating their spike count in response to changes to instantaneous input features, such as slope, phase, amplitude, etc. The stimulus feature that is most efficiently encoded by bursts, however, need not coincide with one of such classical features. We therefore searched for the optimal feature among all those that could be expressed as a linear transformation of the time-dependent input current. We found that bursting neurons transmitted 6 times more information about such more general features. The relevant events in the stimulus were located in a time window spanning ~100 ms before and ~20 ms after burst onset. Most importantly, the neural code employed by the simple and the biologically realistic models was largely the same, implying that the simple thalamic neuron model contains the essential ingredients that account for the computational properties of the thalamic burst code. Thus, our results suggest the n-spike burst code is a general property of thalamic neurons. PMID:26441623

Thalamic neuron models encode stimulus information by burst-size modulation.

PubMed

Elijah, Daniel H; Samengo, Inés; Montemurro, Marcelo A

2015-01-01

Thalamic neurons have been long assumed to fire in tonic mode during perceptive states, and in burst mode during sleep and unconsciousness. However, recent evidence suggests that bursts may also be relevant in the encoding of sensory information. Here, we explore the neural code of such thalamic bursts. In order to assess whether the burst code is generic or whether it depends on the detailed properties of each bursting neuron, we analyzed two neuron models incorporating different levels of biological detail. One of the models contained no information of the biophysical processes entailed in spike generation, and described neuron activity at a phenomenological level. The second model represented the evolution of the individual ionic conductances involved in spiking and bursting, and required a large number of parameters. We analyzed the models' input selectivity using reverse correlation methods and information theory. We found that n-spike bursts from both models transmit information by modulating their spike count in response to changes to instantaneous input features, such as slope, phase, amplitude, etc. The stimulus feature that is most efficiently encoded by bursts, however, need not coincide with one of such classical features. We therefore searched for the optimal feature among all those that could be expressed as a linear transformation of the time-dependent input current. We found that bursting neurons transmitted 6 times more information about such more general features. The relevant events in the stimulus were located in a time window spanning ~100 ms before and ~20 ms after burst onset. Most importantly, the neural code employed by the simple and the biologically realistic models was largely the same, implying that the simple thalamic neuron model contains the essential ingredients that account for the computational properties of the thalamic burst code. Thus, our results suggest the n-spike burst code is a general property of thalamic neurons.

Spatial information outflow from the hippocampal circuit: distributed spatial coding and phase precession in the subiculum.

PubMed

Kim, Steve M; Ganguli, Surya; Frank, Loren M

2012-08-22

Hippocampal place cells convey spatial information through a combination of spatially selective firing and theta phase precession. The way in which this information influences regions like the subiculum that receive input from the hippocampus remains unclear. The subiculum receives direct inputs from area CA1 of the hippocampus and sends divergent output projections to many other parts of the brain, so we examined the firing patterns of rat subicular neurons. We found a substantial transformation in the subicular code for space from sparse to dense firing rate representations along a proximal-distal anatomical gradient: neurons in the proximal subiculum are more similar to canonical, sparsely firing hippocampal place cells, whereas neurons in the distal subiculum have higher firing rates and more distributed spatial firing patterns. Using information theory, we found that the more distributed spatial representation in the subiculum carries, on average, more information about spatial location and context than the sparse spatial representation in CA1. Remarkably, despite the disparate firing rate properties of subicular neurons, we found that neurons at all proximal-distal locations exhibit robust theta phase precession, with similar spiking oscillation frequencies as neurons in area CA1. Our findings suggest that the subiculum is specialized to compress sparse hippocampal spatial codes into highly informative distributed codes suitable for efficient communication to other brain regions. Moreover, despite this substantial compression, the subiculum maintains finer scale temporal properties that may allow it to participate in oscillatory phase coding and spike timing-dependent plasticity in coordination with other regions of the hippocampal circuit.

Theta phase precession and phase selectivity: a cognitive device description of neural coding

NASA Astrophysics Data System (ADS)

Zalay, Osbert C.; Bardakjian, Berj L.

2009-06-01

Information in neural systems is carried by way of phase and rate codes. Neuronal signals are processed through transformative biophysical mechanisms at the cellular and network levels. Neural coding transformations can be represented mathematically in a device called the cognitive rhythm generator (CRG). Incoming signals to the CRG are parsed through a bank of neuronal modes that orchestrate proportional, integrative and derivative transformations associated with neural coding. Mode outputs are then mixed through static nonlinearities to encode (spatio) temporal phase relationships. The static nonlinear outputs feed and modulate a ring device (limit cycle) encoding output dynamics. Small coupled CRG networks were created to investigate coding functionality associated with neuronal phase preference and theta precession in the hippocampus. Phase selectivity was found to be dependent on mode shape and polarity, while phase precession was a product of modal mixing (i.e. changes in the relative contribution or amplitude of mode outputs resulted in shifting phase preference). Nonlinear system identification was implemented to help validate the model and explain response characteristics associated with modal mixing; in particular, principal dynamic modes experimentally derived from a hippocampal neuron were inserted into a CRG and the neuron's dynamic response was successfully cloned. From our results, small CRG networks possessing disynaptic feedforward inhibition in combination with feedforward excitation exhibited frequency-dependent inhibitory-to-excitatory and excitatory-to-inhibitory transitions that were similar to transitions seen in a single CRG with quadratic modal mixing. This suggests nonlinear modal mixing to be a coding manifestation of the effect of network connectivity in shaping system dynamic behavior. We hypothesize that circuits containing disynaptic feedforward inhibition in the nervous system may be candidates for interpreting upstream rate codes to guide downstream processes such as phase precession, because of their demonstrated frequency-selective properties.

Dopamine reward prediction error coding.

PubMed

Schultz, Wolfram

2016-03-01

Reward prediction errors consist of the differences between received and predicted rewards. They are crucial for basic forms of learning about rewards and make us strive for more rewards-an evolutionary beneficial trait. Most dopamine neurons in the midbrain of humans, monkeys, and rodents signal a reward prediction error; they are activated by more reward than predicted (positive prediction error), remain at baseline activity for fully predicted rewards, and show depressed activity with less reward than predicted (negative prediction error). The dopamine signal increases nonlinearly with reward value and codes formal economic utility. Drugs of addiction generate, hijack, and amplify the dopamine reward signal and induce exaggerated, uncontrolled dopamine effects on neuronal plasticity. The striatum, amygdala, and frontal cortex also show reward prediction error coding, but only in subpopulations of neurons. Thus, the important concept of reward prediction errors is implemented in neuronal hardware.

Dopamine reward prediction error coding

PubMed Central

Schultz, Wolfram

2016-01-01

Reward prediction errors consist of the differences between received and predicted rewards. They are crucial for basic forms of learning about rewards and make us strive for more rewards—an evolutionary beneficial trait. Most dopamine neurons in the midbrain of humans, monkeys, and rodents signal a reward prediction error; they are activated by more reward than predicted (positive prediction error), remain at baseline activity for fully predicted rewards, and show depressed activity with less reward than predicted (negative prediction error). The dopamine signal increases nonlinearly with reward value and codes formal economic utility. Drugs of addiction generate, hijack, and amplify the dopamine reward signal and induce exaggerated, uncontrolled dopamine effects on neuronal plasticity. The striatum, amygdala, and frontal cortex also show reward prediction error coding, but only in subpopulations of neurons. Thus, the important concept of reward prediction errors is implemented in neuronal hardware. PMID:27069377

Molecular codes for neuronal individuality and cell assembly in the brain

PubMed Central

Yagi, Takeshi

2012-01-01

The brain contains an enormous, but finite, number of neurons. The ability of this limited number of neurons to produce nearly limitless neural information over a lifetime is typically explained by combinatorial explosion; that is, by the exponential amplification of each neuron's contribution through its incorporation into “cell assemblies” and neural networks. In development, each neuron expresses diverse cellular recognition molecules that permit the formation of the appropriate neural cell assemblies to elicit various brain functions. The mechanism for generating neuronal assemblies and networks must involve molecular codes that give neurons individuality and allow them to recognize one another and join appropriate networks. The extensive molecular diversity of cell-surface proteins on neurons is likely to contribute to their individual identities. The clustered protocadherins (Pcdh) is a large subfamily within the diverse cadherin superfamily. The clustered Pcdh genes are encoded in tandem by three gene clusters, and are present in all known vertebrate genomes. The set of clustered Pcdh genes is expressed in a random and combinatorial manner in each neuron. In addition, cis-tetramers composed of heteromultimeric clustered Pcdh isoforms represent selective binding units for cell-cell interactions. Here I present the mathematical probabilities for neuronal individuality based on the random and combinatorial expression of clustered Pcdh isoforms and their formation of cis-tetramers in each neuron. Notably, clustered Pcdh gene products are known to play crucial roles in correct axonal projections, synaptic formation, and neuronal survival. Their molecular and biological features induce a hypothesis that the diverse clustered Pcdh molecules provide the molecular code by which neuronal individuality and cell assembly permit the combinatorial explosion of networks that supports enormous processing capability and plasticity of the brain. PMID:22518100

Task-phase-specific dynamics of basal forebrain neuronal ensembles

PubMed Central

Tingley, David; Alexander, Andrew S.; Kolbu, Sean; de Sa, Virginia R.; Chiba, Andrea A.; Nitz, Douglas A.

2014-01-01

Cortically projecting basal forebrain neurons play a critical role in learning and attention, and their degeneration accompanies age-related impairments in cognition. Despite the impressive anatomical and cell-type complexity of this system, currently available data suggest that basal forebrain neurons lack complexity in their response fields, with activity primarily reflecting only macro-level brain states such as sleep and wake, onset of relevant stimuli and/or reward obtainment. The current study examined the spiking activity of basal forebrain neuron populations across multiple phases of a selective attention task, addressing, in particular, the issue of complexity in ensemble firing patterns across time. Clustering techniques applied to the full population revealed a large number of distinct categories of task-phase-specific activity patterns. Unique population firing-rate vectors defined each task phase and most categories of task-phase-specific firing had counterparts with opposing firing patterns. An analogous set of task-phase-specific firing patterns was also observed in a population of posterior parietal cortex neurons. Thus, consistent with the known anatomical complexity, basal forebrain population dynamics are capable of differentially modulating their cortical targets according to the unique sets of environmental stimuli, motor requirements, and cognitive processes associated with different task phases. PMID:25309352

Giant multimodal heart motoneurons of Achatina fulica: a new cardioregulatory input in pulmonates.

PubMed

Zhuravlev, V; Bugaj, V; Kodirov, S; Safonova, T; Staruschenko, A

2001-08-01

The regulation of the heartbeat by the two largest neurons, d-VLN and d-RPLN, on the dorsal surface of visceral and right parietal ganglia of Giant African snail, Achatina fulica, was examined. Using the new method of animal preparation, for the first time, discrete biphasic inhibitory-excitatory junction potentials (I-EJPs) in the heart and several muscles of the visceral sac were recorded. The duration of hyperpolarizing phase (H-phase) of biphasic I-EJPs was 269+/-5.6 ms (n=5), which is 2-3 times less than that of the cholinergic inhibitory JPs (682+/-68.5 ms, n=5). The H-phase of I-EJPs was not altered by the application of atropine, picrotoxine, succinylcholinchloride, D-tubocurarine and tetraethylammonium or substitution of Cl(-) ions. Even the low-frequency neuronal discharges (1-2 imp/s) evoked significant facilitation and potentiation of the H-phase. Between the multimodal neurons d-VLN/d-RPLN and mantle or visceral organs there is evidence of direct synaptic connections. These neurons were found to have no axonal branches in the intestinal nerve as once suspected but reach the heart through several other nerves. New giant heart motoneurons do not interact with previously identified cardioregulatory neurons.

Retrieval of long and short lists from long term memory: a functional magnetic resonance imaging study with human subjects.

PubMed

Zysset, S; Müller, K; Lehmann, C; Thöne-Otto, A I; von Cramon, D Y

2001-11-13

Previous studies have shown that reaction time in an item-recognition task with both short and long lists is a quadratic function of list length. This suggests that either different memory retrieval processes are implied for short and long lists or an adaptive process is involved. An event-related functional magnetic resonance imaging study with nine subjects and list lengths varying between 3 and 18 words was conducted to identify the underlying neuronal structures of retrieval from long and short lists. For the retrieval and processing of word-lists a single fronto-parietal network, including premotor, left prefrontal, left precuneal and left parietal regions, was activated. With increasing list length, no additional regions became involved in retrieving information from long-term memory, suggesting that not necessarily different, but highly adaptive retrieval processes are involved.

Developmental Experience Alters Information Coding in Auditory Midbrain and Forebrain Neurons

PubMed Central

Woolley, Sarah M. N.; Hauber, Mark E.; Theunissen, Frederic E.

2010-01-01

In songbirds, species identity and developmental experience shape vocal behavior and behavioral responses to vocalizations. The interaction of species identity and developmental experience may also shape the coding properties of sensory neurons. We tested whether responses of auditory midbrain and forebrain neurons to songs differed between species and between groups of conspecific birds with different developmental exposure to song. We also compared responses of individual neurons to conspecific and heterospecific songs. Zebra and Bengalese finches that were raised and tutored by conspecific birds, and zebra finches that were cross-tutored by Bengalese finches were studied. Single-unit responses to zebra and Bengalese finch songs were recorded and analyzed by calculating mutual information, response reliability, mean spike rate, fluctuations in time-varying spike rate, distributions of time-varying spike rates, and neural discrimination of individual songs. Mutual information quantifies a response’s capacity to encode information about a stimulus. In midbrain and forebrain neurons, mutual information was significantly higher in normal zebra finch neurons than in Bengalese finch and cross-tutored zebra finch neurons, but not between Bengalese finch and cross-tutored zebra finch neurons. Information rate differences were largely due to spike rate differences. Mutual information did not differ between responses to conspecific and heterospecific songs. Therefore, neurons from normal zebra finches encoded more information about songs than did neurons from other birds, but conspecific and heterospecific songs were encoded equally. Neural discrimination of songs and mutual information were highly correlated. Results demonstrate that developmental exposure to vocalizations shapes the information coding properties of songbird auditory neurons. PMID:20039264

Emotion unfolded by motion: a role for parietal lobe in decoding dynamic facial expressions.

PubMed

Sarkheil, Pegah; Goebel, Rainer; Schneider, Frank; Mathiak, Klaus

2013-12-01

Facial expressions convey important emotional and social information and are frequently applied in investigations of human affective processing. Dynamic faces may provide higher ecological validity to examine perceptual and cognitive processing of facial expressions. Higher order processing of emotional faces was addressed by varying the task and virtual face models systematically. Blood oxygenation level-dependent activation was assessed using functional magnetic resonance imaging in 20 healthy volunteers while viewing and evaluating either emotion or gender intensity of dynamic face stimuli. A general linear model analysis revealed that high valence activated a network of motion-responsive areas, indicating that visual motion areas support perceptual coding for the motion-based intensity of facial expressions. The comparison of emotion with gender discrimination task revealed increased activation of inferior parietal lobule, which highlights the involvement of parietal areas in processing of high level features of faces. Dynamic emotional stimuli may help to emphasize functions of the hypothesized 'extended' over the 'core' system for face processing.

Neuronal population coding of perceived and memorized visual features in the lateral prefrontal cortex

PubMed Central

Mendoza-Halliday, Diego; Martinez-Trujillo, Julio C.

2017-01-01

The primate lateral prefrontal cortex (LPFC) encodes visual stimulus features while they are perceived and while they are maintained in working memory. However, it remains unclear whether perceived and memorized features are encoded by the same or different neurons and population activity patterns. Here we record LPFC neuronal activity while monkeys perceive the motion direction of a stimulus that remains visually available, or memorize the direction if the stimulus disappears. We find neurons with a wide variety of combinations of coding strength for perceived and memorized directions: some neurons encode both to similar degrees while others preferentially or exclusively encode either one. Reading out the combined activity of all neurons, a machine-learning algorithm reliably decode the motion direction and determine whether it is perceived or memorized. Our results indicate that a functionally diverse population of LPFC neurons provides a substrate for discriminating between perceptual and mnemonic representations of visual features. PMID:28569756

[Neurodynamic Bases of Imitation Learning and Episodic Memory].

PubMed

Tsukerman, V D

2016-01-01

In this review, three essentially important processes in development of cognitive behavior are considered: knowledge of a spatial environment by means of physical activity, coding and a call of an existential context of episodic memory and imitation learning based on the mirror neural mechanism. The data show that the parietal and frontal system of learning by imitation, allows the developing organism to seize skills of management and motive synergies in perisomatic space, to understand intentions and the purposes of observed actions of other individuals. At the same time a widely distributed parietal and frontal and entorhinal-hippocampal system mediates spatial knowledge and the solution of the navigation tasks important for creation of an existential context of episodic memory.

Predicting spike occurrence and neuronal responsiveness from LFPs in primary somatosensory cortex.

PubMed

Storchi, Riccardo; Zippo, Antonio G; Caramenti, Gian Carlo; Valente, Maurizio; Biella, Gabriele E M

2012-01-01

Local Field Potentials (LFPs) integrate multiple neuronal events like synaptic inputs and intracellular potentials. LFP spatiotemporal features are particularly relevant in view of their applications both in research (e.g. for understanding brain rhythms, inter-areal neural communication and neuronal coding) and in the clinics (e.g. for improving invasive Brain-Machine Interface devices). However the relation between LFPs and spikes is complex and not fully understood. As spikes represent the fundamental currency of neuronal communication this gap in knowledge strongly limits our comprehension of neuronal phenomena underlying LFPs. We investigated the LFP-spike relation during tactile stimulation in primary somatosensory (S-I) cortex in the rat. First we quantified how reliably LFPs and spikes code for a stimulus occurrence. Then we used the information obtained from our analyses to design a predictive model for spike occurrence based on LFP inputs. The model was endowed with a flexible meta-structure whose exact form, both in parameters and structure, was estimated by using a multi-objective optimization strategy. Our method provided a set of nonlinear simple equations that maximized the match between models and true neurons in terms of spike timings and Peri Stimulus Time Histograms. We found that both LFPs and spikes can code for stimulus occurrence with millisecond precision, showing, however, high variability. Spike patterns were predicted significantly above chance for 75% of the neurons analysed. Crucially, the level of prediction accuracy depended on the reliability in coding for the stimulus occurrence. The best predictions were obtained when both spikes and LFPs were highly responsive to the stimuli. Spike reliability is known to depend on neuron intrinsic properties (i.e. on channel noise) and on spontaneous local network fluctuations. Our results suggest that the latter, measured through the LFP response variability, play a dominant role.

Cognitive Control Signals in Posterior Cingulate Cortex

PubMed Central

Hayden, Benjamin Y.; Smith, David V.; Platt, Michael L.

2010-01-01

Efficiently shifting between tasks is a central function of cognitive control. The role of the default network – a constellation of areas with high baseline activity that declines during task performance – in cognitive control remains poorly understood. We hypothesized that task switching demands cognitive control to shift the balance of processing toward the external world, and therefore predicted that switching between the two tasks would require suppression of activity of neurons within the posterior cingulate cortex (CGp). To test this idea, we recorded the activity of single neurons in CGp, a central node in the default network, in monkeys performing two interleaved tasks. As predicted, we found that basal levels of neuronal activity were reduced following a switch from one task to another and gradually returned to pre-switch baseline on subsequent trials. We failed to observe these effects in lateral intraparietal cortex, part of the dorsal fronto-parietal cortical attention network directly connected to CGp. These findings indicate that suppression of neuronal activity in CGp facilitates cognitive control, and suggest that activity in the default network reflects processes that directly compete with control processes elsewhere in the brain. PMID:21160560

Supralinear and Supramodal Integration of Visual and Tactile Signals in Rats: Psychophysics and Neuronal Mechanisms.

PubMed

Nikbakht, Nader; Tafreshiha, Azadeh; Zoccolan, Davide; Diamond, Mathew E

2018-02-07

To better understand how object recognition can be triggered independently of the sensory channel through which information is acquired, we devised a task in which rats judged the orientation of a raised, black and white grating. They learned to recognize two categories of orientation: 0° ± 45° ("horizontal") and 90° ± 45° ("vertical"). Each trial required a visual (V), a tactile (T), or a visual-tactile (VT) discrimination; VT performance was better than that predicted by optimal linear combination of V and T signals, indicating synergy between sensory channels. We examined posterior parietal cortex (PPC) and uncovered key neuronal correlates of the behavioral findings: PPC carried both graded information about object orientation and categorical information about the rat's upcoming choice; single neurons exhibited identical responses under the three modality conditions. Finally, a linear classifier of neuronal population firing replicated the behavioral findings. Taken together, these findings suggest that PPC is involved in the supramodal processing of shape. Copyright © 2018 The Authors. Published by Elsevier Inc. All rights reserved.

Mirror systems.

PubMed

Fogassi, Leonardo; Ferrari, Pier Francesco

2011-01-01

Mirror neurons are a class of visuomotor neurons, discovered in the monkey premotor cortex and in an anatomically connected area of the inferior parietal lobule, that activate both during action execution and action observation. They constitute a circuit dedicated to match actions made by others with the internal motor representations of the observer. It has been proposed that this matching system enables individuals to understand others' behavior and motor intentions. Here we will describe the main features of mirror neurons in monkeys. Then we will present evidence of the presence of a mirror system in humans and of its involvement in several social-cognitive functions, such as imitation, intention, and emotion understanding. This system may have several implications at a cognitive level and could be linked to specific social deficits in humans such as autism. Recent investigations addressed the issue of the plasticity of the mirror neuron system in both monkeys and humans, suggesting also their possible use in rehabilitation. WIREs Cogn Sci 2011 2 22-38 DOI: 10.1002/wcs.89 For further resources related to this article, please visit the WIREs website. Copyright © 2010 John Wiley & Sons, Ltd.

The organization of the posterior parietal cortex devoted to upper limb actions: An fMRI study

PubMed Central

Ferri, Stefania; Rizzolatti, Giacomo

2015-01-01

Abstract The present fMRI study examined whether upper‐limb action classes differing in their motor goal are encoded by different PPC sectors. Action observation was used as a proxy for action execution. Subjects viewed actors performing object‐related (e.g., grasping), skin‐displacing (e.g., rubbing the skin), and interpersonal upper limb actions (e.g., pushing someone). Observation of the three action classes activated a three‐level network including occipito‐temporal, parietal, and premotor cortex. The parietal region common to observing all three action classes was located dorsally to the left intraparietal sulcus (DIPSM/DIPSA border). Regions specific for observing an action class were obtained by combining the interaction between observing action classes and stimulus types with exclusive masking for observing the other classes, while for regions considered preferentially active for a class the interaction was exclusively masked with the regions common to all observed actions. Left putative human anterior intraparietal was specific for observing manipulative actions, and left parietal operculum including putative human SII region, specific for observing skin‐displacing actions. Control experiments demonstrated that this latter activation depended on seeing the skin being moved and not simply on seeing touch. Psychophysiological interactions showed that the two specific parietal regions had similar connectivities. Finally, observing interpersonal actions preferentially activated a dorsal sector of left DIPSA, possibly the homologue of ventral intraparietal coding the impingement of the target person's body into the peripersonal space of the actor. These results support the importance of segregation according to the action class as principle of posterior parietal cortex organization for action observation and by implication for action execution. Hum Brain Mapp 36:3845–3866, 2015. © 2015 The Authors Human Brain Mapping Published by Wiley Periodicals, Inc. PMID:26129732

Cerebral responses to local and global auditory novelty under general anesthesia

PubMed Central

Uhrig, Lynn; Janssen, David; Dehaene, Stanislas; Jarraya, Béchir

2017-01-01

Primate brains can detect a variety of unexpected deviations in auditory sequences. The local-global paradigm dissociates two hierarchical levels of auditory predictive coding by examining the brain responses to first-order (local) and second-order (global) sequence violations. Using the macaque model, we previously demonstrated that, in the awake state, local violations cause focal auditory responses while global violations activate a brain circuit comprising prefrontal, parietal and cingulate cortices. Here we used the same local-global auditory paradigm to clarify the encoding of the hierarchical auditory regularities in anesthetized monkeys and compared their brain responses to those obtained in the awake state as measured with fMRI. Both, propofol, a GABAA-agonist, and ketamine, an NMDA-antagonist, left intact or even enhanced the cortical response to auditory inputs. The local effect vanished during propofol anesthesia and shifted spatially during ketamine anesthesia compared with wakefulness. Under increasing levels of propofol, we observed a progressive disorganization of the global effect in prefrontal, parietal and cingulate cortices and its complete suppression under ketamine anesthesia. Anesthesia also suppressed thalamic activations to the global effect. These results suggest that anesthesia preserves initial auditory processing, but disturbs both short-term and long-term auditory predictive coding mechanisms. The disorganization of auditory novelty processing under anesthesia relates to a loss of thalamic responses to novelty and to a disruption of higher-order functional cortical networks in parietal, prefrontal and cingular cortices. PMID:27502046

Hierarchical differences in population coding within auditory cortex.

PubMed

Downer, Joshua D; Niwa, Mamiko; Sutter, Mitchell L

2017-08-01

Most models of auditory cortical (AC) population coding have focused on primary auditory cortex (A1). Thus our understanding of how neural coding for sounds progresses along the cortical hierarchy remains obscure. To illuminate this, we recorded from two AC fields: A1 and middle lateral belt (ML) of rhesus macaques. We presented amplitude-modulated (AM) noise during both passive listening and while the animals performed an AM detection task ("active" condition). In both fields, neurons exhibit monotonic AM-depth tuning, with A1 neurons mostly exhibiting increasing rate-depth functions and ML neurons approximately evenly distributed between increasing and decreasing functions. We measured noise correlation ( r noise ) between simultaneously recorded neurons and found that whereas engagement decreased average r noise in A1, engagement increased average r noise in ML. This finding surprised us, because attentive states are commonly reported to decrease average r noise We analyzed the effect of r noise on AM coding in both A1 and ML and found that whereas engagement-related shifts in r noise in A1 enhance AM coding, r noise shifts in ML have little effect. These results imply that the effect of r noise differs between sensory areas, based on the distribution of tuning properties among the neurons within each population. A possible explanation of this is that higher areas need to encode nonsensory variables (e.g., attention, choice, and motor preparation), which impart common noise, thus increasing r noise Therefore, the hierarchical emergence of r noise -robust population coding (e.g., as we observed in ML) enhances the ability of sensory cortex to integrate cognitive and sensory information without a loss of sensory fidelity. NEW & NOTEWORTHY Prevailing models of population coding of sensory information are based on a limited subset of neural structures. An important and under-explored question in neuroscience is how distinct areas of sensory cortex differ in their population coding strategies. In this study, we compared population coding between primary and secondary auditory cortex. Our findings demonstrate striking differences between the two areas and highlight the importance of considering the diversity of neural structures as we develop models of population coding. Copyright © 2017 the American Physiological Society.

Sensory Coding by Cerebellar Mossy Fibres through Inhibition-Driven Phase Resetting and Synchronisation

PubMed Central

Holtzman, Tahl; Jörntell, Henrik

2011-01-01

Temporal coding of spike-times using oscillatory mechanisms allied to spike-time dependent plasticity could represent a powerful mechanism for neuronal communication. However, it is unclear how temporal coding is constructed at the single neuronal level. Here we investigate a novel class of highly regular, metronome-like neurones in the rat brainstem which form a major source of cerebellar afferents. Stimulation of sensory inputs evoked brief periods of inhibition that interrupted the regular firing of these cells leading to phase-shifted spike-time advancements and delays. Alongside phase-shifting, metronome cells also behaved as band-pass filters during rhythmic sensory stimulation, with maximal spike-stimulus synchronisation at frequencies close to the idiosyncratic firing frequency of each neurone. Phase-shifting and band-pass filtering serve to temporally align ensembles of metronome cells, leading to sustained volleys of near-coincident spike-times, thereby transmitting synchronised sensory information to downstream targets in the cerebellar cortex. PMID:22046297

Neuronal cell fate specification by the molecular convergence of different spatio-temporal cues on a common initiator terminal selector gene

PubMed Central

Stratmann, Johannes

2017-01-01

The extensive genetic regulatory flows underlying specification of different neuronal subtypes are not well understood at the molecular level. The Nplp1 neuropeptide neurons in the developing Drosophila nerve cord belong to two sub-classes; Tv1 and dAp neurons, generated by two distinct progenitors. Nplp1 neurons are specified by spatial cues; the Hox homeotic network and GATA factor grn, and temporal cues; the hb -> Kr -> Pdm -> cas -> grh temporal cascade. These spatio-temporal cues combine into two distinct codes; one for Tv1 and one for dAp neurons that activate a common terminal selector feedforward cascade of col -> ap/eya -> dimm -> Nplp1. Here, we molecularly decode the specification of Nplp1 neurons, and find that the cis-regulatory organization of col functions as an integratory node for the different spatio-temporal combinatorial codes. These findings may provide a logical framework for addressing spatio-temporal control of neuronal sub-type specification in other systems. PMID:28414802

Sparse bursts optimize information transmission in a multiplexed neural code.

PubMed

Naud, Richard; Sprekeler, Henning

2018-06-22

Many cortical neurons combine the information ascending and descending the cortical hierarchy. In the classical view, this information is combined nonlinearly to give rise to a single firing-rate output, which collapses all input streams into one. We analyze the extent to which neurons can simultaneously represent multiple input streams by using a code that distinguishes spike timing patterns at the level of a neural ensemble. Using computational simulations constrained by experimental data, we show that cortical neurons are well suited to generate such multiplexing. Interestingly, this neural code maximizes information for short and sparse bursts, a regime consistent with in vivo recordings. Neurons can also demultiplex this information, using specific connectivity patterns. The anatomy of the adult mammalian cortex suggests that these connectivity patterns are used by the nervous system to maintain sparse bursting and optimal multiplexing. Contrary to firing-rate coding, our findings indicate that the physiology and anatomy of the cortex may be interpreted as optimizing the transmission of multiple independent signals to different targets. Copyright © 2018 the Author(s). Published by PNAS.

Data-driven inference of network connectivity for modeling the dynamics of neural codes in the insect antennal lobe

PubMed Central

Shlizerman, Eli; Riffell, Jeffrey A.; Kutz, J. Nathan

2014-01-01

The antennal lobe (AL), olfactory processing center in insects, is able to process stimuli into distinct neural activity patterns, called olfactory neural codes. To model their dynamics we perform multichannel recordings from the projection neurons in the AL driven by different odorants. We then derive a dynamic neuronal network from the electrophysiological data. The network consists of lateral-inhibitory neurons and excitatory neurons (modeled as firing-rate units), and is capable of producing unique olfactory neural codes for the tested odorants. To construct the network, we (1) design a projection, an odor space, for the neural recording from the AL, which discriminates between distinct odorants trajectories (2) characterize scent recognition, i.e., decision-making based on olfactory signals and (3) infer the wiring of the neural circuit, the connectome of the AL. We show that the constructed model is consistent with biological observations, such as contrast enhancement and robustness to noise. The study suggests a data-driven approach to answer a key biological question in identifying how lateral inhibitory neurons can be wired to excitatory neurons to permit robust activity patterns. PMID:25165442

Cracking Taste Codes by Tapping into Sensory Neuron Impulse Traffic

PubMed Central

Frank, Marion E.; Lundy, Robert F.; Contreras, Robert J.

2008-01-01

Insights into the biological basis for mammalian taste quality coding began with electrophysiological recordings from “taste” nerves and this technique continues to produce essential information today. Chorda tympani (geniculate ganglion) neurons, which are particularly involved in taste quality discrimination, are specialists or generalists. Specialists respond to stimuli characterized by a single taste quality as defined by behavioral cross-generalization in conditioned taste tests. Generalists respond to electrolytes that elicit multiple aversive qualities. Na+-salt (N) specialists in rodents and sweet-stimulus (S) specialists in multiple orders of mammals are well-characterized. Specialists are associated with species’ nutritional needs and their activation is known to be malleable by internal physiological conditions and contaminated external caloric sources. S specialists, associated with the heterodimeric G-protein coupled receptor: T1R, and N specialists, associated with the epithelial sodium channel: ENaC, are consistent with labeled line coding from taste bud to afferent neuron. Yet, S-specialist neurons and behavior are less specific thanT1R2-3 in encompassing glutamate and E generalist neurons are much less specific than a candidate, PDK TRP channel, sour receptor in encompassing salts and bitter stimuli. Specialist labeled lines for nutrients and generalist patterns for aversive electrolytes may be transmitting taste information to the brain side by side. However, specific roles of generalists in taste quality coding may be resolved by selecting stimuli and stimulus levels found in natural situations. T2Rs, participating in reflexes via the glossopharynygeal nerve, became highly diversified in mammalian phylogenesis as they evolved to deal with dangerous substances within specific environmental niches. Establishing the information afferent neurons traffic to the brain about natural taste stimuli imbedded in dynamic complex mixtures will ultimately “crack taste codes.” PMID:18824076

Emergence of an abstract categorical code enabling the discrimination of temporally structured tactile stimuli

PubMed Central

Rossi-Pool, Román; Salinas, Emilio; Zainos, Antonio; Alvarez, Manuel; Vergara, José; Parga, Néstor; Romo, Ranulfo

2016-01-01

The problem of neural coding in perceptual decision making revolves around two fundamental questions: (i) How are the neural representations of sensory stimuli related to perception, and (ii) what attributes of these neural responses are relevant for downstream networks, and how do they influence decision making? We studied these two questions by recording neurons in primary somatosensory (S1) and dorsal premotor (DPC) cortex while trained monkeys reported whether the temporal pattern structure of two sequential vibrotactile stimuli (of equal mean frequency) was the same or different. We found that S1 neurons coded the temporal patterns in a literal way and only during the stimulation periods and did not reflect the monkeys’ decisions. In contrast, DPC neurons coded the stimulus patterns as broader categories and signaled them during the working memory, comparison, and decision periods. These results show that the initial sensory representation is transformed into an intermediate, more abstract categorical code that combines past and present information to ultimately generate a perceptually informed choice. PMID:27872293

Functional differentiation of macaque visual temporal cortical neurons using a parametric action space.

PubMed

Vangeneugden, Joris; Pollick, Frank; Vogels, Rufin

2009-03-01

Neurons in the rostral superior temporal sulcus (STS) are responsive to displays of body movements. We employed a parametric action space to determine how similarities among actions are represented by visual temporal neurons and how form and motion information contributes to their responses. The stimulus space consisted of a stick-plus-point-light figure performing arm actions and their blends. Multidimensional scaling showed that the responses of temporal neurons represented the ordinal similarity between these actions. Further tests distinguished neurons responding equally strongly to static presentations and to actions ("snapshot" neurons), from those responding much less strongly to static presentations, but responding well when motion was present ("motion" neurons). The "motion" neurons were predominantly found in the upper bank/fundus of the STS, and "snapshot" neurons in the lower bank of the STS and inferior temporal convexity. Most "motion" neurons showed strong response modulation during the course of an action, thus responding to action kinematics. "Motion" neurons displayed a greater average selectivity for these simple arm actions than did "snapshot" neurons. We suggest that the "motion" neurons code for visual kinematics, whereas the "snapshot" neurons code for form/posture, and that both can contribute to action recognition, in agreement with computation models of action recognition.

Cerebellar Nuclear Neurons Use Time and Rate Coding to Transmit Purkinje Neuron Pauses.

PubMed

Sudhakar, Shyam Kumar; Torben-Nielsen, Benjamin; De Schutter, Erik

2015-12-01

Neurons of the cerebellar nuclei convey the final output of the cerebellum to their targets in various parts of the brain. Within the cerebellum their direct upstream connections originate from inhibitory Purkinje neurons. Purkinje neurons have a complex firing pattern of regular spikes interrupted by intermittent pauses of variable length. How can the cerebellar nucleus process this complex input pattern? In this modeling study, we investigate different forms of Purkinje neuron simple spike pause synchrony and its influence on candidate coding strategies in the cerebellar nuclei. That is, we investigate how different alignments of synchronous pauses in synthetic Purkinje neuron spike trains affect either time-locking or rate-changes in the downstream nuclei. We find that Purkinje neuron synchrony is mainly represented by changes in the firing rate of cerebellar nuclei neurons. Pause beginning synchronization produced a unique effect on nuclei neuron firing, while the effect of pause ending and pause overlapping synchronization could not be distinguished from each other. Pause beginning synchronization produced better time-locking of nuclear neurons for short length pauses. We also characterize the effect of pause length and spike jitter on the nuclear neuron firing. Additionally, we find that the rate of rebound responses in nuclear neurons after a synchronous pause is controlled by the firing rate of Purkinje neurons preceding it.

Higher theta and alpha1 coherence when listening to Vedic recitation compared to coherence during Transcendental Meditation practice.

PubMed

Travis, Frederick; Parim, Niyazi; Shrivastava, Amrita

2017-03-01

This study compared subjective experiences and EEG patterns in 37 subjects when listening to live Vedic recitation and when practicing Transcendental Meditation (TM). Content analysis of experiences when listening to Vedic recitation yielded three higher-order code. Experiences during Vedic recitation were: (1) deeper than during TM practice; (2) experienced as an inner process; and (3) characterized by lively silence. EEG patterns support these higher-order codes. Theta2 and alpha1 frontal, parietal, and frontal-parietal coherence were significantly higher when listening to Vedic recitation, than during TM practice. Theta2 coherence is seen when attending to internal mental processes. Higher theta2 coherence supports subjects' descriptions that the Vedic recitations were "not external sounds but internal vibrations." Alpha1 coherence is reported during pure consciousness experiences during TM practice. Higher alpha1 coherence supports subjects' descriptions that they "experienced a depth of experience, rarely experienced even during deep TM practice." These data support the utility of listening to Vedic recitation to culture deep inner experiences. Copyright © 2017 Elsevier Inc. All rights reserved.

Neural networks involved in artistic creativity.

PubMed

Kowatari, Yasuyuki; Lee, Seung Hee; Yamamura, Hiromi; Nagamori, Yusuke; Levy, Pierre; Yamane, Shigeru; Yamamoto, Miyuki

2009-05-01

Creativity has been proposed to be either the result of solely right hemisphere processes or of interhemispheric interactions. Little information is available, however, concerning the neuronal foundations of creativity. In this study, we introduced a new artistic task, designing a new tool (a pen), which let us quantitatively evaluate creativity by three indices of originality. These scores were analyzed in combination with brain activities measured by functional magnetic resonance imaging (fMRI). The results were compared between subjects who had been formally trained in design (experts) and novice subjects. In the experts, creativity was quantitatively correlated with the degree of dominance of the right prefrontal cortex over that of the left, but not with that of the right or left prefrontal cortex alone. In contrast, in novice subjects, only a negative correlation with creativity was observed in the bilateral inferior parietal cortex. We introduced structure equation modeling to analyze the interactions among these four brain areas and originality indices. The results predicted that training exerts a direct effect on the left parietal cortex. Additionally, as a result of the indirect effects, the activity of the right prefrontal cortex was facilitated, and the left prefrontal and right parietal cortices were suppressed. Our results supported the hypothesis that training increases creativity via reorganized intercortical interactions. (c) 2008 Wiley-Liss, Inc.

Visuokinesthetic Perception of Hand Movement is Mediated by Cerebro–Cerebellar Interaction between the Left Cerebellum and Right Parietal Cortex

PubMed Central

Hagura, Nobuhiro; Oouchida, Yutaka; Aramaki, Yu; Okada, Tomohisa; Matsumura, Michikazu; Sadato, Norihiro

2009-01-01

Combination of visual and kinesthetic information is essential to perceive bodily movements. We conducted behavioral and functional magnetic resonance imaging experiments to investigate the neuronal correlates of visuokinesthetic combination in perception of hand movement. Participants experienced illusory flexion movement of their hand elicited by tendon vibration while they viewed video-recorded flexion (congruent: CONG) or extension (incongruent: INCONG) motions of their hand. The amount of illusory experience was graded by the visual velocities only when visual information regarding hand motion was concordant with kinesthetic information (CONG). The left posterolateral cerebellum was specifically recruited under the CONG, and this left cerebellar activation was consistent for both left and right hands. The left cerebellar activity reflected the participants' intensity of illusory hand movement under the CONG, and we further showed that coupling of activity between the left cerebellum and the “right” parietal cortex emerges during this visuokinesthetic combination/perception. The “left” cerebellum, working with the anatomically connected high-order bodily region of the “right” parietal cortex, participates in online combination of exteroceptive (vision) and interoceptive (kinesthesia) information to perceive hand movement. The cerebro–cerebellar interaction may underlie updating of one's “body image,” when perceiving bodily movement from visual and kinesthetic information. PMID:18453537

Vocalization frequency and duration are coded in separate hindbrain nuclei.

PubMed

Chagnaud, Boris P; Baker, Robert; Bass, Andrew H

2011-06-14

Temporal patterning is an essential feature of neural networks producing precisely timed behaviours such as vocalizations that are widely used in vertebrate social communication. Here we show that intrinsic and network properties of separate hindbrain neuronal populations encode the natural call attributes of frequency and duration in vocal fish. Intracellular structure/function analyses indicate that call duration is encoded by a sustained membrane depolarization in vocal prepacemaker neurons that innervate downstream pacemaker neurons. Pacemaker neurons, in turn, encode call frequency by rhythmic, ultrafast oscillations in their membrane potential. Pharmacological manipulations show prepacemaker activity to be independent of pacemaker function, thus accounting for natural variation in duration which is the predominant feature distinguishing call types. Prepacemaker neurons also innervate key hindbrain auditory nuclei thereby effectively serving as a call-duration corollary discharge. We propose that premotor compartmentalization of neurons coding distinct acoustic attributes is a fundamental trait of hindbrain vocal pattern generators among vertebrates.

Vocalization frequency and duration are coded in separate hindbrain nuclei

PubMed Central

Chagnaud, Boris P.; Baker, Robert; Bass, Andrew H.

2011-01-01

Temporal patterning is an essential feature of neural networks producing precisely timed behaviours such as vocalizations that are widely used in vertebrate social communication. Here we show that intrinsic and network properties of separate hindbrain neuronal populations encode the natural call attributes of frequency and duration in vocal fish. Intracellular structure/function analyses indicate that call duration is encoded by a sustained membrane depolarization in vocal prepacemaker neurons that innervate downstream pacemaker neurons. Pacemaker neurons, in turn, encode call frequency by rhythmic, ultrafast oscillations in their membrane potential. Pharmacological manipulations show prepacemaker activity to be independent of pacemaker function, thus accounting for natural variation in duration which is the predominant feature distinguishing call types. Prepacemaker neurons also innervate key hindbrain auditory nuclei thereby effectively serving as a call-duration corollary discharge. We propose that premotor compartmentalization of neurons coding distinct acoustic attributes is a fundamental trait of hindbrain vocal pattern generators among vertebrates. PMID:21673667

Odor-evoked inhibition of olfactory sensory neurons drives olfactory perception in Drosophila.

PubMed

Cao, Li-Hui; Yang, Dong; Wu, Wei; Zeng, Xiankun; Jing, Bi-Yang; Li, Meng-Tong; Qin, Shanshan; Tang, Chao; Tu, Yuhai; Luo, Dong-Gen

2017-11-07

Inhibitory response occurs throughout the nervous system, including the peripheral olfactory system. While odor-evoked excitation in peripheral olfactory cells is known to encode odor information, the molecular mechanism and functional roles of odor-evoked inhibition remain largely unknown. Here, we examined Drosophila olfactory sensory neurons and found that inhibitory odors triggered outward receptor currents by reducing the constitutive activities of odorant receptors, inhibiting the basal spike firing in olfactory sensory neurons. Remarkably, this odor-evoked inhibition of olfactory sensory neurons elicited by itself a full range of olfactory behaviors from attraction to avoidance, as did odor-evoked olfactory sensory neuron excitation. These results indicated that peripheral inhibition is comparable to excitation in encoding sensory signals rather than merely regulating excitation. Furthermore, we demonstrated that a bidirectional code with both odor-evoked inhibition and excitation in single olfactory sensory neurons increases the odor-coding capacity, providing a means of efficient sensory encoding.

Neuropeptide gene expression in brain is differentially regulated by midbrain dopamine neurons.

PubMed

Lindefors, N; Brené, S; Herrera-Marschitz, M; Persson, H

1990-01-01

In situ hybridization was used to study the expression of prepro-neuropeptide Y (NPY), preprosomatostatin (SOM), preprotachykinin (PPT) and preprocholecystokinin (CCK) mRNA in caudate-putamen and frontoparietal cortex of rat brain with unilateral lesion of midbrain dopamine neurons. Neurons expressing NPY and SOM mRNA showed a similar distribution and the expression of both NPY and SOM appears to be regulated by dopamine in a similar fashion. Following a dopamine deafferentation, the numerical density of both NPY and SOM mRNA producing neurons almost doubled in the lesioned caudate-putamen with no change in the average grain density over positive neurons. Hence, in the intact caudate-putamen dopamine appears to suppress expression of these two neuropeptide genes leading to an activation of both NPY and SOM mRNA expression in many non- or low-expressing neurons when the level of dopamine is decreased. In the fronto-parietal cortex, on the other hand, dopamine appears to stimulate NPY and SOM gene expression. Thus, in the absence of dopamine about half of the NPY positive neurons disappeared. However, for SOM the number of positive neurons did not change, but rather most positive neurons appeared to have down-regulated their SOM mRNA expression. No evidence was found for a change in CCK mRNA expression by the dopamine deafferentation, while PPT mRNA expression decreased in the deafferented caudate-putamen. Consequently, dopamine exerts dissimilar effects on the expression of different neuropeptide genes, that in turn do not respond in the same way in different brain regions.

[Mirror neurons: from anatomy to pathophysiological and therapeutic implications].

PubMed

Mathon, B

2013-04-01

Mirror neurons are a special class of neurons discovered in the 1990s. They respond when we perform an action and also when we see someone else perform that action. They play a role in the pathophysiology of some neuropsychiatric diseases. Mirror neurons have been identified in humans: in Broca's area and the inferior parietal cortex. Their responses are qualitative and selective depending on the observed action. Emotions (including disgust) and empathy seem to operate according to a mirror mechanism. Indeed, the mirror system allows us to encode the sensory experience and to simulate the emotional state of others. This results in our improved identification of the emotions in others. Additionally, mirror neurons can encode an observed action in motor stimuli and allow its reproduction; thus, they are involved in imitation and learning. Current studies are assessing the role of mirror neurons in the pathopysiology of social-behavior disorders, including autism and schizophrenia. Understanding this mirror system will allow us to develop psychotherapy practices based on empathic resonance between the patient and the therapist. Also, some authors report that a passive rehabilitation technique, based on stimulation of the mirror-neuron system, has a beneficial effect in the treatment of patients with post-stroke motor deficits. Mirror neurons are an anatomical entity that enables improved understanding of behavior and emotions, and serves as a base for developing new cognitive therapies. Additional studies are needed to clarify the exact role of this neuronal system in social cognition and its role in the development of some neuropsychiatric diseases. Copyright © 2013 Elsevier Masson SAS. All rights reserved.

Reshaping the brain after stroke: The effect of prismatic adaptation in patients with right brain damage.

PubMed

Crottaz-Herbette, Sonia; Fornari, Eleonora; Notter, Michael P; Bindschaedler, Claire; Manzoni, Laura; Clarke, Stephanie

2017-09-01

Prismatic adaptation has been repeatedly reported to alleviate neglect symptoms; in normal subjects, it was shown to enhance the representation of the left visual space within the left inferior parietal cortex. Our study aimed to determine in humans whether similar compensatory mechanisms underlie the beneficial effect of prismatic adaptation in neglect. Fifteen patients with right hemispheric lesions and 11 age-matched controls underwent a prismatic adaptation session which was preceded and followed by fMRI using a visual detection task. In patients, the prismatic adaptation session improved the accuracy of target detection in the left and central space and enhanced the representation of this visual space within the left hemisphere in parts of the temporal convexity, inferior parietal lobule and prefrontal cortex. Across patients, the increase in neuronal activation within the temporal regions correlated with performance improvements in this visual space. In control subjects, prismatic adaptation enhanced the representation of the left visual space within the left inferior parietal lobule and decreased it within the left temporal cortex. Thus, a brief exposure to prismatic adaptation enhances, both in patients and in control subjects, the competence of the left hemisphere for the left space, but the regions extended beyond the inferior parietal lobule to the temporal convexity in patients. These results suggest that the left hemisphere provides compensatory mechanisms in neglect by assuming the representation of the whole space within the ventral attentional system. The rapidity of the change suggests that the underlying mechanism relies on uncovering pre-existing synaptic connections. Copyright © 2017 Elsevier Ltd. All rights reserved.

The mirror neuron system and the strange case of Broca's area.

PubMed

Cerri, Gabriella; Cabinio, Monia; Blasi, Valeria; Borroni, Paola; Iadanza, Antonella; Fava, Enrica; Fornia, Luca; Ferpozzi, Valentina; Riva, Marco; Casarotti, Alessandra; Martinelli Boneschi, Filippo; Falini, Andrea; Bello, Lorenzo

2015-03-01

Mirror neurons, originally described in the monkey premotor area F5, are embedded in a frontoparietal network for action execution and observation. A similar Mirror Neuron System (MNS) exists in humans, including precentral gyrus, inferior parietal lobule, and superior temporal sulcus. Controversial is the inclusion of Broca's area, as homologous to F5, a relevant issue in light of the mirror hypothesis of language evolution, which postulates a key role of Broca's area in action/speech perception/production. We assess "mirror" properties of this area by combining neuroimaging and intraoperative neurophysiological techniques. Our results show that Broca's area is minimally involved in action observation and has no motor output on hand or phonoarticulatory muscles, challenging its inclusion in the MNS. The presence of these functions in premotor BA6 makes this area the likely homologue of F5 suggesting that the MNS may be involved in the representation of articulatory rather than semantic components of speech. © 2014 Wiley Periodicals, Inc.

Computing by robust transience: How the fronto-parietal network performs sequential category-based decisions

PubMed Central

Chaisangmongkon, Warasinee; Swaminathan, Sruthi K.; Freedman, David J.; Wang, Xiao-Jing

2017-01-01

Summary Decision making involves dynamic interplay between internal judgements and external perception, which has been investigated in delayed match-to-category (DMC) experiments. Our analysis of neural recordings shows that, during DMC tasks, LIP and PFC neurons demonstrate mixed, time-varying, and heterogeneous selectivity, but previous theoretical work has not established the link between these neural characteristics and population-level computations. We trained a recurrent network model to perform DMC tasks and found that the model can remarkably reproduce key features of neuronal selectivity at the single-neuron and population levels. Analysis of the trained networks elucidates that robust transient trajectories of the neural population are the key driver of sequential categorical decisions. The directions of trajectories are governed by network self-organized connectivity, defining a ‘neural landscape’, consisting of a task-tailored arrangement of slow states and dynamical tunnels. With this model, we can identify functionally-relevant circuit motifs and generalize the framework to solve other categorization tasks. PMID:28334612

Cross-frequency synchronization connects networks of fast and slow oscillations during visual working memory maintenance.

PubMed

Siebenhühner, Felix; Wang, Sheng H; Palva, J Matias; Palva, Satu

2016-09-26

Neuronal activity in sensory and fronto-parietal (FP) areas underlies the representation and attentional control, respectively, of sensory information maintained in visual working memory (VWM). Within these regions, beta/gamma phase-synchronization supports the integration of sensory functions, while synchronization in theta/alpha bands supports the regulation of attentional functions. A key challenge is to understand which mechanisms integrate neuronal processing across these distinct frequencies and thereby the sensory and attentional functions. We investigated whether such integration could be achieved by cross-frequency phase synchrony (CFS). Using concurrent magneto- and electroencephalography, we found that CFS was load-dependently enhanced between theta and alpha-gamma and between alpha and beta-gamma oscillations during VWM maintenance among visual, FP, and dorsal attention (DA) systems. CFS also connected the hubs of within-frequency-synchronized networks and its strength predicted individual VWM capacity. We propose that CFS integrates processing among synchronized neuronal networks from theta to gamma frequencies to link sensory and attentional functions.

Predicting Spike Occurrence and Neuronal Responsiveness from LFPs in Primary Somatosensory Cortex

PubMed Central

Storchi, Riccardo; Zippo, Antonio G.; Caramenti, Gian Carlo; Valente, Maurizio; Biella, Gabriele E. M.

2012-01-01

Local Field Potentials (LFPs) integrate multiple neuronal events like synaptic inputs and intracellular potentials. LFP spatiotemporal features are particularly relevant in view of their applications both in research (e.g. for understanding brain rhythms, inter-areal neural communication and neronal coding) and in the clinics (e.g. for improving invasive Brain-Machine Interface devices). However the relation between LFPs and spikes is complex and not fully understood. As spikes represent the fundamental currency of neuronal communication this gap in knowledge strongly limits our comprehension of neuronal phenomena underlying LFPs. We investigated the LFP-spike relation during tactile stimulation in primary somatosensory (S-I) cortex in the rat. First we quantified how reliably LFPs and spikes code for a stimulus occurrence. Then we used the information obtained from our analyses to design a predictive model for spike occurrence based on LFP inputs. The model was endowed with a flexible meta-structure whose exact form, both in parameters and structure, was estimated by using a multi-objective optimization strategy. Our method provided a set of nonlinear simple equations that maximized the match between models and true neurons in terms of spike timings and Peri Stimulus Time Histograms. We found that both LFPs and spikes can code for stimulus occurrence with millisecond precision, showing, however, high variability. Spike patterns were predicted significantly above chance for 75% of the neurons analysed. Crucially, the level of prediction accuracy depended on the reliability in coding for the stimulus occurrence. The best predictions were obtained when both spikes and LFPs were highly responsive to the stimuli. Spike reliability is known to depend on neuron intrinsic properties (i.e. on channel noise) and on spontaneous local network fluctuations. Our results suggest that the latter, measured through the LFP response variability, play a dominant role. PMID:22586452

A θ-γ oscillation code for neuronal coordination during motor behavior.

PubMed

Igarashi, Jun; Isomura, Yoshikazu; Arai, Kensuke; Harukuni, Rie; Fukai, Tomoki

2013-11-20

Sequential motor behavior requires a progression of discrete preparation and execution states. However, the organization of state-dependent activity in neuronal ensembles of motor cortex is poorly understood. Here, we recorded neuronal spiking and local field potential activity from rat motor cortex during reward-motivated movement and observed robust behavioral state-dependent coordination between neuronal spiking, γ oscillations, and θ oscillations. Slow and fast γ oscillations appeared during distinct movement states and entrained neuronal firing. γ oscillations, in turn, were coupled to θ oscillations, and neurons encoding different behavioral states fired at distinct phases of θ in a highly layer-dependent manner. These findings indicate that θ and nested dual band γ oscillations serve as the temporal structure for the selection of a conserved set of functional channels in motor cortical layer activity during animal movement. Furthermore, these results also suggest that cross-frequency couplings between oscillatory neuronal ensemble activities are part of the general coding mechanism in cortex.

Conserved mechanisms of vocalization coding in mammalian and songbird auditory midbrain.

PubMed

Woolley, Sarah M N; Portfors, Christine V

2013-11-01

The ubiquity of social vocalizations among animals provides the opportunity to identify conserved mechanisms of auditory processing that subserve communication. Identifying auditory coding properties that are shared across vocal communicators will provide insight into how human auditory processing leads to speech perception. Here, we compare auditory response properties and neural coding of social vocalizations in auditory midbrain neurons of mammalian and avian vocal communicators. The auditory midbrain is a nexus of auditory processing because it receives and integrates information from multiple parallel pathways and provides the ascending auditory input to the thalamus. The auditory midbrain is also the first region in the ascending auditory system where neurons show complex tuning properties that are correlated with the acoustics of social vocalizations. Single unit studies in mice, bats and zebra finches reveal shared principles of auditory coding including tonotopy, excitatory and inhibitory interactions that shape responses to vocal signals, nonlinear response properties that are important for auditory coding of social vocalizations and modulation tuning. Additionally, single neuron responses in the mouse and songbird midbrain are reliable, selective for specific syllables, and rely on spike timing for neural discrimination of distinct vocalizations. We propose that future research on auditory coding of vocalizations in mouse and songbird midbrain neurons adopt similar experimental and analytical approaches so that conserved principles of vocalization coding may be distinguished from those that are specialized for each species. This article is part of a Special Issue entitled "Communication Sounds and the Brain: New Directions and Perspectives". Copyright © 2013 Elsevier B.V. All rights reserved.

Enhanced Sensitivity to Rapid Input Fluctuations by Nonlinear Threshold Dynamics in Neocortical Pyramidal Neurons.

PubMed

Mensi, Skander; Hagens, Olivier; Gerstner, Wulfram; Pozzorini, Christian

2016-02-01

The way in which single neurons transform input into output spike trains has fundamental consequences for network coding. Theories and modeling studies based on standard Integrate-and-Fire models implicitly assume that, in response to increasingly strong inputs, neurons modify their coding strategy by progressively reducing their selective sensitivity to rapid input fluctuations. Combining mathematical modeling with in vitro experiments, we demonstrate that, in L5 pyramidal neurons, the firing threshold dynamics adaptively adjust the effective timescale of somatic integration in order to preserve sensitivity to rapid signals over a broad range of input statistics. For that, a new Generalized Integrate-and-Fire model featuring nonlinear firing threshold dynamics and conductance-based adaptation is introduced that outperforms state-of-the-art neuron models in predicting the spiking activity of neurons responding to a variety of in vivo-like fluctuating currents. Our model allows for efficient parameter extraction and can be analytically mapped to a Generalized Linear Model in which both the input filter--describing somatic integration--and the spike-history filter--accounting for spike-frequency adaptation--dynamically adapt to the input statistics, as experimentally observed. Overall, our results provide new insights on the computational role of different biophysical processes known to underlie adaptive coding in single neurons and support previous theoretical findings indicating that the nonlinear dynamics of the firing threshold due to Na+-channel inactivation regulate the sensitivity to rapid input fluctuations.

Information transmission and detection thresholds in the vestibular nuclei: single neurons vs. population encoding

PubMed Central

Massot, Corentin; Chacron, Maurice J.

2011-01-01

Understanding how sensory neurons transmit information about relevant stimuli remains a major goal in neuroscience. Of particular relevance are the roles of neural variability and spike timing in neural coding. Peripheral vestibular afferents display differential variability that is correlated with the importance of spike timing; regular afferents display little variability and use a timing code to transmit information about sensory input. Irregular afferents, conversely, display greater variability and instead use a rate code. We studied how central neurons within the vestibular nuclei integrate information from both afferent classes by recording from a group of neurons termed vestibular only (VO) that are known to make contributions to vestibulospinal reflexes and project to higher-order centers. We found that, although individual central neurons had sensitivities that were greater than or equal to those of individual afferents, they transmitted less information. In addition, their velocity detection thresholds were significantly greater than those of individual afferents. This is because VO neurons display greater variability, which is detrimental to information transmission and signal detection. Combining activities from multiple VO neurons increased information transmission. However, the information rates were still much lower than those of equivalent afferent populations. Furthermore, combining responses from multiple VO neurons led to lower velocity detection threshold values approaching those measured from behavior (∼2.5 vs. 0.5–1°/s). Our results suggest that the detailed time course of vestibular stimuli encoded by afferents is not transmitted by VO neurons. Instead, they suggest that higher vestibular pathways must integrate information from central vestibular neuron populations to give rise to behaviorally observed detection thresholds. PMID:21307329

Evolution of columns, modules, and domains in the neocortex of primates.

PubMed

Kaas, Jon H

2012-06-26

The specialized regions of neocortex of mammals, called areas, have been divided into smaller functional units called minicolumns, columns, modules, and domains. Here we describe some of these functional subdivisions of areas in primates and suggest when they emerged in mammalian evolution. We distinguish several types of these smaller subdivisions. Minicolumns, vertical arrays of neurons that are more densely interconnected with each other than with laterally neighboring neurons, are present in all cortical areas. Classic columns are defined by a repeating pattern of two or more types of cortex distinguished by having different inputs and neurons with different response properties. Sensory stimuli that continuously vary along a stimulus dimension may activate groups of neurons that vary continuously in location, producing "columns" without specific boundaries. Other groups or columns of cortical neurons are separated by narrow septa of fibers that reflect discontinuities in the receptor sheet. Larger regions of posterior parietal cortex and frontal motor cortex are parts of networks devoted to producing different sequences of movements. We distinguish these larger functionally distinct regions as domains. Columns of several types have evolved independently a number of times. Some of the columns found in primates likely emerged with the first primates, whereas others likely were present in earlier ancestors. The sizes and shapes of columns seem to depend on the balance of neuron activation patterns and molecular signals during development.

Fronto-parietal coding of goal-directed actions performed by artificial agents.

PubMed

Kupferberg, Aleksandra; Iacoboni, Marco; Flanagin, Virginia; Huber, Markus; Kasparbauer, Anna; Baumgartner, Thomas; Hasler, Gregor; Schmidt, Florian; Borst, Christoph; Glasauer, Stefan

2018-03-01

With advances in technology, artificial agents such as humanoid robots will soon become a part of our daily lives. For safe and intuitive collaboration, it is important to understand the goals behind their motor actions. In humans, this process is mediated by changes in activity in fronto-parietal brain areas. The extent to which these areas are activated when observing artificial agents indicates the naturalness and easiness of interaction. Previous studies indicated that fronto-parietal activity does not depend on whether the agent is human or artificial. However, it is unknown whether this activity is modulated by observing grasping (self-related action) and pointing actions (other-related action) performed by an artificial agent depending on the action goal. Therefore, we designed an experiment in which subjects observed human and artificial agents perform pointing and grasping actions aimed at two different object categories suggesting different goals. We found a signal increase in the bilateral inferior parietal lobule and the premotor cortex when tool versus food items were pointed to or grasped by both agents, probably reflecting the association of hand actions with the functional use of tools. Our results show that goal attribution engages the fronto-parietal network not only for observing a human but also a robotic agent for both self-related and social actions. The debriefing after the experiment has shown that actions of human-like artificial agents can be perceived as being goal-directed. Therefore, humans will be able to interact with service robots intuitively in various domains such as education, healthcare, public service, and entertainment. © 2017 Wiley Periodicals, Inc.

Neuronal effects of nicotine during auditory selective attention.

PubMed

Smucny, Jason; Olincy, Ann; Eichman, Lindsay S; Tregellas, Jason R

2015-06-01

Although the attention-enhancing effects of nicotine have been behaviorally and neurophysiologically well-documented, its localized functional effects during selective attention are poorly understood. In this study, we examined the neuronal effects of nicotine during auditory selective attention in healthy human nonsmokers. We hypothesized to observe significant effects of nicotine in attention-associated brain areas, driven by nicotine-induced increases in activity as a function of increasing task demands. A single-blind, prospective, randomized crossover design was used to examine neuronal response associated with a go/no-go task after 7 mg nicotine or placebo patch administration in 20 individuals who underwent functional magnetic resonance imaging at 3T. The task design included two levels of difficulty (ordered vs. random stimuli) and two levels of auditory distraction (silence vs. noise). Significant treatment × difficulty × distraction interaction effects on neuronal response were observed in the hippocampus, ventral parietal cortex, and anterior cingulate. In contrast to our hypothesis, U and inverted U-shaped dependencies were observed between the effects of nicotine on response and task demands, depending on the brain area. These results suggest that nicotine may differentially affect neuronal response depending on task conditions. These results have important theoretical implications for understanding how cholinergic tone may influence the neurobiology of selective attention.

The Mirror Neuron System: A Fresh View

PubMed Central

Casile, Antonino; Caggiano, Vittorio; Ferrari, Pier Francesco

2013-01-01

Mirror neurons are a class of visuomotor neurons in the monkey premotor and parietal cortices that discharge during the execution and observation of goal-directed motor acts. They are deemed to be at the basis of primates’ social abilities. In this review, the authors provide a fresh view about two still open questions about mirror neurons. The first question is their possible functional role. By reviewing recent neurophysiological data, the authors suggest that mirror neurons might represent a flexible system that encodes observed actions in terms of several behaviorally relevant features. The second question concerns the possible developmental mechanisms responsible for their initial emergence. To provide a possible answer to question, the authors review two different aspects of sensorimotor development: facial and hand movements, respectively. The authors suggest that possibly two different “mirror” systems might underlie the development of action understanding and imitative abilities in the two cases. More specifically, a possibly prewired system already present at birth but shaped by the social environment might underlie the early development of facial imitative abilities. On the contrary, an experience-dependent system might subserve perception-action couplings in the case of hand movements. The development of this latter system might be critically dependent on the observation of own movements. PMID:21467305

The neuronal control of cardiac functions in Molluscs☆

PubMed Central

Kodirov, Sodikdjon A.

2017-01-01

In this manuscript, I review the current and relevant classical studies on properties of the Mollusca heart and their central nervous system including ganglia, neurons, and nerves involved in cardiomodulation. Similar to mammalian brain hemispheres, these invertebrates possess symmetrical pairs of ganglia albeit visceral (only one) ganglion and the parietal ganglia (the right ganglion is bigger than the left one). Furthermore, there are two major regulatory drives into the compartments (pericard, auricle, and ventricle) and cardiomyocytes of the heart. These are the excitatory and inhibitory signals that originate from a few designated neurons and their putative neurotransmitters. Many of these neurons are well-identified, their specific locations within the corresponding ganglion are mapped, and some are termed as either heart excitatory (HE) or inhibitory (HI) cells. The remaining neurons are classified as cardio-regulatory, and their direct and indirect actions on the heart’s function have been documented. The cardiovascular anatomy of frequently used experimental animals, Achatina, Aplysia, Helix, and Lymnaea is relatively simple. However, as in humans, it possesses all major components including even trabeculae and atrio-ventricular valves. Since the myocardial cells are enzymatically dispersible, multiple voltage dependent cationic currents in isolated cardiomyocytes are described. The latter include at least the A-type K+, delayed rectifier K+, TTX-sensitive Na+, and L-type Ca2+ channels. PMID:21736949

Modulation of 3H-noradrenaline release by presynaptic opioid, cannabinoid and bradykinin receptors and β-adrenoceptors in mouse tissues

PubMed Central

Trendelenburg, A U; Cox, S L; Schelb, V; Klebroff, W; Khairallah, L; Starke, K

2000-01-01

Release-modulating opioid and cannabinoid (CB) receptors, β-adrenoceptors and bradykinin receptors at noradrenergic axons were studied in mouse tissues (occipito-parietal cortex, heart atria, vas deferens and spleen) preincubated with 3H-noradrenaline. Experiments using the OP1 receptor-selective agonists DPDPE and DSLET, the OP2-selective agonists U50488H and U69593, the OP3-selective agonist DAMGO, the ORL1 receptor-selective agonist nociceptin, and a number of selective antagonists showed that the noradrenergic axons innervating the occipito-parietal cortex possess release-inhibiting OP3 and ORL1 receptors, those innervating atria OP1, ORL1 and possibly OP3 receptors, and those innervating the vas deferens all four opioid receptor types. Experiments using the non-selective CB agonists WIN 55,212-2 and CP 55,940 and the CB1-selective antagonist SR 141716A indicated that the noradrenergic axons of the vas deferens possess release-inhibiting CB1 receptors. Presynaptic CB receptors were not found in the occipito-parietal cortex, in atria or in the spleen. Experiments using the non-selective β-adrenoceptor agonist isoprenaline and the β2-selective agonist salbutamol, as well as subtype-selective antagonists, demonstrated the occurrence of release-enhancing β2-adrenoceptors at the sympathetic axons of atria and the spleen, but demonstrated their absence in the occipito-parietal cortex and the vas deferens. Experiments with bradykinin and the B2-selective antagonist Hoe 140 showed the operation of release-enhancing B2 receptors at the sympathetic axons of atria, the vas deferens and the spleen, but showed their absence in the occipito-parietal cortex. The experiments document a number of new presynaptic receptor locations. They confirm and extend the existence of marked tissue and species differences in presynaptic receptors at noradrenergic neurons. PMID:10807669

Spinal afferent neurons projecting to the rat lung and pleura express acid sensitive channels

PubMed Central

Groth, Michael; Helbig, Tanja; Grau, Veronika; Kummer, Wolfgang; Haberberger, Rainer V

2006-01-01

Background The acid sensitive ion channels TRPV1 (transient receptor potential vanilloid receptor-1) and ASIC3 (acid sensing ion channel-3) respond to tissue acidification in the range that occurs during painful conditions such as inflammation and ischemia. Here, we investigated to which extent they are expressed by rat dorsal root ganglion neurons projecting to lung and pleura, respectively. Methods The tracer DiI was either injected into the left lung or applied to the costal pleura. Retrogradely labelled dorsal root ganglion neurons were subjected to triple-labelling immunohistochemistry using antisera against TRPV1, ASIC3 and neurofilament 68 (marker for myelinated neurons), and their soma diameter was measured. Results Whereas 22% of pulmonary spinal afferents contained neither channel-immunoreactivity, at least one is expressed by 97% of pleural afferents. TRPV1+/ASIC3- neurons with probably slow conduction velocity (small soma, neurofilament 68-negative) were significantly more frequent among pleural (35%) than pulmonary afferents (20%). TRPV1+/ASIC3+ neurons amounted to 14 and 10% respectively. TRPV1-/ASIC3+ neurons made up between 44% (lung) and 48% (pleura) of neurons, and half of them presumably conducted in the A-fibre range (larger soma, neurofilament 68-positive). Conclusion Rat pleural and pulmonary spinal afferents express at least two different acid-sensitive channels that make them suitable to monitor tissue acidification. Patterns of co-expression and structural markers define neuronal subgroups that can be inferred to subserve different functions and may initiate specific reflex responses. The higher prevalence of TRPV1+/ASIC3- neurons among pleural afferents probably reflects the high sensitivity of the parietal pleura to painful stimuli. PMID:16813657

Large-scale two-photon imaging revealed super-sparse population codes in the V1 superficial layer of awake monkeys.

PubMed

Tang, Shiming; Zhang, Yimeng; Li, Zhihao; Li, Ming; Liu, Fang; Jiang, Hongfei; Lee, Tai Sing

2018-04-26

One general principle of sensory information processing is that the brain must optimize efficiency by reducing the number of neurons that process the same information. The sparseness of the sensory representations in a population of neurons reflects the efficiency of the neural code. Here, we employ large-scale two-photon calcium imaging to examine the responses of a large population of neurons within the superficial layers of area V1 with single-cell resolution, while simultaneously presenting a large set of natural visual stimuli, to provide the first direct measure of the population sparseness in awake primates. The results show that only 0.5% of neurons respond strongly to any given natural image - indicating a ten-fold increase in the inferred sparseness over previous measurements. These population activities are nevertheless necessary and sufficient to discriminate visual stimuli with high accuracy, suggesting that the neural code in the primary visual cortex is both super-sparse and highly efficient. © 2018, Tang et al.

Efficient coding of spectrotemporal binaural sounds leads to emergence of the auditory space representation

PubMed Central

Młynarski, Wiktor

2014-01-01

To date a number of studies have shown that receptive field shapes of early sensory neurons can be reproduced by optimizing coding efficiency of natural stimulus ensembles. A still unresolved question is whether the efficient coding hypothesis explains formation of neurons which explicitly represent environmental features of different functional importance. This paper proposes that the spatial selectivity of higher auditory neurons emerges as a direct consequence of learning efficient codes for natural binaural sounds. Firstly, it is demonstrated that a linear efficient coding transform—Independent Component Analysis (ICA) trained on spectrograms of naturalistic simulated binaural sounds extracts spatial information present in the signal. A simple hierarchical ICA extension allowing for decoding of sound position is proposed. Furthermore, it is shown that units revealing spatial selectivity can be learned from a binaural recording of a natural auditory scene. In both cases a relatively small subpopulation of learned spectrogram features suffices to perform accurate sound localization. Representation of the auditory space is therefore learned in a purely unsupervised way by maximizing the coding efficiency and without any task-specific constraints. This results imply that efficient coding is a useful strategy for learning structures which allow for making behaviorally vital inferences about the environment. PMID:24639644

A paradoxical improvement of misreaching in optic ataxia: new evidence for two separate neural systems for visual localization.

PubMed

Milner, A D; Paulignan, Y; Dijkerman, H C; Michel, F; Jeannerod, M

1999-11-07

We tested a patient (A. T.) with bilateral brain damage to the parietal lobes, whose resulting 'optic ataxia' causes her to make large pointing errors when asked to locate single light emitting diodes presented in her visual field. We report here that, unlike normal individuals, A. T.'s pointing accuracy improved when she was required to wait for 5 s before responding. This counter-intuitive result is interpreted as reflecting the very brief time-scale on which visuomotor control systems in the superior parietal lobe operate. When an immediate response was required, A. T.'s damaged visuomotor system caused her to make large errors; but when a delay was required, a different, more flexible, visuospatial coding system--presumably relatively intact in her brain--came into play, resulting in much more accurate responses. The data are consistent with a dual processing theory whereby motor responses made directly to visual stimuli are guided by a dedicated system in the superior parietal and premotor cortices, while responses to remembered stimuli depend on perceptual processing and may thus crucially involve processing within the temporal neocortex.

Cognitive impairments accompanying rodent mild traumatic brain injury involve p53-dependent neuronal cell death and are ameliorated by the tetrahydrobenzothiazole PFT-α.

PubMed

Rachmany, Lital; Tweedie, David; Rubovitch, Vardit; Yu, Qian-Sheng; Li, Yazhou; Wang, Jia-Yi; Pick, Chaim G; Greig, Nigel H

2013-01-01

With parallels to concussive mild traumatic brain injury (mTBI) occurring in humans, anesthetized mice subjected to a single 30 g weight drop mTBI event to the right parietal cortex exhibited significant diffuse neuronal degeneration that was accompanied by delayed impairments in recognition and spatial memory. To elucidate the involvement of reversible p53-dependent apoptosis in this neuronal loss and associated cognitive deficits, mice were subjected to experimental mTBI followed by the systemic administration of the tetrahydrobenzothiazole p53 inactivator, PFT-α, or vehicle. Neuronal loss was quantified immunohistochemically at 72 hr. post-injury by the use of fluoro-Jade B and NeuN within the dentate gyrus on both sides of the brain, and recognition and spatial memory were assessed by novel object recognition and Y-maze paradigms at 7 and 30 days post injury. Systemic administration of a single dose of PFT-α 1 hr. post-injury significantly ameliorated both neuronal cell death and cognitive impairments, which were no different from sham control animals. Cellular studies on human SH-SY5Y cells and rat primary neurons challenged with glutamate excitotoxicity and H2O2 induced oxidative stress, confirmed the ability of PFT-α and a close analog to protect against these TBI associated mechanisms mediating neuronal loss. These studies suggest that p53-dependent apoptotic mechanisms underpin the neuronal and cognitive losses accompanying mTBI, and that these are potentially reversible by p53 inactivation.

Entracking as a Brain Stem Code for Pitch: The Butte Hypothesis.

PubMed

Joris, Philip X

2016-01-01

The basic nature of pitch is much debated. A robust code for pitch exists in the auditory nerve in the form of an across-fiber pooled interspike interval (ISI) distribution, which resembles the stimulus autocorrelation. An unsolved question is how this representation can be "read out" by the brain. A new view is proposed in which a known brain-stem property plays a key role in the coding of periodicity, which I refer to as "entracking", a contraction of "entrained phase-locking". It is proposed that a scalar rather than vector code of periodicity exists by virtue of coincidence detectors that code the dominant ISI directly into spike rate through entracking. Perfect entracking means that a neuron fires one spike per stimulus-waveform repetition period, so that firing rate equals the repetition frequency. Key properties are invariance with SPL and generalization across stimuli. The main limitation in this code is the upper limit of firing (~ 500 Hz). It is proposed that entracking provides a periodicity tag which is superimposed on a tonotopic analysis: at low SPLs and fundamental frequencies > 500 Hz, a spectral or place mechanism codes for pitch. With increasing SPL the place code degrades but entracking improves and first occurs in neurons with low thresholds for the spectral components present. The prediction is that populations of entracking neurons, extended across characteristic frequency, form plateaus ("buttes") of firing rate tied to periodicity.

Nonspatial Sequence Coding in CA1 Neurons

PubMed Central

Allen, Timothy A.; Salz, Daniel M.; McKenzie, Sam

2016-01-01

The hippocampus is critical to the memory for sequences of events, a defining feature of episodic memory. However, the fundamental neuronal mechanisms underlying this capacity remain elusive. While considerable research indicates hippocampal neurons can represent sequences of locations, direct evidence of coding for the memory of sequential relationships among nonspatial events remains lacking. To address this important issue, we recorded neural activity in CA1 as rats performed a hippocampus-dependent sequence-memory task. Briefly, the task involves the presentation of repeated sequences of odors at a single port and requires rats to identify each item as “in sequence” or “out of sequence”. We report that, while the animals' location and behavior remained constant, hippocampal activity differed depending on the temporal context of items—in this case, whether they were presented in or out of sequence. Some neurons showed this effect across items or sequence positions (general sequence cells), while others exhibited selectivity for specific conjunctions of item and sequence position information (conjunctive sequence cells) or for specific probe types (probe-specific sequence cells). We also found that the temporal context of individual trials could be accurately decoded from the activity of neuronal ensembles, that sequence coding at the single-cell and ensemble level was linked to sequence memory performance, and that slow-gamma oscillations (20–40 Hz) were more strongly modulated by temporal context and performance than theta oscillations (4–12 Hz). These findings provide compelling evidence that sequence coding extends beyond the domain of spatial trajectories and is thus a fundamental function of the hippocampus. SIGNIFICANCE STATEMENT The ability to remember the order of life events depends on the hippocampus, but the underlying neural mechanisms remain poorly understood. Here we addressed this issue by recording neural activity in hippocampal region CA1 while rats performed a nonspatial sequence memory task. We found that hippocampal neurons code for the temporal context of items (whether odors were presented in the correct or incorrect sequential position) and that this activity is linked with memory performance. The discovery of this novel form of temporal coding in hippocampal neurons advances our fundamental understanding of the neurobiology of episodic memory and will serve as a foundation for our cross-species, multitechnique approach aimed at elucidating the neural mechanisms underlying memory impairments in aging and dementia. PMID:26843637

Electroencephalogram evidence for the activation of human mirror neuron system during the observation of intransitive shadow and line drawing actions☆

PubMed Central

Zhu, Huaping; Sun, Yaoru; Wang, Fang

2013-01-01

Previous studies have demonstrated that hand shadows may activate the motor cortex associated with the mirror neuron system in human brain. However, there is no evidence of activity of the human mirror neuron system during the observation of intransitive movements by shadows and line drawings of hands. This study examined the suppression of electroencephalography mu waves (8–13 Hz) induced by observation of stimuli in 18 healthy students. Three stimuli were used: real hand actions, hand shadow actions and actions made by line drawings of hands. The results showed significant desynchronization of the mu rhythm (“mu suppression”) across the sensorimotor cortex (recorded at C3, Cz and C4), the frontal cortex (recorded at F3, Fz and F4) and the central and right posterior parietal cortex (recorded at Pz and P4) under all three conditions. Our experimental findings suggest that the observation of “impoverished hand actions”, such as intransitive movements of shadows and line drawings of hands, is able to activate widespread cortical areas related to the putative human mirror neuron system. PMID:25206595

FMRI evidence of 'mirror' responses to geometric shapes.

PubMed

Press, Clare; Catmur, Caroline; Cook, Richard; Widmann, Hannah; Heyes, Cecilia; Bird, Geoffrey

2012-01-01

Mirror neurons may be a genetic adaptation for social interaction. Alternatively, the associative hypothesis proposes that the development of mirror neurons is driven by sensorimotor learning, and that, given suitable experience, mirror neurons will respond to any stimulus. This hypothesis was tested using fMRI adaptation to index populations of cells with mirror properties. After sensorimotor training, where geometric shapes were paired with hand actions, BOLD response was measured while human participants experienced runs of events in which shape observation alternated with action execution or observation. Adaptation from shapes to action execution, and critically, observation, occurred in ventral premotor cortex (PMv) and inferior parietal lobule (IPL). Adaptation from shapes to execution indicates that neuronal populations responding to the shapes had motor properties, while adaptation to observation demonstrates that these populations had mirror properties. These results indicate that sensorimotor training induced populations of cells with mirror properties in PMv and IPL to respond to the observation of arbitrary shapes. They suggest that the mirror system has not been shaped by evolution to respond in a mirror fashion to biological actions; instead, its development is mediated by stimulus-general processes of learning within a system adapted for visuomotor control.

fMRI Evidence of ‘Mirror’ Responses to Geometric Shapes

PubMed Central

Press, Clare; Catmur, Caroline; Cook, Richard; Widmann, Hannah; Heyes, Cecilia; Bird, Geoffrey

2012-01-01

Mirror neurons may be a genetic adaptation for social interaction [1]. Alternatively, the associative hypothesis [2], [3] proposes that the development of mirror neurons is driven by sensorimotor learning, and that, given suitable experience, mirror neurons will respond to any stimulus. This hypothesis was tested using fMRI adaptation to index populations of cells with mirror properties. After sensorimotor training, where geometric shapes were paired with hand actions, BOLD response was measured while human participants experienced runs of events in which shape observation alternated with action execution or observation. Adaptation from shapes to action execution, and critically, observation, occurred in ventral premotor cortex (PMv) and inferior parietal lobule (IPL). Adaptation from shapes to execution indicates that neuronal populations responding to the shapes had motor properties, while adaptation to observation demonstrates that these populations had mirror properties. These results indicate that sensorimotor training induced populations of cells with mirror properties in PMv and IPL to respond to the observation of arbitrary shapes. They suggest that the mirror system has not been shaped by evolution to respond in a mirror fashion to biological actions; instead, its development is mediated by stimulus-general processes of learning within a system adapted for visuomotor control. PMID:23251653

Sparse orthogonal population representation of spatial context in the retrosplenial cortex.

PubMed

Mao, Dun; Kandler, Steffen; McNaughton, Bruce L; Bonin, Vincent

2017-08-15

Sparse orthogonal coding is a key feature of hippocampal neural activity, which is believed to increase episodic memory capacity and to assist in navigation. Some retrosplenial cortex (RSC) neurons convey distributed spatial and navigational signals, but place-field representations such as observed in the hippocampus have not been reported. Combining cellular Ca 2+ imaging in RSC of mice with a head-fixed locomotion assay, we identified a population of RSC neurons, located predominantly in superficial layers, whose ensemble activity closely resembles that of hippocampal CA1 place cells during the same task. Like CA1 place cells, these RSC neurons fire in sequences during movement, and show narrowly tuned firing fields that form a sparse, orthogonal code correlated with location. RSC 'place' cell activity is robust to environmental manipulations, showing partial remapping similar to that observed in CA1. This population code for spatial context may assist the RSC in its role in memory and/or navigation.Neurons in the retrosplenial cortex (RSC) encode spatial and navigational signals. Here the authors use calcium imaging to show that, similar to the hippocampus, RSC neurons also encode place cell-like activity in a sparse orthogonal representation, partially anchored to the allocentric cues on the linear track.

Canonical microcircuits for predictive coding

PubMed Central

Bastos, Andre M.; Usrey, W. Martin; Adams, Rick A.; Mangun, George R.; Fries, Pascal; Friston, Karl J.

2013-01-01

Summary This review considers the influential notion of a canonical (cortical) microcircuit in light of recent theories about neuronal processing. Specifically, we conciliate quantitative studies of microcircuitry and the functional logic of neuronal computations. We revisit the established idea that message passing among hierarchical cortical areas implements a form of Bayesian inference – paying careful attention to the implications for intrinsic connections among neuronal populations. By deriving canonical forms for these computations, one can associate specific neuronal populations with specific computational roles. This analysis discloses a remarkable correspondence between the microcircuitry of the cortical column and the connectivity implied by predictive coding. Furthermore, it provides some intuitive insights into the functional asymmetries between feedforward and feedback connections and the characteristic frequencies over which they operate. PMID:23177956

Levels of integration in cognitive control and sequence processing in the prefrontal cortex.

PubMed

Bahlmann, Jörg; Korb, Franziska M; Gratton, Caterina; Friederici, Angela D

2012-01-01

Cognitive control is necessary to flexibly act in changing environments. Sequence processing is needed in language comprehension to build the syntactic structure in sentences. Functional imaging studies suggest that sequence processing engages the left ventrolateral prefrontal cortex (PFC). In contrast, cognitive control processes additionally recruit bilateral rostral lateral PFC regions. The present study aimed to investigate these two types of processes in one experimental paradigm. Sequence processing was manipulated using two different sequencing rules varying in complexity. Cognitive control was varied with different cue-sets that determined the choice of a sequencing rule. Univariate analyses revealed distinct PFC regions for the two types of processing (i.e. sequence processing: left ventrolateral PFC and cognitive control processing: bilateral dorsolateral and rostral PFC). Moreover, in a common brain network (including left lateral PFC and intraparietal sulcus) no interaction between sequence and cognitive control processing was observed. In contrast, a multivariate pattern analysis revealed an interaction of sequence and cognitive control processing, such that voxels in left lateral PFC and parietal cortex showed different tuning functions for tasks involving different sequencing and cognitive control demands. These results suggest that the difference between the process of rule selection (i.e. cognitive control) and the process of rule-based sequencing (i.e. sequence processing) find their neuronal underpinnings in distinct activation patterns in lateral PFC. Moreover, the combination of rule selection and rule sequencing can shape the response of neurons in lateral PFC and parietal cortex.

Levels of Integration in Cognitive Control and Sequence Processing in the Prefrontal Cortex

PubMed Central

Bahlmann, Jörg; Korb, Franziska M.; Gratton, Caterina; Friederici, Angela D.

2012-01-01

Cognitive control is necessary to flexibly act in changing environments. Sequence processing is needed in language comprehension to build the syntactic structure in sentences. Functional imaging studies suggest that sequence processing engages the left ventrolateral prefrontal cortex (PFC). In contrast, cognitive control processes additionally recruit bilateral rostral lateral PFC regions. The present study aimed to investigate these two types of processes in one experimental paradigm. Sequence processing was manipulated using two different sequencing rules varying in complexity. Cognitive control was varied with different cue-sets that determined the choice of a sequencing rule. Univariate analyses revealed distinct PFC regions for the two types of processing (i.e. sequence processing: left ventrolateral PFC and cognitive control processing: bilateral dorsolateral and rostral PFC). Moreover, in a common brain network (including left lateral PFC and intraparietal sulcus) no interaction between sequence and cognitive control processing was observed. In contrast, a multivariate pattern analysis revealed an interaction of sequence and cognitive control processing, such that voxels in left lateral PFC and parietal cortex showed different tuning functions for tasks involving different sequencing and cognitive control demands. These results suggest that the difference between the process of rule selection (i.e. cognitive control) and the process of rule-based sequencing (i.e. sequence processing) find their neuronal underpinnings in distinct activation patterns in lateral PFC. Moreover, the combination of rule selection and rule sequencing can shape the response of neurons in lateral PFC and parietal cortex. PMID:22952762

Perinatal methadone exposure affects dopamine, norepinephrine, and serotonin in the weanling rat.

PubMed

Robinson, S E; Maher, J R; Wallace, M J; Kunko, P M

1997-01-01

On gestational day 7 pregnant rats were implanted with osmotic minipumps containing either methadone hydrochloride (initial dose, 9 mg/kg/day) or sterile water. Their offspring were cross-fostered so that they were exposed to methadone prenatally and/or postnatally. On postnatal day 21, dopamine (DA), norepinephrine (NE), serotonin (5-HT), and their metabolites were analyzed. Perinatal methadone exposure disrupted dopaminergic, noradrenergic, and serotonergic activity in a brain region- and gender-specific fashion. The ratio of the DA metabolite 3,4-dihydroxyphenylacetic acid (DOPAC) to DA was reduced in the frontal cortex of males exposed to methadone postnatally. No effects of perinatal methadone exposure were observed on DA and DOPAC in the striatum. The ratio of 3-methoxy-4-hydroxyphenylglycol (MOPEG) to NE in the hippocampus was increased significantly in males exposed to methadone prenatally. Striatal and parietal cortical 5-hydroxyindoleacetic acid (5-HIAA), but not its ratio to 5-HT, was increased slightly in rats exposed to methadone postnatally. Although parietal cortical 5-HT, 5-HIAA, and 5-hydroxytryptophan were all affected by perinatal methadone exposure, the ratios of metabolite and precursor to 5-HT were not affected. Effects of methadone exposure appeared to depend upon the developmental stage at which exposure occurred and did not appear to result from the phenomenon of neonatal withdrawal. Changes in activity of these three neurotransmitter systems may contribute to the effect of perinatal methadone on the activity of other neurons, such as cholinergic neurons.

Altered spontaneous brain activity in adolescent boys with pure conduct disorder revealed by regional homogeneity analysis.

PubMed

Wu, Qiong; Zhang, Xiaocui; Dong, Daifeng; Wang, Xiang; Yao, Shuqiao

2017-07-01

Functional magnetic resonance imaging (fMRI) studies have revealed abnormal neural activity in several brain regions of adolescents with conduct disorder (CD) performing various tasks. However, little is known about the spontaneous neural activity in people with CD in a resting state. The aims of this study were to investigate CD-associated regional activity abnormalities and to explore the relationship between behavioral impulsivity and regional activity abnormalities. Resting-state fMRI (rs-fMRI) scans were administered to 28 adolescents with CD and 28 age-, gender-, and IQ-matched healthy controls (HCs). The rs-fMRI data were subjected to regional homogeneity (ReHo) analysis. ReHo can demonstrate the temporal synchrony of regional blood oxygen level-dependent signals and reflect the coordination of local neuronal activity facilitating similar goals or representations. Compared to HCs, the CD group showed increased ReHo bilaterally in the insula as well as decreased ReHo in the right inferior parietal lobule, right middle temporal gyrus and right fusiform gyrus, left anterior cerebellum anterior, and right posterior cerebellum. In the CD group, mean ReHo values in the left and the right insula correlated positively with Barratt Impulsivity Scale (BIS) total scores. The results suggest that CD is associated with abnormal intrinsic brain activity, mainly in the cerebellum and temporal-parietal-limbic cortices, regions that are related to emotional and cognitive processing. BIS scores in adolescents with CD may reflect severity of abnormal neuronal synchronization in the insula.

Feasibility of Functional Near-Infrared Spectroscopy (fNIRS) to Investigate the Mirror Neuron System: An Experimental Study in a Real-Life Situation

PubMed Central

Sun, Pei-Pei; Tan, Fu-Lun; Zhang, Zong; Jiang, Yi-Han; Zhao, Yang; Zhu, Chao-Zhe

2018-01-01

The mirror neuron system (MNS), mainly including the premotor cortex (PMC), inferior frontal gyrus (IFG), superior parietal lobule (SPL), and rostral inferior parietal lobule (IPL), has attracted extensive attention as a possible neural mechanism of social interaction. Owing to high ecological validity, functional near-infrared spectroscopy (fNIRS) has become an ideal approach for exploring the MNS. Unfortunately, for the feasibility of fNIRS to detect the MNS, none of the four dominant regions were found in previous studies, implying a very limited capacity of fNIRS to investigate the MNS. Here, we adopted an experimental paradigm in a real-life situation to evaluate whether the MNS activity, including four dominant regions, can be detected by using fNIRS. Specifically, 30 right-handed subjects were asked to complete a table-setting task that included action execution and action observation. A double density probe configuration covered the four regions of the MNS in the left hemisphere. We used a traditional channel-based group analysis and also a ROI-based group analysis to find which regions are activated during both action execution and action observation. The results showed that the IFG, adjacent PMC, SPL, and IPL were involved in both conditions, indicating the feasibility of fNIRS to detect the MNS. Our findings provide a foundation for future research to explore the functional role of the MNS in social interaction and various disorders using fNIRS. PMID:29556185

The evolution of the complex sensory and motor systems of the human brain.

PubMed

Kaas, Jon H

2008-03-18

Inferences about how the complex sensory and motor systems of the human brain evolved are based on the results of comparative studies of brain organization across a range of mammalian species, and evidence from the endocasts of fossil skulls of key extinct species. The endocasts of the skulls of early mammals indicate that they had small brains with little neocortex. Evidence from comparative studies of cortical organization from small-brained mammals of the six major branches of mammalian evolution supports the conclusion that the small neocortex of early mammals was divided into roughly 20-25 cortical areas, including primary and secondary sensory fields. In early primates, vision was the dominant sense, and cortical areas associated with vision in temporal and occipital cortex underwent a significant expansion. Comparative studies indicate that early primates had 10 or more visual areas, and somatosensory areas with expanded representations of the forepaw. Posterior parietal cortex was also expanded, with a caudal half dominated by visual inputs, and a rostral half dominated by somatosensory inputs with outputs to an array of seven or more motor and visuomotor areas of the frontal lobe. Somatosensory areas and posterior parietal cortex became further differentiated in early anthropoid primates. As larger brains evolved in early apes and in our hominin ancestors, the number of cortical areas increased to reach an estimated 200 or so in present day humans, and hemispheric specializations emerged. The large human brain grew primarily by increasing neuron number rather than increasing average neuron size.

Sequential inference as a mode of cognition and its correlates in fronto-parietal and hippocampal brain regions

PubMed Central

Friston, Karl J.; Dolan, Raymond J.

2017-01-01

Normative models of human cognition often appeal to Bayesian filtering, which provides optimal online estimates of unknown or hidden states of the world, based on previous observations. However, in many cases it is necessary to optimise beliefs about sequences of states rather than just the current state. Importantly, Bayesian filtering and sequential inference strategies make different predictions about beliefs and subsequent choices, rendering them behaviourally dissociable. Taking data from a probabilistic reversal task we show that subjects’ choices provide strong evidence that they are representing short sequences of states. Between-subject measures of this implicit sequential inference strategy had a neurobiological underpinning and correlated with grey matter density in prefrontal and parietal cortex, as well as the hippocampus. Our findings provide, to our knowledge, the first evidence for sequential inference in human cognition, and by exploiting between-subject variation in this measure we provide pointers to its neuronal substrates. PMID:28486504

Distinct roles of visual, parietal, and frontal motor cortices in memory-guided sensorimotor decisions.

PubMed

Goard, Michael J; Pho, Gerald N; Woodson, Jonathan; Sur, Mriganka

2016-08-04

Mapping specific sensory features to future motor actions is a crucial capability of mammalian nervous systems. We investigated the role of visual (V1), posterior parietal (PPC), and frontal motor (fMC) cortices for sensorimotor mapping in mice during performance of a memory-guided visual discrimination task. Large-scale calcium imaging revealed that V1, PPC, and fMC neurons exhibited heterogeneous responses spanning all task epochs (stimulus, delay, response). Population analyses demonstrated unique encoding of stimulus identity and behavioral choice information across regions, with V1 encoding stimulus, fMC encoding choice even early in the trial, and PPC multiplexing the two variables. Optogenetic inhibition during behavior revealed that all regions were necessary during the stimulus epoch, but only fMC was required during the delay and response epochs. Stimulus identity can thus be rapidly transformed into behavioral choice, requiring V1, PPC, and fMC during the transformation period, but only fMC for maintaining the choice in memory prior to execution.

Decoding a Decision Process in the Neuronal Population of Dorsal Premotor Cortex.

PubMed

Rossi-Pool, Román; Zainos, Antonio; Alvarez, Manuel; Zizumbo, Jerónimo; Vergara, José; Romo, Ranulfo

2017-12-20

When trained monkeys discriminate the temporal structure of two sequential vibrotactile stimuli, dorsal premotor cortex (DPC) showed high heterogeneity among its neuronal responses. Notably, DPC neurons coded stimulus patterns as broader categories and signaled them during working memory, comparison, and postponed decision periods. Here, we show that such population activity can be condensed into two major coding components: one that persistently represented in working memory both the first stimulus identity and the postponed informed choice and another that transiently coded the initial sensory information and the result of the comparison between the two stimuli. Additionally, we identified relevant signals that coded the timing of task events. These temporal and task-parameter readouts were shown to be strongly linked to the monkeys' behavior when contrasted to those obtained in a non-demanding cognitive control task and during error trials. These signals, hidden in the heterogeneity, were prominently represented by the DPC population response. Copyright © 2017 Elsevier Inc. All rights reserved.

Empirical validation of the triple-code model of numerical processing for complex math operations using functional MRI and group Independent Component Analysis of the mental addition and subtraction of fractions.

PubMed

Schmithorst, Vincent J; Brown, Rhonda Douglas

2004-07-01

The suitability of a previously hypothesized triple-code model of numerical processing, involving analog magnitude, auditory verbal, and visual Arabic codes of representation, was investigated for the complex mathematical task of the mental addition and subtraction of fractions. Functional magnetic resonance imaging (fMRI) data from 15 normal adult subjects were processed using exploratory group Independent Component Analysis (ICA). Separate task-related components were found with activation in bilateral inferior parietal, left perisylvian, and ventral occipitotemporal areas. These results support the hypothesized triple-code model corresponding to the activated regions found in the individual components and indicate that the triple-code model may be a suitable framework for analyzing the neuropsychological bases of the performance of complex mathematical tasks. Copyright 2004 Elsevier Inc.

Multidimensional Characterization and Differentiation of Neurons in the Anteroventral Cochlear Nucleus

PubMed Central

Typlt, Marei; Englitz, Bernhard; Sonntag, Mandy; Dehmel, Susanne; Kopp-Scheinpflug, Cornelia; Ruebsamen, Rudolf

2012-01-01

Multiple parallel auditory pathways ascend from the cochlear nucleus. It is generally accepted that the origin of these pathways are distinct groups of neurons differing in their anatomical and physiological properties. In extracellular in vivo recordings these neurons are typically classified on the basis of their peri-stimulus time histogram. In the present study we reconsider the question of classification of neurons in the anteroventral cochlear nucleus (AVCN) by taking a wider range of response properties into account. The study aims at a better understanding of the AVCN's functional organization and its significance as the source of different ascending auditory pathways. The analyses were based on 223 neurons recorded in the AVCN of the Mongolian gerbil. The range of analysed parameters encompassed spontaneous activity, frequency coding, sound level coding, as well as temporal coding. In order to categorize the unit sample without any presumptions as to the relevance of certain response parameters, hierarchical cluster analysis and additional principal component analysis were employed which both allow a classification on the basis of a multitude of parameters simultaneously. Even with the presently considered wider range of parameters, high number of neurons and more advanced analytical methods, no clear boundaries emerged which would separate the neurons based on their physiology. At the current resolution of the analysis, we therefore conclude that the AVCN units more likely constitute a multi-dimensional continuum with different physiological characteristics manifested at different poles. However, more complex stimuli could be useful to uncover physiological differences in future studies. PMID:22253838

The vestibular-related frontal cortex and its role in smooth-pursuit eye movements and vestibular-pursuit interactions

PubMed Central

Fukushima, Junko; Akao, Teppei; Kurkin, Sergei; Kaneko, Chris R.S.; Fukushima, Kikuro

2006-01-01

In order to see clearly when a target is moving slowly, primates with high acuity foveae use smooth-pursuit and vergence eye movements. The former rotates both eyes in the same direction to track target motion in frontal planes, while the latter rotates left and right eyes in opposite directions to track target motion in depth. Together, these two systems pursue targets precisely and maintain their images on the foveae of both eyes. During head movements, both systems must interact with the vestibular system to minimize slip of the retinal images. The primate frontal cortex contains two pursuit-related areas; the caudal part of the frontal eye fields (FEF) and supplementary eye fields (SEF). Evoked potential studies have demonstrated vestibular projections to both areas and pursuit neurons in both areas respond to vestibular stimulation. The majority of FEF pursuit neurons code parameters of pursuit such as pursuit and vergence eye velocity, gaze velocity, and retinal image motion for target velocity in frontal and depth planes. Moreover, vestibular inputs contribute to the predictive pursuit responses of FEF neurons. In contrast, the majority of SEF pursuit neurons do not code pursuit metrics and many SEF neurons are reported to be active in more complex tasks. These results suggest that FEF- and SEF-pursuit neurons are involved in different aspects of vestibular-pursuit interactions and that eye velocity coding of SEF pursuit neurons is specialized for the task condition. PMID:16917164

Enhanced Sensitivity to Rapid Input Fluctuations by Nonlinear Threshold Dynamics in Neocortical Pyramidal Neurons

PubMed Central

Mensi, Skander; Hagens, Olivier; Gerstner, Wulfram; Pozzorini, Christian

2016-01-01

The way in which single neurons transform input into output spike trains has fundamental consequences for network coding. Theories and modeling studies based on standard Integrate-and-Fire models implicitly assume that, in response to increasingly strong inputs, neurons modify their coding strategy by progressively reducing their selective sensitivity to rapid input fluctuations. Combining mathematical modeling with in vitro experiments, we demonstrate that, in L5 pyramidal neurons, the firing threshold dynamics adaptively adjust the effective timescale of somatic integration in order to preserve sensitivity to rapid signals over a broad range of input statistics. For that, a new Generalized Integrate-and-Fire model featuring nonlinear firing threshold dynamics and conductance-based adaptation is introduced that outperforms state-of-the-art neuron models in predicting the spiking activity of neurons responding to a variety of in vivo-like fluctuating currents. Our model allows for efficient parameter extraction and can be analytically mapped to a Generalized Linear Model in which both the input filter—describing somatic integration—and the spike-history filter—accounting for spike-frequency adaptation—dynamically adapt to the input statistics, as experimentally observed. Overall, our results provide new insights on the computational role of different biophysical processes known to underlie adaptive coding in single neurons and support previous theoretical findings indicating that the nonlinear dynamics of the firing threshold due to Na+-channel inactivation regulate the sensitivity to rapid input fluctuations. PMID:26907675

Melatonin attenuates neuronal apoptosis through up-regulation of K(+) -Cl(-) cotransporter KCC2 expression following traumatic brain injury in rats.

PubMed

Wu, Haijian; Shao, Anwen; Zhao, Mingfei; Chen, Sheng; Yu, Jun; Zhou, Jingyi; Liang, Feng; Shi, Ligen; Dixon, Brandon J; Wang, Zhen; Ling, Chenhan; Hong, Yuan; Zhang, Jianmin

2016-09-01

Traumatic brain injury (TBI) initiates a complex cascade of neurochemical and signaling changes that leads to neuronal apoptosis, which contributes to poor outcomes for patients with TBI. The neuron-specific K(+) -Cl(-) cotransporter-2 (KCC2), the principal Cl(-) extruder in adult neurons, plays an important role in Cl(-) homeostasis and neuronal function. This present study was designed to investigate the expression pattern of KCC2 following TBI and to evaluate whether or not melatonin is able to prevent neuronal apoptosis by modulating KCC2 expression in a Sprague Dawley rat controlled cortical impact model of TBI. The time course study showed decreased mRNA and protein expression of KCC2 in the ipsilateral peri-core parietal cortex after TBI. Double immunofluorescence staining demonstrated that KCC2 is located in the plasma membrane of neurons. In addition, melatonin (10 mg/kg) was injected intraperitoneally at 5 minutes and repeated at 1, 2, 3, and 4 hours after brain trauma, and brain samples were extracted 24 hours after TBI. Compared to the vehicle group, melatonin treatment altered the down-regulation of KCC2 expression in both mRNA and protein levels after TBI. Also, melatonin treatment increased the protein levels of brain-derived neurotrophic factor (BDNF) and phosphorylated extracellular signal-regulated kinase (p-ERK). Simultaneously, melatonin administration ameliorated cortical neuronal apoptosis, reduced brain edema, and attenuated neurological deficits after TBI. In conclusion, our findings suggested that melatonin restores KCC2 expression, inhibits neuronal apoptosis and attenuates secondary brain injury after TBI, partially through activation of BDNF/ERK pathway. © 2016 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.

Transformation of a Spatial Map across the Hippocampal-Lateral Septal Circuit.

PubMed

Tingley, David; Buzsáki, György

2018-05-15

The hippocampus constructs a map of the environment. How this "cognitive map" is utilized by other brain regions to guide behavior remains unexplored. To examine how neuronal firing patterns in the hippocampus are transmitted and transformed, we recorded neurons in its principal subcortical target, the lateral septum (LS). We observed that LS neurons carry reliable spatial information in the phase of action potentials, relative to hippocampal theta oscillations, while the firing rates of LS neurons remained uninformative. Furthermore, this spatial phase code had an anatomical microstructure within the LS and was bound to the hippocampal spatial code by synchronous gamma frequency cell assemblies. Using a data-driven model, we show that rate-independent spatial tuning arises through the dynamic weighting of CA1 and CA3 cell assemblies. Our findings demonstrate that transformation of the hippocampal spatial map depends on higher-order theta-dependent neuronal sequences. Copyright © 2018 Elsevier Inc. All rights reserved.

Phasic and tonic neuron ensemble codes for stimulus-environment conjunctions in the lateral entorhinal cortex.

PubMed

Pilkiw, Maryna; Insel, Nathan; Cui, Younghua; Finney, Caitlin; Morrissey, Mark D; Takehara-Nishiuchi, Kaori

2017-07-06

The lateral entorhinal cortex (LEC) is thought to bind sensory events with the environment where they took place. To compare the relative influence of transient events and temporally stable environmental stimuli on the firing of LEC cells, we recorded neuron spiking patterns in the region during blocks of a trace eyeblink conditioning paradigm performed in two environments and with different conditioning stimuli. Firing rates of some neurons were phasically selective for conditioned stimuli in a way that depended on which room the rat was in; nearly all neurons were tonically selective for environments in a way that depended on which stimuli had been presented in those environments. As rats moved from one environment to another, tonic neuron ensemble activity exhibited prospective information about the conditioned stimulus associated with the environment. Thus, the LEC formed phasic and tonic codes for event-environment associations, thereby accurately differentiating multiple experiences with overlapping features.

Decoding thalamic afferent input using microcircuit spiking activity

PubMed Central

Sederberg, Audrey J.; Palmer, Stephanie E.

2015-01-01

A behavioral response appropriate to a sensory stimulus depends on the collective activity of thousands of interconnected neurons. The majority of cortical connections arise from neighboring neurons, and thus understanding the cortical code requires characterizing information representation at the scale of the cortical microcircuit. Using two-photon calcium imaging, we densely sampled the thalamically evoked response of hundreds of neurons spanning multiple layers and columns in thalamocortical slices of mouse somatosensory cortex. We then used a biologically plausible decoder to characterize the representation of two distinct thalamic inputs, at the level of the microcircuit, to reveal those aspects of the activity pattern that are likely relevant to downstream neurons. Our data suggest a sparse code, distributed across lamina, in which a small population of cells carries stimulus-relevant information. Furthermore, we find that, within this subset of neurons, decoder performance improves when noise correlations are taken into account. PMID:25695647

Decoding thalamic afferent input using microcircuit spiking activity.

PubMed

Sederberg, Audrey J; Palmer, Stephanie E; MacLean, Jason N

2015-04-01

A behavioral response appropriate to a sensory stimulus depends on the collective activity of thousands of interconnected neurons. The majority of cortical connections arise from neighboring neurons, and thus understanding the cortical code requires characterizing information representation at the scale of the cortical microcircuit. Using two-photon calcium imaging, we densely sampled the thalamically evoked response of hundreds of neurons spanning multiple layers and columns in thalamocortical slices of mouse somatosensory cortex. We then used a biologically plausible decoder to characterize the representation of two distinct thalamic inputs, at the level of the microcircuit, to reveal those aspects of the activity pattern that are likely relevant to downstream neurons. Our data suggest a sparse code, distributed across lamina, in which a small population of cells carries stimulus-relevant information. Furthermore, we find that, within this subset of neurons, decoder performance improves when noise correlations are taken into account. Copyright © 2015 the American Physiological Society.

Automatic Adaptation to Fast Input Changes in a Time-Invariant Neural Circuit

PubMed Central

Bharioke, Arjun; Chklovskii, Dmitri B.

2015-01-01

Neurons must faithfully encode signals that can vary over many orders of magnitude despite having only limited dynamic ranges. For a correlated signal, this dynamic range constraint can be relieved by subtracting away components of the signal that can be predicted from the past, a strategy known as predictive coding, that relies on learning the input statistics. However, the statistics of input natural signals can also vary over very short time scales e.g., following saccades across a visual scene. To maintain a reduced transmission cost to signals with rapidly varying statistics, neuronal circuits implementing predictive coding must also rapidly adapt their properties. Experimentally, in different sensory modalities, sensory neurons have shown such adaptations within 100 ms of an input change. Here, we show first that linear neurons connected in a feedback inhibitory circuit can implement predictive coding. We then show that adding a rectification nonlinearity to such a feedback inhibitory circuit allows it to automatically adapt and approximate the performance of an optimal linear predictive coding network, over a wide range of inputs, while keeping its underlying temporal and synaptic properties unchanged. We demonstrate that the resulting changes to the linearized temporal filters of this nonlinear network match the fast adaptations observed experimentally in different sensory modalities, in different vertebrate species. Therefore, the nonlinear feedback inhibitory network can provide automatic adaptation to fast varying signals, maintaining the dynamic range necessary for accurate neuronal transmission of natural inputs. PMID:26247884

Topographic Organization for Delayed Saccades in Human Posterior Parietal Cortex

PubMed Central

Schluppeck, Denis; Glimcher, Paul; Heeger, David J.

2008-01-01

Posterior parietal cortex (PPC) is thought to play a critical role in decision making, sensory attention, motor intention, and/or working memory. Research on the PPC in non-human primates has focused on the lateral intraparietal area (LIP) in the intraparietal sulcus (IPS). Neurons in LIP respond after the onset of visual targets, just before saccades to those targets, and during the delay period in between. To study the function of posterior parietal cortex in humans, it will be crucial to have a routine and reliable method for localizing specific parietal areas in individual subjects. Here, we show that human PPC contains at least two topographically organized regions, which are candidates for the human homologue of LIP. We mapped the topographic organization of human PPC for delayed (memory guided) saccades using fMRI. Subjects were instructed to fixate centrally while a peripheral target was briefly presented. After a further 3-s delay, subjects made a saccade to the remembered target location followed by a saccade back to fixation and a 1-s inter-trial interval. Targets appeared at successive locations “around the clock” (same eccentricity, ≈30° angular steps), to produce a traveling wave of activity in areas that are topographically organized. PPC exhibited topographic organization for delayed saccades. We defined two areas in each hemisphere that contained topographic maps of the contralateral visual field. These two areas were immediately rostral to V7 as defined by standard retinotopic mapping. The two areas were separated from each other and from V7 by reversals in visual field orientation. However, we leave open the possibility that these two areas will be further subdivided in future studies. Our results demonstrate that topographic maps tile the cortex continuously from V1 well into PPC. PMID:15817644

Inter-synaptic learning of combination rules in a cortical network model

PubMed Central

Lavigne, Frédéric; Avnaïm, Francis; Dumercy, Laurent

2014-01-01

Selecting responses in working memory while processing combinations of stimuli depends strongly on their relations stored in long-term memory. However, the learning of XOR-like combinations of stimuli and responses according to complex rules raises the issue of the non-linear separability of the responses within the space of stimuli. One proposed solution is to add neurons that perform a stage of non-linear processing between the stimuli and responses, at the cost of increasing the network size. Based on the non-linear integration of synaptic inputs within dendritic compartments, we propose here an inter-synaptic (IS) learning algorithm that determines the probability of potentiating/depressing each synapse as a function of the co-activity of the other synapses within the same dendrite. The IS learning is effective with random connectivity and without either a priori wiring or additional neurons. Our results show that IS learning generates efficacy values that are sufficient for the processing of XOR-like combinations, on the basis of the sole correlational structure of the stimuli and responses. We analyze the types of dendrites involved in terms of the number of synapses from pre-synaptic neurons coding for the stimuli and responses. The synaptic efficacy values obtained show that different dendrites specialize in the detection of different combinations of stimuli. The resulting behavior of the cortical network model is analyzed as a function of inter-synaptic vs. Hebbian learning. Combinatorial priming effects show that the retrospective activity of neurons coding for the stimuli trigger XOR-like combination-selective prospective activity of neurons coding for the expected response. The synergistic effects of inter-synaptic learning and of mixed-coding neurons are simulated. The results show that, although each mechanism is sufficient by itself, their combined effects improve the performance of the network. PMID:25221529

Astrocyte and Neuronal Plasticity in the Somatosensory System

PubMed Central

Sims, Robert E.; Butcher, John B.; Parri, H. Rheinallt; Glazewski, Stanislaw

2015-01-01

Changing the whisker complement on a rodent's snout can lead to two forms of experience-dependent plasticity (EDP) in the neurons of the barrel cortex, where whiskers are somatotopically represented. One form, termed coding plasticity, concerns changes in synaptic transmission and connectivity between neurons. This is thought to underlie learning and memory processes and so adaptation to a changing environment. The second, called homeostatic plasticity, serves to maintain a restricted dynamic range of neuronal activity thus preventing its saturation or total downregulation. Current explanatory models of cortical EDP are almost exclusively neurocentric. However, in recent years, increasing evidence has emerged on the role of astrocytes in brain function, including plasticity. Indeed, astrocytes appear as necessary partners of neurons at the core of the mechanisms of coding and homeostatic plasticity recorded in neurons. In addition to neuronal plasticity, several different forms of astrocytic plasticity have recently been discovered. They extend from changes in receptor expression and dynamic changes in morphology to alteration in gliotransmitter release. It is however unclear how astrocytic plasticity contributes to the neuronal EDP. Here, we review the known and possible roles for astrocytes in the barrel cortex, including its plasticity. PMID:26345481

Neuronal Reward and Decision Signals: From Theories to Data

PubMed Central

Schultz, Wolfram

2015-01-01

Rewards are crucial objects that induce learning, approach behavior, choices, and emotions. Whereas emotions are difficult to investigate in animals, the learning function is mediated by neuronal reward prediction error signals which implement basic constructs of reinforcement learning theory. These signals are found in dopamine neurons, which emit a global reward signal to striatum and frontal cortex, and in specific neurons in striatum, amygdala, and frontal cortex projecting to select neuronal populations. The approach and choice functions involve subjective value, which is objectively assessed by behavioral choices eliciting internal, subjective reward preferences. Utility is the formal mathematical characterization of subjective value and a prime decision variable in economic choice theory. It is coded as utility prediction error by phasic dopamine responses. Utility can incorporate various influences, including risk, delay, effort, and social interaction. Appropriate for formal decision mechanisms, rewards are coded as object value, action value, difference value, and chosen value by specific neurons. Although all reward, reinforcement, and decision variables are theoretical constructs, their neuronal signals constitute measurable physical implementations and as such confirm the validity of these concepts. The neuronal reward signals provide guidance for behavior while constraining the free will to act. PMID:26109341

Haptically Guided Grasping. fMRI Shows Right-Hemisphere Parietal Stimulus Encoding, and Bilateral Dorso-Ventral Parietal Gradients of Object- and Action-Related Processing during Grasp Execution

PubMed Central

Marangon, Mattia; Kubiak, Agnieszka; Króliczak, Gregory

2016-01-01

The neural bases of haptically-guided grasp planning and execution are largely unknown, especially for stimuli having no visual representations. Therefore, we used functional magnetic resonance imaging (fMRI) to monitor brain activity during haptic exploration of novel 3D complex objects, subsequent grasp planning, and the execution of the pre-planned grasps. Haptic object exploration, involving extraction of shape, orientation, and length of the to-be-grasped targets, was associated with the fronto-parietal, temporo-occipital, and insular cortex activity. Yet, only the anterior divisions of the posterior parietal cortex (PPC) of the right hemisphere were significantly more engaged in exploration of complex objects (vs. simple control disks). None of these regions were re-recruited during the planning phase. Even more surprisingly, the left-hemisphere intraparietal, temporal, and occipital areas that were significantly invoked for grasp planning did not show sensitivity to object features. Finally, grasp execution, involving the re-recruitment of the critical right-hemisphere PPC clusters, was also significantly associated with two kinds of bilateral parieto-frontal processes. The first represents transformations of grasp-relevant target features and is linked to the dorso-dorsal (lateral and medial) parieto-frontal networks. The second monitors grasp kinematics and belongs to the ventro-dorsal networks. Indeed, signal modulations associated with these distinct functions follow dorso-ventral gradients, with left aIPS showing significant sensitivity to both target features and the characteristics of the required grasp. Thus, our results from the haptic domain are consistent with the notion that the parietal processing for action guidance reflects primarily transformations from object-related to effector-related coding, and these mechanisms are rather independent of sensory input modality. PMID:26779002

Haptically Guided Grasping. fMRI Shows Right-Hemisphere Parietal Stimulus Encoding, and Bilateral Dorso-Ventral Parietal Gradients of Object- and Action-Related Processing during Grasp Execution.

PubMed

Marangon, Mattia; Kubiak, Agnieszka; Króliczak, Gregory

2015-01-01

The neural bases of haptically-guided grasp planning and execution are largely unknown, especially for stimuli having no visual representations. Therefore, we used functional magnetic resonance imaging (fMRI) to monitor brain activity during haptic exploration of novel 3D complex objects, subsequent grasp planning, and the execution of the pre-planned grasps. Haptic object exploration, involving extraction of shape, orientation, and length of the to-be-grasped targets, was associated with the fronto-parietal, temporo-occipital, and insular cortex activity. Yet, only the anterior divisions of the posterior parietal cortex (PPC) of the right hemisphere were significantly more engaged in exploration of complex objects (vs. simple control disks). None of these regions were re-recruited during the planning phase. Even more surprisingly, the left-hemisphere intraparietal, temporal, and occipital areas that were significantly invoked for grasp planning did not show sensitivity to object features. Finally, grasp execution, involving the re-recruitment of the critical right-hemisphere PPC clusters, was also significantly associated with two kinds of bilateral parieto-frontal processes. The first represents transformations of grasp-relevant target features and is linked to the dorso-dorsal (lateral and medial) parieto-frontal networks. The second monitors grasp kinematics and belongs to the ventro-dorsal networks. Indeed, signal modulations associated with these distinct functions follow dorso-ventral gradients, with left aIPS showing significant sensitivity to both target features and the characteristics of the required grasp. Thus, our results from the haptic domain are consistent with the notion that the parietal processing for action guidance reflects primarily transformations from object-related to effector-related coding, and these mechanisms are rather independent of sensory input modality.

Effects of erythropoietin on memory-relevant neurocircuitry activity and recall in mood disorders.

PubMed

Miskowiak, K W; Macoveanu, J; Vinberg, M; Assentoft, E; Randers, L; Harmer, C J; Ehrenreich, H; Paulson, O B; Knudsen, G M; Siebner, H R; Kessing, L V

2016-09-01

Erythropoietin (EPO) improves verbal memory and reverses subfield hippocampal volume loss across depression and bipolar disorder (BD). This study aimed to investigate with functional magnetic resonance imaging (fMRI) whether these effects were accompanied by functional changes in memory-relevant neuro-circuits in this cohort. Eighty-four patients with treatment-resistant unipolar depression who were moderately depressed or BD in remission were randomized to eight weekly EPO (40 000 IU) or saline infusions in a double-blind, parallel-group design. Participants underwent whole-brain fMRI at 3T, mood ratings, and blood tests at baseline and week 14. During fMRI, participants performed a picture encoding task followed by postscan recall. Sixty-two patients had complete data (EPO: N = 32, saline: N = 30). EPO improved picture recall and increased encoding-related activity in dorsolateral prefrontal cortex (dlPFC) and temporo-parietal regions, but not in hippocampus. Recall correlated with activity in the identified dlPFC and temporo-parietal regions at baseline, and change in recall correlated with activity change in these regions from baseline to follow-up across the entire cohort. The effects of EPO were not correlated with change in mood, red blood cells, blood pressure, or medication. The findings highlight enhanced encoding-related dlPFC and temporo-parietal activity as key neuronal underpinnings of EPO-associated memory improvement. © 2016 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.

Dynamic state estimation based on Poisson spike trains—towards a theory of optimal encoding

NASA Astrophysics Data System (ADS)

Susemihl, Alex; Meir, Ron; Opper, Manfred

2013-03-01

Neurons in the nervous system convey information to higher brain regions by the generation of spike trains. An important question in the field of computational neuroscience is how these sensory neurons encode environmental information in a way which may be simply analyzed by subsequent systems. Many aspects of the form and function of the nervous system have been understood using the concepts of optimal population coding. Most studies, however, have neglected the aspect of temporal coding. Here we address this shortcoming through a filtering theory of inhomogeneous Poisson processes. We derive exact relations for the minimal mean squared error of the optimal Bayesian filter and, by optimizing the encoder, obtain optimal codes for populations of neurons. We also show that a class of non-Markovian, smooth stimuli are amenable to the same treatment, and provide results for the filtering and prediction error which hold for a general class of stochastic processes. This sets a sound mathematical framework for a population coding theory that takes temporal aspects into account. It also formalizes a number of studies which discussed temporal aspects of coding using time-window paradigms, by stating them in terms of correlation times and firing rates. We propose that this kind of analysis allows for a systematic study of temporal coding and will bring further insights into the nature of the neural code.

State Dependency of Chemosensory Coding in the Gustatory Thalamus (VPMpc) of Alert Rats

PubMed Central

Liu, Haixin

2015-01-01

The parvicellular portion of the ventroposteromedial nucleus (VPMpc) is the part of the thalamus that processes gustatory information. Anatomical evidence shows that the VPMpc receives ascending gustatory inputs from the parabrachial nucleus (PbN) in the brainstem and sends projections to the gustatory cortex (GC). Although taste processing in PbN and GC has been the subject of intense investigation in behaving rodents, much less is known on how VPMpc neurons encode gustatory information. Here we present results from single-unit recordings in the VPMpc of alert rats receiving multiple tastants. Thalamic neurons respond to taste with time-varying modulations of firing rates, consistent with those observed in GC and PbN. These responses encode taste quality as well as palatability. Comparing responses to tastants either passively delivered, or self-administered after a cue, unveiled the effects of general expectation on taste processing in VPMpc. General expectation led to an improvement of taste coding by modulating response dynamics, and single neuron ability to encode multiple tastants. Our results demonstrate that the time course of taste coding as well as single neurons' ability to encode for multiple qualities are not fixed but rather can be altered by the state of the animal. Together, the data presented here provide the first description that taste coding in VPMpc is dynamic and state-dependent. SIGNIFICANCE STATEMENT Over the past years, a great deal of attention has been devoted to understanding taste coding in the brainstem and cortex of alert rodents. Thanks to this research, we now know that taste coding is dynamic, distributed, and context-dependent. Alas, virtually nothing is known on how the gustatory thalamus (VPMpc) processes gustatory information in behaving rats. This manuscript investigates taste processing in the VPMpc of behaving rats. Our results show that thalamic neurons encode taste and palatability with time-varying patterns of activity and that thalamic coding of taste is modulated by general expectation. Our data will appeal not only to researchers interested in taste, but also to a broader audience of sensory and systems neuroscientists interested in the thalamocortical system. PMID:26609147

Roles for Coincidence Detection in Coding Amplitude-Modulated Sounds

PubMed Central

Ashida, Go; Kretzberg, Jutta; Tollin, Daniel J.

2016-01-01

Many sensory neurons encode temporal information by detecting coincident arrivals of synaptic inputs. In the mammalian auditory brainstem, binaural neurons of the medial superior olive (MSO) are known to act as coincidence detectors, whereas in the lateral superior olive (LSO) roles of coincidence detection have remained unclear. LSO neurons receive excitatory and inhibitory inputs driven by ipsilateral and contralateral acoustic stimuli, respectively, and vary their output spike rates according to interaural level differences. In addition, LSO neurons are also sensitive to binaural phase differences of low-frequency tones and envelopes of amplitude-modulated (AM) sounds. Previous physiological recordings in vivo found considerable variations in monaural AM-tuning across neurons. To investigate the underlying mechanisms of the observed temporal tuning properties of LSO and their sources of variability, we used a simple coincidence counting model and examined how specific parameters of coincidence detection affect monaural and binaural AM coding. Spike rates and phase-locking of evoked excitatory and spontaneous inhibitory inputs had only minor effects on LSO output to monaural AM inputs. In contrast, the coincidence threshold of the model neuron affected both the overall spike rates and the half-peak positions of the AM-tuning curve, whereas the width of the coincidence window merely influenced the output spike rates. The duration of the refractory period affected only the low-frequency portion of the monaural AM-tuning curve. Unlike monaural AM coding, temporal factors, such as the coincidence window and the effective duration of inhibition, played a major role in determining the trough positions of simulated binaural phase-response curves. In addition, empirically-observed level-dependence of binaural phase-coding was reproduced in the framework of our minimalistic coincidence counting model. These modeling results suggest that coincidence detection of excitatory and inhibitory synaptic inputs is essential for LSO neurons to encode both monaural and binaural AM sounds. PMID:27322612

Dysfunction of the Human Mirror Neuron System in Ideomotor Apraxia: Evidence from Mu Suppression.

PubMed

Frenkel-Toledo, Silvi; Liebermann, Dario G; Bentin, Shlomo; Soroker, Nachum

2016-06-01

Stroke patients with ideomotor apraxia (IMA) have difficulties controlling voluntary motor actions, as clearly seen when asked to imitate simple gestures performed by the examiner. Despite extensive research, the neurophysiological mechanisms underlying failure to imitate gestures in IMA remain controversial. The aim of the current study was to explore the relationship between imitation failure in IMA and mirror neuron system (MNS) functioning. Mirror neurons were found to play a crucial role in movement imitation and in imitation-based motor learning. Their recruitment during movement observation and execution is signaled in EEG recordings by suppression of the lower (8-10 Hz) mu range. We examined the modulation of EEG in this range in stroke patients with left (n = 21) and right (n = 15) hemisphere damage during observation of video clips showing different manual movements. IMA severity was assessed by the DeRenzi standardized diagnostic test. Results showed that failure to imitate observed manual movements correlated with diminished mu suppression in patients with damage to the right inferior parietal lobule and in patients with damage to the right inferior frontal gyrus pars opercularis-areas where major components of the human MNS are assumed to reside. Voxel-based lesion symptom mapping revealed a significant impact on imitation capacity for the left inferior and superior parietal lobules and the left post central gyrus. Both left and right hemisphere damages were associated with imitation failure typical of IMA, yet a clear demonstration of relationship to the MNS was obtained only in the right hemisphere damage group. Suppression of the 8-10 Hz range was stronger in central compared with occipital sites, pointing to a dominant implication of mu rather than alpha rhythms. However, the suppression correlated with De Renzi's apraxia test scores not only in central but also in occipital sites, suggesting a multifactorial mechanism for IMA, with a possible impact for deranged visual attention (alpha suppression) beyond the effect of MNS damage (mu suppression).

Simultaneous perception of a spoken and a signed language: The brain basis of ASL-English code-blends

PubMed Central

Weisberg, Jill; McCullough, Stephen; Emmorey, Karen

2018-01-01

Code-blends (simultaneous words and signs) are a unique characteristic of bimodal bilingual communication. Using fMRI, we investigated code-blend comprehension in hearing native ASL-English bilinguals who made a semantic decision (edible?) about signs, audiovisual words, and semantically equivalent code-blends. English and ASL recruited a similar fronto-temporal network with expected modality differences: stronger activation for English in auditory regions of bilateral superior temporal cortex, and stronger activation for ASL in bilateral occipitotemporal visual regions and left parietal cortex. Code-blend comprehension elicited activity in a combination of these regions, and no cognitive control regions were additionally recruited. Furthermore, code-blends elicited reduced activation relative to ASL presented alone in bilateral prefrontal and visual extrastriate cortices, and relative to English alone in auditory association cortex. Consistent with behavioral facilitation observed during semantic decisions, the findings suggest that redundant semantic content induces more efficient neural processing in language and sensory regions during bimodal language integration. PMID:26177161

Heterogeneity of spine density in pyramidal neurons of isocortex of mongoose, Herpestes edwardsii (É. Geoffroy Saint-Hilaire 1818).

PubMed

Srivastava, U C; Singh, Sippy; Chauhan, Prashant

2013-08-01

The characteristics of pyramidal neurons within six layers of Indian gray mongoose (Herpestes edwardsii) isocortex have been investigated using Golgi and Cresyl-Violet methods. Pyramidal neurons and the cytoarchitecture of isocortex of mongoose were photographed with the help of computer aided Nikon eclipse 80i microscope whereas the lucida drawings were made by simple light microscope equipped with camera lucida. The cortical neurons exhibit marked regional differences in phenotype. The differences occur in morphology and distribution of spines within the cortical neurons not only among different species but also within an animal's brain. The present investigation aims at studying the features of pyramidal neurons and to find out the differences if any in distribution of spines in different layers (II-VI) as well as regions (Frontal, Temporal, Parietal, and Occipital) of isocortex of mongoose, which will provide information regarding importance of different layer and region. This piece of work embarks the findings that spine density shows inter-regional as well as interlaminar variations within isocortex of mongoose indicating that pyramidal cells present in varied layer and region are not equally functional and there do exists differences in activity among layers and regions. Among regions, the Temporal region possessing highest spine density contributes more toward functioning of mongoose isocortex and might play significant role in predatory nature of mongoose because this region in mammals is associated with auditory, visual perception, and object recognition. Copyright © 2013 Wiley Periodicals, Inc.

Learning Midlevel Auditory Codes from Natural Sound Statistics.

PubMed

Młynarski, Wiktor; McDermott, Josh H

2018-03-01

Interaction with the world requires an organism to transform sensory signals into representations in which behaviorally meaningful properties of the environment are made explicit. These representations are derived through cascades of neuronal processing stages in which neurons at each stage recode the output of preceding stages. Explanations of sensory coding may thus involve understanding how low-level patterns are combined into more complex structures. To gain insight into such midlevel representations for sound, we designed a hierarchical generative model of natural sounds that learns combinations of spectrotemporal features from natural stimulus statistics. In the first layer, the model forms a sparse convolutional code of spectrograms using a dictionary of learned spectrotemporal kernels. To generalize from specific kernel activation patterns, the second layer encodes patterns of time-varying magnitude of multiple first-layer coefficients. When trained on corpora of speech and environmental sounds, some second-layer units learned to group similar spectrotemporal features. Others instantiate opponency between distinct sets of features. Such groupings might be instantiated by neurons in the auditory cortex, providing a hypothesis for midlevel neuronal computation.

Regulatory consequences of neuronal ELAV-like protein binding to coding and non-coding RNAs in human brain

PubMed Central

Scheckel, Claudia; Drapeau, Elodie; Frias, Maria A; Park, Christopher Y; Fak, John; Zucker-Scharff, Ilana; Kou, Yan; Haroutunian, Vahram; Ma'ayan, Avi

2016-01-01

Neuronal ELAV-like (nELAVL) RNA binding proteins have been linked to numerous neurological disorders. We performed crosslinking-immunoprecipitation and RNAseq on human brain, and identified nELAVL binding sites on 8681 transcripts. Using knockout mice and RNAi in human neuroblastoma cells, we showed that nELAVL intronic and 3' UTR binding regulates human RNA splicing and abundance. We validated hundreds of nELAVL targets among which were important neuronal and disease-associated transcripts, including Alzheimer's disease (AD) transcripts. We therefore investigated RNA regulation in AD brain, and observed differential splicing of 150 transcripts, which in some cases correlated with differential nELAVL binding. Unexpectedly, the most significant change of nELAVL binding was evident on non-coding Y RNAs. nELAVL/Y RNA complexes were specifically remodeled in AD and after acute UV stress in neuroblastoma cells. We propose that the increased nELAVL/Y RNA association during stress may lead to nELAVL sequestration, redistribution of nELAVL target binding, and altered neuronal RNA splicing. DOI: http://dx.doi.org/10.7554/eLife.10421.001 PMID:26894958

Spatiotemporal Coding of Individual Chemicals by the Gustatory System

PubMed Central

Reiter, Sam; Campillo Rodriguez, Chelsey; Sun, Kui

2015-01-01

Four of the five major sensory systems (vision, olfaction, somatosensation, and audition) are thought to use different but partially overlapping sets of neurons to form unique representations of vast numbers of stimuli. The only exception is gustation, which is thought to represent only small numbers of basic taste categories. However, using new methods for delivering tastant chemicals and making electrophysiological recordings from the tractable gustatory system of the moth Manduca sexta, we found chemical-specific information is as follows: (1) initially encoded in the population of gustatory receptor neurons as broadly distributed spatiotemporal patterns of activity; (2) dramatically integrated and temporally transformed as it propagates to monosynaptically connected second-order neurons; and (3) observed in tastant-specific behavior. Our results are consistent with an emerging view of the gustatory system: rather than constructing basic taste categories, it uses a spatiotemporal population code to generate unique neural representations of individual tastant chemicals. SIGNIFICANCE STATEMENT Our results provide a new view of taste processing. Using a new, relatively simple model system and a new set of techniques to deliver taste stimuli and to examine gustatory receptor neurons and their immediate followers, we found no evidence for labeled line connectivity, or basic taste categories such as sweet, salty, bitter, and sour. Rather, individual tastant chemicals are represented as patterns of spiking activity distributed across populations of receptor neurons. These representations are transformed substantially as multiple types of receptor neurons converge upon follower neurons, leading to a combinatorial coding format that uniquely, rapidly, and efficiently represents individual taste chemicals. Finally, we found that the information content of these neurons can drive tastant-specific behavior. PMID:26338341

Spatiotemporal Coding of Individual Chemicals by the Gustatory System.

PubMed

Reiter, Sam; Campillo Rodriguez, Chelsey; Sun, Kui; Stopfer, Mark

2015-09-02

Four of the five major sensory systems (vision, olfaction, somatosensation, and audition) are thought to use different but partially overlapping sets of neurons to form unique representations of vast numbers of stimuli. The only exception is gustation, which is thought to represent only small numbers of basic taste categories. However, using new methods for delivering tastant chemicals and making electrophysiological recordings from the tractable gustatory system of the moth Manduca sexta, we found chemical-specific information is as follows: (1) initially encoded in the population of gustatory receptor neurons as broadly distributed spatiotemporal patterns of activity; (2) dramatically integrated and temporally transformed as it propagates to monosynaptically connected second-order neurons; and (3) observed in tastant-specific behavior. Our results are consistent with an emerging view of the gustatory system: rather than constructing basic taste categories, it uses a spatiotemporal population code to generate unique neural representations of individual tastant chemicals. Our results provide a new view of taste processing. Using a new, relatively simple model system and a new set of techniques to deliver taste stimuli and to examine gustatory receptor neurons and their immediate followers, we found no evidence for labeled line connectivity, or basic taste categories such as sweet, salty, bitter, and sour. Rather, individual tastant chemicals are represented as patterns of spiking activity distributed across populations of receptor neurons. These representations are transformed substantially as multiple types of receptor neurons converge upon follower neurons, leading to a combinatorial coding format that uniquely, rapidly, and efficiently represents individual taste chemicals. Finally, we found that the information content of these neurons can drive tastant-specific behavior. Copyright © 2015 the authors 0270-6474/15/3512309-13$15.00/0.

Training of Attentional Filtering, but Not of Memory Storage, Enhances Working Memory Efficiency by Strengthening the Neuronal Gatekeeper Network.

PubMed

Schmicker, Marlen; Schwefel, Melanie; Vellage, Anne-Katrin; Müller, Notger G

2016-04-01

Memory training (MT) in older adults with memory deficits often leads to frustration and, therefore, is usually not recommended. Here, we pursued an alternative approach and looked for transfer effects of 1-week attentional filter training (FT) on working memory performance and its neuronal correlates in young healthy humans. The FT effects were compared with pure MT, which lacked the necessity to filter out irrelevant information. Before and after training, all participants performed an fMRI experiment that included a combined task in which stimuli had to be both filtered based on color and stored in memory. We found that training induced processing changes by biasing either filtering or storage. FT induced larger transfer effects on the untrained cognitive function than MT. FT increased neuronal activity in frontal parts of the neuronal gatekeeper network, which is proposed to hinder irrelevant information from being unnecessarily stored in memory. MT decreased neuronal activity in the BG part of the gatekeeper network but enhanced activity in the parietal storage node. We take these findings as evidence that FT renders working memory more efficient by strengthening the BG-prefrontal gatekeeper network. MT, on the other hand, simply stimulates storage of any kind of information. These findings illustrate a tight connection between working memory and attention, and they may open up new avenues for ameliorating memory deficits in patients with cognitive impairments.

Coding of odors by temporal binding within a model network of the locust antennal lobe.

PubMed

Patel, Mainak J; Rangan, Aaditya V; Cai, David

2013-01-01

The locust olfactory system interfaces with the external world through antennal receptor neurons (ORNs), which represent odors in a distributed, combinatorial manner. ORN axons bundle together to form the antennal nerve, which relays sensory information centrally to the antennal lobe (AL). Within the AL, an odor generates a dynamically evolving ensemble of active cells, leading to a stimulus-specific temporal progression of neuronal spiking. This experimental observation has led to the hypothesis that an odor is encoded within the AL by a dynamically evolving trajectory of projection neuron (PN) activity that can be decoded piecewise to ascertain odor identity. In order to study information coding within the locust AL, we developed a scaled-down model of the locust AL using Hodgkin-Huxley-type neurons and biologically realistic connectivity parameters and current components. Using our model, we examined correlations in the precise timing of spikes across multiple neurons, and our results suggest an alternative to the dynamic trajectory hypothesis. We propose that the dynamical interplay of fast and slow inhibition within the locust AL induces temporally stable correlations in the spiking activity of an odor-dependent neural subset, giving rise to a temporal binding code that allows rapid stimulus detection by downstream elements.

The Vestibular System Implements a Linear–Nonlinear Transformation In Order to Encode Self-Motion

PubMed Central

Massot, Corentin; Schneider, Adam D.; Chacron, Maurice J.; Cullen, Kathleen E.

2012-01-01

Although it is well established that the neural code representing the world changes at each stage of a sensory pathway, the transformations that mediate these changes are not well understood. Here we show that self-motion (i.e. vestibular) sensory information encoded by VIIIth nerve afferents is integrated nonlinearly by post-synaptic central vestibular neurons. This response nonlinearity was characterized by a strong (∼50%) attenuation in neuronal sensitivity to low frequency stimuli when presented concurrently with high frequency stimuli. Using computational methods, we further demonstrate that a static boosting nonlinearity in the input-output relationship of central vestibular neurons accounts for this unexpected result. Specifically, when low and high frequency stimuli are presented concurrently, this boosting nonlinearity causes an intensity-dependent bias in the output firing rate, thereby attenuating neuronal sensitivities. We suggest that nonlinear integration of afferent input extends the coding range of central vestibular neurons and enables them to better extract the high frequency features of self-motion when embedded with low frequency motion during natural movements. These findings challenge the traditional notion that the vestibular system uses a linear rate code to transmit information and have important consequences for understanding how the representation of sensory information changes across sensory pathways. PMID:22911113

Structural and functional evaluation of cortical motor areas in Amyotrophic Lateral Sclerosis.

PubMed

Cosottini, Mirco; Pesaresi, Ilaria; Piazza, Selina; Diciotti, Stefano; Cecchi, Paolo; Fabbri, Serena; Carlesi, Cecilia; Mascalchi, Mario; Siciliano, Gabriele

2012-03-01

The structural and functional data gathered with Magnetic Resonance Imaging (MRI) techniques about the brain cortical motor damage in Amyotrophic Lateral Sclerosis (ALS) are controversial. In fact some structural MRI studies showed foci of gray matter (GM) atrophy in the precentral gyrus, even in the early stage, while others did not. Most functional MRI (fMRI) studies in ALS reported hyperactivation of extra-primary motor cortices, while contradictory results were obtained on the activation of the primary motor cortex. We aimed to investigate the cortical motor circuitries in ALS patients by a combined structural and functional approach. Twenty patients with definite ALS and 16 healthy subjects underwent a structural examination with acquisition of a 3D T1-weighted sequence and fMRI examination during a maximal force handgrip task executed with the right-hand, the left-hand and with both hands simultaneously. The T1-weighted images were analyzed with Voxel-Based Morphometry (VBM) that showed several clusters of reduced cortical GM in ALS patients compared to controls including the pre and postcentral gyri, the superior, middle and inferior frontal gyri, the supplementary motor area, the superior and inferior parietal cortices and the temporal lobe, bilaterally but more extensive on the right side. In ALS patients a significant hypoactivation of the primary sensory motor cortex and frontal dorsal premotor areas as compared to controls was observed. The hypoactivated areas matched with foci of cortical atrophy demonstrated by VBM. The fMRI analysis also showed an enhanced activation in the ventral premotor frontal areas and in the parietal cortex pertaining to the fronto-parietal motor circuit which paralleled with disease progression rate and matched with cortical regions of atrophy. The hyperactivation of the fronto-parietal circuit was asymmetric and prevalent in the left hemisphere. VBM and fMRI identified structural and functional markers of an extended cortical damage within the motor circuit of ALS patients. The functional changes in non-primary motor cortices pertaining to fronto-parietal circuit suggest an over-recruitment of a pre-existing physiological sensory-motor network. However, the concomitant fronto-parietal cortical atrophy arises the possibility that such a hyper-activation reflects cortical hyper-excitability due to loss of inhibitory inter-neurons. Copyright © 2011 Elsevier Inc. All rights reserved.

Neuronal Assemblies Evidence Distributed Interactions within a Tactile Discrimination Task in Rats

PubMed Central

Deolindo, Camila S.; Kunicki, Ana C. B.; da Silva, Maria I.; Lima Brasil, Fabrício; Moioli, Renan C.

2018-01-01

Accumulating evidence suggests that neural interactions are distributed and relate to animal behavior, but many open questions remain. The neural assembly hypothesis, formulated by Hebb, states that synchronously active single neurons may transiently organize into functional neural circuits—neuronal assemblies (NAs)—and that would constitute the fundamental unit of information processing in the brain. However, the formation, vanishing, and temporal evolution of NAs are not fully understood. In particular, characterizing NAs in multiple brain regions over the course of behavioral tasks is relevant to assess the highly distributed nature of brain processing. In the context of NA characterization, active tactile discrimination tasks with rats are elucidative because they engage several cortical areas in the processing of information that are otherwise masked in passive or anesthetized scenarios. In this work, we investigate the dynamic formation of NAs within and among four different cortical regions in long-range fronto-parieto-occipital networks (primary somatosensory, primary visual, prefrontal, and posterior parietal cortices), simultaneously recorded from seven rats engaged in an active tactile discrimination task. Our results first confirm that task-related neuronal firing rate dynamics in all four regions is significantly modulated. Notably, a support vector machine decoder reveals that neural populations contain more information about the tactile stimulus than the majority of single neurons alone. Then, over the course of the task, we identify the emergence and vanishing of NAs whose participating neurons are shown to contain more information about animal behavior than randomly chosen neurons. Taken together, our results further support the role of multiple and distributed neurons as the functional unit of information processing in the brain (NA hypothesis) and their link to active animal behavior. PMID:29375324

Effects of Different Modes of Hypobaric Hypoxia on the Content of Epigenetic Factors in the Rat in Neurons of Rat Neocortex.

PubMed

Samoilov, M O; Churilova, A V; Glushchenko, T S; Rybnikova, E A

2017-04-01

We studied the effects of different modes of hypobaric hypoxia on the content of epigenetic factors acH3K24, meH3K9, and meDNA modulating conformational characteristics of chromatin and gene expression in neurons of associative complex of rat parietal neocortex. Severe destructive hypoxia dramatically reduced the level of acH3K24 in 3 h after the end of exposure and increased meH3K9 and meDNA content. By contrast, 3-fold (but not single) adaptive exposure to moderate hypobaric hypoxia that produced a neuroprotective effect enhanced neuronal acH3K24 expression and decreased both meH3K9 and meDNA levels. Elevated acH3K24 content facilitates, while increased content of meH3K9 hampers binding of transcription factors to the target genes. At the same time, increased expression of meDNA suppresses transcription. The role of modification of epigenetic mechanisms in the regulation of proadaptive genes under the effects of hypoxic exposure according to various protocols is discussed.

Cross-frequency synchronization connects networks of fast and slow oscillations during visual working memory maintenance

PubMed Central

Siebenhühner, Felix; Wang, Sheng H; Palva, J Matias; Palva, Satu

2016-01-01

Neuronal activity in sensory and fronto-parietal (FP) areas underlies the representation and attentional control, respectively, of sensory information maintained in visual working memory (VWM). Within these regions, beta/gamma phase-synchronization supports the integration of sensory functions, while synchronization in theta/alpha bands supports the regulation of attentional functions. A key challenge is to understand which mechanisms integrate neuronal processing across these distinct frequencies and thereby the sensory and attentional functions. We investigated whether such integration could be achieved by cross-frequency phase synchrony (CFS). Using concurrent magneto- and electroencephalography, we found that CFS was load-dependently enhanced between theta and alpha–gamma and between alpha and beta-gamma oscillations during VWM maintenance among visual, FP, and dorsal attention (DA) systems. CFS also connected the hubs of within-frequency-synchronized networks and its strength predicted individual VWM capacity. We propose that CFS integrates processing among synchronized neuronal networks from theta to gamma frequencies to link sensory and attentional functions. DOI: http://dx.doi.org/10.7554/eLife.13451.001 PMID:27669146

The effect of word concreteness on recognition memory.

PubMed

Fliessbach, K; Weis, S; Klaver, P; Elger, C E; Weber, B

2006-09-01

Concrete words that are readily imagined are better remembered than abstract words. Theoretical explanations for this effect either claim a dual coding of concrete words in the form of both a verbal and a sensory code (dual-coding theory), or a more accessible semantic network for concrete words than for abstract words (context-availability theory). However, the neural mechanisms of improved memory for concrete versus abstract words are poorly understood. Here, we investigated the processing of concrete and abstract words during encoding and retrieval in a recognition memory task using event-related functional magnetic resonance imaging (fMRI). As predicted, memory performance was significantly better for concrete words than for abstract words. Abstract words elicited stronger activations of the left inferior frontal cortex both during encoding and recognition than did concrete words. Stronger activation of this area was also associated with successful encoding for both abstract and concrete words. Concrete words elicited stronger activations bilaterally in the posterior inferior parietal lobe during recognition. The left parietal activation was associated with correct identification of old stimuli. The anterior precuneus, left cerebellar hemisphere and the posterior and anterior cingulate cortex showed activations both for successful recognition of concrete words and for online processing of concrete words during encoding. Additionally, we observed a correlation across subjects between brain activity in the left anterior fusiform gyrus and hippocampus during recognition of learned words and the strength of the concreteness effect. These findings support the idea of specific brain processes for concrete words, which are reactivated during successful recognition.

Transformation of the neural code for tactile detection from thalamus to cortex.

PubMed

Vázquez, Yuriria; Salinas, Emilio; Romo, Ranulfo

2013-07-09

To understand how sensory-driven neural activity gives rise to perception, it is essential to characterize how various relay stations in the brain encode stimulus presence. Neurons in the ventral posterior lateral (VPL) nucleus of the somatosensory thalamus and in primary somatosensory cortex (S1) respond to vibrotactile stimulation with relatively slow modulations (∼100 ms) of their firing rate. In addition, faster modulations (∼10 ms) time-locked to the stimulus waveform are observed in both areas, but their contribution to stimulus detection is unknown. Furthermore, it is unclear whether VPL and S1 neurons encode stimulus presence with similar accuracy and via the same response features. To address these questions, we recorded single neurons while trained monkeys judged the presence or absence of a vibrotactile stimulus of variable amplitude, and their activity was analyzed with a unique decoding method that is sensitive to the time scale of the firing rate fluctuations. We found that the maximum detection accuracy of single neurons is similar in VPL and S1. However, VPL relies more heavily on fast rate modulations than S1, and as a consequence, the neural code in S1 is more tolerant: its performance degrades less when the readout method or the time scale of integration is suboptimal. Therefore, S1 neurons implement a more robust code, one less sensitive to the temporal integration window used to infer stimulus presence downstream. The differences between VPL and S1 responses signaling the appearance of a stimulus suggest a transformation of the neural code from thalamus to cortex.

Associative memory of phase-coded spatiotemporal patterns in leaky Integrate and Fire networks.

PubMed

Scarpetta, Silvia; Giacco, Ferdinando

2013-04-01

We study the collective dynamics of a Leaky Integrate and Fire network in which precise relative phase relationship of spikes among neurons are stored, as attractors of the dynamics, and selectively replayed at different time scales. Using an STDP-based learning process, we store in the connectivity several phase-coded spike patterns, and we find that, depending on the excitability of the network, different working regimes are possible, with transient or persistent replay activity induced by a brief signal. We introduce an order parameter to evaluate the similarity between stored and recalled phase-coded pattern, and measure the storage capacity. Modulation of spiking thresholds during replay changes the frequency of the collective oscillation or the number of spikes per cycle, keeping preserved the phases relationship. This allows a coding scheme in which phase, rate and frequency are dissociable. Robustness with respect to noise and heterogeneity of neurons parameters is studied, showing that, since dynamics is a retrieval process, neurons preserve stable precise phase relationship among units, keeping a unique frequency of oscillation, even in noisy conditions and with heterogeneity of internal parameters of the units.

Potential roles of cholinergic modulation in the neural coding of location and movement speed

PubMed Central

Dannenberg, Holger; Hinman, James R.; Hasselmo, Michael E.

2016-01-01

Behavioral data suggest that cholinergic modulation may play a role in certain aspects of spatial memory, and neurophysiological data demonstrate neurons that fire in response to spatial dimensions, including grid cells and place cells that respond on the basis of location and running speed. These neurons show firing responses that depend upon the visual configuration of the environment, due to coding in visually-responsive regions of the neocortex. This review focuses on the physiological effects of acetylcholine that may influence the sensory coding of spatial dimensions relevant to behavior. In particular, the local circuit effects of acetylcholine within the cortex regulate the influence of sensory input relative to internal memory representations, via presynaptic inhibition of excitatory and inhibitory synaptic transmission, and the modulation of intrinsic currents in cortical excitatory and inhibitory neurons. In addition, circuit effects of acetylcholine regulate the dynamics of cortical circuits including oscillations at theta and gamma frequencies. These effects of acetylcholine on local circuits and network dynamics could underlie the role of acetylcholine in coding of spatial information for the performance of spatial memory tasks. PMID:27677935

The NEST Dry-Run Mode: Efficient Dynamic Analysis of Neuronal Network Simulation Code.

PubMed

Kunkel, Susanne; Schenck, Wolfram

2017-01-01

NEST is a simulator for spiking neuronal networks that commits to a general purpose approach: It allows for high flexibility in the design of network models, and its applications range from small-scale simulations on laptops to brain-scale simulations on supercomputers. Hence, developers need to test their code for various use cases and ensure that changes to code do not impair scalability. However, running a full set of benchmarks on a supercomputer takes up precious compute-time resources and can entail long queuing times. Here, we present the NEST dry-run mode, which enables comprehensive dynamic code analysis without requiring access to high-performance computing facilities. A dry-run simulation is carried out by a single process, which performs all simulation steps except communication as if it was part of a parallel environment with many processes. We show that measurements of memory usage and runtime of neuronal network simulations closely match the corresponding dry-run data. Furthermore, we demonstrate the successful application of the dry-run mode in the areas of profiling and performance modeling.

The NEST Dry-Run Mode: Efficient Dynamic Analysis of Neuronal Network Simulation Code

PubMed Central

Kunkel, Susanne; Schenck, Wolfram

2017-01-01

NEST is a simulator for spiking neuronal networks that commits to a general purpose approach: It allows for high flexibility in the design of network models, and its applications range from small-scale simulations on laptops to brain-scale simulations on supercomputers. Hence, developers need to test their code for various use cases and ensure that changes to code do not impair scalability. However, running a full set of benchmarks on a supercomputer takes up precious compute-time resources and can entail long queuing times. Here, we present the NEST dry-run mode, which enables comprehensive dynamic code analysis without requiring access to high-performance computing facilities. A dry-run simulation is carried out by a single process, which performs all simulation steps except communication as if it was part of a parallel environment with many processes. We show that measurements of memory usage and runtime of neuronal network simulations closely match the corresponding dry-run data. Furthermore, we demonstrate the successful application of the dry-run mode in the areas of profiling and performance modeling. PMID:28701946

Automatic Fitting of Spiking Neuron Models to Electrophysiological Recordings

PubMed Central

Rossant, Cyrille; Goodman, Dan F. M.; Platkiewicz, Jonathan; Brette, Romain

2010-01-01

Spiking models can accurately predict the spike trains produced by cortical neurons in response to somatically injected currents. Since the specific characteristics of the model depend on the neuron, a computational method is required to fit models to electrophysiological recordings. The fitting procedure can be very time consuming both in terms of computer simulations and in terms of code writing. We present algorithms to fit spiking models to electrophysiological data (time-varying input and spike trains) that can run in parallel on graphics processing units (GPUs). The model fitting library is interfaced with Brian, a neural network simulator in Python. If a GPU is present it uses just-in-time compilation to translate model equations into optimized code. Arbitrary models can then be defined at script level and run on the graphics card. This tool can be used to obtain empirically validated spiking models of neurons in various systems. We demonstrate its use on public data from the INCF Quantitative Single-Neuron Modeling 2009 competition by comparing the performance of a number of neuron spiking models. PMID:20224819

A neuronal reward inequity signal in primate striatum

PubMed Central

van Coeverden, Charlotte R.; Schultz, Wolfram

2015-01-01

Primates are social animals, and their survival depends on social interactions with others. Especially important for social interactions and welfare is the observation of rewards obtained by other individuals and the comparison with own reward. The fundamental social decision variable for the comparison process is reward inequity, defined by an asymmetric reward distribution among individuals. An important brain structure for coding reward inequity may be the striatum, a component of the basal ganglia involved in goal-directed behavior. Two rhesus monkeys were seated opposite each other and contacted a touch-sensitive table placed between them to obtain specific magnitudes of reward that were equally or unequally distributed among them. Response times in one of the animals demonstrated differential behavioral sensitivity to reward inequity. A group of neurons in the striatum showed distinct signals reflecting disadvantageous and advantageous reward inequity. These neuronal signals occurred irrespective of, or in conjunction with, own reward coding. These data demonstrate that striatal neurons of macaque monkeys sense the differences between other's and own reward. The neuronal activities are likely to contribute crucial reward information to neuronal mechanisms involved in social interactions. PMID:26378202

Evolutionarily conserved coding properties of auditory neurons across grasshopper species

PubMed Central

Neuhofer, Daniela; Wohlgemuth, Sandra; Stumpner, Andreas; Ronacher, Bernhard

2008-01-01

We investigated encoding properties of identified auditory interneurons in two not closely related grasshopper species (Acrididae). The neurons can be homologized on the basis of their similar morphologies and physiologies. As test stimuli, we used the species-specific stridulation signals of Chorthippus biguttulus, which evidently are not relevant for the other species, Locusta migratoria. We recorded spike trains produced in response to these signals from several neuron types at the first levels of the auditory pathway in both species. Using a spike train metric to quantify differences between neuronal responses, we found a high similarity in the responses of homologous neurons: interspecific differences between the responses of homologous neurons in the two species were not significantly larger than intraspecific differences (between several specimens of a neuron in one species). These results suggest that the elements of the thoracic auditory pathway have been strongly conserved during the evolutionary divergence of these species. According to the ‘efficient coding’ hypothesis, an adaptation of the thoracic auditory pathway to the specific needs of acoustic communication could be expected. We conclude that there must have been stabilizing selective forces at work that conserved coding characteristics and prevented such an adaptation. PMID:18505715

Supranormal orientation selectivity of visual neurons in orientation-restricted animals.

PubMed

Sasaki, Kota S; Kimura, Rui; Ninomiya, Taihei; Tabuchi, Yuka; Tanaka, Hiroki; Fukui, Masayuki; Asada, Yusuke C; Arai, Toshiya; Inagaki, Mikio; Nakazono, Takayuki; Baba, Mika; Kato, Daisuke; Nishimoto, Shinji; Sanada, Takahisa M; Tani, Toshiki; Imamura, Kazuyuki; Tanaka, Shigeru; Ohzawa, Izumi

2015-11-16

Altered sensory experience in early life often leads to remarkable adaptations so that humans and animals can make the best use of the available information in a particular environment. By restricting visual input to a limited range of orientations in young animals, this investigation shows that stimulus selectivity, e.g., the sharpness of tuning of single neurons in the primary visual cortex, is modified to match a particular environment. Specifically, neurons tuned to an experienced orientation in orientation-restricted animals show sharper orientation tuning than neurons in normal animals, whereas the opposite was true for neurons tuned to non-experienced orientations. This sharpened tuning appears to be due to elongated receptive fields. Our results demonstrate that restricted sensory experiences can sculpt the supranormal functions of single neurons tailored for a particular environment. The above findings, in addition to the minimal population response to orientations close to the experienced one, agree with the predictions of a sparse coding hypothesis in which information is represented efficiently by a small number of activated neurons. This suggests that early brain areas adopt an efficient strategy for coding information even when animals are raised in a severely limited visual environment where sensory inputs have an unnatural statistical structure.

Supranormal orientation selectivity of visual neurons in orientation-restricted animals

PubMed Central

Sasaki, Kota S.; Kimura, Rui; Ninomiya, Taihei; Tabuchi, Yuka; Tanaka, Hiroki; Fukui, Masayuki; Asada, Yusuke C.; Arai, Toshiya; Inagaki, Mikio; Nakazono, Takayuki; Baba, Mika; Kato, Daisuke; Nishimoto, Shinji; Sanada, Takahisa M.; Tani, Toshiki; Imamura, Kazuyuki; Tanaka, Shigeru; Ohzawa, Izumi

2015-01-01

Altered sensory experience in early life often leads to remarkable adaptations so that humans and animals can make the best use of the available information in a particular environment. By restricting visual input to a limited range of orientations in young animals, this investigation shows that stimulus selectivity, e.g., the sharpness of tuning of single neurons in the primary visual cortex, is modified to match a particular environment. Specifically, neurons tuned to an experienced orientation in orientation-restricted animals show sharper orientation tuning than neurons in normal animals, whereas the opposite was true for neurons tuned to non-experienced orientations. This sharpened tuning appears to be due to elongated receptive fields. Our results demonstrate that restricted sensory experiences can sculpt the supranormal functions of single neurons tailored for a particular environment. The above findings, in addition to the minimal population response to orientations close to the experienced one, agree with the predictions of a sparse coding hypothesis in which information is represented efficiently by a small number of activated neurons. This suggests that early brain areas adopt an efficient strategy for coding information even when animals are raised in a severely limited visual environment where sensory inputs have an unnatural statistical structure. PMID:26567927

Two different streams form the dorsal visual system: anatomy and functions.

PubMed

Rizzolatti, Giacomo; Matelli, Massimo

2003-11-01

There are two radically different views on the functional role of the dorsal visual stream. One considers it as a system involved in space perception. The other is of a system that codes visual information for action organization. On the basis of new anatomical data and a reconsideration of previous functional and clinical data, we propose that the dorsal stream and its recipient parietal areas form two distinct functional systems: the dorso-dorsal stream (d-d stream) and the ventro-dorsal stream (v-d stream). The d-d stream is formed by area V6 (main d-d extrastriate visual node) and areas V6A and MIP of the superior parietal lobule. Its major functional role is the control of actions "on line". Its damage leads to optic ataxia. The v-d stream is formed by area MT (main v-d extrastriate visual node) and by the visual areas of the inferior parietal lobule. As the d-d stream, v-d stream is responsible for action organization. It, however, also plays a crucial role in space perception and action understanding. The putative mechanisms linking action and perception in the v-d stream is discussed.

Dynamic Integration of Task-Relevant Visual Features in Posterior Parietal Cortex

PubMed Central

Freedman, David J.

2014-01-01

Summary The primate visual system consists of multiple hierarchically organized cortical areas, each specialized for processing distinct aspects of the visual scene. For example, color and form are encoded in ventral pathway areas such as V4 and inferior temporal cortex, while motion is preferentially processed in dorsal pathway areas such as the middle temporal area. Such representations often need to be integrated perceptually to solve tasks which depend on multiple features. We tested the hypothesis that the lateral intraparietal area (LIP) integrates disparate task-relevant visual features by recording from LIP neurons in monkeys trained to identify target stimuli composed of conjunctions of color and motion features. We show that LIP neurons exhibit integrative representations of both color and motion features when they are task relevant, and task-dependent shifts of both direction and color tuning. This suggests that LIP plays a role in flexibly integrating task-relevant sensory signals. PMID:25199703

Neuronal correlates of personal space intrusion in violent offenders.

PubMed

Schienle, Anne; Wabnegger, Albert; Leitner, Mario; Leutgeb, Verena

2017-04-01

Personal space (PS) is defined as the imagery region immediately surrounding our body, which acts as safety zone. It has been suggested that PS is enlarged in violent offenders and that this group shows an enhanced sensitivity to the reduction of interpersonal distance. In the present fMRI study high-risk violent offenders and noncriminal controls were presented with photos of neutral facial expressions by men and women. All images were shown twice, as static photos, and animated (i.e., appearing to approach the subject) in order to simulate PS intrusion. Approaching faces generally provoked activation of a fronto-parietal network and the insula. Offenders responded with greater insula activation to approaching faces, especially when the person was male. Insular activation has been recognized before as a neuronal correlate of potential threat and harm detection in PS. The increased reactivity of violent offenders is possibly a result of their hostile attribution bias.

Encoding of Olfactory Information with Oscillating Neural Assemblies

NASA Astrophysics Data System (ADS)

Laurent, Gilles; Davidowitz, Hananel

1994-09-01

In the brain, fast oscillations of local field potentials, which are thought to arise from the coherent and rhythmic activity of large numbers of neurons, were observed first in the olfactory system and have since been described in many neocortical areas. The importance of these oscillations in information coding, however, is controversial. Here, local field potential and intracellular recordings were obtained from the antennal lobe and mushroom body of the locust Schistocerca americana. Different odors evoked coherent oscillations in different, but usually overlapping, ensembles of neurons. The phase of firing of individual neurons relative to the population was not dependent on the odor. The components of a coherently oscillating ensemble of neurons changed over the duration of a single exposure to an odor. It is thus proposed that odors are encoded by specific but dynamic assemblies of coherently oscillating neurons. Such distributed and temporal representation of complex sensory signals may facilitate combinatorial coding and associative learning in these, and possibly other, sensory networks.

Phasic and tonic neuron ensemble codes for stimulus-environment conjunctions in the lateral entorhinal cortex

PubMed Central

Pilkiw, Maryna; Insel, Nathan; Cui, Younghua; Finney, Caitlin; Morrissey, Mark D; Takehara-Nishiuchi, Kaori

2017-01-01

The lateral entorhinal cortex (LEC) is thought to bind sensory events with the environment where they took place. To compare the relative influence of transient events and temporally stable environmental stimuli on the firing of LEC cells, we recorded neuron spiking patterns in the region during blocks of a trace eyeblink conditioning paradigm performed in two environments and with different conditioning stimuli. Firing rates of some neurons were phasically selective for conditioned stimuli in a way that depended on which room the rat was in; nearly all neurons were tonically selective for environments in a way that depended on which stimuli had been presented in those environments. As rats moved from one environment to another, tonic neuron ensemble activity exhibited prospective information about the conditioned stimulus associated with the environment. Thus, the LEC formed phasic and tonic codes for event-environment associations, thereby accurately differentiating multiple experiences with overlapping features. DOI: http://dx.doi.org/10.7554/eLife.28611.001 PMID:28682237

Divergent Routing of Positive and Negative Information from the Amygdala during Memory Retrieval.

PubMed

Beyeler, Anna; Namburi, Praneeth; Glober, Gordon F; Simonnet, Clémence; Calhoon, Gwendolyn G; Conyers, Garrett F; Luck, Robert; Wildes, Craig P; Tye, Kay M

2016-04-20

Although the basolateral amygdala (BLA) is known to play a critical role in the formation of memories of both positive and negative valence, the coding and routing of valence-related information is poorly understood. Here, we recorded BLA neurons during the retrieval of associative memories and used optogenetic-mediated phototagging to identify populations of neurons that synapse in the nucleus accumbens (NAc), the central amygdala (CeA), or ventral hippocampus (vHPC). We found that despite heterogeneous neural responses within each population, the proportions of BLA-NAc neurons excited by reward predictive cues and of BLA-CeA neurons excited by aversion predictive cues were higher than within the entire BLA. Although the BLA-vHPC projection is known to drive behaviors of innate negative valence, these neurons did not preferentially code for learned negative valence. Together, these findings suggest that valence encoding in the BLA is at least partially mediated via divergent activity of anatomically defined neural populations. Copyright © 2016 Elsevier Inc. All rights reserved.

Regulation of Cortical Dynamic Range by Background Synaptic Noise and Feedforward Inhibition

PubMed Central

Khubieh, Ayah; Ratté, Stéphanie; Lankarany, Milad; Prescott, Steven A.

2016-01-01

The cortex encodes a broad range of inputs. This breadth of operation requires sensitivity to weak inputs yet non-saturating responses to strong inputs. If individual pyramidal neurons were to have a narrow dynamic range, as previously claimed, then staggered all-or-none recruitment of those neurons would be necessary for the population to achieve a broad dynamic range. Contrary to this explanation, we show here through dynamic clamp experiments in vitro and computer simulations that pyramidal neurons have a broad dynamic range under the noisy conditions that exist in the intact brain due to background synaptic input. Feedforward inhibition capitalizes on those noise effects to control neuronal gain and thereby regulates the population dynamic range. Importantly, noise allows neurons to be recruited gradually and occludes the staggered recruitment previously attributed to heterogeneous excitation. Feedforward inhibition protects spike timing against the disruptive effects of noise, meaning noise can enable the gain control required for rate coding without compromising the precise spike timing required for temporal coding. PMID:26209846

Brain activity and prosocial behavior in a simulated life-threatening situation.

PubMed

Zanon, Marco; Novembre, Giovanni; Zangrando, Nicola; Chittaro, Luca; Silani, Giorgia

2014-09-01

To study the neuronal basis of altruistic behavior, we investigated functional connectivity within brain networks of participants who exhibited either a self-benefit behavior or an altruistic one in a life-threatening situation simulated in a virtual environment. In particular, participants were asked to evacuate a virtual building on fire and, without being previously informed, they were faced with a decision on whether to stop and help a trapped virtual human, at the possible cost of losing their own life in the virtual experience. Group independent component analysis (gICA) applied on blood-oxygen-level-dependent (BOLD) functional images revealed significant differences between the group of participants who showed selfish behavior and those who acted prosocially. Specifically, an increased functional connectivity in the salience network, comprising the anterior insula (AI) and the anterior mid cingulate cortex (aMCC), was observed in the selfish group compared to the prosocial one. Conversely, higher ICA weights in the medial prefrontal cortex and temporo-parietal junction (TPJ), were observed in the prosocial group. The findings show that an increased functional connectivity of the salience network, which suggests an enhanced sensitivity to the threatening situation and potential danger for the individual, resulted in more selfish choices, while the engagement of the medial prefrontal and temporo-parietal cortices subserved prosocial behavior, possibly due to their role in perspective-taking. The study provides the first online neurophysiological measurement of prosocial decision-making during threatening situations, opening new avenues to the investigation of neuronal substrates of complex social behaviors. Copyright © 2014 Elsevier Inc. All rights reserved.

Longitudinal course of cortical thickness decline in amyotrophic lateral sclerosis.

PubMed

Schuster, Christina; Kasper, Elisabeth; Machts, Judith; Bittner, Daniel; Kaufmann, Jörn; Benecke, Reiner; Teipel, Stefan; Vielhaber, Stefan; Prudlo, Johannes

2014-10-01

To determine longitudinal rates of cortical atrophy in classical Amyotrophic lateral sclerosis (ALS) and ALS variants. Rates of cortical thinning were determined between 2 scans, 3-15 months apart, in 77 ALS patients: 51 classical, 12 upper motor neuron (UMN), and 14 lower motor neuron (LMN) ALS variants. Cortical thickness at the first assessment was compared with 60 healthy controls matched by age and gender. Atrophy rates were compared between patient sub-groups and correlated with disease duration, progression, and severity. Using a cross-sectional analysis, we found a significant difference in cortical thickness between ALS patients and controls in the motor and extra-motor areas (left medial orbito frontal gyrus, left inferior parietal gyrus, bilateral insular cortex, right fusiform gyrus, bilateral precuneus). Using a longitudinal analysis, we found a significant decline of cortical thickness in frontal, temporal, and parietal regions over the course of the study in ALS patients. Effects were independent of the clinical subtype, with exception of the precentral gyrus (p < 0.001). The LMN ALS variants demonstrated the highest rates of cortical thinning in the precentral gyrus, the UMN-dominant subjects exhibited intermediate rates of atrophy, and the classical ALS patients exhibited no such change. Atrophy of the precentral gyrus in classical ALS indicates a floor effect at the first assessment, resulting in a lack of further atrophy over time. Structural loss of the precentral gyrus appears to be an early sign of classical ALS. Over time, patterns of cortical thinning in extra-motor areas can be identified in ALS, regardless of the phenotype.

Fear processing and social networking in the absence of a functional amygdala.

PubMed

Becker, Benjamin; Mihov, Yoan; Scheele, Dirk; Kendrick, Keith M; Feinstein, Justin S; Matusch, Andreas; Aydin, Merve; Reich, Harald; Urbach, Horst; Oros-Peusquens, Ana-Maria; Shah, Nadim J; Kunz, Wolfram S; Schlaepfer, Thomas E; Zilles, Karl; Maier, Wolfgang; Hurlemann, René

2012-07-01

The human amygdala plays a crucial role in processing social signals, such as face expressions, particularly fearful ones, and facilitates responses to them in face-sensitive cortical regions. This contributes to social competence and individual amygdala size correlates with that of social networks. While rare patients with focal bilateral amygdala lesion typically show impaired recognition of fearful faces, this deficit is variable, and an intriguing possibility is that other brain regions can compensate to support fear and social signal processing. To investigate the brain's functional compensation of selective bilateral amygdala damage, we performed a series of behavioral, psychophysiological, and functional magnetic resonance imaging experiments in two adult female monozygotic twins (patient 1 and patient 2) with equivalent, extensive bilateral amygdala pathology as a sequela of lipoid proteinosis due to Urbach-Wiethe disease. Patient 1, but not patient 2, showed preserved recognition of fearful faces, intact modulation of acoustic startle responses by fear-eliciting scenes, and a normal-sized social network. Functional magnetic resonance imaging revealed that patient 1 showed potentiated responses to fearful faces in her left premotor cortex face area and bilaterally in the inferior parietal lobule. The premotor cortex face area and inferior parietal lobule are both implicated in the cortical mirror-neuron system, which mediates learning of observed actions and may thereby promote both imitation and empathy. Taken together, our findings suggest that despite the pre-eminent role of the amygdala in processing social information, the cortical mirror-neuron system may sometimes adaptively compensate for its pathology. Copyright © 2012 Society of Biological Psychiatry. Published by Elsevier Inc. All rights reserved.

The evolution of the complex sensory and motor systems of the human brain

PubMed Central

Kaas, Jon H.

2008-01-01

Inferences about how the complex sensory and motor systems of the human brain evolved are based on the results of comparative studies of brain organization across a range of mammalian species, and evidence from the endocasts of fossil skulls of key extinct species. The endocasts of the skulls of early mammals indicate that they had small brains with little neocortex. Evidence from comparative studies of cortical organization from small-brained mammals of the six major branches of mammalian evolution supports the conclusion that the small neocortex of early mammals was divided into roughly 20–25 cortical areas, including primary and secondary sensory fields. In early primates, vision was the dominant sense, and cortical areas associated with vision in temporal and occipital cortex underwent a significant expansion. Comparative studies indicate that early primates had 10 or more visual areas, and somatosensory areas with expanded representations of the forepaw. Posterior parietal cortex was also expanded, with a caudal half dominated by visual inputs, and a rostral half dominated by somatosensory inputs with outputs to an array of seven or more motor and visuomotor areas of the frontal lobe. Somatosensory areas and posterior parietal cortex became further differentiated in early anthropoid primates. As larger brains evolved in early apes and in our hominin ancestors, the number of cortical areas increased to reach an estimated 200 or so in present day humans, and hemispheric specializations emerged. The large human brain grew primarily by increasing neuron number rather than increasing average neuron size. PMID:18331903

The opponent channel population code of sound location is an efficient representation of natural binaural sounds.

PubMed

Młynarski, Wiktor

2015-05-01

In mammalian auditory cortex, sound source position is represented by a population of broadly tuned neurons whose firing is modulated by sounds located at all positions surrounding the animal. Peaks of their tuning curves are concentrated at lateral position, while their slopes are steepest at the interaural midline, allowing for the maximum localization accuracy in that area. These experimental observations contradict initial assumptions that the auditory space is represented as a topographic cortical map. It has been suggested that a "panoramic" code has evolved to match specific demands of the sound localization task. This work provides evidence suggesting that properties of spatial auditory neurons identified experimentally follow from a general design principle- learning a sparse, efficient representation of natural stimuli. Natural binaural sounds were recorded and served as input to a hierarchical sparse-coding model. In the first layer, left and right ear sounds were separately encoded by a population of complex-valued basis functions which separated phase and amplitude. Both parameters are known to carry information relevant for spatial hearing. Monaural input converged in the second layer, which learned a joint representation of amplitude and interaural phase difference. Spatial selectivity of each second-layer unit was measured by exposing the model to natural sound sources recorded at different positions. Obtained tuning curves match well tuning characteristics of neurons in the mammalian auditory cortex. This study connects neuronal coding of the auditory space with natural stimulus statistics and generates new experimental predictions. Moreover, results presented here suggest that cortical regions with seemingly different functions may implement the same computational strategy-efficient coding.

Independent Neuronal Representation of Facial and Vocal Identity in the Monkey Hippocampus and Inferotemporal Cortex.

PubMed

Sliwa, Julia; Planté, Aurélie; Duhamel, Jean-René; Wirth, Sylvia

2016-03-01

Social interactions make up to a large extent the prime material of episodic memories. We therefore asked how social signals are coded by neurons in the hippocampus. Human hippocampus is home to neurons representing familiar individuals in an abstract and invariant manner ( Quian Quiroga et al. 2009). In contradistinction, activity of rat hippocampal cells is only weakly altered by the presence of other rats ( von Heimendahl et al. 2012; Zynyuk et al. 2012). We probed the activity of monkey hippocampal neurons to faces and voices of familiar and unfamiliar individuals (monkeys and humans). Thirty-one percent of neurons recorded without prescreening responded to faces or to voices. Yet responses to faces were more informative about individuals than responses to voices and neuronal responses to facial and vocal identities were not correlated, indicating that in our sample identity information was not conveyed in an invariant manner like in human neurons. Overall, responses displayed by monkey hippocampal neurons were similar to the ones of neurons recorded simultaneously in inferotemporal cortex, whose role in face perception is established. These results demonstrate that the monkey hippocampus participates in the read-out of social information contrary to the rat hippocampus, but possibly lack an explicit conceptual coding of as found in humans. © The Author 2014. Published by Oxford University Press. All rights reserved. For Permissions, please e-mail: journals.permissions@oup.com.

Monkey primary somatosensory cortical activity during the early reaction time period differs with cues that guide movements

PubMed Central

Liu, Yu; Denton, John M.; Nelson, Randall J.

2009-01-01

Vibration-related neurons in monkey primary somatosensory cortex (SI) discharge rhythmically when vibratory stimuli are presented. It remains unclear how functional information carried by vibratory inputs is coded in rhythmic neuronal activity. In the present study, we compared neuronal activity during wrist movements in response to two sets of cues. In the first, movements were guided by vibratory cue only (VIB trials). In the second, movements were guided by simultaneous presentation of both vibratory and visual cues (COM trials). SI neurons were recorded extracellularly during both wrist extensions and flexions. Neuronal activity during the instructed delay period (IDP) and the early reaction time period (RTP) were analyzed. A total of 96 cases from 48 neurons (each neuron contributed two cases, one each for extension and flexion) showed significant vibration entrainment during the early RTPs, as determined by circular statistics (Rayleigh test). Of these, 50 cases had cutaneous (CUTA) and 46 had deep (DEEP) receptive fields. The CUTA neurons showed lower firing rates during the IDPs and greater firing rate changes during the early RTPs when compared with the DEEP neurons. The CUTA neurons also demonstrated decreases in activity entrainment during VIB trials when compared with COM trials. For the DEEP neurons, the difference of entrainment between VIB and COM trials was not statistically significant. The results suggest that somatic vibratory input is coded by both the firing rate and the activity entrainment of the CUTA neurons in SI. The results also suggest that when vibratory inputs are required for successful task completion, the activity of the CUTA neurons increases but the entrainment degrades. The DEEP neurons may be tuned before movement initiation for processing information encoded by proprioceptive afferents. PMID:18288475

Monkey primary somatosensory cortical activity during the early reaction time period differs with cues that guide movements.

PubMed

Liu, Yu; Denton, John M; Nelson, Randall J

2008-05-01

Vibration-related neurons in monkey primary somatosensory cortex (SI) discharge rhythmically when vibratory stimuli are presented. It remains unclear how functional information carried by vibratory inputs is coded in rhythmic neuronal activity. In the present study, we compared neuronal activity during wrist movements in response to two sets of cues. In the first, movements were guided by vibratory cue only (VIB trials). In the second, movements were guided by simultaneous presentation of both vibratory and visual cues (COM trials). SI neurons were recorded extracellularly during both wrist extensions and flexions. Neuronal activity during the instructed delay period (IDP) and the early reaction time period (RTP) were analyzed. A total of 96 cases from 48 neurons (each neuron contributed two cases, one each for extension and flexion) showed significant vibration entrainment during the early RTPs, as determined by circular statistics (Rayleigh test). Of these, 50 cases had cutaneous (CUTA) and 46 had deep (DEEP) receptive fields. The CUTA neurons showed lower firing rates during the IDPs and greater firing rate changes during the early RTPs when compared with the DEEP neurons. The CUTA neurons also demonstrated decreases in activity entrainment during VIB trials when compared with COM trials. For the DEEP neurons, the difference of entrainment between VIB and COM trials was not statistically significant. The results suggest that somatic vibratory input is coded by both the firing rate and the activity entrainment of the CUTA neurons in SI. The results also suggest that when vibratory inputs are required for successful task completion, the activity of the CUTA neurons increases but the entrainment degrades. The DEEP neurons may be tuned before movement initiation for processing information encoded by proprioceptive afferents.

A functional hierarchy within the parietofrontal network in stimulus selection and attention control.

PubMed

Ibos, Guilhem; Duhamel, Jean-René; Ben Hamed, Suliann

2013-05-08

Although we are confronted with an ever-changing environment, we do not have the capacity to analyze all incoming sensory information. Perception is selective and is guided both by salient events occurring in our visual field and by cognitive premises about what needs our attention. Although the lateral intraparietal area (LIP) and frontal eye field (FEF) are known to represent the position of visual attention, their respective contributions to its control are still unclear. Here, we report LIP and FEF neuronal activities recorded while monkeys performed a voluntary attention-orientation target-detection task. We show that both encode behaviorally significant events, but that the FEF plays a specific role in mapping abstract cue instructions onto a spatial priority map to voluntarily guide attention. On the basis of a latency analysis, we show that the coding of stimulus identity and position precedes the emergence of an explicit attentional signal within the FEF. We also describe dynamic temporal hierarchies between LIP and FEF: stimuli carrying the highest intrinsic saliency are signaled by LIP before FEF, whereas stimuli carrying the highest extrinsic saliency are signaled in FEF before LIP. This suggests that whereas the parietofrontal attentional network most probably processes visual information in a recurrent way, exogenous processing predominates in the parietal cortex and the endogenous control of attention takes place in the FEF.

Overview of long non-coding RNA and mRNA expression in response to methamphetamine treatment in vitro.

PubMed

Xiong, Kun; Long, Lingling; Zhang, Xudong; Qu, Hongke; Deng, Haixiao; Ding, Yanjun; Cai, Jifeng; Wang, Shuchao; Wang, Mi; Liao, Lvshuang; Huang, Jufang; Yi, Chun-Xia; Yan, Jie

2017-10-01

Long non-coding RNAs (lncRNAs) display multiple functions including regulation of neuronal injury. However, their impact in methamphetamine (METH)-induced neurotoxicity has rarely been reported. Here, using microarray analysis, we investigated the expression profiling of lncRNAs and mRNAs in primary cultured prefrontal cortical neurons after METH treatment. We observed a difference in lncRNA and mRNA expression between the experimental and sham control groups. Using bioinformatics, we analyzed the highest enriched gene ontology (GO) terms of biological process, cellular component, and molecular function, and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway and pathway network analysis. Furthermore, an lncRNA-mRNA co-expression sub-network for aberrantly expressed terms revealed possible interactions of lncRNA NR_110713 and NR_027943 with their related genes. Afterwards, three lncRNAs (NR_110713, NR_027943, GAS5) and two mRNAs (Ddit3, Casp12) were targeted to validate the microarray data by qRT-PCR. This presented an overview of lncRNA and mRNA expression profiling and indicated that lncRNA might participate in METH-induced neuronal apoptosis by regulating the coding genes of neurons. Copyright © 2017 Elsevier Ltd. All rights reserved.

Mapping visual stimuli to perceptual decisions via sparse decoding of mesoscopic neural activity.

PubMed

Sajda, Paul

2010-01-01

In this talk I will describe our work investigating sparse decoding of neural activity, given a realistic mapping of the visual scene to neuronal spike trains generated by a model of primary visual cortex (V1). We use a linear decoder which imposes sparsity via an L1 norm. The decoder can be viewed as a decoding neuron (linear summation followed by a sigmoidal nonlinearity) in which there are relatively few non-zero synaptic weights. We find: (1) the best decoding performance is for a representation that is sparse in both space and time, (2) decoding of a temporal code results in better performance than a rate code and is also a better fit to the psychophysical data, (3) the number of neurons required for decoding increases monotonically as signal-to-noise in the stimulus decreases, with as little as 1% of the neurons required for decoding at the highest signal-to-noise levels, and (4) sparse decoding results in a more accurate decoding of the stimulus and is a better fit to psychophysical performance than a distributed decoding, for example one imposed by an L2 norm. We conclude that sparse coding is well-justified from a decoding perspective in that it results in a minimum number of neurons and maximum accuracy when sparse representations can be decoded from the neural dynamics.

A Radial Glia Fascicle Leads Principal Neurons from the Pallial-Subpallial Boundary into the Developing Human Insula.

PubMed

González-Arnay, Emilio; González-Gómez, Miriam; Meyer, Gundela

2017-01-01

The human insular lobe, in the depth of the Sylvian fissure, displays three main cytoarchitectonic divisions defined by the differentiation of granular layers II and IV. These comprise a rostro-ventral agranular area, an intermediate dysgranular area, and a dorso-caudal granular area. Immunohistochemistry in human embryos and fetuses using antibodies against PCNA, Vimentin, Nestin, Tbr1, and Tb2 reveals that the insular cortex is unique in that it develops far away from the ventricular zone (VZ), with most of its principal neurons deriving from the subventricular zone (SVZ) of the pallial-subpallial boundary (PSB). In human embryos (Carnegie stage 16/17), the rostro-ventral insula is the first cortical region to develop; its Tbr1+ neurons migrate from the PSB along the lateral cortical stream. From 10 gestational weeks (GW) onward, lateral ventricle, ganglionic eminences, and PSB grow forming a C-shaped curvature. The SVZ of the PSB gives rise to a distinct radial glia fiber fascicle (RGF), which courses lateral to the putamen in the external capsule. In the RGF, four components can be established: PF, descending from the prefrontal PSB to the anterior insula; FP, descending from the fronto-parietal PSB toward the intermediate insula; PT, coursing from the PSB near the parieto-temporal junction to the posterior insula, and T, ascending from the temporal PSB and merging with components FP and PT. The RGF fans out at different dorso-ventral and rostro-caudal levels of the insula, with descending fibers predominating over ascending ones. The RGF guides migrating principal neurons toward the future agranular, dysgranular, and granular insular areas, which show an adult-like definition at 32 GW. Despite the narrow subplate, and the absence of an intermediate zone except in the caudal insula, most insular subdivisions develop into a 6-layered isocortex, possibly due to the well developed outer SVZ at the PSB, which is particularly prominent at the level of the dorso-caudal insula. The small size of the initial PSB sector may, however, determine the limited surface expansion of the insula, which is in contrast to the exuberant growth of the opercula deriving from the adjacent frontal-parietal and temporal VZ/SVZ.

Correlated activity supports efficient cortical processing

PubMed Central

Hung, Chou P.; Cui, Ding; Chen, Yueh-peng; Lin, Chia-pei; Levine, Matthew R.

2015-01-01

Visual recognition is a computational challenge that is thought to occur via efficient coding. An important concept is sparseness, a measure of coding efficiency. The prevailing view is that sparseness supports efficiency by minimizing redundancy and correlations in spiking populations. Yet, we recently reported that “choristers”, neurons that behave more similarly (have correlated stimulus preferences and spontaneous coincident spiking), carry more generalizable object information than uncorrelated neurons (“soloists”) in macaque inferior temporal (IT) cortex. The rarity of choristers (as low as 6% of IT neurons) indicates that they were likely missed in previous studies. Here, we report that correlation strength is distinct from sparseness (choristers are not simply broadly tuned neurons), that choristers are located in non-granular output layers, and that correlated activity predicts human visual search efficiency. These counterintuitive results suggest that a redundant correlational structure supports efficient processing and behavior. PMID:25610392

Differences in the emergent coding properties of cortical and striatal ensembles

PubMed Central

Ma, L.; Hyman, J.M.; Lindsay, A.J.; Phillips, A.G.; Seamans, J.K.

2016-01-01

The function of a given brain region is often defined by the coding properties of its individual neurons, yet how this information is combined at the ensemble level is an equally important consideration. In the present study, multiple neurons from the anterior cingulate cortex (ACC) and the dorsal striatum (DS) were recorded simultaneously as rats performed different sequences of the same three actions. Sequence and lever decoding was remarkably similar on a per-neuron basis in the two regions. At the ensemble level, sequence-specific representations in the DS appeared synchronously but transiently along with the representation of lever location, while these two streams of information appeared independently and asynchronously in the ACC. As a result the ACC achieved superior ensemble decoding accuracy overall. Thus, the manner in which information was combined across neurons in an ensemble determined the functional separation of the ACC and DS on this task. PMID:24974796

Coding and Plasticity in the Mammalian Thermosensory System.

PubMed

Yarmolinsky, David A; Peng, Yueqing; Pogorzala, Leah A; Rutlin, Michael; Hoon, Mark A; Zuker, Charles S

2016-12-07

Perception of the thermal environment begins with the activation of peripheral thermosensory neurons innervating the body surface. To understand how temperature is represented in vivo, we used genetically encoded calcium indicators to measure temperature-evoked responses in hundreds of neurons across the trigeminal ganglion. Our results show how warm, hot, and cold stimuli are represented by distinct population responses, uncover unique functional classes of thermosensory neurons mediating heat and cold sensing, and reveal the molecular logic for peripheral warmth sensing. Next, we examined how the peripheral somatosensory system is functionally reorganized to produce altered perception of the thermal environment after injury. We identify fundamental transformations in sensory coding, including the silencing and recruitment of large ensembles of neurons, providing a cellular basis for perceptual changes in temperature sensing, including heat hypersensitivity, persistence of heat perception, cold hyperalgesia, and cold analgesia. Copyright © 2016 Elsevier Inc. All rights reserved.

Temporal and Rate Coding for Discrete Event Sequences in the Hippocampus.

PubMed

Terada, Satoshi; Sakurai, Yoshio; Nakahara, Hiroyuki; Fujisawa, Shigeyoshi

2017-06-21

Although the hippocampus is critical to episodic memory, neuronal representations supporting this role, especially relating to nonspatial information, remain elusive. Here, we investigated rate and temporal coding of hippocampal CA1 neurons in rats performing a cue-combination task that requires the integration of sequentially provided sound and odor cues. The majority of CA1 neurons displayed sensory cue-, combination-, or choice-specific (simply, "event"-specific) elevated discharge activities, which were sustained throughout the event period. These event cells underwent transient theta phase precession at event onset, followed by sustained phase locking to the early theta phases. As a result of this unique single neuron behavior, the theta sequences of CA1 cell assemblies of the event sequences had discrete representations. These results help to update the conceptual framework for space encoding toward a more general model of episodic event representations in the hippocampus. Copyright © 2017 Elsevier Inc. All rights reserved.

Resting-state fMRI study of patients with fragile X syndrome

NASA Astrophysics Data System (ADS)

Isanova, E.; Petrovskiy, E.; Savelov, A.; Yudkin, D.; Tulupov, A.

2017-08-01

The study aimed to assess the neural activity of different brain regions in patients with fragile X syndrome (FXS) and the healthy volunteers by resting-state functional magnetic resonance imaging (fMRI) on a 1.5 T MRI Achieva scanner (Philips). Results: The fMRI study showed a DMN of brain function in patients with FXS, as well as in the healthy volunteers. Furthermore, it was found that a default mode network of the brain in patients with FXS and healthy volunteers does not have statistically significant differences (p>0.05), which may indicate that the basal activity of neurons in patients with FXS is not reduced. In addition, we have found a significant (p<0.001) increase in the FC within the right inferior parietal and right angular gyrus in the resting state in patients with FXS. Conclusion: New data of functional status of the brain in patients with FXS were received. The significant increase in the resting state functional connectivity within the right inferior parietal and right angular gyrus (p<0.001) in patients with FXS was found.

Distinct roles of visual, parietal, and frontal motor cortices in memory-guided sensorimotor decisions

PubMed Central

Goard, Michael J; Pho, Gerald N; Woodson, Jonathan; Sur, Mriganka

2016-01-01

Mapping specific sensory features to future motor actions is a crucial capability of mammalian nervous systems. We investigated the role of visual (V1), posterior parietal (PPC), and frontal motor (fMC) cortices for sensorimotor mapping in mice during performance of a memory-guided visual discrimination task. Large-scale calcium imaging revealed that V1, PPC, and fMC neurons exhibited heterogeneous responses spanning all task epochs (stimulus, delay, response). Population analyses demonstrated unique encoding of stimulus identity and behavioral choice information across regions, with V1 encoding stimulus, fMC encoding choice even early in the trial, and PPC multiplexing the two variables. Optogenetic inhibition during behavior revealed that all regions were necessary during the stimulus epoch, but only fMC was required during the delay and response epochs. Stimulus identity can thus be rapidly transformed into behavioral choice, requiring V1, PPC, and fMC during the transformation period, but only fMC for maintaining the choice in memory prior to execution. DOI: http://dx.doi.org/10.7554/eLife.13764.001 PMID:27490481

Plasticity and response to action observation: a longitudinal FMRI study of potential mirror neurons in patients with subacute stroke.

PubMed

Brunner, Iris C; Skouen, Jan Sture; Ersland, Lars; Grüner, Renate

2014-01-01

Action observation has been suggested as a possible gateway to retraining arm motor function post stroke. However, it is unclear if the neuronal response to action observation is affected by stroke and if it changes during the course of recovery. To examine longitudinal changes in neuronal activity in a group of patients with subacute stroke when observing and executing a bimanual movement task. Eighteen patients were examined twice using 3-T functional magnetic resonance imaging; 1 to 2 weeks and 3 months post stroke symptom onset. Eighteen control participants were examined once. Image time series were analyzed (SPM8) and correlated with clinical motor function scores. During action observation and execution, an overlap of neuronal activation was observed in the superior and inferior parietal lobe, precentral gyrus, insula, and inferior temporal gyrus in both control participants and patients (P < .05; false discovery rate corrected). The neuronal response in the observation task increased from 1 to 2 weeks to 3 months after stroke. Most activated clusters were observed in the inferior temporal gyrus, the thalamus and movement-related areas, such as the premotor, supplementary and motor cortex (BA4, BA6). Increased activation of cerebellum and premotor area correlated with improved arm motor function. Most patients had regained full movement ability. Plastic changes in neurons responding to action observation and action execution occurred in accordance with clinical recovery. The involvement of motor areas when observing actions early and later after stroke may constitute a possible access to the motor system. © The Author(s) 2014.

Multimodal representation of limb endpoint position in the posterior parietal cortex.

PubMed

Shi, Ying; Apker, Gregory; Buneo, Christopher A

2013-04-01

Understanding the neural representation of limb position is important for comprehending the control of limb movements and the maintenance of body schema, as well as for the development of neuroprosthetic systems designed to replace lost limb function. Multiple subcortical and cortical areas contribute to this representation, but its multimodal basis has largely been ignored. Regarding the parietal cortex, previous results suggest that visual information about arm position is not strongly represented in area 5, although these results were obtained under conditions in which animals were not using their arms to interact with objects in their environment, which could have affected the relative weighting of relevant sensory signals. Here we examined the multimodal basis of limb position in the superior parietal lobule (SPL) as monkeys reached to and actively maintained their arm position at multiple locations in a frontal plane. On half of the trials both visual and nonvisual feedback of the endpoint of the arm were available, while on the other trials visual feedback was withheld. Many neurons were tuned to arm position, while a smaller number were modulated by the presence/absence of visual feedback. Visual modulation generally took the form of a decrease in both firing rate and variability with limb vision and was associated with more accurate decoding of position at the population level under these conditions. These findings support a multimodal representation of limb endpoint position in the SPL but suggest that visual signals are relatively weakly represented in this area, and only at the population level.

Constructing Neuronal Network Models in Massively Parallel Environments.

PubMed

Ippen, Tammo; Eppler, Jochen M; Plesser, Hans E; Diesmann, Markus

2017-01-01

Recent advances in the development of data structures to represent spiking neuron network models enable us to exploit the complete memory of petascale computers for a single brain-scale network simulation. In this work, we investigate how well we can exploit the computing power of such supercomputers for the creation of neuronal networks. Using an established benchmark, we divide the runtime of simulation code into the phase of network construction and the phase during which the dynamical state is advanced in time. We find that on multi-core compute nodes network creation scales well with process-parallel code but exhibits a prohibitively large memory consumption. Thread-parallel network creation, in contrast, exhibits speedup only up to a small number of threads but has little overhead in terms of memory. We further observe that the algorithms creating instances of model neurons and their connections scale well for networks of ten thousand neurons, but do not show the same speedup for networks of millions of neurons. Our work uncovers that the lack of scaling of thread-parallel network creation is due to inadequate memory allocation strategies and demonstrates that thread-optimized memory allocators recover excellent scaling. An analysis of the loop order used for network construction reveals that more complex tests on the locality of operations significantly improve scaling and reduce runtime by allowing construction algorithms to step through large networks more efficiently than in existing code. The combination of these techniques increases performance by an order of magnitude and harnesses the increasingly parallel compute power of the compute nodes in high-performance clusters and supercomputers.

Constructing Neuronal Network Models in Massively Parallel Environments

PubMed Central

Ippen, Tammo; Eppler, Jochen M.; Plesser, Hans E.; Diesmann, Markus

2017-01-01

Recent advances in the development of data structures to represent spiking neuron network models enable us to exploit the complete memory of petascale computers for a single brain-scale network simulation. In this work, we investigate how well we can exploit the computing power of such supercomputers for the creation of neuronal networks. Using an established benchmark, we divide the runtime of simulation code into the phase of network construction and the phase during which the dynamical state is advanced in time. We find that on multi-core compute nodes network creation scales well with process-parallel code but exhibits a prohibitively large memory consumption. Thread-parallel network creation, in contrast, exhibits speedup only up to a small number of threads but has little overhead in terms of memory. We further observe that the algorithms creating instances of model neurons and their connections scale well for networks of ten thousand neurons, but do not show the same speedup for networks of millions of neurons. Our work uncovers that the lack of scaling of thread-parallel network creation is due to inadequate memory allocation strategies and demonstrates that thread-optimized memory allocators recover excellent scaling. An analysis of the loop order used for network construction reveals that more complex tests on the locality of operations significantly improve scaling and reduce runtime by allowing construction algorithms to step through large networks more efficiently than in existing code. The combination of these techniques increases performance by an order of magnitude and harnesses the increasingly parallel compute power of the compute nodes in high-performance clusters and supercomputers. PMID:28559808

Long-Term Temporal Imprecision of Information Coding in the Anterior Cingulate Cortex of Mice with Peripheral Inflammation or Nerve Injury

PubMed Central

Li, Xiang-Yao; Wang, Ning; Wang, Yong-Jie; Zuo, Zhen-Xing; Koga, Kohei; Luo, Fei

2014-01-01

Temporal properties of spike firing in the central nervous system (CNS) are critical for neuronal coding and the precision of information storage. Chronic pain has been reported to affect cognitive and emotional functions, in addition to trigger long-term plasticity in sensory synapses and behavioral sensitization. Less is known about the possible changes in temporal precision of cortical neurons in chronic pain conditions. In the present study, we investigated the temporal precision of action potential firing in the anterior cingulate cortex (ACC) by using both in vivo and in vitro electrophysiological approaches. We found that peripheral inflammation caused by complete Freund's adjuvant (CFA) increased the standard deviation (SD) of spikes latency (also called jitter) of ∼51% of recorded neurons in the ACC of adult rats in vivo. Similar increases in jitter were found in ACC neurons using in vitro brain slices from adult mice with peripheral inflammation or nerve injury. Bath application of glutamate receptor antagonists CNQX and AP5 abolished the enhancement of jitter induced by CFA injection or nerve injury, suggesting that the increased jitter depends on the glutamatergic synaptic transmission. Activation of adenylyl cyclases (ACs) by bath application of forskolin increased jitter, whereas genetic deletion of AC1 abolished the change of jitter caused by CFA inflammation. Our study provides strong evidence for long-term changes of temporal precision of information coding in cortical neurons after peripheral injuries and explains neuronal mechanism for chronic pain caused cognitive and emotional impairment. PMID:25100600

The tactile motion aftereffect suggests an intensive code for speed in neurons sensitive to both speed and direction of motion

PubMed Central

Birznieks, I.; Vickery, R. M.; Holcombe, A. O.; Seizova-Cajic, T.

2016-01-01

Neurophysiological studies in primates have found that direction-sensitive neurons in the primary somatosensory cortex (SI) generally increase their response rate with increasing speed of object motion across the skin and show little evidence of speed tuning. We employed psychophysics to determine whether human perception of motion direction could be explained by features of such neurons and whether evidence can be found for a speed-tuned process. After adaptation to motion across the skin, a subsequently presented dynamic test stimulus yields an impression of motion in the opposite direction. We measured the strength of this tactile motion aftereffect (tMAE) induced with different combinations of adapting and test speeds. Distal-to-proximal or proximal-to-distal adapting motion was applied to participants' index fingers using a tactile array, after which participants reported the perceived direction of a bidirectional test stimulus. An intensive code for speed, like that observed in SI neurons, predicts greater adaptation (and a stronger tMAE) the faster the adapting speed, regardless of the test speed. In contrast, speed tuning of direction-sensitive neurons predicts the greatest tMAE when the adapting and test stimuli have matching speeds. We found that the strength of the tMAE increased monotonically with adapting speed, regardless of the test speed, showing no evidence of speed tuning. Our data are consistent with neurophysiological findings that suggest an intensive code for speed along the motion processing pathways comprising neurons sensitive both to speed and direction of motion. PMID:26823511

In monkeys making value-based decisions, amygdala neurons are sensitive to cue value as distinct from cue salience.

PubMed

Leathers, Marvin L; Olson, Carl R

2017-04-01

Neurons in the lateral intraparietal (LIP) area of macaque monkey parietal cortex respond to cues predicting rewards and penalties of variable size in a manner that depends on the motivational salience of the predicted outcome (strong for both large reward and large penalty) rather than on its value (positive for large reward and negative for large penalty). This finding suggests that LIP mediates the capture of attention by salient events and does not encode value in the service of value-based decision making. It leaves open the question whether neurons elsewhere in the brain encode value in the identical task. To resolve this issue, we recorded neuronal activity in the amygdala in the context of the task employed in the LIP study. We found that responses to reward-predicting cues were similar between areas, with the majority of reward-sensitive neurons responding more strongly to cues that predicted large reward than to those that predicted small reward. Responses to penalty-predicting cues were, however, markedly different. In the amygdala, unlike LIP, few neurons were sensitive to penalty size, few penalty-sensitive neurons favored large over small penalty, and the dependence of firing rate on penalty size was negatively correlated with its dependence on reward size. These results indicate that amygdala neurons encoded cue value under circumstances in which LIP neurons exhibited sensitivity to motivational salience. However, the representation of negative value, as reflected in sensitivity to penalty size, was weaker than the representation of positive value, as reflected in sensitivity to reward size. NEW & NOTEWORTHY This is the first study to characterize amygdala neuronal responses to cues predicting rewards and penalties of variable size in monkeys making value-based choices. Manipulating reward and penalty size allowed distinguishing activity dependent on motivational salience from activity dependent on value. This approach revealed in a previous study that neurons of the lateral intraparietal (LIP) area encode motivational salience. Here, it reveals that amygdala neurons encode value. The results establish a sharp functional distinction between the two areas. Copyright © 2017 the American Physiological Society.

Dynamic Excitatory and Inhibitory Gain Modulation Can Produce Flexible, Robust and Optimal Decision-making

PubMed Central

Niyogi, Ritwik K.; Wong-Lin, KongFatt

2013-01-01

Behavioural and neurophysiological studies in primates have increasingly shown the involvement of urgency signals during the temporal integration of sensory evidence in perceptual decision-making. Neuronal correlates of such signals have been found in the parietal cortex, and in separate studies, demonstrated attention-induced gain modulation of both excitatory and inhibitory neurons. Although previous computational models of decision-making have incorporated gain modulation, their abstract forms do not permit an understanding of the contribution of inhibitory gain modulation. Thus, the effects of co-modulating both excitatory and inhibitory neuronal gains on decision-making dynamics and behavioural performance remain unclear. In this work, we incorporate time-dependent co-modulation of the gains of both excitatory and inhibitory neurons into our previous biologically based decision circuit model. We base our computational study in the context of two classic motion-discrimination tasks performed in animals. Our model shows that by simultaneously increasing the gains of both excitatory and inhibitory neurons, a variety of the observed dynamic neuronal firing activities can be replicated. In particular, the model can exhibit winner-take-all decision-making behaviour with higher firing rates and within a significantly more robust model parameter range. It also exhibits short-tailed reaction time distributions even when operating near a dynamical bifurcation point. The model further shows that neuronal gain modulation can compensate for weaker recurrent excitation in a decision neural circuit, and support decision formation and storage. Higher neuronal gain is also suggested in the more cognitively demanding reaction time than in the fixed delay version of the task. Using the exact temporal delays from the animal experiments, fast recruitment of gain co-modulation is shown to maximize reward rate, with a timescale that is surprisingly near the experimentally fitted value. Our work provides insights into the simultaneous and rapid modulation of excitatory and inhibitory neuronal gains, which enables flexible, robust, and optimal decision-making. PMID:23825935

Spiking network simulation code for petascale computers.

PubMed

Kunkel, Susanne; Schmidt, Maximilian; Eppler, Jochen M; Plesser, Hans E; Masumoto, Gen; Igarashi, Jun; Ishii, Shin; Fukai, Tomoki; Morrison, Abigail; Diesmann, Markus; Helias, Moritz

2014-01-01

Brain-scale networks exhibit a breathtaking heterogeneity in the dynamical properties and parameters of their constituents. At cellular resolution, the entities of theory are neurons and synapses and over the past decade researchers have learned to manage the heterogeneity of neurons and synapses with efficient data structures. Already early parallel simulation codes stored synapses in a distributed fashion such that a synapse solely consumes memory on the compute node harboring the target neuron. As petaflop computers with some 100,000 nodes become increasingly available for neuroscience, new challenges arise for neuronal network simulation software: Each neuron contacts on the order of 10,000 other neurons and thus has targets only on a fraction of all compute nodes; furthermore, for any given source neuron, at most a single synapse is typically created on any compute node. From the viewpoint of an individual compute node, the heterogeneity in the synaptic target lists thus collapses along two dimensions: the dimension of the types of synapses and the dimension of the number of synapses of a given type. Here we present a data structure taking advantage of this double collapse using metaprogramming techniques. After introducing the relevant scaling scenario for brain-scale simulations, we quantitatively discuss the performance on two supercomputers. We show that the novel architecture scales to the largest petascale supercomputers available today.

Spiking network simulation code for petascale computers

PubMed Central

Kunkel, Susanne; Schmidt, Maximilian; Eppler, Jochen M.; Plesser, Hans E.; Masumoto, Gen; Igarashi, Jun; Ishii, Shin; Fukai, Tomoki; Morrison, Abigail; Diesmann, Markus; Helias, Moritz

2014-01-01

Brain-scale networks exhibit a breathtaking heterogeneity in the dynamical properties and parameters of their constituents. At cellular resolution, the entities of theory are neurons and synapses and over the past decade researchers have learned to manage the heterogeneity of neurons and synapses with efficient data structures. Already early parallel simulation codes stored synapses in a distributed fashion such that a synapse solely consumes memory on the compute node harboring the target neuron. As petaflop computers with some 100,000 nodes become increasingly available for neuroscience, new challenges arise for neuronal network simulation software: Each neuron contacts on the order of 10,000 other neurons and thus has targets only on a fraction of all compute nodes; furthermore, for any given source neuron, at most a single synapse is typically created on any compute node. From the viewpoint of an individual compute node, the heterogeneity in the synaptic target lists thus collapses along two dimensions: the dimension of the types of synapses and the dimension of the number of synapses of a given type. Here we present a data structure taking advantage of this double collapse using metaprogramming techniques. After introducing the relevant scaling scenario for brain-scale simulations, we quantitatively discuss the performance on two supercomputers. We show that the novel architecture scales to the largest petascale supercomputers available today. PMID:25346682

Rank-order-selective neurons form a temporal basis set for the generation of motor sequences.

PubMed

Salinas, Emilio

2009-04-08

Many behaviors are composed of a series of elementary motor actions that must occur in a specific order, but the neuronal mechanisms by which such motor sequences are generated are poorly understood. In particular, if a sequence consists of a few motor actions, a primate can learn to replicate it from memory after practicing it for just a few trials. How do the motor and premotor areas of the brain assemble motor sequences so fast? The network model presented here reveals part of the solution to this problem. The model is based on experiments showing that, during the performance of motor sequences, some cortical neurons are always activated at specific times, regardless of which motor action is being executed. In the model, a population of such rank-order-selective (ROS) cells drives a layer of downstream motor neurons so that these generate specific movements at different times in different sequences. A key ingredient of the model is that the amplitude of the ROS responses must be modulated by sequence identity. Because of this modulation, which is consistent with experimental reports, the network is able not only to produce multiple sequences accurately but also to learn a new sequence with minimal changes in connectivity. The ROS neurons modulated by sequence identity thus serve as a basis set for constructing arbitrary sequences of motor responses downstream. The underlying mechanism is analogous to the mechanism described in parietal areas for generating coordinate transformations in the spatial domain.

Comparison of neural damage induced by electrical stimulation with faradaic and capacitor electrodes.

PubMed

McCreery, D B; Agnew, W F; Yuen, T G; Bullara, L A

1988-01-01

Arrays of platinum (faradaic) and anodized, sintered tantalum pentoxide (capacitor) electrodes were implanted bilaterally in the subdural space of the parietal cortex of the cat. Two weeks after implantation both types of electrodes were pulsed for seven hours with identical waveforms consisting of controlled-current, charge-balanced, symmetric, anodic-first pulse pairs, 400 microseconds/phase and a charge density of 80-100 microC/cm2 (microcoulombs per square cm) at 50 pps (pulses per second). One group of animals was sacrificed immediately following stimulation and a second smaller group one week after stimulation. Tissues beneath both types of pulsed electrodes were damaged, but the difference in damage for the two electrode types was not statistically significant. Tissue beneath unpulsed electrodes was normal. At the ultrastructural level, in animals killed immediately after stimulation, shrunken and hyperchromic neurons were intermixed with neurons showing early intracellular edema. Glial cells appeared essentially normal. In animals killed one week after stimulation most of the damaged neurons had recovered, but the presence of shrunken, vacuolated and degenerating neurons showed that some of the cells were damaged irreversibly. It is concluded that most of the neural damage from stimulations of the brain surface at the level used in this study derives from processes associated with passage of the stimulus current through tissue, such as neuronal hyperactivity rather than electrochemical reactions associated with current injection across the electrode-tissue interface, since such reactions occur only with the faradaic electrodes.

RANK-ORDER-SELECTIVE NEURONS FORM A TEMPORAL BASIS SET FOR THE GENERATION OF MOTOR SEQUENCES

PubMed Central

Salinas, Emilio

2009-01-01

Many behaviors are composed of a series of elementary motor actions that must occur in a specific order, but the neuronal mechanisms by which such motor sequences are generated are poorly understood. In particular, if a sequence consists of a few motor actions, a primate can learn to replicate it from memory after practicing it for just a few trials. How do the motor and premotor areas of the brain assemble motor sequences so fast? The network model presented here reveals part of the solution to this problem. The model is based on experiments showing that, during the performance of motor sequences, some cortical neurons are always activated at specific times, regardless of which motor action is being executed. In the model, a population of such rank-order-selective (ROS) cells drives a layer of downstream motor neurons so that these generate specific movements at different times in different sequences. A key ingredient of the model is that the amplitude of the ROS responses must be modulated by sequence identity. Because of this modulation, which is consistent with experimental reports, the network is able not only to produce multiple sequences accurately but also to learn a new sequence with minimal changes in connectivity. The ROS neurons modulated by sequence identity thus serve as a basis set for constructing arbitrary sequences of motor responses downstream. The underlying mechanism is analogous to the mechanism described in parietal areas for generating coordinate transformations in the spatial domain. PMID:19357265

Information processing in the CNS: a supramolecular chemistry?

PubMed

Tozzi, Arturo

2015-10-01

How does central nervous system process information? Current theories are based on two tenets: (a) information is transmitted by action potentials, the language by which neurons communicate with each other-and (b) homogeneous neuronal assemblies of cortical circuits operate on these neuronal messages where the operations are characterized by the intrinsic connectivity among neuronal populations. In this view, the size and time course of any spike is stereotypic and the information is restricted to the temporal sequence of the spikes; namely, the "neural code". However, an increasing amount of novel data point towards an alternative hypothesis: (a) the role of neural code in information processing is overemphasized. Instead of simply passing messages, action potentials play a role in dynamic coordination at multiple spatial and temporal scales, establishing network interactions across several levels of a hierarchical modular architecture, modulating and regulating the propagation of neuronal messages. (b) Information is processed at all levels of neuronal infrastructure from macromolecules to population dynamics. For example, intra-neuronal (changes in protein conformation, concentration and synthesis) and extra-neuronal factors (extracellular proteolysis, substrate patterning, myelin plasticity, microbes, metabolic status) can have a profound effect on neuronal computations. This means molecular message passing may have cognitive connotations. This essay introduces the concept of "supramolecular chemistry", involving the storage of information at the molecular level and its retrieval, transfer and processing at the supramolecular level, through transitory non-covalent molecular processes that are self-organized, self-assembled and dynamic. Finally, we note that the cortex comprises extremely heterogeneous cells, with distinct regional variations, macromolecular assembly, receptor repertoire and intrinsic microcircuitry. This suggests that every neuron (or group of neurons) embodies different molecular information that hands an operational effect on neuronal computation.

The Opponent Channel Population Code of Sound Location Is an Efficient Representation of Natural Binaural Sounds

PubMed Central

Młynarski, Wiktor

2015-01-01

In mammalian auditory cortex, sound source position is represented by a population of broadly tuned neurons whose firing is modulated by sounds located at all positions surrounding the animal. Peaks of their tuning curves are concentrated at lateral position, while their slopes are steepest at the interaural midline, allowing for the maximum localization accuracy in that area. These experimental observations contradict initial assumptions that the auditory space is represented as a topographic cortical map. It has been suggested that a “panoramic” code has evolved to match specific demands of the sound localization task. This work provides evidence suggesting that properties of spatial auditory neurons identified experimentally follow from a general design principle- learning a sparse, efficient representation of natural stimuli. Natural binaural sounds were recorded and served as input to a hierarchical sparse-coding model. In the first layer, left and right ear sounds were separately encoded by a population of complex-valued basis functions which separated phase and amplitude. Both parameters are known to carry information relevant for spatial hearing. Monaural input converged in the second layer, which learned a joint representation of amplitude and interaural phase difference. Spatial selectivity of each second-layer unit was measured by exposing the model to natural sound sources recorded at different positions. Obtained tuning curves match well tuning characteristics of neurons in the mammalian auditory cortex. This study connects neuronal coding of the auditory space with natural stimulus statistics and generates new experimental predictions. Moreover, results presented here suggest that cortical regions with seemingly different functions may implement the same computational strategy-efficient coding. PMID:25996373

Encoding of Spatial Attention by Primate Prefrontal Cortex Neuronal Ensembles

PubMed Central

Treue, Stefan

2018-01-01

Abstract Single neurons in the primate lateral prefrontal cortex (LPFC) encode information about the allocation of visual attention and the features of visual stimuli. However, how this compares to the performance of neuronal ensembles at encoding the same information is poorly understood. Here, we recorded the responses of neuronal ensembles in the LPFC of two macaque monkeys while they performed a task that required attending to one of two moving random dot patterns positioned in different hemifields and ignoring the other pattern. We found single units selective for the location of the attended stimulus as well as for its motion direction. To determine the coding of both variables in the population of recorded units, we used a linear classifier and progressively built neuronal ensembles by iteratively adding units according to their individual performance (best single units), or by iteratively adding units based on their contribution to the ensemble performance (best ensemble). For both methods, ensembles of relatively small sizes (n < 60) yielded substantially higher decoding performance relative to individual single units. However, the decoder reached similar performance using fewer neurons with the best ensemble building method compared with the best single units method. Our results indicate that neuronal ensembles within the LPFC encode more information about the attended spatial and nonspatial features of visual stimuli than individual neurons. They further suggest that efficient coding of attention can be achieved by relatively small neuronal ensembles characterized by a certain relationship between signal and noise correlation structures. PMID:29568798

Neural coding of sound envelope in reverberant environments.

PubMed

Slama, Michaël C C; Delgutte, Bertrand

2015-03-11

Speech reception depends critically on temporal modulations in the amplitude envelope of the speech signal. Reverberation encountered in everyday environments can substantially attenuate these modulations. To assess the effect of reverberation on the neural coding of amplitude envelope, we recorded from single units in the inferior colliculus (IC) of unanesthetized rabbit using sinusoidally amplitude modulated (AM) broadband noise stimuli presented in simulated anechoic and reverberant environments. Although reverberation degraded both rate and temporal coding of AM in IC neurons, in most neurons, the degradation in temporal coding was smaller than the AM attenuation in the stimulus. This compensation could largely be accounted for by the compressive shape of the modulation input-output function (MIOF), which describes the nonlinear transformation of modulation depth from acoustic stimuli into neural responses. Additionally, in a subset of neurons, the temporal coding of AM was better for reverberant stimuli than for anechoic stimuli having the same modulation depth at the ear. Using hybrid anechoic stimuli that selectively possess certain properties of reverberant sounds, we show that this reverberant advantage is not caused by envelope distortion, static interaural decorrelation, or spectral coloration. Overall, our results suggest that the auditory system may possess dual mechanisms that make the coding of amplitude envelope relatively robust in reverberation: one general mechanism operating for all stimuli with small modulation depths, and another mechanism dependent on very specific properties of reverberant stimuli, possibly the periodic fluctuations in interaural correlation at the modulation frequency. Copyright © 2015 the authors 0270-6474/15/354452-17$15.00/0.

Decoding complex flow-field patterns in visual working memory.

PubMed

Christophel, Thomas B; Haynes, John-Dylan

2014-05-01

There has been a long history of research on visual working memory. Whereas early studies have focused on the role of lateral prefrontal cortex in the storage of sensory information, this has been challenged by research in humans that has directly assessed the encoding of perceptual contents, pointing towards a role of visual and parietal regions during storage. In a previous study we used pattern classification to investigate the storage of complex visual color patterns across delay periods. This revealed coding of such contents in early visual and parietal brain regions. Here we aim to investigate whether the involvement of visual and parietal cortex is also observable for other types of complex, visuo-spatial pattern stimuli. Specifically, we used a combination of fMRI and multivariate classification to investigate the retention of complex flow-field stimuli defined by the spatial patterning of motion trajectories of random dots. Subjects were trained to memorize the precise spatial layout of these stimuli and to retain this information during an extended delay. We used a multivariate decoding approach to identify brain regions where spatial patterns of activity encoded the memorized stimuli. Content-specific memory signals were observable in motion sensitive visual area MT+ and in posterior parietal cortex that might encode spatial information in a modality independent manner. Interestingly, we also found information about the memorized visual stimulus in somatosensory cortex, suggesting a potential crossmodal contribution to memory. Our findings thus indicate that working memory storage of visual percepts might be distributed across unimodal, multimodal and even crossmodal brain regions. Copyright © 2014 Elsevier Inc. All rights reserved.

Regulation of Cortical Dynamic Range by Background Synaptic Noise and Feedforward Inhibition.

PubMed

Khubieh, Ayah; Ratté, Stéphanie; Lankarany, Milad; Prescott, Steven A

2016-08-01

The cortex encodes a broad range of inputs. This breadth of operation requires sensitivity to weak inputs yet non-saturating responses to strong inputs. If individual pyramidal neurons were to have a narrow dynamic range, as previously claimed, then staggered all-or-none recruitment of those neurons would be necessary for the population to achieve a broad dynamic range. Contrary to this explanation, we show here through dynamic clamp experiments in vitro and computer simulations that pyramidal neurons have a broad dynamic range under the noisy conditions that exist in the intact brain due to background synaptic input. Feedforward inhibition capitalizes on those noise effects to control neuronal gain and thereby regulates the population dynamic range. Importantly, noise allows neurons to be recruited gradually and occludes the staggered recruitment previously attributed to heterogeneous excitation. Feedforward inhibition protects spike timing against the disruptive effects of noise, meaning noise can enable the gain control required for rate coding without compromising the precise spike timing required for temporal coding. © The Author 2015. Published by Oxford University Press. All rights reserved. For Permissions, please e-mail: journals.permissions@oup.com.

Integration of Visual and Proprioceptive Limb Position Information in Human Posterior Parietal, Premotor, and Extrastriate Cortex.

PubMed

Limanowski, Jakub; Blankenburg, Felix

2016-03-02

The brain constructs a flexible representation of the body from multisensory information. Previous work on monkeys suggests that the posterior parietal cortex (PPC) and ventral premotor cortex (PMv) represent the position of the upper limbs based on visual and proprioceptive information. Human experiments on the rubber hand illusion implicate similar regions, but since such experiments rely on additional visuo-tactile interactions, they cannot isolate visuo-proprioceptive integration. Here, we independently manipulated the position (palm or back facing) of passive human participants' unseen arm and of a photorealistic virtual 3D arm. Functional magnetic resonance imaging (fMRI) revealed that matching visual and proprioceptive information about arm position engaged the PPC, PMv, and the body-selective extrastriate body area (EBA); activity in the PMv moreover reflected interindividual differences in congruent arm ownership. Further, the PPC, PMv, and EBA increased their coupling with the primary visual cortex during congruent visuo-proprioceptive position information. These results suggest that human PPC, PMv, and EBA evaluate visual and proprioceptive position information and, under sufficient cross-modal congruence, integrate it into a multisensory representation of the upper limb in space. The position of our limbs in space constantly changes, yet the brain manages to represent limb position accurately by combining information from vision and proprioception. Electrophysiological recordings in monkeys have revealed neurons in the posterior parietal and premotor cortices that seem to implement and update such a multisensory limb representation, but this has been difficult to demonstrate in humans. Our fMRI experiment shows that human posterior parietal, premotor, and body-selective visual brain areas respond preferentially to a virtual arm seen in a position corresponding to one's unseen hidden arm, while increasing their communication with regions conveying visual information. These brain areas thus likely integrate visual and proprioceptive information into a flexible multisensory body representation. Copyright © 2016 the authors 0270-6474/16/362582-08$15.00/0.

Identification of degenerate neuronal systems based on intersubject variability.

PubMed

Noppeney, Uta; Penny, Will D; Price, Cathy J; Flandin, Guillaume; Friston, Karl J

2006-04-15

Group studies implicitly assume that all subjects activate one common system to sustain a particular cognitive task. Intersubject variability is generally treated as well-behaved and uninteresting noise. However, intersubject variability might result from subjects engaging different degenerate neuronal systems that are each sufficient for task performance. This would produce a multimodal distribution of intersubject variability. We have explored this idea with the help of Gaussian Mixture Modeling and Bayesian model comparison procedures. We illustrate our approach using a crossmodal priming paradigm, in which subjects perform a semantic decision on environmental sounds or their spoken names that were preceded by a semantically congruent or incongruent picture or written name. All subjects consistently activated the superior temporal gyri bilaterally, the left fusiform gyrus and the inferior frontal sulcus. Comparing a One and Two Gaussian Mixture Model of the unexplained residuals provided very strong evidence for two groups with distinct activation patterns: 6 subjects exhibited additional activations in the superior temporal sulci bilaterally, the right superior frontal and central sulcus. 11 subjects showed increased activation in the striate and the right inferior parietal cortex. These results suggest that semantic decisions on auditory-visual compound stimuli might be accomplished by two overlapping degenerate neuronal systems.

Impaired cortical activation in autistic children: is the mirror neuron system involved?

PubMed

Martineau, Joëlle; Cochin, Stéphanie; Magne, Rémy; Barthelemy, Catherine

2008-04-01

The inability to imitate becomes obvious early in autistic children and seems to contribute to learning delay and to disorders of communication and contact. Posture, motility and imitation disorders in autistic syndrome might be the consequence of an abnormality of sensori-motor integration, related to the visual perception of movement, and could reflect impairment of the mirror neuron system (MNS). We compared EEG activity during the observation of videos showing actions or still scenes in 14 right-handed autistic children and 14 right-handed, age- and gender-matched control children (3 girls and 11 boys, aged 5 years 3 months-7 years 11 months). We showed desynchronisation of the EEG in the motor cerebral cortex and the frontal and temporal areas during observation of human actions in the group of healthy children. No such desynchronisation was found in autistic children. Moreover, inversion of the pattern of hemispheric activation was found in autistic children, with increased cortical activity in the right hemisphere in the posterior region, including the centro-parietal and temporo-occipital sites. These results are in agreement with the hypothesis of impairment of the mirror neuron system in autistic disorder.

A review on functional and structural brain connectivity in numerical cognition

PubMed Central

Moeller, Korbinian; Willmes, Klaus; Klein, Elise

2015-01-01

Only recently has the complex anatomo-functional system underlying numerical cognition become accessible to evaluation in the living brain. We identified 27 studies investigating brain connectivity in numerical cognition. Despite considerable heterogeneity regarding methodological approaches, populations investigated, and assessment procedures implemented, the results provided largely converging evidence regarding the underlying brain connectivity involved in numerical cognition. Analyses of both functional/effective as well as structural connectivity have consistently corroborated the assumption that numerical cognition is subserved by a fronto-parietal network including (intra)parietal as well as (pre)frontal cortex sites. Evaluation of structural connectivity has indicated the involvement of fronto-parietal association fibers encompassing the superior longitudinal fasciculus dorsally and the external capsule/extreme capsule system ventrally. Additionally, commissural fibers seem to connect the bilateral intraparietal sulci when number magnitude information is processed. Finally, the identification of projection fibers such as the superior corona radiata indicates connections between cortex and basal ganglia as well as the thalamus in numerical cognition. Studies on functional/effective connectivity further indicated a specific role of the hippocampus. These specifications of brain connectivity augment the triple-code model of number processing and calculation with respect to how gray matter areas associated with specific number-related representations may work together. PMID:26029075

Temporal characteristics of gustatory responses in rat parabrachial neurons vary by stimulus and chemosensitive neuron type.

PubMed

Geran, Laura; Travers, Susan

2013-01-01

It has been demonstrated that temporal features of spike trains can increase the amount of information available for gustatory processing. However, the nature of these temporal characteristics and their relationship to different taste qualities and neuron types are not well-defined. The present study analyzed the time course of taste responses from parabrachial (PBN) neurons elicited by multiple applications of "sweet" (sucrose), "salty" (NaCl), "sour" (citric acid), and "bitter" (quinine and cycloheximide) stimuli in an acute preparation. Time course varied significantly by taste stimulus and best-stimulus classification. Across neurons, the ensemble code for the three electrolytes was similar initially but quinine diverged from NaCl and acid during the second 500 ms of stimulation and all four qualities became distinct just after 1s. This temporal evolution was reflected in significantly broader tuning during the initial response. Metric space analyses of quality discrimination by individual neurons showed that increases in information (H) afforded by temporal factors was usually explained by differences in rate envelope, which had a greater impact during the initial 2s (22.5% increase in H) compared to the later response (9.5%). Moreover, timing had a differential impact according to cell type, with between-quality discrimination in neurons activated maximally by NaCl or citric acid most affected. Timing was also found to dramatically improve within-quality discrimination (80% increase in H) in neurons that responded optimally to bitter stimuli (B-best). Spikes from B-best neurons were also more likely to occur in bursts. These findings suggest that among PBN taste neurons, time-dependent increases in mutual information can arise from stimulus- and neuron-specific differences in response envelope during the initial dynamic period. A stable rate code predominates in later epochs.

Temporal Characteristics of Gustatory Responses in Rat Parabrachial Neurons Vary by Stimulus and Chemosensitive Neuron Type

PubMed Central

Geran, Laura; Travers, Susan

2013-01-01

It has been demonstrated that temporal features of spike trains can increase the amount of information available for gustatory processing. However, the nature of these temporal characteristics and their relationship to different taste qualities and neuron types are not well-defined. The present study analyzed the time course of taste responses from parabrachial (PBN) neurons elicited by multiple applications of “sweet” (sucrose), “salty” (NaCl), “sour” (citric acid), and “bitter” (quinine and cycloheximide) stimuli in an acute preparation. Time course varied significantly by taste stimulus and best-stimulus classification. Across neurons, the ensemble code for the three electrolytes was similar initially but quinine diverged from NaCl and acid during the second 500ms of stimulation and all four qualities became distinct just after 1s. This temporal evolution was reflected in significantly broader tuning during the initial response. Metric space analyses of quality discrimination by individual neurons showed that increases in information (H) afforded by temporal factors was usually explained by differences in rate envelope, which had a greater impact during the initial 2s (22.5% increase in H) compared to the later response (9.5%). Moreover, timing had a differential impact according to cell type, with between-quality discrimination in neurons activated maximally by NaCl or citric acid most affected. Timing was also found to dramatically improve within-quality discrimination (80% increase in H) in neurons that responded optimally to bitter stimuli (B-best). Spikes from B-best neurons were also more likely to occur in bursts. These findings suggest that among PBN taste neurons, time-dependent increases in mutual information can arise from stimulus- and neuron-specific differences in response envelope during the initial dynamic period. A stable rate code predominates in later epochs. PMID:24124597

Evidence for similar patterns of neural activity elicited by picture- and word-based representations of natural scenes.

PubMed

Kumar, Manoj; Federmeier, Kara D; Fei-Fei, Li; Beck, Diane M

2017-07-15

A long-standing core question in cognitive science is whether different modalities and representation types (pictures, words, sounds, etc.) access a common store of semantic information. Although different input types have been shown to activate a shared network of brain regions, this does not necessitate that there is a common representation, as the neurons in these regions could still differentially process the different modalities. However, multi-voxel pattern analysis can be used to assess whether, e.g., pictures and words evoke a similar pattern of activity, such that the patterns that separate categories in one modality transfer to the other. Prior work using this method has found support for a common code, but has two limitations: they have either only examined disparate categories (e.g. animals vs. tools) that are known to activate different brain regions, raising the possibility that the pattern separation and inferred similarity reflects only large scale differences between the categories or they have been limited to individual object representations. By using natural scene categories, we not only extend the current literature on cross-modal representations beyond objects, but also, because natural scene categories activate a common set of brain regions, we identify a more fine-grained (i.e. higher spatial resolution) common representation. Specifically, we studied picture- and word-based representations of natural scene stimuli from four different categories: beaches, cities, highways, and mountains. Participants passively viewed blocks of either phrases (e.g. "sandy beach") describing scenes or photographs from those same scene categories. To determine whether the phrases and pictures evoke a common code, we asked whether a classifier trained on one stimulus type (e.g. phrase stimuli) would transfer (i.e. cross-decode) to the other stimulus type (e.g. picture stimuli). The analysis revealed cross-decoding in the occipitotemporal, posterior parietal and frontal cortices. This similarity of neural activity patterns across the two input types, for categories that co-activate local brain regions, provides strong evidence of a common semantic code for pictures and words in the brain. Copyright © 2017 Elsevier Inc. All rights reserved.

Interplay between low threshold voltage-gated K+ channels and synaptic inhibition in neurons of the chicken nucleus laminaris along its frequency axis

PubMed Central

Hamlet, William R.; Liu, Yu-Wei; Tang, Zheng-Quan; Lu, Yong

2014-01-01

Central auditory neurons that localize sound in horizontal space have specialized intrinsic and synaptic cellular mechanisms to tightly control the threshold and timing for action potential generation. However, the critical interplay between intrinsic voltage-gated conductances and extrinsic synaptic conductances in determining neuronal output are not well understood. In chicken, neurons in the nucleus laminaris (NL) encode sound location using interaural time difference (ITD) as a cue. Along the tonotopic axis of NL, there exist robust differences among low, middle, and high frequency (LF, MF, and HF, respectively) neurons in a variety of neuronal properties such as low threshold voltage-gated K+ (LTK) channels and depolarizing inhibition. This establishes NL as an ideal model to examine the interactions between LTK currents and synaptic inhibition across the tonotopic axis. Using whole-cell patch clamp recordings prepared from chicken embryos (E17–E18), we found that LTK currents were larger in MF and HF neurons than in LF neurons. Kinetic analysis revealed that LTK currents in MF neurons activated at lower voltages than in LF and HF neurons, whereas the inactivation of the currents was similar across the tonotopic axis. Surprisingly, blockade of LTK currents using dendrotoxin-I (DTX) tended to broaden the duration and increase the amplitude of the depolarizing inhibitory postsynaptic potentials (IPSPs) in NL neurons without dependence on coding frequency regions. Analyses of the effects of DTX on inhibitory postsynaptic currents led us to interpret this unexpected observation as a result of primarily postsynaptic effects of LTK currents on MF and HF neurons, and combined presynaptic and postsynaptic effects in LF neurons. Furthermore, DTX transferred subthreshold IPSPs to spikes. Taken together, the results suggest a critical role for LTK currents in regulating inhibitory synaptic strength in ITD-coding neurons at various frequencies. PMID:24904297

Interplay between low threshold voltage-gated K(+) channels and synaptic inhibition in neurons of the chicken nucleus laminaris along its frequency axis.

PubMed

Hamlet, William R; Liu, Yu-Wei; Tang, Zheng-Quan; Lu, Yong

2014-01-01

Central auditory neurons that localize sound in horizontal space have specialized intrinsic and synaptic cellular mechanisms to tightly control the threshold and timing for action potential generation. However, the critical interplay between intrinsic voltage-gated conductances and extrinsic synaptic conductances in determining neuronal output are not well understood. In chicken, neurons in the nucleus laminaris (NL) encode sound location using interaural time difference (ITD) as a cue. Along the tonotopic axis of NL, there exist robust differences among low, middle, and high frequency (LF, MF, and HF, respectively) neurons in a variety of neuronal properties such as low threshold voltage-gated K(+) (LTK) channels and depolarizing inhibition. This establishes NL as an ideal model to examine the interactions between LTK currents and synaptic inhibition across the tonotopic axis. Using whole-cell patch clamp recordings prepared from chicken embryos (E17-E18), we found that LTK currents were larger in MF and HF neurons than in LF neurons. Kinetic analysis revealed that LTK currents in MF neurons activated at lower voltages than in LF and HF neurons, whereas the inactivation of the currents was similar across the tonotopic axis. Surprisingly, blockade of LTK currents using dendrotoxin-I (DTX) tended to broaden the duration and increase the amplitude of the depolarizing inhibitory postsynaptic potentials (IPSPs) in NL neurons without dependence on coding frequency regions. Analyses of the effects of DTX on inhibitory postsynaptic currents led us to interpret this unexpected observation as a result of primarily postsynaptic effects of LTK currents on MF and HF neurons, and combined presynaptic and postsynaptic effects in LF neurons. Furthermore, DTX transferred subthreshold IPSPs to spikes. Taken together, the results suggest a critical role for LTK currents in regulating inhibitory synaptic strength in ITD-coding neurons at various frequencies.

ANNarchy: a code generation approach to neural simulations on parallel hardware

PubMed Central

Vitay, Julien; Dinkelbach, Helge Ü.; Hamker, Fred H.

2015-01-01

Many modern neural simulators focus on the simulation of networks of spiking neurons on parallel hardware. Another important framework in computational neuroscience, rate-coded neural networks, is mostly difficult or impossible to implement using these simulators. We present here the ANNarchy (Artificial Neural Networks architect) neural simulator, which allows to easily define and simulate rate-coded and spiking networks, as well as combinations of both. The interface in Python has been designed to be close to the PyNN interface, while the definition of neuron and synapse models can be specified using an equation-oriented mathematical description similar to the Brian neural simulator. This information is used to generate C++ code that will efficiently perform the simulation on the chosen parallel hardware (multi-core system or graphical processing unit). Several numerical methods are available to transform ordinary differential equations into an efficient C++code. We compare the parallel performance of the simulator to existing solutions. PMID:26283957

Iterative free-energy optimization for recurrent neural networks (INFERNO).

PubMed

Pitti, Alexandre; Gaussier, Philippe; Quoy, Mathias

2017-01-01

The intra-parietal lobe coupled with the Basal Ganglia forms a working memory that demonstrates strong planning capabilities for generating robust yet flexible neuronal sequences. Neurocomputational models however, often fails to control long range neural synchrony in recurrent spiking networks due to spontaneous activity. As a novel framework based on the free-energy principle, we propose to see the problem of spikes' synchrony as an optimization problem of the neurons sub-threshold activity for the generation of long neuronal chains. Using a stochastic gradient descent, a reinforcement signal (presumably dopaminergic) evaluates the quality of one input vector to move the recurrent neural network to a desired activity; depending on the error made, this input vector is strengthened to hill-climb the gradient or elicited to search for another solution. This vector can be learned then by one associative memory as a model of the basal-ganglia to control the recurrent neural network. Experiments on habit learning and on sequence retrieving demonstrate the capabilities of the dual system to generate very long and precise spatio-temporal sequences, above two hundred iterations. Its features are applied then to the sequential planning of arm movements. In line with neurobiological theories, we discuss its relevance for modeling the cortico-basal working memory to initiate flexible goal-directed neuronal chains of causation and its relation to novel architectures such as Deep Networks, Neural Turing Machines and the Free-Energy Principle.

Functional Neuroimaging of Spike-Wave Seizures

PubMed Central

Motelow, Joshua E.; Blumenfeld, Hal

2013-01-01

Generalized spike-wave seizures are typically brief events associated with dynamic changes in brain physiology, metabolism, and behavior. Functional magnetic resonance imaging (fMRI) provides a relatively high spatio-temporal resolution method for imaging cortical-subcortical network activity during spike-wave seizures. Patients with spike-wave seizures often have episodes of staring and unresponsiveness which interfere with normal behavior. Results from human fMRI studies suggest that spike-wave seizures disrupt specific networks in the thalamus and fronto-parietal association cortex which are critical for normal attentive consciousness. However, the neuronal activity underlying imaging changes seen during fMRI is not well understood, particularly in abnormal conditions such as seizures. Animal models have begun to provide important fundamental insights into the neuronal basis for fMRI changes during spike-wave activity. Work from these models including both fMRI and direct neuronal recordings suggest that, like in humans, specific cortical-subcortical networks are involved in spike-wave, while other regions are spared. Regions showing fMRI increases demonstrate correlated increases in neuronal activity in animal models. The mechanisms of fMRI decreases in spike-wave will require further investigation. A better understanding of the specific brain regions involved in generating spike-wave seizures may help guide efforts to develop targeted therapies aimed at preventing or reversing abnormal excitability in these brain regions, ultimately leading to a cure for this disorder. PMID:18839093

Neural correlates of learning and trajectory planning in the posterior parietal cortex

PubMed Central

Torres, Elizabeth B.; Quian Quiroga, Rodrigo; Cui, He; Buneo, Christopher A.

2013-01-01

The posterior parietal cortex (PPC) is thought to play an important role in the planning of visually-guided reaching movements. However, the relative roles of the various subdivisions of the PPC in this function are still poorly understood. For example, studies of dorsal area 5 point to a representation of reaches in both extrinsic (endpoint) and intrinsic (joint or muscle) coordinates, as evidenced by partial changes in preferred directions and positional discharge with changes in arm posture. In contrast, recent findings suggest that the adjacent medial intraparietal area (MIP) is involved in more abstract representations, e.g., encoding reach target in visual coordinates. Such a representation is suitable for planning reach trajectories involving shortest distance paths to targets straight ahead. However, it is currently unclear how MIP contributes to the planning of other types of trajectories, including those with various degrees of curvature. Such curved trajectories recruit different joint excursions and might help us address whether their representation in the PPC is purely in extrinsic coordinates or in intrinsic ones as well. Here we investigated the role of the PPC in these processes during an obstacle avoidance task for which the animals had not been explicitly trained. We found that PPC planning activity was predictive of both the spatial and temporal aspects of upcoming trajectories. The same PPC neurons predicted the upcoming trajectory in both endpoint and joint coordinates. The predictive power of these neurons remained stable and accurate despite concomitant motor learning across task conditions. These findings suggest the role of the PPC can be extended from specifying abstract movement goals to expressing these plans as corresponding trajectories in both endpoint and joint coordinates. Thus, the PPC appears to contribute to reach planning and approach-avoidance arm motions at multiple levels of representation. PMID:23730275

Changes of cerebral current source by audiovisual erotic stimuli in premature ejaculation patients.

PubMed

Hyun, Jae-Seog; Kam, Sung-Chul; Kwon, Oh-Young

2008-06-01

Premature ejaculation (PE) is one of the most common forms of male sexual dysfunction. The mechanisms of PE remain poorly understood, despite its high prevalence. To investigate the pathophysiology and causes of PE in the central nervous system, we tried to observe the changes in brain current source distribution by audiovisual induction of sexual arousal. Electroencephalograpies were recorded in patients with PE (45.0 +/- 10.3 years old, N = 18) and in controls (45.6 +/- 9.8 years old, N = 18) during four 10-minute segments of resting, watching a music video excerpt, resting, and watching an erotic video excerpt. Five artifact-free 5-second segments were used to obtain cross-spectral low-resolution brain electromagnetic tomography (LORETA) images. Statistical nonparametric maps (SnPM) were obtained to detect the current density changes of six frequency bands between the erotic video session and the music video session in each group. Comparisons were also made between the two groups in the erotic video session. In the SnPM of each spectrum in patients with PE, the current source density of the alpha band was significantly reduced in the right precentral gyrus, the right insula, and both superior parietal lobules (P < 0.01). Comparing the two groups in the erotic video session, the current densities of the beta-2 and -3 bands in the PE group were significantly decreased in the right parahippocampal gyrus and left middle temporal gyrus (P < 0.01). Neuronal activity in the right precental gyrus, the right insula, both the superior parietal lobule, the right parahippocampal gyrus, and the left middle temporal gyrus may be decreased in PE patients upon sexual arousal. Further studies are needed to evaluate the meaning of decreased neuronal activities in PE patients.

The problem of gestalt in neurobiology.

PubMed

Sokolov, E N

1997-01-01

The question of gestalts is discussed within the framework of its neuronal mechanisms. Two basic hypotheses are considered: 1) that of gestalts as a result of the hierarchical organization of neurons (gnostic units), and 2) that of gestalts as a result of the synchronization of neurons of a given level. Analysis of published data led to the conclusion that gestalts result from vector coding in the hierarchical organization of neurons. High-frequency oscillations in the gamma range (40-200 Hz) are of endogenous origin, and their function is to reinforce the synaptic inputs to those neurons which are involved in the synthesis of a gestalt.

Synchrony and neural coding in cerebellar circuits

PubMed Central

Person, Abigail L.; Raman, Indira M.

2012-01-01

The cerebellum regulates complex movements and is also implicated in cognitive tasks, and cerebellar dysfunction is consequently associated not only with movement disorders, but also with conditions like autism and dyslexia. How information is encoded by specific cerebellar firing patterns remains debated, however. A central question is how the cerebellar cortex transmits its integrated output to the cerebellar nuclei via GABAergic synapses from Purkinje neurons. Possible answers come from accumulating evidence that subsets of Purkinje cells synchronize their firing during behaviors that require the cerebellum. Consistent with models predicting that coherent activity of inhibitory networks has the capacity to dictate firing patterns of target neurons, recent experimental work supports the idea that inhibitory synchrony may regulate the response of cerebellar nuclear cells to Purkinje inputs, owing to the interplay between unusually fast inhibitory synaptic responses and high rates of intrinsic activity. Data from multiple laboratories lead to a working hypothesis that synchronous inhibitory input from Purkinje cells can set the timing and rate of action potentials produced by cerebellar nuclear cells, thereby relaying information out of the cerebellum. If so, then changing spatiotemporal patterns of Purkinje activity would allow different subsets of inhibitory neurons to control cerebellar output at different times. Here we explore the evidence for and against the idea that a synchrony code defines, at least in part, the input–output function between the cerebellar cortex and nuclei. We consider the literature on the existence of simple spike synchrony, convergence of Purkinje neurons onto nuclear neurons, and intrinsic properties of nuclear neurons that contribute to responses to inhibition. Finally, we discuss factors that may disrupt or modulate a synchrony code and describe the potential contributions of inhibitory synchrony to other motor circuits. PMID:23248585

Toward heterogeneity in feedforward network with synaptic delays based on FitzHugh-Nagumo model

NASA Astrophysics Data System (ADS)

Qin, Ying-Mei; Men, Cong; Zhao, Jia; Han, Chun-Xiao; Che, Yan-Qiu

2018-01-01

We focus on the role of heterogeneity on the propagation of firing patterns in feedforward network (FFN). Effects of heterogeneities both in parameters of neuronal excitability and synaptic delays are investigated systematically. Neuronal heterogeneity is found to modulate firing rates and spiking regularity by changing the excitability of the network. Synaptic delays are strongly related with desynchronized and synchronized firing patterns of the FFN, which indicate that synaptic delays may play a significant role in bridging rate coding and temporal coding. Furthermore, quasi-coherence resonance (quasi-CR) phenomenon is observed in the parameter domain of connection probability and delay-heterogeneity. All these phenomena above enable a detailed characterization of neuronal heterogeneity in FFN, which may play an indispensable role in reproducing the important properties of in vivo experiments.

Predicting Intentions of a Familiar Significant Other Beyond the Mirror Neuron System

PubMed Central

Cacioppo, Stephanie; Juan, Elsa; Monteleone, George

2017-01-01

Inferring intentions of others is one of the most intriguing issues in interpersonal interaction. Theories of embodied cognition and simulation suggest that this mechanism takes place through a direct and automatic matching process that occurs between an observed action and past actions. This process occurs via the reactivation of past self-related sensorimotor experiences within the inferior frontoparietal network (including the mirror neuron system, MNS). The working model is that the anticipatory representations of others' behaviors require internal predictive models of actions formed from pre-established, shared representations between the observer and the actor. This model suggests that observers should be better at predicting intentions performed by a familiar actor, rather than a stranger. However, little is known about the modulations of the intention brain network as a function of the familiarity between the observer and the actor. Here, we combined functional magnetic resonance imaging (fMRI) with a behavioral intention inference task, in which participants were asked to predict intentions from three types of actors: A familiar actor (their significant other), themselves (another familiar actor), and a non-familiar actor (a stranger). Our results showed that the participants were better at inferring intentions performed by familiar actors than non-familiar actors and that this better performance was associated with greater activation within and beyond the inferior frontoparietal network i.e., in brain areas related to familiarity (e.g., precuneus). In addition, and in line with Hebbian principles of neural modulations, the more the participants reported being cognitively close to their partner, the less the brain areas associated with action self-other comparison (e.g., inferior parietal lobule), attention (e.g., superior parietal lobule), recollection (hippocampus), and pair bond (ventral tegmental area, VTA) were recruited, suggesting that the more a shared mental representation has been pre-established, the more neurons show suppression in their response to the presentation of information to which they are sensitive. These results suggest that the relation of performance to the extent of neural activation during intention understanding may display differential relationships based on the cognitive domain, brain region, and the cognitive interdependence between the observer and the actor. PMID:28890691

Direction-selective circuits shape noise to ensure a precise population code

PubMed Central

Zylberberg, Joel; Cafaro, Jon; Turner, Maxwell H

2016-01-01

Summary Neural responses are noisy, and circuit structure can correlate this noise across neurons. Theoretical studies show that noise correlations can have diverse effects on population coding, but these studies rarely explore stimulus dependence of noise correlations. Here, we show that noise correlations in responses of ON-OFF direction-selective retinal ganglion cells are strongly stimulus dependent and we uncover the circuit mechanisms producing this stimulus dependence. A population model based on these mechanistic studies shows that stimulus-dependent noise correlations improve the encoding of motion direction two-fold compared to independent noise. This work demonstrates a mechanism by which a neural circuit effectively shapes its signal and noise in concert, minimizing corruption of signal by noise. Finally, we generalize our findings beyond direction coding in the retina and show that stimulus-dependent correlations will generally enhance information coding in populations of diversely tuned neurons. PMID:26796691

Sound sensitivity of neurons in rat hippocampus during performance of a sound-guided task

PubMed Central

Vinnik, Ekaterina; Honey, Christian; Schnupp, Jan; Diamond, Mathew E.

2012-01-01

To investigate how hippocampal neurons encode sound stimuli, and the conjunction of sound stimuli with the animal's position in space, we recorded from neurons in the CA1 region of hippocampus in rats while they performed a sound discrimination task. Four different sounds were used, two associated with water reward on the right side of the animal and the other two with water reward on the left side. This allowed us to separate neuronal activity related to sound identity from activity related to response direction. To test the effect of spatial context on sound coding, we trained rats to carry out the task on two identical testing platforms at different locations in the same room. Twenty-one percent of the recorded neurons exhibited sensitivity to sound identity, as quantified by the difference in firing rate for the two sounds associated with the same response direction. Sensitivity to sound identity was often observed on only one of the two testing platforms, indicating an effect of spatial context on sensory responses. Forty-three percent of the neurons were sensitive to response direction, and the probability that any one neuron was sensitive to response direction was statistically independent from its sensitivity to sound identity. There was no significant coding for sound identity when the rats heard the same sounds outside the behavioral task. These results suggest that CA1 neurons encode sound stimuli, but only when those sounds are associated with actions. PMID:22219030

Activity-Dependent Human Brain Coding/Noncoding Gene Regulatory Networks

PubMed Central

Lipovich, Leonard; Dachet, Fabien; Cai, Juan; Bagla, Shruti; Balan, Karina; Jia, Hui; Loeb, Jeffrey A.

2012-01-01

While most gene transcription yields RNA transcripts that code for proteins, a sizable proportion of the genome generates RNA transcripts that do not code for proteins, but may have important regulatory functions. The brain-derived neurotrophic factor (BDNF) gene, a key regulator of neuronal activity, is overlapped by a primate-specific, antisense long noncoding RNA (lncRNA) called BDNFOS. We demonstrate reciprocal patterns of BDNF and BDNFOS transcription in highly active regions of human neocortex removed as a treatment for intractable seizures. A genome-wide analysis of activity-dependent coding and noncoding human transcription using a custom lncRNA microarray identified 1288 differentially expressed lncRNAs, of which 26 had expression profiles that matched activity-dependent coding genes and an additional 8 were adjacent to or overlapping with differentially expressed protein-coding genes. The functions of most of these protein-coding partner genes, such as ARC, include long-term potentiation, synaptic activity, and memory. The nuclear lncRNAs NEAT1, MALAT1, and RPPH1, composing an RNAse P-dependent lncRNA-maturation pathway, were also upregulated. As a means to replicate human neuronal activity, repeated depolarization of SY5Y cells resulted in sustained CREB activation and produced an inverse pattern of BDNF-BDNFOS co-expression that was not achieved with a single depolarization. RNAi-mediated knockdown of BDNFOS in human SY5Y cells increased BDNF expression, suggesting that BDNFOS directly downregulates BDNF. Temporal expression patterns of other lncRNA-messenger RNA pairs validated the effect of chronic neuronal activity on the transcriptome and implied various lncRNA regulatory mechanisms. lncRNAs, some of which are unique to primates, thus appear to have potentially important regulatory roles in activity-dependent human brain plasticity. PMID:22960213

The Sign Rule and Beyond: Boundary Effects, Flexibility, and Noise Correlations in Neural Population Codes

PubMed Central

Hu, Yu; Zylberberg, Joel; Shea-Brown, Eric

2014-01-01

Over repeat presentations of the same stimulus, sensory neurons show variable responses. This “noise” is typically correlated between pairs of cells, and a question with rich history in neuroscience is how these noise correlations impact the population's ability to encode the stimulus. Here, we consider a very general setting for population coding, investigating how information varies as a function of noise correlations, with all other aspects of the problem – neural tuning curves, etc. – held fixed. This work yields unifying insights into the role of noise correlations. These are summarized in the form of theorems, and illustrated with numerical examples involving neurons with diverse tuning curves. Our main contributions are as follows. (1) We generalize previous results to prove a sign rule (SR) — if noise correlations between pairs of neurons have opposite signs vs. their signal correlations, then coding performance will improve compared to the independent case. This holds for three different metrics of coding performance, and for arbitrary tuning curves and levels of heterogeneity. This generality is true for our other results as well. (2) As also pointed out in the literature, the SR does not provide a necessary condition for good coding. We show that a diverse set of correlation structures can improve coding. Many of these violate the SR, as do experimentally observed correlations. There is structure to this diversity: we prove that the optimal correlation structures must lie on boundaries of the possible set of noise correlations. (3) We provide a novel set of necessary and sufficient conditions, under which the coding performance (in the presence of noise) will be as good as it would be if there were no noise present at all. PMID:24586128

Neuron selection based on deflection coefficient maximization for the neural decoding of dexterous finger movements.

PubMed

Kim, Yong-Hee; Thakor, Nitish V; Schieber, Marc H; Kim, Hyoung-Nam

2015-05-01

Future generations of brain-machine interface (BMI) will require more dexterous motion control such as hand and finger movements. Since a population of neurons in the primary motor cortex (M1) area is correlated with finger movements, neural activities recorded in M1 area are used to reconstruct an intended finger movement. In a BMI system, decoding discrete finger movements from a large number of input neurons does not guarantee a higher decoding accuracy in spite of the increase in computational burden. Hence, we hypothesize that selecting neurons important for coding dexterous flexion/extension of finger movements would improve the BMI performance. In this paper, two metrics are presented to quantitatively measure the importance of each neuron based on Bayes risk minimization and deflection coefficient maximization in a statistical decision problem. Since motor cortical neurons are active with movements of several different fingers, the proposed method is more suitable for a discrete decoding of flexion-extension finger movements than the previous methods for decoding reaching movements. In particular, the proposed metrics yielded high decoding accuracies across all subjects and also in the case of including six combined two-finger movements. While our data acquisition and analysis was done off-line and post processing, our results point to the significance of highly coding neurons in improving BMI performance.

Neuron Selection Based on Deflection Coefficient Maximization for the Neural Decoding of Dexterous Finger Movements

PubMed Central

Kim, Yong-Hee; Thakor, Nitish V.; Schieber, Marc H.; Kim, Hyoung-Nam

2015-01-01

Future generations of brain-machine interface (BMI) will require more dexterous motion control such as hand and finger movements. Since a population of neurons in the primary motor cortex (M1) area is correlated with finger movements, neural activities recorded in M1 area are used to reconstruct an intended finger movement. In a BMI system, decoding discrete finger movements from a large number of input neurons does not guarantee a higher decoding accuracy in spite of the increase in computational burden. Hence, we hypothesize that selecting neurons important for coding dexterous flexion/extension of finger movements would improve the BMI performance. In this paper, two metrics are presented to quantitatively measure the importance of each neuron based on Bayes risk minimization and deflection coefficient maximization in a statistical decision problem. Since motor cortical neurons are active with movements of several different fingers, the proposed method is more suitable for a discrete decoding of flexion-extension finger movements than the previous methods for decoding reaching movements. In particular, the proposed metrics yielded high decoding accuracies across all subjects and also in the case of including six combined two-finger movements. While our data acquisition and analysis was done off-line and post processing, our results point to the significance of highly coding neurons in improving BMI performance. PMID:25347884

Action potential bursts in central snail neurons elicited by paeonol: roles of ionic currents

PubMed Central

Chen, Yi-hung; Lin, Pei-lin; Hsu, Hui-yu; Wu, Ya-ting; Yang, Han-yin; Lu, Dah-yuu; Huang, Shiang-suo; Hsieh, Ching-liang; Lin, Jaung-geng

2010-01-01

Aim: To investigate the effects of 2′-hydroxy-4′-methoxyacetophenone (paeonol) on the electrophysiological behavior of a central neuron (right parietal 4; RP4) of the giant African snail (Achatina fulica Ferussac). Methods: Intracellular recordings and the two-electrode voltage clamp method were used to study the effects of paeonol on the RP4 neuron. Results: The RP4 neuron generated spontaneous action potentials. Bath application of paeonol at a concentration of ≥500 μmol/L reversibly elicited action potential bursts in a concentration-dependent manner. Immersing the neurons in Co2+-substituted Ca2+-free solution did not block paeonol-elicited bursting. Pretreatment with the protein kinase A (PKA) inhibitor KT-5720 or the protein kinase C (PKC) inhibitor Ro 31-8220 did not affect the action potential bursts. Voltage-clamp studies revealed that paeonol at a concentration of 500 μmol/L had no remarkable effects on the total inward currents, whereas paeonol decreased the delayed rectifying K+ current (IKD) and the fast-inactivating K+ current (IA). Application of 4-aminopyridine (4-AP 5 mmol/L), an inhibitor of IA, or charybdotoxin 250 nmol/L, an inhibitor of the Ca2+-activated K+ current (IK(Ca)), failed to elicit action potential bursts, whereas tetraethylammonium chloride (TEA 50 mmol/L), an IKD blocker, successfully elicited action potential bursts. At a lower concentration of 5 mmol/L, TEA facilitated the induction of action potential bursts elicited by paeonol. Conclusion: Paeonol elicited a bursting firing pattern of action potentials in the RP4 neuron and this activity relates closely to the inhibitory effects of paeonol on the IKD. PMID:21042287

Potassium-induced cortical spreading depression bilaterally suppresses the electroencephalogram but only ipsilaterally affects red blood cell velocity in intraparenchymal capillaries.

PubMed

Unekawa, Miyuki; Tomita, Yutaka; Toriumi, Haruki; Masamoto, Kazuto; Kanno, Iwao; Suzuki, Norihiro

2013-04-01

Cortical spreading depression (CSD) is a repetitive, propagating profile of mass depolarization of neuronal and glial cells, followed by sustained suppression of spontaneous neuronal activity. We have reported a long-lasting suppressive effect on red blood cell (RBC) velocities in intraparenchymal capillaries. Here, to test the hypothesis that the prolonged decrease of RBC velocity in capillaries is due to suppression of neuronal activity, we measured CSD-elicited changes in the electroencephalogram (EEG) as an index of neuronal activity. In isoflurane-anesthetized rats, DC potential, EEG, partial pressure of oxygen (PO₂), and cerebral blood flow (CBF) were simultaneously recorded in the temporo-parietal region. The velocities of fluorescently labeled RBCs were evaluated by high-speed camera laser scanning confocal fluorescence microscopy with our original software, KEIO-IS2. Transient deflection of DC potential and PO₂ and increase of CBF were repeatedly detected only in the ipsilateral hemisphere following topical KCl application. On the other hand, the relative spectral power of EEG was reduced bilaterally, showing the lowest value at 5 min after KCl application, when the other parameters had already returned to the baseline after the passage of CSD. Mean RBC velocity in capillaries was slightly but significantly reduced during and after passage of CSD in the ipsilateral hemisphere but did not change in the contralateral hemisphere in the same rats. We suggest that mass depolarization of neuronal and glial cells might transiently decelerate RBCs in nearby capillaries, but the sustained reduction of ipsilateral RBC velocity might be a result of the prolonged effect of CSD, not of neuronal suppression alone. Copyright © 2013 Wiley Periodicals, Inc.

Extremely Scalable Spiking Neuronal Network Simulation Code: From Laptops to Exascale Computers.

PubMed

Jordan, Jakob; Ippen, Tammo; Helias, Moritz; Kitayama, Itaru; Sato, Mitsuhisa; Igarashi, Jun; Diesmann, Markus; Kunkel, Susanne

2018-01-01

State-of-the-art software tools for neuronal network simulations scale to the largest computing systems available today and enable investigations of large-scale networks of up to 10 % of the human cortex at a resolution of individual neurons and synapses. Due to an upper limit on the number of incoming connections of a single neuron, network connectivity becomes extremely sparse at this scale. To manage computational costs, simulation software ultimately targeting the brain scale needs to fully exploit this sparsity. Here we present a two-tier connection infrastructure and a framework for directed communication among compute nodes accounting for the sparsity of brain-scale networks. We demonstrate the feasibility of this approach by implementing the technology in the NEST simulation code and we investigate its performance in different scaling scenarios of typical network simulations. Our results show that the new data structures and communication scheme prepare the simulation kernel for post-petascale high-performance computing facilities without sacrificing performance in smaller systems.

Extremely Scalable Spiking Neuronal Network Simulation Code: From Laptops to Exascale Computers

PubMed Central

Jordan, Jakob; Ippen, Tammo; Helias, Moritz; Kitayama, Itaru; Sato, Mitsuhisa; Igarashi, Jun; Diesmann, Markus; Kunkel, Susanne

2018-01-01

State-of-the-art software tools for neuronal network simulations scale to the largest computing systems available today and enable investigations of large-scale networks of up to 10 % of the human cortex at a resolution of individual neurons and synapses. Due to an upper limit on the number of incoming connections of a single neuron, network connectivity becomes extremely sparse at this scale. To manage computational costs, simulation software ultimately targeting the brain scale needs to fully exploit this sparsity. Here we present a two-tier connection infrastructure and a framework for directed communication among compute nodes accounting for the sparsity of brain-scale networks. We demonstrate the feasibility of this approach by implementing the technology in the NEST simulation code and we investigate its performance in different scaling scenarios of typical network simulations. Our results show that the new data structures and communication scheme prepare the simulation kernel for post-petascale high-performance computing facilities without sacrificing performance in smaller systems. PMID:29503613

Maturation profile of inferior olivary neurons expressing ionotropic glutamate receptors in rats: role in coding linear accelerations.

PubMed

Li, Chuan; Han, Lei; Ma, Chun-Wai; Lai, Suk-King; Lai, Chun-Hong; Shum, Daisy Kwok Yan; Chan, Ying-Shing

2013-07-01

Using sinusoidal oscillations of linear acceleration along both the horizontal and vertical planes to stimulate otolith organs in the inner ear, we charted the postnatal time at which responsive neurons in the rat inferior olive (IO) first showed Fos expression, an indicator of neuronal recruitment into the otolith circuit. Neurons in subnucleus dorsomedial cell column (DMCC) were activated by vertical stimulation as early as P9 and by horizontal (interaural) stimulation as early as P11. By P13, neurons in the β subnucleus of IO (IOβ) became responsive to horizontal stimulation along the interaural and antero-posterior directions. By P21, neurons in the rostral IOβ became also responsive to vertical stimulation, but those in the caudal IOβ remained responsive only to horizontal stimulation. Nearly all functionally activated neurons in DMCC and IOβ were immunopositive for the NR1 subunit of the NMDA receptor and the GluR2/3 subunit of the AMPA receptor. In situ hybridization studies further indicated abundant mRNA signals of the glutamate receptor subunits by the end of the second postnatal week. This is reinforced by whole-cell patch-clamp data in which glutamate receptor-mediated miniature excitatory postsynaptic currents of rostral IOβ neurons showed postnatal increase in amplitude, reaching the adult level by P14. Further, these neurons exhibited subthreshold oscillations in membrane potential as from P14. Taken together, our results support that ionotropic glutamate receptors in the IO enable postnatal coding of gravity-related information and that the rostral IOβ is the only IO subnucleus that encodes spatial orientations in 3-D.

Temporally diverse firing patterns in olfactory receptor neurons underlie spatiotemporal neural codes for odors

PubMed Central

Raman, Baranidharan; Joseph, Joby; Tang, Jeff; Stopfer, Mark

2010-01-01

Odorants are represented as spatiotemporal patterns of spikes in neurons of the antennal lobe (AL, insects) and olfactory bulb (OB, vertebrates). These response patterns have been thought to arise primarily from interactions within the AL/OB, an idea supported, in part, by the assumption that olfactory receptor neurons (ORNs) respond to odorants with simple firing patterns. However, activating the AL directly with simple pulses of current evoked responses in AL neurons that were much less diverse, complex, and enduring than responses elicited by odorants. Similarly, models of the AL driven by simplistic inputs generated relatively simple output. How then are dynamic neural codes for odors generated? Consistent with recent results from several other species, our recordings from locust ORNs showed a great diversity of temporal structure. Further, we found that, viewed as a population, many response features of ORNs were remarkably similar to those observed within the AL. Using a set of computational models constrained by our electrophysiological recordings, we found that the temporal heterogeneity of responses of ORNs critically underlies the generation of spatiotemporal odor codes in the AL. A test then performed in vivo confirmed that, given temporally homogeneous input, the AL cannot create diverse spatiotemporal patterns on its own; however, given temporally heterogeneous input, the AL generated realistic firing patterns. Finally, given the temporally structured input provided by ORNs, we clarified several separate, additional contributions of the AL to olfactory information processing. Thus, our results demonstrate the origin and subsequent reformatting of spatiotemporal neural codes for odors. PMID:20147528

Distinct Correlation Structure Supporting a Rate-Code for Sound Localization in the Owl’s Auditory Forebrain

PubMed Central

2017-01-01

Abstract While a topographic map of auditory space exists in the vertebrate midbrain, it is absent in the forebrain. Yet, both brain regions are implicated in sound localization. The heterogeneous spatial tuning of adjacent sites in the forebrain compared to the midbrain reflects different underlying circuitries, which is expected to affect the correlation structure, i.e., signal (similarity of tuning) and noise (trial-by-trial variability) correlations. Recent studies have drawn attention to the impact of response correlations on the information readout from a neural population. We thus analyzed the correlation structure in midbrain and forebrain regions of the barn owl’s auditory system. Tetrodes were used to record in the midbrain and two forebrain regions, Field L and the downstream auditory arcopallium (AAr), in anesthetized owls. Nearby neurons in the midbrain showed high signal and noise correlations (RNCs), consistent with shared inputs. As previously reported, Field L was arranged in random clusters of similarly tuned neurons. Interestingly, AAr neurons displayed homogeneous monotonic azimuth tuning, while response variability of nearby neurons was significantly less correlated than the midbrain. Using a decoding approach, we demonstrate that low RNC in AAr restricts the potentially detrimental effect it can have on information, assuming a rate code proposed for mammalian sound localization. This study harnesses the power of correlation structure analysis to investigate the coding of auditory space. Our findings demonstrate distinct correlation structures in the auditory midbrain and forebrain, which would be beneficial for a rate-code framework for sound localization in the nontopographic forebrain representation of auditory space. PMID:28674698

Multiple Neuropeptide-Coding Genes Involved in Planarian Pharynx Extension.

PubMed

Shimoyama, Seira; Inoue, Takeshi; Kashima, Makoto; Agata, Kiyokazu

2016-06-01

Planarian feeding behavior involves three steps: moving toward food, extending the pharynx from their planarian's ventral side after arriving at the food, and ingesting the food through the pharynx. Although pharynx extension is a remarkable behavior, it remains unknown what neuronal cell types are involved in its regulation. To identify neurons involved in regulating pharynx extension, we quantitatively analyzed pharynx extension and sought to identify these neurons by RNA interference (RNAi) and in situ hybridization. This assay, when performed using planarians with amputation of various body parts, clearly showed that the head portion is indispensable for inducing pharynx extension. We thus tested the effects of knockdown of brain neurons such as serotonergic, GABAergic, and dopaminergic neurons by RNAi, but did not observe any effects on pharynx extension behavior. However, animals with RNAi of the Prohormone Convertase 2 (PC2, a neuropeptide processing enzyme) gene did not perform the pharynx extension behavior, suggesting the possible involvement of neuropeptide(s in the regulation of pharynx extension. We screened 24 neuropeptide-coding genes, analyzed their functions by RNAi using the pharynx extension assay system, and identified at least five neuropeptide genes involved in pharynx extension. These was expressed in different cells or neurons, and some of them were expressed in the brain, suggesting complex regulation of planarian feeding behavior by the nervous system.

A Hebbian learning rule gives rise to mirror neurons and links them to control theoretic inverse models.

PubMed

Hanuschkin, A; Ganguli, S; Hahnloser, R H R

2013-01-01

Mirror neurons are neurons whose responses to the observation of a motor act resemble responses measured during production of that act. Computationally, mirror neurons have been viewed as evidence for the existence of internal inverse models. Such models, rooted within control theory, map-desired sensory targets onto the motor commands required to generate those targets. To jointly explore both the formation of mirrored responses and their functional contribution to inverse models, we develop a correlation-based theory of interactions between a sensory and a motor area. We show that a simple eligibility-weighted Hebbian learning rule, operating within a sensorimotor loop during motor explorations and stabilized by heterosynaptic competition, naturally gives rise to mirror neurons as well as control theoretic inverse models encoded in the synaptic weights from sensory to motor neurons. Crucially, we find that the correlational structure or stereotypy of the neural code underlying motor explorations determines the nature of the learned inverse model: random motor codes lead to causal inverses that map sensory activity patterns to their motor causes; such inverses are maximally useful, by allowing the imitation of arbitrary sensory target sequences. By contrast, stereotyped motor codes lead to less useful predictive inverses that map sensory activity to future motor actions. Our theory generalizes previous work on inverse models by showing that such models can be learned in a simple Hebbian framework without the need for error signals or backpropagation, and it makes new conceptual connections between the causal nature of inverse models, the statistical structure of motor variability, and the time-lag between sensory and motor responses of mirror neurons. Applied to bird song learning, our theory can account for puzzling aspects of the song system, including necessity of sensorimotor gating and selectivity of auditory responses to bird's own song (BOS) stimuli.

A Hebbian learning rule gives rise to mirror neurons and links them to control theoretic inverse models

PubMed Central

Hanuschkin, A.; Ganguli, S.; Hahnloser, R. H. R.

2013-01-01

Mirror neurons are neurons whose responses to the observation of a motor act resemble responses measured during production of that act. Computationally, mirror neurons have been viewed as evidence for the existence of internal inverse models. Such models, rooted within control theory, map-desired sensory targets onto the motor commands required to generate those targets. To jointly explore both the formation of mirrored responses and their functional contribution to inverse models, we develop a correlation-based theory of interactions between a sensory and a motor area. We show that a simple eligibility-weighted Hebbian learning rule, operating within a sensorimotor loop during motor explorations and stabilized by heterosynaptic competition, naturally gives rise to mirror neurons as well as control theoretic inverse models encoded in the synaptic weights from sensory to motor neurons. Crucially, we find that the correlational structure or stereotypy of the neural code underlying motor explorations determines the nature of the learned inverse model: random motor codes lead to causal inverses that map sensory activity patterns to their motor causes; such inverses are maximally useful, by allowing the imitation of arbitrary sensory target sequences. By contrast, stereotyped motor codes lead to less useful predictive inverses that map sensory activity to future motor actions. Our theory generalizes previous work on inverse models by showing that such models can be learned in a simple Hebbian framework without the need for error signals or backpropagation, and it makes new conceptual connections between the causal nature of inverse models, the statistical structure of motor variability, and the time-lag between sensory and motor responses of mirror neurons. Applied to bird song learning, our theory can account for puzzling aspects of the song system, including necessity of sensorimotor gating and selectivity of auditory responses to bird's own song (BOS) stimuli. PMID:23801941

Spike synchrony reveals emergence of proto-objects in visual cortex.

PubMed

Martin, Anne B; von der Heydt, Rüdiger

2015-04-29

Neurons at early stages of the visual cortex signal elemental features, such as pieces of contour, but how these signals are organized into perceptual objects is unclear. Theories have proposed that spiking synchrony between these neurons encodes how features are grouped (binding-by-synchrony), but recent studies did not find the predicted increase in synchrony with binding. Here we propose that features are grouped to "proto-objects" by intrinsic feedback circuits that enhance the responses of the participating feature neurons. This hypothesis predicts synchrony exclusively between feature neurons that receive feedback from the same grouping circuit. We recorded from neurons in macaque visual cortex and used border-ownership selectivity, an intrinsic property of the neurons, to infer whether or not two neurons are part of the same grouping circuit. We found that binding produced synchrony between same-circuit neurons, but not between other pairs of neurons, as predicted by the grouping hypothesis. In a selective attention task, synchrony emerged with ignored as well as attended objects, and higher synchrony was associated with faster behavioral responses, as would be expected from early grouping mechanisms that provide the structure for object-based processing. Thus, synchrony could be produced by automatic activation of intrinsic grouping circuits. However, the binding-related elevation of synchrony was weak compared with its random fluctuations, arguing against synchrony as a code for binding. In contrast, feedback grouping circuits encode binding by modulating the response strength of related feature neurons. Thus, our results suggest a novel coding mechanism that might underlie the proto-objects of perception. Copyright © 2015 the authors 0270-6474/15/356860-11$15.00/0.

The Chronotron: A Neuron That Learns to Fire Temporally Precise Spike Patterns

PubMed Central

Florian, Răzvan V.

2012-01-01

In many cases, neurons process information carried by the precise timings of spikes. Here we show how neurons can learn to generate specific temporally precise output spikes in response to input patterns of spikes having precise timings, thus processing and memorizing information that is entirely temporally coded, both as input and as output. We introduce two new supervised learning rules for spiking neurons with temporal coding of information (chronotrons), one that provides high memory capacity (E-learning), and one that has a higher biological plausibility (I-learning). With I-learning, the neuron learns to fire the target spike trains through synaptic changes that are proportional to the synaptic currents at the timings of real and target output spikes. We study these learning rules in computer simulations where we train integrate-and-fire neurons. Both learning rules allow neurons to fire at the desired timings, with sub-millisecond precision. We show how chronotrons can learn to classify their inputs, by firing identical, temporally precise spike trains for different inputs belonging to the same class. When the input is noisy, the classification also leads to noise reduction. We compute lower bounds for the memory capacity of chronotrons and explore the influence of various parameters on chronotrons' performance. The chronotrons can model neurons that encode information in the time of the first spike relative to the onset of salient stimuli or neurons in oscillatory networks that encode information in the phases of spikes relative to the background oscillation. Our results show that firing one spike per cycle optimizes memory capacity in neurons encoding information in the phase of firing relative to a background rhythm. PMID:22879876

Neural correlates of individual performance differences in resolving perceptual conflict.

PubMed

Labrenz, Franziska; Themann, Maria; Wascher, Edmund; Beste, Christian; Pfleiderer, Bettina

2012-01-01

Attentional mechanisms are a crucial prerequisite to organize behavior. Most situations may be characterized by a 'competition' between salient, but irrelevant stimuli and less salient, relevant stimuli. In such situations top-down and bottom-up mechanisms interact with each other. In the present fMRI study, we examined how interindividual differences in resolving situations of perceptual conflict are reflected in brain networks mediating attentional selection. Doing so, we employed a change detection task in which subjects had to detect luminance changes in the presence and absence of competing distractors. The results show that good performers presented increased activation in the orbitofrontal cortex (BA 11), anterior cingulate (BA 25), inferior parietal lobule (BA 40) and visual areas V2 and V3 but decreased activation in BA 39. This suggests that areas mediating top-down attentional control are stronger activated in this group. Increased activity in visual areas reflects distinct neuronal enhancement relating to selective attentional mechanisms in order to solve the perceptual conflict. Opposed to good performers, brain areas activated by poor performers comprised the left inferior parietal lobule (BA 39) and fronto-parietal and visual regions were continuously deactivated, suggesting that poor performers perceive stronger conflict than good performers. Moreover, the suppression of neural activation in visual areas might indicate a strategy of poor performers to inhibit the processing of the irrelevant non-target feature. These results indicate that high sensitivity in perceptual areas and increased attentional control led to less conflict in stimulus processing and consequently to higher performance in competitive attentional selection.

Functional anatomy of visuo-spatial working memory during mental rotation is influenced by sex, menstrual cycle, and sex steroid hormones.

PubMed

Schöning, S; Engelien, A; Kugel, H; Schäfer, S; Schiffbauer, H; Zwitserlood, P; Pletziger, E; Beizai, P; Kersting, A; Ohrmann, P; Greb, R R; Lehmann, W; Heindel, W; Arolt, V; Konrad, C

2007-11-05

Recent observations indicate that sex and level of steroid hormones may influence cortical networks associated with specific cognitive functions, in particular visuo-spatial abilities. The present study probed the influence of sex, menstrual cycle, and sex steroid hormones on 3D mental rotation and brain function using 3-T fMRI. Twelve healthy women and 12 men were investigated. Menstrual cycle and hormone levels were assessed. The early follicular and midluteal phase of the menstrual cycle were chosen to examine short-term cyclical changes. Parietal and frontal areas were activated during mental rotation in both sexes. Significant differences between men and women were revealed in both phases of menstrual cycle. In men we observed a significant correlation of activation levels with testosterone levels in the left parietal lobe (BA 40). In women, a cycle-dependent correlation pattern was observed for testosterone: brain activation correlated with this male hormone only during the early follicular phase. In both cycle phases females' brain activation was significantly correlated with estradiol in frontal and parietal areas. Our study provides evidence that fMRI-related activity during performance of cognitive tasks varies across sex and phases of the menstrual cycle. The variation might be partly explained by better task performance in men, but our results indicate that further explanations like basic neuronal or neurovascular effects modulated by steroid hormones must be considered. Both estradiol and testosterone levels may influence fMRI signals of cognitive tasks, which should affect selection of subjects for future fMRI studies.

Higher cortical and lower subcortical metabolism in detoxified methamphetamine abusers.

PubMed

Volkow, N D; Chang, L; Wang, G J; Fowler, J S; Franceschi, D; Sedler, M J; Gatley, S J; Hitzemann, R; Ding, Y S; Wong, C; Logan, J

2001-03-01

Methamphetamine has raised concerns because it may be neurotoxic to the human brain. Although prior work has focused primarily on the effects of methamphetamine on dopamine cells, there is evidence that other neuronal types are affected. The authors measured regional brain glucose metabolism, which serves as a marker of brain function, to assess if there is evidence of functional changes in methamphetamine abusers in regions other than those innervated by dopamine cells. Fifteen detoxified methamphetamine abusers and 21 comparison subjects underwent positron emission tomography following administration of [(18)F]fluorodeoxyglucose. Whole brain metabolism in the methamphetamine abusers was 14% higher than that of comparison subjects; the differences were most accentuated in the parietal cortex (20%). After normalization for whole brain metabolism, methamphetamine abusers exhibited significantly lower metabolism in the thalamus (17% difference) and striatum (where the differences were larger for the caudate [12%] than for the putamen [6%]). Statistical parametric mapping analyses corroborated these findings, revealing higher metabolism in the parietal cortex and lower metabolism in the thalamus and striatum of methamphetamine abusers. The fact that the parietal cortex is a region devoid of any significant dopaminergic innervation suggests that the higher metabolism seen in this region in the methamphetamine abusers is the result of methamphetamine effects in circuits other than those modulated by dopamine. In addition, the lower metabolism in the striatum and thalamus (major outputs of dopamine signals into the cortex) is likely to reflect the functional consequence of methamphetamine in dopaminergic circuits. These results provide evidence that, in humans, methamphetamine abuse results in changes in function of dopamine- and nondopamine-innervated brain regions.

Abnormal functional connectivity density in children with anisometropic amblyopia at resting-state.

PubMed

Wang, Tianyue; Li, Qian; Guo, Mingxia; Peng, Yanmin; Li, Qingji; Qin, Wen; Yu, Chunshui

2014-05-14

Amblyopia is a developmental disorder resulting from anomalous binocular visual input in early life. Task-based neuroimaging studies have widely investigated cortical functional impairments in amblyopia, but changes in spontaneous neuronal functional activities in amblyopia remain largely unknown. In the present study, functional connectivity density (FCD) mapping, an ultrafast data-driven method based on fMRI, was applied for the first time to investigate changes in cortical functional connectivities in amblyopia during the resting-state. We quantified and compared both short- and long-range FCD in both the brains of children with anisometropic amblyopia (AAC) and normal sighted children (NSC). In contrast to the NSC, the AAC showed significantly decreased short-range FCD in the inferior temporal/fusiform gyri, parieto-occipital and rostrolateral prefrontal cortices, as well as decreased long-range FCD in the premotor cortex, dorsal inferior parietal lobule, frontal-insular and dorsal prefrontal cortices. Furthermore, most regions with reduced long-range FCD in the AAC showed decreased functional connectivity with occipital and posterior parietal cortices in the AAC. The results suggest that chronically poor visual input in amblyopia not only impairs the brain's short-range functional connections in visual pathways and in the frontal cortex, which is important for cognitive control, but also affects long-range functional connections among the visual areas, posterior parietal and frontal cortices that subserve visuomotor and visual-guided actions, visuospatial attention modulation and the integration of salient information. This study provides evidence for abnormal spontaneous brain activities in amblyopia. Copyright © 2014 Elsevier B.V. All rights reserved.

Brain plasticity in Parkinson's disease with freezing of gait induced by action observation training.

PubMed

Agosta, Federica; Gatti, Roberto; Sarasso, Elisabetta; Volonté, Maria Antonietta; Canu, Elisa; Meani, Alessandro; Sarro, Lidia; Copetti, Massimiliano; Cattrysse, Erik; Kerckhofs, Eric; Comi, Giancarlo; Falini, Andrea; Filippi, Massimo

2017-01-01

Gait disorders represent a therapeutic challenge in Parkinson's disease (PD). This study investigated the efficacy of 4-week action observation training (AOT) on disease severity, freezing of gait and motor abilities in PD, and evaluated treatment-related brain functional changes. 25 PD patients with freezing of gait were randomized into two groups: AOT (action observation combined with practicing the observed actions) and "Landscape" (same physical training combined with landscape-videos observation). At baseline and 4-week, patients underwent clinical evaluation and fMRI. Clinical assessment was repeated at 8-week. At 4-week, both groups showed reduced freezing of gait severity, improved walking speed and quality of life. Moreover, AOT was associated with reduced motor disability and improved balance. AOT group showed a sustained positive effect on motor disability, walking speed, balance and quality of life at 8-week, with a trend toward a persisting reduced freezing of gait severity. At 4-week vs. baseline, AOT group showed increased recruitment of fronto-parietal areas during fMRI tasks, while the Landscape group showed a reduced fMRI activity of the left postcentral and inferior parietal gyri and right rolandic operculum and supramarginal gyrus. In AOT group, functional brain changes were associated with clinical improvements at 4-week and predicted clinical evolution at 8-week. AOT has a more lasting effect in improving motor function, gait and quality of life in PD patients relative to physical therapy alone. AOT-related performance gains are associated with an increased recruitment of motor regions and fronto-parietal mirror neuron and attentional control areas.

Dura mater graft-associated Creutzfeldt-Jakob disease with 30-year incubation period.

PubMed

Shijo, Masahiro; Honda, Hiroyuki; Koyama, Sachiko; Ishitsuka, Koji; Maeda, Koichiro; Kuroda, Junya; Tanii, Mitsugu; Kitazono, Takanari; Iwaki, Toru

2017-06-01

Over 60% of all patients with dura mater graft-associated Creutzfeldt-Jakob disease (dCJD) have been diagnosed in Japan. The incubation period has ranged from 1 to 30 years and the age at onset from 15 to 80 years. Here, we report a 77-year-old male Japanese autopsied dCJD case with the longest incubation period so far in Japan. He received a cadaveric dural graft at the right cranial convexity following a craniotomy for meningioma at the age of 46. At 30 years post-dural graft placement, disorientation was observed as an initial symptom of dCJD. He rapidly began to present with inconsistent speech, cognitive impairment and tremor of the left upper extremity. Occasional myoclonic jerks were predominantly observed on the left side. Brain MRI presented hyperintense signals on diffusion-weighted and T2-weighted images, at the right cerebral cortex. The most hyperintense lesion was located at the right parietal lobe, where the dura mater graft had been transplanted. Single-photon emission CT scan showed markedly decreased cerebral blood flow at the right parietal lobe. EEG revealed diffuse and slow activities with periodic sharp-wave complex discharges seen in the right parietal, temporal and occipital lobes. He died of pneumonia 9 months after onset. Brain pathology revealed non-plaque-type dCJD. Laterality of neuropathological changes, including spongiform change, neuronal loss, gliosis or PrP deposits, was not evident. Western blot analysis showed type 1 PrP CJD . Alzheimer-type pathology and PSP-like pathology were also observed. © 2016 Japanese Society of Neuropathology.

Control of cerebral cortical blood flow by stimulation of basal forebrain cholinergic areas in mice.

PubMed

Hotta, Harumi; Uchida, Sae; Kagitani, Fusako; Maruyama, Naoki

2011-05-01

We examined whether activity of the nucleus basalis of Meynert (NBM) regulates regional cerebral cortical blood flow (rCBF) in mice, using laser speckle and laser Doppler flowmetry. In anesthetized mice, unilateral focal stimulation, either electrical or chemical, of the NBM increased rCBF of the ipsilateral cerebral cortex in the frontal, parietal and occipital lobes, independent of changes in systemic blood pressure. Most of vasodilative responses to low intensity stimuli (2 times threshold intensity: 2T) were abolished by atropine (a muscarinic cholinergic blocker), whereas responses to higher intensity stimuli (3T) were abolished by atropine and mecamylamine (a nicotinic cholinergic blocker). Blood flow changes were largest when the tip of the electrode was located within the area containing cholinergic neurons shown by choline acetyltransferase-immunocytochemistry. These results suggest that cholinergic projections from basal forebrain neurons in mice cause vasodilation in the ipsilateral cerebral cortex by a combination of muscarinic and nicotinic mechanisms, as previously found in rats and cats.

Large-scale cortical correlation structure of spontaneous oscillatory activity

PubMed Central

Hipp, Joerg F.; Hawellek, David J.; Corbetta, Maurizio; Siegel, Markus; Engel, Andreas K.

2013-01-01

Little is known about the brain-wide correlation of electrophysiological signals. Here we show that spontaneous oscillatory neuronal activity exhibits frequency-specific spatial correlation structure in the human brain. We developed an analysis approach that discounts spurious correlation of signal power caused by the limited spatial resolution of electrophysiological measures. We applied this approach to source estimates of spontaneous neuronal activity reconstructed from magnetoencephalography (MEG). Overall, correlation of power across cortical regions was strongest in the alpha to beta frequency range (8–32 Hz) and correlation patterns depended on the underlying oscillation frequency. Global hubs resided in the medial temporal lobe in the theta frequency range (4–6 Hz), in lateral parietal areas in the alpha to beta frequency range (8–23 Hz), and in sensorimotor areas for higher frequencies (32–45 Hz). Our data suggest that interactions in various large-scale cortical networks may be reflected in frequency specific power-envelope correlations. PMID:22561454

Early Exposure to Haloperidol or Olanzapine Induces Long-Term Alterations of Dendritic Form

PubMed Central

Frost, Douglas O.; Page, Stephanie Cerceo; Carroll, Cathy; Kolb, Bryan

2009-01-01

Exposure of the developing brain to a wide variety of drugs of abuse (eg., stimulants, opioids, ethanol, etc.) can induce life-long changes in behavior and neural circuitry. However, the long-term effects of exposure to therapeutic, psychotropic drugs have only recently begun to be appreciated. Antipsychotic drugs are little studied in this regard. Here we quantitatively analyzed dendritic architecture in adult mice treated with paradigmatic typical- (haloperidol) or atypical (olanzapine) antipsychotic drugs at developmental stages corresponding to fetal or fetal plus early childhood stages in humans. In layer 3 pyramidal cells of the medial and orbital prefrontal cortices and the parietal cortex and in spiny neurons of the core of the nucleus accumbens, both drugs induced significant changes (predominantly reductions) in the amount and complexity of dendritic arbor and the density of dendritic spines. The drug-induced plasticity of dendritic architecture suggests changes in patterns of neuronal connectivity in multiple brain regions that are likely to be functionally significant. PMID:19862684

Topological self-organization and prediction learning support both action and lexical chains in the brain.

PubMed

Chersi, Fabian; Ferro, Marcello; Pezzulo, Giovanni; Pirrelli, Vito

2014-07-01

A growing body of evidence in cognitive psychology and neuroscience suggests a deep interconnection between sensory-motor and language systems in the brain. Based on recent neurophysiological findings on the anatomo-functional organization of the fronto-parietal network, we present a computational model showing that language processing may have reused or co-developed organizing principles, functionality, and learning mechanisms typical of premotor circuit. The proposed model combines principles of Hebbian topological self-organization and prediction learning. Trained on sequences of either motor or linguistic units, the network develops independent neuronal chains, formed by dedicated nodes encoding only context-specific stimuli. Moreover, neurons responding to the same stimulus or class of stimuli tend to cluster together to form topologically connected areas similar to those observed in the brain cortex. Simulations support a unitary explanatory framework reconciling neurophysiological motor data with established behavioral evidence on lexical acquisition, access, and recall. Copyright © 2014 Cognitive Science Society, Inc.

[The motor organization of cerebral cortex and the role of the mirror neuron system. Clinical impact for rehabilitation].

PubMed

Sallés, Laia; Gironès, Xavier; Lafuente, José Vicente

2015-01-06

The basic characteristics of Penfield homunculus (somatotopy and unique representation) have been questioned. The existence of a defined anatomo-functional organization within different segments of the same region is controversial. The presence of multiple motor representations in the primary motor area and in the parietal lobe interconnected by parieto-frontal circuits, which are widely overlapped, form a complex organization. Both features support the recovery of functions after brain injury. Regarding the movement organization, it is possible to yield a relevant impact through the understanding of actions and intentions of others, which is mediated by the activation of mirror-neuron systems. The implementation of cognitive functions (observation, image of the action and imitation) from the acute treatment phase allows the activation of motor representations without having to perform the action and it plays an important role in learning motor patterns. Copyright © 2013 Elsevier España, S.L.U. All rights reserved.

Systemic and anti-neuronal auto-antibodies in patients with paraneoplastic neurological disease.

PubMed

Moll, J W; Hooijkaas, H; van Goorbergh, B C; Roos, L G; Henzen-Logmans, S C; Vecht, C J

1996-01-01

Sera from 23 patients with paraneoplastic disease of the central nervous system (PNS) were examined for the presence of anti-neuronal (anti-Hu, anti-Yo/PCA) and anti-Ri) and systemic auto-antibodies, including antibodies against DNA, centromeres, nRNP, Sm antigen, Scl-70, Ro(SS-A), La(SS-B), mitochondria, thyroid antigens, parietal calls, brush border antigen and rheumatoid factor. As controls, sera from 33 patients with small cell lung cancer, 33 with ovarian cancer and 7 with breast cancer and from 107 aged-matched healthy persons were used. Systemic auto-antibodies were found in 52% of patients with paraneoplastic neurological syndromes compared with only 16% (P = 0.001) in the control group with cancer only and 15% in the group of healthy controls. The relatively high percentage of systemic auto-antibodies in patients with PNS indicates that there is a genetic susceptibility to the development of auto-immune phenomena. This may provide an explanation for the relatively rare occurrence of PNS in patients with cancer.

Local and downstream effects of excitotoxic lesions in the rat medial prefrontal cortex on In vivo 1H-MRS signals.

PubMed

Roffman, J L; Lipska, B K; Bertolino, A; Van Gelderen, P; Olson, A W; Khaing, Z Z; Weinberger, D R

2000-04-01

The rat medial prefrontal cortex (mPFC) regulates subcortical dopamine transmission via projections to the striatum and ventral tegmental area. We used in vivo proton magnetic resonance spectroscopy (1H-MRS) at 4.7 T to determine whether excitotoxic lesions of the mPFC result in alterations of N-acetylaspartate (NAA), a marker of neuronal integrity, both locally and downstream in the striatum. Lesioned rats exhibited persistent reductions of NAA and other metabolites within the prefrontal cortex; selective reductions of NAA were seen in the striatum, but not in the parietal cortex. Consistent with earlier reports, lesioned rats exhibited a transient enhancement in amphetamine-induced hyperlocomotion. Prefrontal NAA losses correlated with lesion extent. In the striatum, while there was no change in tissue volume, expression of striatal glutamic acid decarboxylase-67 mRNA was significantly reduced. In vivo NAA levels thus appear sensitive to both local and downstream alterations in neuronal integrity, and may signal meaningful effects at cellular and behavioral levels.

Synchronous beta rhythms of frontoparietal networks support only behaviorally relevant representations

PubMed Central

Antzoulatos, Evan G; Miller, Earl K

2016-01-01

Categorization has been associated with distributed networks of the primate brain, including the prefrontal cortex (PFC) and posterior parietal cortex (PPC). Although category-selective spiking in PFC and PPC has been established, the frequency-dependent dynamic interactions of frontoparietal networks are largely unexplored. We trained monkeys to perform a delayed-match-to-spatial-category task while recording spikes and local field potentials from the PFC and PPC with multiple electrodes. We found category-selective beta- and delta-band synchrony between and within the areas. However, in addition to the categories, delta synchrony and spiking activity also reflected irrelevant stimulus dimensions. By contrast, beta synchrony only conveyed information about the task-relevant categories. Further, category-selective PFC neurons were synchronized with PPC beta oscillations, while neurons that carried irrelevant information were not. These results suggest that long-range beta-band synchrony could act as a filter that only supports neural representations of the variables relevant to the task at hand. DOI: http://dx.doi.org/10.7554/eLife.17822.001 PMID:27841747

GeNN: a code generation framework for accelerated brain simulations

NASA Astrophysics Data System (ADS)

Yavuz, Esin; Turner, James; Nowotny, Thomas

2016-01-01

Large-scale numerical simulations of detailed brain circuit models are important for identifying hypotheses on brain functions and testing their consistency and plausibility. An ongoing challenge for simulating realistic models is, however, computational speed. In this paper, we present the GeNN (GPU-enhanced Neuronal Networks) framework, which aims to facilitate the use of graphics accelerators for computational models of large-scale neuronal networks to address this challenge. GeNN is an open source library that generates code to accelerate the execution of network simulations on NVIDIA GPUs, through a flexible and extensible interface, which does not require in-depth technical knowledge from the users. We present performance benchmarks showing that 200-fold speedup compared to a single core of a CPU can be achieved for a network of one million conductance based Hodgkin-Huxley neurons but that for other models the speedup can differ. GeNN is available for Linux, Mac OS X and Windows platforms. The source code, user manual, tutorials, Wiki, in-depth example projects and all other related information can be found on the project website http://genn-team.github.io/genn/.

GeNN: a code generation framework for accelerated brain simulations.

PubMed

Yavuz, Esin; Turner, James; Nowotny, Thomas

2016-01-07

Large-scale numerical simulations of detailed brain circuit models are important for identifying hypotheses on brain functions and testing their consistency and plausibility. An ongoing challenge for simulating realistic models is, however, computational speed. In this paper, we present the GeNN (GPU-enhanced Neuronal Networks) framework, which aims to facilitate the use of graphics accelerators for computational models of large-scale neuronal networks to address this challenge. GeNN is an open source library that generates code to accelerate the execution of network simulations on NVIDIA GPUs, through a flexible and extensible interface, which does not require in-depth technical knowledge from the users. We present performance benchmarks showing that 200-fold speedup compared to a single core of a CPU can be achieved for a network of one million conductance based Hodgkin-Huxley neurons but that for other models the speedup can differ. GeNN is available for Linux, Mac OS X and Windows platforms. The source code, user manual, tutorials, Wiki, in-depth example projects and all other related information can be found on the project website http://genn-team.github.io/genn/.

GeNN: a code generation framework for accelerated brain simulations

PubMed Central

Yavuz, Esin; Turner, James; Nowotny, Thomas

2016-01-01

Large-scale numerical simulations of detailed brain circuit models are important for identifying hypotheses on brain functions and testing their consistency and plausibility. An ongoing challenge for simulating realistic models is, however, computational speed. In this paper, we present the GeNN (GPU-enhanced Neuronal Networks) framework, which aims to facilitate the use of graphics accelerators for computational models of large-scale neuronal networks to address this challenge. GeNN is an open source library that generates code to accelerate the execution of network simulations on NVIDIA GPUs, through a flexible and extensible interface, which does not require in-depth technical knowledge from the users. We present performance benchmarks showing that 200-fold speedup compared to a single core of a CPU can be achieved for a network of one million conductance based Hodgkin-Huxley neurons but that for other models the speedup can differ. GeNN is available for Linux, Mac OS X and Windows platforms. The source code, user manual, tutorials, Wiki, in-depth example projects and all other related information can be found on the project website http://genn-team.github.io/genn/. PMID:26740369

Lentiviral Infection of Rhesus Macaques Causes Long-Term Injury to Cortical and Hippocampal Projections of Prostaglandin-Expressing Cholinergic Basal Forebrain Neurons

PubMed Central

Depboylu, Candan; Weihe, Eberhard; Eiden, Lee E.

2011-01-01

The simian immunodeficiency virus (SIV) macaque model resembles human HIV-AIDS and associated brain dysfunction. Altered expression of synaptic markers and transmitters in neuro-AIDS has been reported, but limited data exist for the cholinergic system and lipid mediators such as prostaglandins. Here, we analyzed cholinergic basal forebrain neurons with their telencephalic projections and the rate-limiting enzymes for prostaglandin synthesis, cyclooxygenases 1 and 2 (COX1 and 2) in brains of SIV-infected macaques with and without encephalitis and antiretroviral therapy, and uninfected controls. COX1 but not COX2 was co-expressed with markers of cholinergic phenotype, i.e. choline acetyltransferase and vesicular acetylcholine transporter (VAChT), in basal forebrain neurons of monkey, as well as human samples. COX1 was decreased in basal forebrain neurons in macaques with AIDS vs. uninfected and asymptomatic SIV-infected macaques. VAChT-positive fiber density was reduced in frontal, parietal and hippocampal-entorhinal cortex. Although brain SIV burden and associated COX1- and COX2-positive mononuclear and endothelial inflammatory reactions were mostly reversed in AIDS-diseased macaques that received 6-chloro-2′,3′-dideoxyguanosine treatment, decreased VAChT-positive terminal density and reduced cholinergic COX1 expression were not. Thus, COX1 expression is a feature of primate cholinergic basal forebrain neurons; it may be functionally important and a critical biomarker of cholinergic dysregulation accompanying lentiviral encephalopathy. These results imply that insufficiently prompt initiation of antiretroviral therapy in lentiviral infection may lead to neurostructurally unremarkable but neurochemically prominent, irreversible brain damage. PMID:22157616

Conversion of Phase Information into a Spike-Count Code by Bursting Neurons

PubMed Central

Samengo, Inés; Montemurro, Marcelo A.

2010-01-01

Single neurons in the cerebral cortex are immersed in a fluctuating electric field, the local field potential (LFP), which mainly originates from synchronous synaptic input into the local neural neighborhood. As shown by recent studies in visual and auditory cortices, the angular phase of the LFP at the time of spike generation adds significant extra information about the external world, beyond the one contained in the firing rate alone. However, no biologically plausible mechanism has yet been suggested that allows downstream neurons to infer the phase of the LFP at the soma of their pre-synaptic afferents. Therefore, so far there is no evidence that the nervous system can process phase information. Here we study a model of a bursting pyramidal neuron, driven by a time-dependent stimulus. We show that the number of spikes per burst varies systematically with the phase of the fluctuating input at the time of burst onset. The mapping between input phase and number of spikes per burst is a robust response feature for a broad range of stimulus statistics. Our results suggest that cortical bursting neurons could play a crucial role in translating LFP phase information into an easily decodable spike count code. PMID:20300632

Transient extracellular application of gold nanostars increases hippocampal neuronal activity.

PubMed

Salinas, Kirstie; Kereselidze, Zurab; DeLuna, Frank; Peralta, Xomalin G; Santamaria, Fidel

2014-08-20

With the increased use of nanoparticles in biomedical applications there is a growing need to understand the effects that nanoparticles may have on cell function. Identifying these effects and understanding the mechanism through which nanoparticles interfere with the normal functioning of a cell is necessary for any therapeutic or diagnostic application. The aim of this study is to evaluate if gold nanoparticles can affect the normal function of neurons, namely their activity and coding properties. We synthesized star shaped gold nanoparticles of 180 nm average size. We applied the nanoparticles to acute mouse hippocampal slices while recording the action potentials from single neurons in the CA3 region. Our results show that CA3 hippocampal neurons increase their firing rate by 17% after the application of gold nanostars. The increase in excitability lasted for as much as 50 minutes after a transient 5 min application of the nanoparticles. Further analyses of the action potential shape and computational modeling suggest that nanoparticles block potassium channels responsible for the repolarization of the action potentials, thus allowing the cell to increase its firing rate. Our results show that gold nanoparticles can affect the coding properties of neurons by modifying their excitability.

How do auditory cortex neurons represent communication sounds?

PubMed

Gaucher, Quentin; Huetz, Chloé; Gourévitch, Boris; Laudanski, Jonathan; Occelli, Florian; Edeline, Jean-Marc

2013-11-01

A major goal in auditory neuroscience is to characterize how communication sounds are represented at the cortical level. The present review aims at investigating the role of auditory cortex in the processing of speech, bird songs and other vocalizations, which all are spectrally and temporally highly structured sounds. Whereas earlier studies have simply looked for neurons exhibiting higher firing rates to particular conspecific vocalizations over their modified, artificially synthesized versions, more recent studies determined the coding capacity of temporal spike patterns, which are prominent in primary and non-primary areas (and also in non-auditory cortical areas). In several cases, this information seems to be correlated with the behavioral performance of human or animal subjects, suggesting that spike-timing based coding strategies might set the foundations of our perceptive abilities. Also, it is now clear that the responses of auditory cortex neurons are highly nonlinear and that their responses to natural stimuli cannot be predicted from their responses to artificial stimuli such as moving ripples and broadband noises. Since auditory cortex neurons cannot follow rapid fluctuations of the vocalizations envelope, they only respond at specific time points during communication sounds, which can serve as temporal markers for integrating the temporal and spectral processing taking place at subcortical relays. Thus, the temporal sparse code of auditory cortex neurons can be considered as a first step for generating high level representations of communication sounds independent of the acoustic characteristic of these sounds. This article is part of a Special Issue entitled "Communication Sounds and the Brain: New Directions and Perspectives". Copyright © 2013 Elsevier B.V. All rights reserved.

Contour Curvature As an Invariant Code for Objects in Visual Area V4

PubMed Central

Pasupathy, Anitha

2016-01-01

Size-invariant object recognition—the ability to recognize objects across transformations of scale—is a fundamental feature of biological and artificial vision. To investigate its basis in the primate cerebral cortex, we measured single neuron responses to stimuli of varying size in visual area V4, a cornerstone of the object-processing pathway, in rhesus monkeys (Macaca mulatta). Leveraging two competing models for how neuronal selectivity for the bounding contours of objects may depend on stimulus size, we show that most V4 neurons (∼70%) encode objects in a size-invariant manner, consistent with selectivity for a size-independent parameter of boundary form: for these neurons, “normalized” curvature, rather than “absolute” curvature, provided a better account of responses. Our results demonstrate the suitability of contour curvature as a basis for size-invariant object representation in the visual cortex, and posit V4 as a foundation for behaviorally relevant object codes. SIGNIFICANCE STATEMENT Size-invariant object recognition is a bedrock for many perceptual and cognitive functions. Despite growing neurophysiological evidence for invariant object representations in the primate cortex, we still lack a basic understanding of the encoding rules that govern them. Classic work in the field of visual shape theory has long postulated that a representation of objects based on information about their bounding contours is well suited to mediate such an invariant code. In this study, we provide the first empirical support for this hypothesis, and its instantiation in single neurons of visual area V4. PMID:27194333

L-type calcium channels refine the neural population code of sound level

PubMed Central

Grimsley, Calum Alex; Green, David Brian

2016-01-01

The coding of sound level by ensembles of neurons improves the accuracy with which listeners identify how loud a sound is. In the auditory system, the rate at which neurons fire in response to changes in sound level is shaped by local networks. Voltage-gated conductances alter local output by regulating neuronal firing, but their role in modulating responses to sound level is unclear. We tested the effects of L-type calcium channels (CaL: CaV1.1–1.4) on sound-level coding in the central nucleus of the inferior colliculus (ICC) in the auditory midbrain. We characterized the contribution of CaL to the total calcium current in brain slices and then examined its effects on rate-level functions (RLFs) in vivo using single-unit recordings in awake mice. CaL is a high-threshold current and comprises ∼50% of the total calcium current in ICC neurons. In vivo, CaL activates at sound levels that evoke high firing rates. In RLFs that increase monotonically with sound level, CaL boosts spike rates at high sound levels and increases the maximum firing rate achieved. In different populations of RLFs that change nonmonotonically with sound level, CaL either suppresses or enhances firing at sound levels that evoke maximum firing. CaL multiplies the gain of monotonic RLFs with dynamic range and divides the gain of nonmonotonic RLFs with the width of the RLF. These results suggest that a single broad class of calcium channels activates enhancing and suppressing local circuits to regulate the sensitivity of neuronal populations to sound level. PMID:27605536

Efficiency turns the table on neural encoding, decoding and noise.

PubMed

Deneve, Sophie; Chalk, Matthew

2016-04-01

Sensory neurons are usually described with an encoding model, for example, a function that predicts their response from the sensory stimulus using a receptive field (RF) or a tuning curve. However, central to theories of sensory processing is the notion of 'efficient coding'. We argue here that efficient coding implies a completely different neural coding strategy. Instead of a fixed encoding model, neural populations would be described by a fixed decoding model (i.e. a model reconstructing the stimulus from the neural responses). Because the population solves a global optimization problem, individual neurons are variable, but not noisy, and have no truly invariant tuning curve or receptive field. We review recent experimental evidence and implications for neural noise correlations, robustness and adaptation. Copyright © 2016. Published by Elsevier Ltd.

Structure and expression of canary myc family genes.

PubMed Central

Collum, R G; Clayton, D F; Alt, F W

1991-01-01

We found that the canary N-myc gene is highly related to mammalian N-myc genes in both the protein-coding region and the long 3' untranslated region. Examined coding regions of the canary c-myc gene were also highly related to their mammalian counterparts, but in contrast to N-myc, the canary and mammalian c-myc genes were quite divergent in their 3' untranslated regions. We readily detected N-myc and c-myc expression in the adult canary brain and found N-myc expression both at sites of proliferating neuronal precursors and in mature neurons. Images PMID:1996121

Parameter as a Switch Between Dynamical States of a Network in Population Decoding.

PubMed

Yu, Jiali; Mao, Hua; Yi, Zhang

2017-04-01

Population coding is a method to represent stimuli using the collective activities of a number of neurons. Nevertheless, it is difficult to extract information from these population codes with the noise inherent in neuronal responses. Moreover, it is a challenge to identify the right parameter of the decoding model, which plays a key role for convergence. To address the problem, a population decoding model is proposed for parameter selection. Our method successfully identified the key conditions for a nonzero continuous attractor. Both the theoretical analysis and the application studies demonstrate the correctness and effectiveness of this strategy.

Discrete coding of stimulus value, reward expectation, and reward prediction error in the dorsal striatum.

PubMed

Oyama, Kei; Tateyama, Yukina; Hernádi, István; Tobler, Philippe N; Iijima, Toshio; Tsutsui, Ken-Ichiro

2015-11-01

To investigate how the striatum integrates sensory information with reward information for behavioral guidance, we recorded single-unit activity in the dorsal striatum of head-fixed rats participating in a probabilistic Pavlovian conditioning task with auditory conditioned stimuli (CSs) in which reward probability was fixed for each CS but parametrically varied across CSs. We found that the activity of many neurons was linearly correlated with the reward probability indicated by the CSs. The recorded neurons could be classified according to their firing patterns into functional subtypes coding reward probability in different forms such as stimulus value, reward expectation, and reward prediction error. These results suggest that several functional subgroups of dorsal striatal neurons represent different kinds of information formed through extensive prior exposure to CS-reward contingencies. Copyright © 2015 the American Physiological Society.

Discrete coding of stimulus value, reward expectation, and reward prediction error in the dorsal striatum

PubMed Central

Oyama, Kei; Tateyama, Yukina; Hernádi, István; Tobler, Philippe N.; Iijima, Toshio

2015-01-01

To investigate how the striatum integrates sensory information with reward information for behavioral guidance, we recorded single-unit activity in the dorsal striatum of head-fixed rats participating in a probabilistic Pavlovian conditioning task with auditory conditioned stimuli (CSs) in which reward probability was fixed for each CS but parametrically varied across CSs. We found that the activity of many neurons was linearly correlated with the reward probability indicated by the CSs. The recorded neurons could be classified according to their firing patterns into functional subtypes coding reward probability in different forms such as stimulus value, reward expectation, and reward prediction error. These results suggest that several functional subgroups of dorsal striatal neurons represent different kinds of information formed through extensive prior exposure to CS-reward contingencies. PMID:26378201

Parietal and temporal activity during a multimodal dance video game: an fNIRS study.

PubMed

Tachibana, Atsumichi; Noah, J Adam; Bronner, Shaw; Ono, Yumie; Onozuka, Minoru

2011-10-03

Using functional near infrared spectroscopy (fNIRS) we studied how playing a dance video game employs coordinated activation of sensory-motor integration centers of the superior parietal lobe (SPL) and superior temporal gyrus (STG). Subjects played a dance video game, in a block design with 30s of activity alternating with 30s of rest, while changes in oxy-hemoglobin (oxy-Hb) levels were continuously measured. The game was modified to compare difficult (4-arrow), simple (2-arrow), and stepping conditions. Oxy-Hb levels were greatest with increased task difficulty. The quick-onset, trapezoidal time-course increase in SPL oxy-Hb levels reflected the on-off neuronal response of spatial orienting and rhythmic motor timing that were required during the activity. Slow-onset, bell-shaped increases in oxy-Hb levels observed in STG suggested the gradually increasing load of directing multisensory information to downstream processing centers associated with motor behavior and control. Differences in temporal relationships of SPL and STG oxy-Hb concentration levels may reflect the functional roles of these brain structures during the task period. NIRS permits insights into temporal relationships of cortical hemodynamics during real motor tasks. Copyright © 2011 Elsevier Ireland Ltd. All rights reserved.

Lateralization of the human mirror neuron system.

PubMed

Aziz-Zadeh, Lisa; Koski, Lisa; Zaidel, Eran; Mazziotta, John; Iacoboni, Marco

2006-03-15

A cortical network consisting of the inferior frontal, rostral inferior parietal, and posterior superior temporal cortices has been implicated in representing actions in the primate brain and is critical to imitation in humans. This neural circuitry may be an evolutionary precursor of neural systems associated with language. However, language is predominantly lateralized to the left hemisphere, whereas the degree of lateralization of the imitation circuitry in humans is unclear. We conducted a functional magnetic resonance imaging study of imitation of finger movements with lateralized stimuli and responses. During imitation, activity in the inferior frontal and rostral inferior parietal cortex, although fairly bilateral, was stronger in the hemisphere ipsilateral to the visual stimulus and response hand. This ipsilateral pattern is at variance with the typical contralateral activity of primary visual and motor areas. Reliably increased signal in the right superior temporal sulcus (STS) was observed for both left-sided and right-sided imitation tasks, although subthreshold activity was also observed in the left STS. Overall, the data indicate that visual and motor components of the human mirror system are not left-lateralized. The left hemisphere superiority for language, then, must be have been favored by other types of language precursors, perhaps auditory or multimodal action representations.

Rana computatrix to human language: towards a computational neuroethology of language evolution.

PubMed

Arbib, Michael A

2003-10-15

Walter's Machina speculatrix inspired the name Rana computatrix for a family of models of visuomotor coordination in the frog, which contributed to the development of computational neuroethology. We offer here an 'evolutionary' perspective on models in the same tradition for rat, monkey and human. For rat, we show how the frog-like taxon affordance model provides a basis for the spatial navigation mechanisms that involve the hippocampus and other brain regions. For monkey, we recall two models of neural mechanisms for visuomotor coordination. The first, for saccades, shows how interactions between the parietal and frontal cortex augment superior colliculus seen as the homologue of frog tectum. The second, for grasping, continues the theme of parieto-frontal interactions, linking parietal affordances to motor schemas in premotor cortex. It further emphasizes the mirror system for grasping, in which neurons are active both when the monkey executes a specific grasp and when it observes a similar grasp executed by others. The model of human-brain mechanisms is based on the mirror-system hypothesis of the evolution of the language-ready brain, which sees the human Broca's area as an evolved extension of the mirror system for grasping.

What Neural Substrates Trigger the Adept Scientific Pattern Discovery by Biologists?

NASA Astrophysics Data System (ADS)

Lee, Jun-Ki; Kwon, Yong-Ju

2011-04-01

This study investigated the neural correlates of experts and novices during biological object pattern detection using an fMRI approach in order to reveal the neural correlates of a biologist's superior pattern discovery ability. Sixteen healthy male participants (8 biologists and 8 non-biologists) volunteered for the study. Participants were shown fifteen series of organism pictures and asked to detect patterns amid stimulus pictures. Primary findings showed significant activations in the right middle temporal gyrus and inferior parietal lobule amongst participants in the biologist (expert) group. Interestingly, the left superior temporal gyrus was activated in participants from the non-biologist (novice) group. These results suggested that superior pattern discovery ability could be related to a functional facilitation of the parieto-temporal network, which is particularly driven by the right middle temporal gyrus and inferior parietal lobule in addition to the recruitment of additional brain regions. Furthermore, the functional facilitation of the network might actually pertain to high coherent processing skills and visual working memory capacity. Hence, study results suggested that adept scientific thinking ability can be detected by neuronal substrates, which may be used as criteria for developing and evaluating a brain-based science curriculum and test instrument.

Relative timing: from behaviour to neurons

PubMed Central

Aghdaee, S. Mehdi; Battelli, Lorella; Assad, John A.

2014-01-01

Processing of temporal information is critical to behaviour. Here, we review the phenomenology and mechanism of relative timing, ordinal comparisons between the timing of occurrence of events. Relative timing can be an implicit component of particular brain computations or can be an explicit, conscious judgement. Psychophysical measurements of explicit relative timing have revealed clues about the interaction of sensory signals in the brain as well as in the influence of internal states, such as attention, on those interactions. Evidence from human neurophysiological and functional imaging studies, neuropsychological examination in brain-lesioned patients, and temporary disruptive interventions such as transcranial magnetic stimulation (TMS), point to a role of the parietal cortex in relative timing. Relative timing has traditionally been modelled as a ‘race’ between competing neural signals. We propose an updated race process based on the integration of sensory evidence towards a decision threshold rather than simple signal propagation. The model suggests a general approach for identifying brain regions involved in relative timing, based on looking for trial-by-trial correlations between neural activity and temporal order judgements (TOJs). Finally, we show how the paradigm can be used to reveal signals related to TOJs in parietal cortex of monkeys trained in a TOJ task. PMID:24446505

Altered cortical communication in amyotrophic lateral sclerosis.

PubMed

Blain-Moraes, Stefanie; Mashour, George A; Lee, Heonsoo; Huggins, Jane E; Lee, Uncheol

2013-05-24

Amyotrophic lateral sclerosis (ALS) is a disorder associated primarily with the degeneration of the motor system. More recently, functional connectivity studies have demonstrated potentially adaptive changes in ALS brain organization, but disease-related changes in cortical communication remain unknown. We recruited individuals with ALS and age-matched controls to operate a brain-computer interface while electroencephalography was recorded over three sessions. Using normalized symbolic transfer entropy, we measured directed functional connectivity from frontal to parietal (feedback connectivity) and parietal to frontal (feedforward connectivity) regions. Feedback connectivity was not significantly different between groups, but feedforward connectivity was significantly higher in individuals with ALS. This result was consistent across a broad electroencephalographic spectrum (4-35 Hz), and in theta, alpha and beta frequency bands. Feedback connectivity has been associated with conscious state and was found to be independent of ALS symptom severity in this study, which may have significant implications for the detection of consciousness in individuals with advanced ALS. We suggest that increases in feedforward connectivity represent a compensatory response to the ALS-related loss of input such that sensory stimuli have sufficient strength to cross the threshold necessary for conscious processing in the global neuronal workspace. Copyright © 2013 Elsevier Ireland Ltd. All rights reserved.

Chromatic aberration and the roles of double-opponent and color-luminance neurons in color vision.

PubMed

Vladusich, Tony

2007-03-01

How does the visual cortex encode color? I summarize a theory in which cortical double-opponent color neurons perform a role in color constancy and a complementary set of color-luminance neurons function to selectively correct for color fringes induced by chromatic aberration in the eye. The theory may help to resolve an ongoing debate concerning the functional properties of cortical receptive fields involved in color coding.

Laminar Differences in Associative Memory Signals in Monkey Perirhinal Cortex.

PubMed

Vogels, Rufin

2016-10-19

New research published in Neuron describes assignment of cortical layer to single neurons recorded in awake monkeys. Applying the procedure to perirhinal cortex, Koyano et al. (2016) found marked and unsuspected differences among layers in the coding of associative memory signals. Copyright © 2016. Published by Elsevier Inc.

Dopamine neurons share common response function for reward prediction error

PubMed Central

Eshel, Neir; Tian, Ju; Bukwich, Michael; Uchida, Naoshige

2016-01-01

Dopamine neurons are thought to signal reward prediction error, or the difference between actual and predicted reward. How dopamine neurons jointly encode this information, however, remains unclear. One possibility is that different neurons specialize in different aspects of prediction error; another is that each neuron calculates prediction error in the same way. We recorded from optogenetically-identified dopamine neurons in the lateral ventral tegmental area (VTA) while mice performed classical conditioning tasks. Our tasks allowed us to determine the full prediction error functions of dopamine neurons and compare them to each other. We found striking homogeneity among individual dopamine neurons: their responses to both unexpected and expected rewards followed the same function, just scaled up or down. As a result, we could describe both individual and population responses using just two parameters. Such uniformity ensures robust information coding, allowing each dopamine neuron to contribute fully to the prediction error signal. PMID:26854803

Neurocognitive processing of body representations in artistic and photographic images.

PubMed

Lutz, Aline; Nassehi, Armin; Bao, Yan; Pöppel, Ernst; Sztrókay, Anikó; Reiser, Maximilian; Fehse, Kai; Gutyrchik, Evgeny

2013-02-01

Visual art because of its artistic context can be related to the general idea of providing alternative perceptual experiences. However, research examining the neural basis of art beyond the paradigm of beauty has been neglected. This study seeks to determine how the perception of a body in an artwork can be distinguished from the perception of a body in a non-artistic photography. While viewing different body representations in both artworks and photographs, subjects were required to evaluate the appeal of the portrayed persons. By using functional magnetic resonance imaging (fMRI) we show that the perception of a body within the context of art leads to a higher activation in the right parietal cortex and the extrastriate cortex bilaterally. Relating this result to concepts from previous research, we suggest that the perception of art is linked to visuo-spatial coding and also motor mapping. In contrast, the higher activity in the ventromedial prefrontal cortex and the primary visual cortex during the perception of a body in a non-artistic frame of reference, i.e. in a photograph, can be linked to processes of person evaluation. Possibly, the task to judge the appeal of a person in a photograph might be more daunting and, thus, cause emotional and even moral challenges being reflected in the ventromedial prefrontal activity. Taken together, perceptual experiences within an artistic vs. a non-artistic frame of reference are based on distinct patterns of neuronal activity. Copyright © 2012 Elsevier Inc. All rights reserved.

Response of anterior parietal cortex to cutaneous flutter versus vibration.

PubMed

Tommerdahl, M; Delemos, K A; Whitsel, B L; Favorov, O V; Metz, C B

1999-07-01

The response of anesthetized squirrel monkey anterior parietal (SI) cortex to 25 or 200 Hz sinusoidal vertical skin displacement stimulation was studied using the method of optical intrinsic signal (OIS) imaging. Twenty-five-Hertz ("flutter") stimulation of a discrete skin site on either the hindlimb or forelimb for 3-30 s evoked a prominent increase in absorbance within cytoarchitectonic areas 3b and 1 in the contralateral hemisphere. This response was confined to those area 3b/1 regions occupied by neurons with a receptive field (RF) that includes the stimulated skin site. In contrast, same-site 200-Hz stimulation ("vibration") for 3-30 s evoked a decrease in absorbance in a much larger territory (most frequently involving areas 3b, 1, and area 3a, but in some subjects area 2 as well) than the region that undergoes an increase in absorbance during 25-Hz flutter stimulation. The increase in absorbance evoked by 25-Hz flutter developed quickly and remained relatively constant for as long as stimulation continued (stimulus duration never exceeded 30 s). At 1-3 s after stimulus onset, the response to 200-Hz stimulation, like the response to 25-Hz flutter, consisted of a localized increase in absorbance limited to the topographically appropriate region of area 3b and/or area 1. With continuing 200-Hz stimulation, however, the early response declined, and by 4-6 s after stimulus onset, it was replaced by a prominent and spatially extensive decrease in absorbance. The spike train responses of single quickly adapting (QA) neurons were recorded extracellularly during microelectrode penetrations that traverse the optically responding regions of areas 3b and 1. Onset of either 25- or 200-Hz stimulation at a site within the cutaneous RF of a QA neuron was accompanied by a substantial increase in mean spike firing rate. With continued 200-Hz stimulation, however, QA neuron mean firing rate declined rapidly (typically within 0.5-1.0 s) to a level below that recorded at the same time after onset of same-site 25-Hz stimulation. For some neurons, the mean firing rate after the initial 0.5-1 s of an exposure to 200-Hz stimulation of the RF decreased to a level below the level of background ("spontaneous") activity. The decline in both the stimulus-evoked increases in absorbance in areas 3b/1 and spike discharge activity of area 3b/1 neurons within only a few seconds of the onset of 200-Hz skin stimulation raised the possibility that the predominant effect of continuous 200-Hz stimulation for >3 s is inhibition of area 3b/1 QA neurons. This possibility was evaluated at the neuronal population level by comparing the intrinsic signal evoked in areas 3b/1 by 25-Hz skin stimulation to the intrinsic signal evoked by a same-site skin stimulus containing both 25- and 200-Hz sinusoidal components (a "complex waveform stimulus"). Such experiments revealed that the increase in absorbance evoked in areas 3b/1 by a stimulus having both 25- and 200-Hz components was substantially smaller (especially at times >3 s after stimulus onset) than the increase in absorbance evoked by "pure" 25-Hz stimulation of the same skin site. It is concluded that within a brief time (within 1-3 s) after stimulus onset, 200-Hz skin stimulation elicits a powerful inhibitory action on area 3b/1 QA neurons. The findings appear generally consistent with the suggestion that the activity of neurons in cortical regions other than areas 3b and 1 play the leading role in the processing of high-frequency (>/=200 Hz) vibrotactile stimuli.

Natural image sequences constrain dynamic receptive fields and imply a sparse code.

PubMed

Häusler, Chris; Susemihl, Alex; Nawrot, Martin P

2013-11-06

In their natural environment, animals experience a complex and dynamic visual scenery. Under such natural stimulus conditions, neurons in the visual cortex employ a spatially and temporally sparse code. For the input scenario of natural still images, previous work demonstrated that unsupervised feature learning combined with the constraint of sparse coding can predict physiologically measured receptive fields of simple cells in the primary visual cortex. This convincingly indicated that the mammalian visual system is adapted to the natural spatial input statistics. Here, we extend this approach to the time domain in order to predict dynamic receptive fields that can account for both spatial and temporal sparse activation in biological neurons. We rely on temporal restricted Boltzmann machines and suggest a novel temporal autoencoding training procedure. When tested on a dynamic multi-variate benchmark dataset this method outperformed existing models of this class. Learning features on a large dataset of natural movies allowed us to model spatio-temporal receptive fields for single neurons. They resemble temporally smooth transformations of previously obtained static receptive fields and are thus consistent with existing theories. A neuronal spike response model demonstrates how the dynamic receptive field facilitates temporal and population sparseness. We discuss the potential mechanisms and benefits of a spatially and temporally sparse representation of natural visual input. Copyright © 2013 The Authors. Published by Elsevier B.V. All rights reserved.

Frontotemporal dementia with the C9ORF72 hexanucleotide repeat expansion: clinical, neuroanatomical and neuropathological features

PubMed Central

Mahoney, Colin J.; Beck, Jon; Rohrer, Jonathan D.; Lashley, Tammaryn; Mok, Kin; Shakespeare, Tim; Yeatman, Tom; Warrington, Elizabeth K.; Schott, Jonathan M.; Fox, Nick C.; Rossor, Martin N.; Hardy, John; Collinge, John; Revesz, Tamas; Mead, Simon

2012-01-01

An expanded hexanucleotide repeat in the C9ORF72 gene has recently been identified as a major cause of familial frontotemporal lobar degeneration and motor neuron disease, including cases previously identified as linked to chromosome 9. Here we present a detailed retrospective clinical, neuroimaging and histopathological analysis of a C9ORF72 mutation case series in relation to other forms of genetically determined frontotemporal lobar degeneration ascertained at a specialist centre. Eighteen probands (19 cases in total) were identified, representing 35% of frontotemporal lobar degeneration cases with identified mutations, 36% of cases with clinical evidence of motor neuron disease and 7% of the entire cohort. Thirty-three per cent of these C9ORF72 cases had no identified relevant family history. Families showed wide variation in clinical onset (43–68 years) and duration (1.7–22 years). The most common presenting syndrome (comprising a half of cases) was behavioural variant frontotemporal dementia, however, there was substantial clinical heterogeneity across the C9ORF72 mutation cohort. Sixty per cent of cases developed clinical features consistent with motor neuron disease during the period of follow-up. Anxiety and agitation and memory impairment were prominent features (between a half to two-thirds of cases), and dominant parietal dysfunction was also frequent. Affected individuals showed variable magnetic resonance imaging findings; however, relative to healthy controls, the group as a whole showed extensive thinning of frontal, temporal and parietal cortices, subcortical grey matter atrophy including thalamus and cerebellum and involvement of long intrahemispheric, commissural and corticospinal tracts. The neuroimaging profile of the C9ORF72 expansion was significantly more symmetrical than progranulin mutations with significantly less temporal lobe involvement than microtubule-associated protein tau mutations. Neuropathological examination in six cases with C9ORF72 mutation from the frontotemporal lobar degeneration series identified histomorphological features consistent with either type A or B TAR DNA-binding protein-43 deposition; however, p62-positive (in excess of TAR DNA-binding protein-43 positive) neuronal cytoplasmic inclusions in hippocampus and cerebellum were a consistent feature of these cases, in contrast to the similar frequency of p62 and TAR DNA-binding protein-43 deposition in 53 control cases with frontotemporal lobar degeneration–TAR DNA-binding protein. These findings corroborate the clinical importance of the C9ORF72 mutation in frontotemporal lobar degeneration, delineate phenotypic and neuropathological features that could help to guide genetic testing, and suggest hypotheses for elucidating the neurobiology of a culprit subcortical network. PMID:22366791

Coding and decoding with adapting neurons: a population approach to the peri-stimulus time histogram.

PubMed

Naud, Richard; Gerstner, Wulfram

2012-01-01

The response of a neuron to a time-dependent stimulus, as measured in a Peri-Stimulus-Time-Histogram (PSTH), exhibits an intricate temporal structure that reflects potential temporal coding principles. Here we analyze the encoding and decoding of PSTHs for spiking neurons with arbitrary refractoriness and adaptation. As a modeling framework, we use the spike response model, also known as the generalized linear neuron model. Because of refractoriness, the effect of the most recent spike on the spiking probability a few milliseconds later is very strong. The influence of the last spike needs therefore to be described with high precision, while the rest of the neuronal spiking history merely introduces an average self-inhibition or adaptation that depends on the expected number of past spikes but not on the exact spike timings. Based on these insights, we derive a 'quasi-renewal equation' which is shown to yield an excellent description of the firing rate of adapting neurons. We explore the domain of validity of the quasi-renewal equation and compare it with other rate equations for populations of spiking neurons. The problem of decoding the stimulus from the population response (or PSTH) is addressed analogously. We find that for small levels of activity and weak adaptation, a simple accumulator of the past activity is sufficient to decode the original input, but when refractory effects become large decoding becomes a non-linear function of the past activity. The results presented here can be applied to the mean-field analysis of coupled neuron networks, but also to arbitrary point processes with negative self-interaction.

Temporal dynamics of retinal and extraretinal signals in the FEFsem during smooth pursuit eye movements

PubMed Central

Bakst, Leah; Fleuriet, Jérome

2017-01-01

Neurons in the smooth eye movement subregion of the frontal eye field (FEFsem) are known to play an important role in voluntary smooth pursuit eye movements. Underlying this function are projections to parietal and prefrontal visual association areas and subcortical structures, all known to play vital but differing roles in the execution of smooth pursuit. Additionally, the FEFsem has been shown to carry a diverse array of signals (e.g., eye velocity, acceleration, gain control). We hypothesized that distinct subpopulations of FEFsem neurons subserve these diverse functions and projections, and that the relative weights of retinal and extraretinal signals could form the basis for categorization of units. To investigate this, we used a step-ramp tracking task with a target blink to determine the relative contributions of retinal and extraretinal signals in individual FEFsem neurons throughout pursuit. We found that the contributions of retinal and extraretinal signals to neuronal activity and behavior change throughout the time course of pursuit. A clustering algorithm revealed three distinct neuronal subpopulations: cluster 1 was defined by a higher sensitivity to eye velocity, acceleration, and retinal image motion; cluster 2 had greater activity during blinks; and cluster 3 had significantly greater eye position sensitivity. We also performed a comparison with a sample of medial superior temporal neurons to assess similarities and differences between the two areas. Our results indicate the utility of simple tests such as the target blink for parsing the complex and multifaceted roles of cortical areas in behavior. NEW & NOTEWORTHY The frontal eye field (FEF) is known to play a critical role in volitional smooth pursuit, carrying a variety of signals that are distributed throughout the brain. This study used a novel application of a target blink task during step ramp tracking to determine, in combination with a clustering algorithm, the relative contributions of retinal and extraretinal signals to FEF activity and the extent to which these contributions could form the basis for a categorization of neurons. PMID:28202571

Functional Anatomy of Writing with the Dominant Hand

PubMed Central

Najee-ullah, Muslimah ‘Ali; Hallett, Mark

2013-01-01

While writing performed by any body part is similar in style, indicating a common program, writing with the dominant hand is particularly skilled. We hypothesized that this skill utilizes a special motor network supplementing the motor equivalence areas. Using functional magnetic resonance imaging in 13 normal subjects, we studied nine conditions: writing, zigzagging and tapping, each with the right hand, left hand and right foot. We identified brain regions activated with the right (dominant) hand writing task, exceeding the activation common to right-hand use and the writing program, both identified without right-hand writing itself. Right-hand writing significantly differed from the other tasks. First, we observed stronger activations in the left dorsal prefrontal cortex, left intraparietal sulcus and right cerebellum. Second, the left anterior putamen was required to initiate all the tested tasks, but only showed sustained activation during the right-hand writing condition. Lastly, an exploratory analysis showed clusters in the left ventral premotor cortex and inferior and superior parietal cortices were only significantly active for right-hand writing. The increased activation with right-hand writing cannot be ascribed to increased effort, since this is a well-practiced task much easier to perform than some of the other tasks studied. Because parietal-premotor connections code for particular skills, it would seem that the parietal and premotor regions, together with basal ganglia-sustained activation likely underlie the special skill of handwriting with the dominant hand. PMID:23844132

Functional anatomy of writing with the dominant hand.

PubMed

Horovitz, Silvina G; Gallea, Cecile; Najee-Ullah, Muslimah 'ali; Hallett, Mark

2013-01-01

While writing performed by any body part is similar in style, indicating a common program, writing with the dominant hand is particularly skilled. We hypothesized that this skill utilizes a special motor network supplementing the motor equivalence areas. Using functional magnetic resonance imaging in 13 normal subjects, we studied nine conditions: writing, zigzagging and tapping, each with the right hand, left hand and right foot. We identified brain regions activated with the right (dominant) hand writing task, exceeding the activation common to right-hand use and the writing program, both identified without right-hand writing itself. Right-hand writing significantly differed from the other tasks. First, we observed stronger activations in the left dorsal prefrontal cortex, left intraparietal sulcus and right cerebellum. Second, the left anterior putamen was required to initiate all the tested tasks, but only showed sustained activation during the right-hand writing condition. Lastly, an exploratory analysis showed clusters in the left ventral premotor cortex and inferior and superior parietal cortices were only significantly active for right-hand writing. The increased activation with right-hand writing cannot be ascribed to increased effort, since this is a well-practiced task much easier to perform than some of the other tasks studied. Because parietal-premotor connections code for particular skills, it would seem that the parietal and premotor regions, together with basal ganglia-sustained activation likely underlie the special skill of handwriting with the dominant hand.

Dance expertise modulates visual sensitivity to complex biological movements.

PubMed

Orlandi, Andrea; Zani, Alberto; Proverbio, Alice Mado

2017-09-01

Motor resonance processes that occur when observing an individual perform an action may be modulated by acquired visuomotor expertise. We used the event-related potential (EEG/ERP) technique to investigate the ability to automatically recognize a subtle difference between very similar novel contemporary dance movements. Twelve professional dancers and twelve non-dancers were shown 212 pairs of videos of complex whole-body movements that lasted 3s. The second of each pair was the repetition of the previous movement or a slight variation of it (deviance). The participants were engaged in a secondary attentional task. Modulation of a larger centro-parietal N400 effect and a reduction of the Late Positivity amplitude (repetition suppression effect) were identified in response to deviant stimuli only in the dancers. Source reconstruction (swLORETA) showed activations in biological motion, body and face processing related areas, and fronto-parietal and limbic systems. The current findings provide evidence that acquired dance expertise modifies the ability to visually code whole-body complex movements. Copyright © 2017 Elsevier Ltd. All rights reserved.

The functional architectures of addition and subtraction: Network discovery using fMRI and DCM.

PubMed

Yang, Yang; Zhong, Ning; Friston, Karl; Imamura, Kazuyuki; Lu, Shengfu; Li, Mi; Zhou, Haiyan; Wang, Haiyuan; Li, Kuncheng; Hu, Bin

2017-06-01

The neuronal mechanisms underlying arithmetic calculations are not well understood but the differences between mental addition and subtraction could be particularly revealing. Using fMRI and dynamic causal modeling (DCM), this study aimed to identify the distinct neuronal architectures engaged by the cognitive processes of simple addition and subtraction. Our results revealed significantly greater activation during subtraction in regions along the dorsal pathway, including the left inferior frontal gyrus (IFG), middle portion of dorsolateral prefrontal cortex (mDLPFC), and supplementary motor area (SMA), compared with addition. Subsequent analysis of the underlying changes in connectivity - with DCM - revealed a common circuit processing basic (numeric) attributes and the retrieval of arithmetic facts. However, DCM showed that addition was more likely to engage (numeric) retrieval-based circuits in the left hemisphere, while subtraction tended to draw on (magnitude) processing in bilateral parietal cortex, especially the right intraparietal sulcus (IPS). Our findings endorse previous hypotheses about the differences in strategic implementation, dominant hemisphere, and the neuronal circuits underlying addition and subtraction. Moreover, for simple arithmetic, our connectivity results suggest that subtraction calls on more complex processing than addition: auxiliary phonological, visual, and motor processes, for representing numbers, were engaged by subtraction, relative to addition. Hum Brain Mapp 38:3210-3225, 2017. © 2017 Wiley Periodicals, Inc. © 2017 Wiley Periodicals, Inc.

Neuronal Oscillations Indicate Sleep-dependent Changes in the Cortical Memory Trace.

PubMed

Köster, Moritz; Finger, Holger; Kater, Maren-Jo; Schenk, Christoph; Gruber, Thomas

2017-04-01

Sleep promotes the consolidation of newly acquired associative memories. Here we used neuronal oscillations in the human EEG to investigate sleep-dependent changes in the cortical memory trace. The retrieval activity for object-color associations was assessed immediately after encoding and after 3 hr of sleep or wakefulness. Sleep had beneficial effects on memory performance and led to reduced event-related theta and gamma power during the retrieval of associative memories. Furthermore, event-related alpha suppression was attenuated in the wake group for memorized and novel stimuli. There were no sleep-dependent changes in retrieval activity for missed items or items retrieved without color. Thus, the sleep-dependent reduction in theta and gamma oscillations was specific for the retrieval of associative memories. In line with theoretical accounts on sleep-dependent memory consolidation, decreased theta may indicate reduced mediotemporal activity because of a transfer of information into neocortical networks during sleep, whereas reduced parietal gamma may reflect effects of synaptic downscaling. Changes in alpha suppression in the wake group possibly index reduced attentional resources that may also contribute to a lower memory performance in this group. These findings indicate that the consolidation of associative memories during sleep is associated with profound changes in the cortical memory trace and relies on multiple neuronal processes working in concert.

Discontinuous Patterns of Brain Activation in the Psychotherapy Process of Obsessive-Compulsive Disorder: Converging Results from Repeated fMRI and Daily Self-Reports

PubMed Central

Schiepek, Günter; Tominschek, Igor; Heinzel, Stephan; Aigner, Martin; Dold, Markus; Unger, Annemarie; Lenz, Gerhard; Windischberger, Christian; Moser, Ewald; Plöderl, Martin; Lutz, Jürgen; Meindl, Thomas; Zaudig, Michael; Pogarell, Oliver; Karch, Susanne

2013-01-01

This study investigates neuronal activation patterns during the psychotherapeutic process, assuming that change dynamics undergo critical instabilities and discontinuous transitions. An internet-based system was used to collect daily self-assessments during inpatient therapies. A dynamic complexity measure was applied to the resulting time series. Critical phases of the change process were indicated by the maxima of the varying complexity. Repeated functional magnetic resonance imaging (fMRI) measurements were conducted over the course of the therapy. The study was realized with 9 patients suffering from obsessive-compulsive disorder (subtype: washing/contamination fear) and 9 matched healthy controls. For symptom-provocative stimulation individualized pictures from patients’ personal environments were used. The neuronal responses to these disease-specific pictures were compared to the responses during standardized disgust-provoking and neutral pictures. Considerably larger neuronal changes in therapy-relevant brain areas (cingulate cortex/supplementary motor cortex, bilateral dorsolateral prefrontal cortex, bilateral insula, bilateral parietal cortex, cuneus) were observed during critical phases (order transitions), as compared to non-critical phases, and also compared to healthy controls. The data indicate that non-stationary changes play a crucial role in the psychotherapeutic process supporting self-organization and complexity models of therapeutic change. PMID:23977168

Action observation and mirror neuron network: a tool for motor stroke rehabilitation.

PubMed

Sale, P; Franceschini, M

2012-06-01

Mirror neurons are a specific class of neurons that are activated and discharge both during observation of the same or similar motor act performed by another individual and during the execution of a motor act. Different studies based on non invasive neuroelectrophysiological assessment or functional brain imaging techniques have demonstrated the presence of the mirror neuron and their mechanism in humans. Various authors have demonstrated that in the human these networks are activated when individuals learn motor actions via execution (as in traditional motor learning), imitation, observation (as in observational learning) and motor imagery. Activation of these brain areas (inferior parietal lobe and the ventral premotor cortex, as well as the caudal part of the inferior frontal gyrus [IFG]) following observation or motor imagery may thereby facilitate subsequent movement execution by directly matching the observed or imagined action to the internal simulation of that action. It is therefore believed that this multi-sensory action-observation system enables individuals to (re) learn impaired motor functions through the activation of these internal action-related representations. In humans, the mirror mechanism is also located in various brain segment: in Broca's area, which is involved in language processing and speech production and not only in centres that mediate voluntary movement, but also in cortical areas that mediate visceromotor emotion-related behaviours. On basis of this finding, during the last 10 years various studies were carry out regarding the clinical use of action observation for motor rehabilitation of sub-acute and chronic stroke patients.

Double dissociation of value computations in orbitofrontal and anterior cingulate neurons

PubMed Central

Kennerley, Steven W.; Behrens, Timothy E. J.; Wallis, Jonathan D.

2011-01-01

Damage to prefrontal cortex (PFC) impairs decision-making, but the underlying value computations that might cause such impairments remain unclear. Here we report that value computations are doubly dissociable within PFC neurons. While many PFC neurons encoded chosen value, they used opponent encoding schemes such that averaging the neuronal population eliminated value coding. However, a special population of neurons in anterior cingulate cortex (ACC) - but not orbitofrontal cortex (OFC) - multiplex chosen value across decision parameters using a unified encoding scheme, and encoded reward prediction errors. In contrast, neurons in OFC - but not ACC - encoded chosen value relative to the recent history of choice values. Together, these results suggest complementary valuation processes across PFC areas: OFC neurons dynamically evaluate current choices relative to recent choice values, while ACC neurons encode choice predictions and prediction errors using a common valuation currency reflecting the integration of multiple decision parameters. PMID:22037498

Reliable sex and strain discrimination in the mouse vomeronasal organ and accessory olfactory bulb.

PubMed

Tolokh, Illya I; Fu, Xiaoyan; Holy, Timothy E

2013-08-21

Animals modulate their courtship and territorial behaviors in response to olfactory cues produced by other animals. In rodents, detecting these cues is the primary role of the accessory olfactory system (AOS). We sought to systematically investigate the natural stimulus coding logic and robustness in neurons of the first two stages of accessory olfactory processing, the vomeronasal organ (VNO) and accessory olfactory bulb (AOB). We show that firing rate responses of just a few well-chosen mouse VNO or AOB neurons can be used to reliably encode both sex and strain of other mice from cues contained in urine. Additionally, we show that this population code can generalize to new concentrations of stimuli and appears to represent stimulus identity in terms of diverging paths in coding space. Together, the results indicate that firing rate code on the temporal order of seconds is sufficient for accurate classification of pheromonal patterns at different concentrations and may be used by AOS neural circuitry to discriminate among naturally occurring urine stimuli.

Quantitative Profiling of Peptides from RNAs classified as non-coding

PubMed Central

Prabakaran, Sudhakaran; Hemberg, Martin; Chauhan, Ruchi; Winter, Dominic; Tweedie-Cullen, Ry Y.; Dittrich, Christian; Hong, Elizabeth; Gunawardena, Jeremy; Steen, Hanno; Kreiman, Gabriel; Steen, Judith A.

2014-01-01

Only a small fraction of the mammalian genome codes for messenger RNAs destined to be translated into proteins, and it is generally assumed that a large portion of transcribed sequences - including introns and several classes of non-coding RNAs (ncRNAs) do not give rise to peptide products. A systematic examination of translation and physiological regulation of ncRNAs has not been conducted. Here, we use computational methods to identify the products of non-canonical translation in mouse neurons by analyzing unannotated transcripts in combination with proteomic data. This study supports the existence of non-canonical translation products from both intragenic and extragenic genomic regions, including peptides derived from anti-sense transcripts and introns. Moreover, the studied novel translation products exhibit temporal regulation similar to that of proteins known to be involved in neuronal activity processes. These observations highlight a potentially large and complex set of biologically regulated translational events from transcripts formerly thought to lack coding potential. PMID:25403355

A thesaurus for a neural population code

PubMed Central

Ganmor, Elad; Segev, Ronen; Schneidman, Elad

2015-01-01

Information is carried in the brain by the joint spiking patterns of large groups of noisy, unreliable neurons. This noise limits the capacity of the neural code and determines how information can be transmitted and read-out. To accurately decode, the brain must overcome this noise and identify which patterns are semantically similar. We use models of network encoding noise to learn a thesaurus for populations of neurons in the vertebrate retina responding to artificial and natural videos, measuring the similarity between population responses to visual stimuli based on the information they carry. This thesaurus reveals that the code is organized in clusters of synonymous activity patterns that are similar in meaning but may differ considerably in their structure. This organization is highly reminiscent of the design of engineered codes. We suggest that the brain may use this structure and show how it allows accurate decoding of novel stimuli from novel spiking patterns. DOI: http://dx.doi.org/10.7554/eLife.06134.001 PMID:26347983

Medial orbitofrontal cortex codes relative rather than absolute value of financial rewards in humans.

PubMed

Elliott, R; Agnew, Z; Deakin, J F W

2008-05-01

Functional imaging studies in recent years have confirmed the involvement of orbitofrontal cortex (OFC) in human reward processing and have suggested that OFC responses are context-dependent. A seminal electrophysiological experiment in primates taught animals to associate abstract visual stimuli with differently valuable food rewards. Subsequently, pairs of these learned abstract stimuli were presented and firing of OFC neurons to the medium-value stimulus was measured. OFC firing was shown to depend on the relative value context. In this study, we developed a human analogue of this paradigm and scanned subjects using functional magnetic resonance imaging. The analysis compared neuronal responses to two superficially identical events, which differed only in terms of the preceding context. Medial OFC response to the same perceptual stimulus was greater when the stimulus predicted the more valuable of two rewards than when it predicted the less valuable. Additional responses were observed in other components of reward circuitry, the amygdala and ventral striatum. The central finding is consistent with the primate results and suggests that OFC neurons code relative rather than absolute reward value. Amygdala and striatal involvement in coding reward value is also consistent with recent functional imaging data. By using a simpler and less confounded paradigm than many functional imaging studies, we are able to demonstrate that relative financial reward value per se is coded in distinct subregions of an extended reward and decision-making network.

Modelling Odor Decoding in the Antennal Lobe by Combining Sequential Firing Rate Models with Bayesian Inference

PubMed Central

Cuevas Rivera, Dario; Bitzer, Sebastian; Kiebel, Stefan J.

2015-01-01

The olfactory information that is received by the insect brain is encoded in the form of spatiotemporal patterns in the projection neurons of the antennal lobe. These dense and overlapping patterns are transformed into a sparse code in Kenyon cells in the mushroom body. Although it is clear that this sparse code is the basis for rapid categorization of odors, it is yet unclear how the sparse code in Kenyon cells is computed and what information it represents. Here we show that this computation can be modeled by sequential firing rate patterns using Lotka-Volterra equations and Bayesian online inference. This new model can be understood as an ‘intelligent coincidence detector’, which robustly and dynamically encodes the presence of specific odor features. We found that the model is able to qualitatively reproduce experimentally observed activity in both the projection neurons and the Kenyon cells. In particular, the model explains mechanistically how sparse activity in the Kenyon cells arises from the dense code in the projection neurons. The odor classification performance of the model proved to be robust against noise and time jitter in the observed input sequences. As in recent experimental results, we found that recognition of an odor happened very early during stimulus presentation in the model. Critically, by using the model, we found surprising but simple computational explanations for several experimental phenomena. PMID:26451888

Circuit mechanisms encoding odors and driving aging-associated behavioral declines in Caenorhabditis elegans.

PubMed

Leinwand, Sarah G; Yang, Claire J; Bazopoulou, Daphne; Chronis, Nikos; Srinivasan, Jagan; Chalasani, Sreekanth H

2015-09-22

Chemosensory neurons extract information about chemical cues from the environment. How is the activity in these sensory neurons transformed into behavior? Using Caenorhabditis elegans, we map a novel sensory neuron circuit motif that encodes odor concentration. Primary neurons, AWC(ON) and AWA, directly detect the food odor benzaldehyde (BZ) and release insulin-like peptides and acetylcholine, respectively, which are required for odor-evoked responses in secondary neurons, ASEL and AWB. Consistently, both primary and secondary neurons are required for BZ attraction. Unexpectedly, this combinatorial code is altered in aged animals: odor-evoked activity in secondary, but not primary, olfactory neurons is reduced. Moreover, experimental manipulations increasing neurotransmission from primary neurons rescues aging-associated neuronal deficits. Finally, we correlate the odor responsiveness of aged animals with their lifespan. Together, these results show how odors are encoded by primary and secondary neurons and suggest reduced neurotransmission as a novel mechanism driving aging-associated sensory neural activity and behavioral declines.

Circuit mechanisms encoding odors and driving aging-associated behavioral declines in Caenorhabditis elegans

PubMed Central

Leinwand, Sarah G; Yang, Claire J; Bazopoulou, Daphne; Chronis, Nikos; Srinivasan, Jagan; Chalasani, Sreekanth H

2015-01-01

Chemosensory neurons extract information about chemical cues from the environment. How is the activity in these sensory neurons transformed into behavior? Using Caenorhabditis elegans, we map a novel sensory neuron circuit motif that encodes odor concentration. Primary neurons, AWCON and AWA, directly detect the food odor benzaldehyde (BZ) and release insulin-like peptides and acetylcholine, respectively, which are required for odor-evoked responses in secondary neurons, ASEL and AWB. Consistently, both primary and secondary neurons are required for BZ attraction. Unexpectedly, this combinatorial code is altered in aged animals: odor-evoked activity in secondary, but not primary, olfactory neurons is reduced. Moreover, experimental manipulations increasing neurotransmission from primary neurons rescues aging-associated neuronal deficits. Finally, we correlate the odor responsiveness of aged animals with their lifespan. Together, these results show how odors are encoded by primary and secondary neurons and suggest reduced neurotransmission as a novel mechanism driving aging-associated sensory neural activity and behavioral declines. DOI: http://dx.doi.org/10.7554/eLife.10181.001 PMID:26394000

SpineCreator: a Graphical User Interface for the Creation of Layered Neural Models.

PubMed

Cope, A J; Richmond, P; James, S S; Gurney, K; Allerton, D J

2017-01-01

There is a growing requirement in computational neuroscience for tools that permit collaborative model building, model sharing, combining existing models into a larger system (multi-scale model integration), and are able to simulate models using a variety of simulation engines and hardware platforms. Layered XML model specification formats solve many of these problems, however they are difficult to write and visualise without tools. Here we describe a new graphical software tool, SpineCreator, which facilitates the creation and visualisation of layered models of point spiking neurons or rate coded neurons without requiring the need for programming. We demonstrate the tool through the reproduction and visualisation of published models and show simulation results using code generation interfaced directly into SpineCreator. As a unique application for the graphical creation of neural networks, SpineCreator represents an important step forward for neuronal modelling.

A predictive coding account of MMN reduction in schizophrenia.

PubMed

Wacongne, Catherine

2016-04-01

The mismatch negativity (MMN) is thought to be an index of the automatic activation of a specialized network for active prediction and deviance detection in the auditory cortex. It is consistently reduced in schizophrenic patients and has received a lot of interest as a clinical and translational tool. The main neuronal hypothesis regarding the mechanisms leading to a reduced MMN in schizophrenic patients is a dysfunction of NMDA receptors (NMDA-R). However, this hypothesis has never been implemented in a neuronal model. In this paper, we examine the consequences of NMDA-R dysfunction in a neuronal model of MMN based on predictive coding principle. I also investigate how predictive processes may interact with synaptic adaptation in MMN generations and examine the consequences of this interaction for the use of MMN paradigms in schizophrenia research. Copyright © 2015 Elsevier B.V. All rights reserved.

Neurons selective to the number of visual items in the corvid songbird endbrain

PubMed Central

Ditz, Helen M.; Nieder, Andreas

2015-01-01

It is unknown whether anatomical specializations in the endbrains of different vertebrates determine the neuronal code to represent numerical quantity. Therefore, we recorded single-neuron activity from the endbrain of crows trained to judge the number of items in displays. Many neurons were tuned for numerosities irrespective of the physical appearance of the items, and their activity correlated with performance outcome. Comparison of both behavioral and neuronal representations of numerosity revealed that the data are best described by a logarithmically compressed scaling of numerical information, as postulated by the Weber–Fechner law. The behavioral and neuronal numerosity representations in the crow reflect surprisingly well those found in the primate association cortex. This finding suggests that distantly related vertebrates with independently developed endbrains adopted similar neuronal solutions to process quantity. PMID:26056278

Decoding Information for Grasping from the Macaque Dorsomedial Visual Stream.

PubMed

Filippini, Matteo; Breveglieri, Rossella; Akhras, M Ali; Bosco, Annalisa; Chinellato, Eris; Fattori, Patrizia

2017-04-19

Neurodecoders have been developed by researchers mostly to control neuroprosthetic devices, but also to shed new light on neural functions. In this study, we show that signals representing grip configurations can be reliably decoded from neural data acquired from area V6A of the monkey medial posterior parietal cortex. Two Macaca fascicularis monkeys were trained to perform an instructed-delay reach-to-grasp task in the dark and in the light toward objects of different shapes. Population neural activity was extracted at various time intervals on vision of the objects, the delay before movement, and grasp execution. This activity was used to train and validate a Bayes classifier used for decoding objects and grip types. Recognition rates were well over chance level for all the epochs analyzed in this study. Furthermore, we detected slightly different decoding accuracies, depending on the task's visual condition. Generalization analysis was performed by training and testing the system during different time intervals. This analysis demonstrated that a change of code occurred during the course of the task. Our classifier was able to discriminate grasp types fairly well in advance with respect to grasping onset. This feature might be important when the timing is critical to send signals to external devices before the movement start. Our results suggest that the neural signals from the dorsomedial visual pathway can be a good substrate to feed neural prostheses for prehensile actions. SIGNIFICANCE STATEMENT Recordings of neural activity from nonhuman primate frontal and parietal cortex have led to the development of methods of decoding movement information to restore coordinated arm actions in paralyzed human beings. Our results show that the signals measured from the monkey medial posterior parietal cortex are valid for correctly decoding information relevant for grasping. Together with previous studies on decoding reach trajectories from the medial posterior parietal cortex, this highlights the medial parietal cortex as a target site for transforming neural activity into control signals to command prostheses to allow human patients to dexterously perform grasping actions. Copyright © 2017 the authors 0270-6474/17/374311-12$15.00/0.

L-type calcium channels refine the neural population code of sound level.

PubMed

Grimsley, Calum Alex; Green, David Brian; Sivaramakrishnan, Shobhana

2016-12-01

The coding of sound level by ensembles of neurons improves the accuracy with which listeners identify how loud a sound is. In the auditory system, the rate at which neurons fire in response to changes in sound level is shaped by local networks. Voltage-gated conductances alter local output by regulating neuronal firing, but their role in modulating responses to sound level is unclear. We tested the effects of L-type calcium channels (Ca L : Ca V 1.1-1.4) on sound-level coding in the central nucleus of the inferior colliculus (ICC) in the auditory midbrain. We characterized the contribution of Ca L to the total calcium current in brain slices and then examined its effects on rate-level functions (RLFs) in vivo using single-unit recordings in awake mice. Ca L is a high-threshold current and comprises ∼50% of the total calcium current in ICC neurons. In vivo, Ca L activates at sound levels that evoke high firing rates. In RLFs that increase monotonically with sound level, Ca L boosts spike rates at high sound levels and increases the maximum firing rate achieved. In different populations of RLFs that change nonmonotonically with sound level, Ca L either suppresses or enhances firing at sound levels that evoke maximum firing. Ca L multiplies the gain of monotonic RLFs with dynamic range and divides the gain of nonmonotonic RLFs with the width of the RLF. These results suggest that a single broad class of calcium channels activates enhancing and suppressing local circuits to regulate the sensitivity of neuronal populations to sound level. Copyright © 2016 the American Physiological Society.

Motor neuron disease mortality rates in New Zealand 1992-2013.

PubMed

Cao, Maize C; Chancellor, Andrew; Charleston, Alison; Dragunow, Mike; Scotter, Emma L

2018-05-01

We determined the mortality rates of motor neuron disease (MND) in New Zealand over 22 years from 1992 to 2013. Previous studies have found an unusually high and/or increasing incidence of MND in certain regions of New Zealand; however, no studies have examined MND rates nationwide to corroborate this. Death certificate data coded G12.2 by International Classification of Diseases (ICD)-10 coding, or 335.2 by ICD-9 coding were obtained. These codes specify amyotrophic lateral sclerosis, progressive bulbar palsy, or other motor neuron diseases as the underlying cause of death. Mortality rates for MND deaths in New Zealand were age-standardized to the European Standard Population and compared with rates from international studies that also examined death certificate data and were age-standardized to the same standard population. The age-standardized mortality from MND in New Zealand was 2.3 per 100,000 per year from 1992-2007 and 2.8 per 100,000 per year from 2008-2013. These rates were 3.3 and 4.0 per 100,000 per year, respectively, for the population 20 years and older. The increase in rate between these two time periods was likely due to changes in MND death coding from 2008. Contrary to a previous regional study of MND incidence, nationwide mortality rates did not increase steadily over this time period once aging was accounted for. However, New Zealand MND mortality rate was higher than comparable studies we examined internationally (mean 1.67 per 100,000 per year), suggesting that further analysis of MND burden in New Zealand is warranted.

Burst Firing is a Neural Code in an Insect Auditory System

PubMed Central

Eyherabide, Hugo G.; Rokem, Ariel; Herz, Andreas V. M.; Samengo, Inés

2008-01-01

Various classes of neurons alternate between high-frequency discharges and silent intervals. This phenomenon is called burst firing. To analyze burst activity in an insect system, grasshopper auditory receptor neurons were recorded in vivo for several distinct stimulus types. The experimental data show that both burst probability and burst characteristics are strongly influenced by temporal modulations of the acoustic stimulus. The tendency to burst, hence, is not only determined by cell-intrinsic processes, but also by their interaction with the stimulus time course. We study this interaction quantitatively and observe that bursts containing a certain number of spikes occur shortly after stimulus deflections of specific intensity and duration. Our findings suggest a sparse neural code where information about the stimulus is represented by the number of spikes per burst, irrespective of the detailed interspike-interval structure within a burst. This compact representation cannot be interpreted as a firing-rate code. An information-theoretical analysis reveals that the number of spikes per burst reliably conveys information about the amplitude and duration of sound transients, whereas their time of occurrence is reflected by the burst onset time. The investigated neurons encode almost half of the total transmitted information in burst activity. PMID:18946533

Voltage-dependent K+ channels improve the energy efficiency of signalling in blowfly photoreceptors

PubMed Central

2017-01-01

Voltage-dependent conductances in many spiking neurons are tuned to reduce action potential energy consumption, so improving the energy efficiency of spike coding. However, the contribution of voltage-dependent conductances to the energy efficiency of analogue coding, by graded potentials in dendrites and non-spiking neurons, remains unclear. We investigate the contribution of voltage-dependent conductances to the energy efficiency of analogue coding by modelling blowfly R1-6 photoreceptor membrane. Two voltage-dependent delayed rectifier K+ conductances (DRs) shape the membrane's voltage response and contribute to light adaptation. They make two types of energy saving. By reducing membrane resistance upon depolarization they convert the cheap, low bandwidth membrane needed in dim light to the expensive high bandwidth membrane needed in bright light. This investment of energy in bandwidth according to functional requirements can halve daily energy consumption. Second, DRs produce negative feedback that reduces membrane impedance and increases bandwidth. This negative feedback allows an active membrane with DRs to consume at least 30% less energy than a passive membrane with the same capacitance and bandwidth. Voltage-dependent conductances in other non-spiking neurons, and in dendrites, might be organized to make similar savings. PMID:28381642

Voltage-dependent K+ channels improve the energy efficiency of signalling in blowfly photoreceptors.

PubMed

Heras, Francisco J H; Anderson, John; Laughlin, Simon B; Niven, Jeremy E

2017-04-01

Voltage-dependent conductances in many spiking neurons are tuned to reduce action potential energy consumption, so improving the energy efficiency of spike coding. However, the contribution of voltage-dependent conductances to the energy efficiency of analogue coding, by graded potentials in dendrites and non-spiking neurons, remains unclear. We investigate the contribution of voltage-dependent conductances to the energy efficiency of analogue coding by modelling blowfly R1-6 photoreceptor membrane. Two voltage-dependent delayed rectifier K + conductances (DRs) shape the membrane's voltage response and contribute to light adaptation. They make two types of energy saving. By reducing membrane resistance upon depolarization they convert the cheap, low bandwidth membrane needed in dim light to the expensive high bandwidth membrane needed in bright light. This investment of energy in bandwidth according to functional requirements can halve daily energy consumption. Second, DRs produce negative feedback that reduces membrane impedance and increases bandwidth. This negative feedback allows an active membrane with DRs to consume at least 30% less energy than a passive membrane with the same capacitance and bandwidth. Voltage-dependent conductances in other non-spiking neurons, and in dendrites, might be organized to make similar savings. © 2017 The Author(s).

Differential plastic changes in synthesis and binding in the mouse somatostatin system after electroconvulsive stimulation.

PubMed

Olesen, Mikkel Vestergaard; Gøtzsche, Casper René; Christiansen, Søren Hofman; Woldbye, David Paul Drucker

2018-03-21

Electroconvulsive therapy (ECT) is regularly used to treat patients with severe major depression, but the mechanisms underlying the beneficial effects remain uncertain. Electroconvulsive stimulation (ECS) regulates diverse neurotransmitter systems and induces anticonvulsant effects, properties implicated in mediating therapeutic effects of ECT. Somatostatin (SST) is a candidate for mediating these effects because it is upregulated by ECS and exerts seizure-suppressant effects. However, little is known about how ECS might affect the SST receptor system. The present study examined effects of single and repeated ECS on the synthesis of SST receptors (SSTR1-4) and SST, and SST receptor binding ([125I]LTT-SST28) in mouse hippocampal regions and piriform/parietal cortices. A complex pattern of plastic changes was observed. In the dentate gyrus, SST and SSTR1 expression and the number of hilar SST immunoreactive cells were significantly increased at 1 week after repeated ECS while SSTR2 expression was downregulated by single ECS, and SSTR3 mRNA and SST binding were elevated 24 h after repeated ECS. In hippocampal CA1 and parietal/piriform cortices, we found elevated SST mRNA levels 1 week after repeated ECS and elevated SST binding after single ECS and 24 h after repeated ECS. In hippocampal CA3, repeated ECS increased SST expression 1 week after and SST binding 24 h after. In the parietal cortex, SSTR2 mRNA expression was downregulated after single ECS while SSTR4 mRNA expression was upregulated 24 h after repeated ECS. Considering the known anticonvulsant effects of SST, it is likely that these ECS-induced neuroplastic changes in the SST system could participate in modulating neuronal excitability and potentially contribute to therapeutic effects of ECT.

Differential white matter involvement associated with distinct visuospatial deficits after right hemisphere stroke.

PubMed

Carter, Alex R; McAvoy, Mark P; Siegel, Joshua S; Hong, Xin; Astafiev, Serguei V; Rengachary, Jennifer; Zinn, Kristi; Metcalf, Nicholas V; Shulman, Gordon L; Corbetta, Maurizio

2017-03-01

Visuospatial attention depends on the integration of multiple processes, and people with right hemisphere lesions after a stroke may exhibit severe or no visuospatial deficits. The anatomy of core components of visuospatial attention is an area of intense interest. Here we examine the relationship between the disruption of core components of attention and lesion distribution in a heterogeneous group (N = 70) of patients with right hemisphere strokes regardless of the presence of clinical neglect. Deficits of lateralized spatial orienting, measured as the difference in reaction times for responding to visual targets in the contralesional or ipsilesional visual field, and deficits in re-orienting attention, as measured by the difference in reaction times for invalidly versus validly cued targets, were measured using a computerized spatial orienting task. Both measures were related through logistic regression and a novel ridge regression method to anatomical damage measured with magnetic resonance imaging. While many regions were common to both deficit maps, a deficit in lateralized spatial orienting was more associated with lesions in the white matter underlying the posterior parietal cortex, and middle and inferior frontal gyri. A deficit in re-orienting of attention toward unattended locations was associated with lesions in the white matter of the posterior parietal cortex, insular cortex and less so with white matter involvement of the anterior frontal lobe. An hodological analysis also supports this partial dissociation between the white matter tracts that are damaged in lateralized spatial biases versus impaired re-orienting. Our results underscore that the integrity of fronto-parietal white matter tracts is crucial for visuospatial attention and that different attention components are mediated by partially distinct neuronal substrates. Copyright © 2016 Elsevier Ltd. All rights reserved.

Spatiotemporal Phase Synchronization in Adaptive Reconfiguration from Action Observation Network to Mentalizing Network for Understanding Other's Action Intention.

PubMed

Zhang, Li; Gan, John Q; Zheng, Wenming; Wang, Haixian

2018-05-01

In action intention understanding, the mirror system is involved in perception-action matching process and the mentalizing system underlies higher-level intention inference. By analyzing the dynamic functional connectivity in α (8-12 Hz) and β (12-30 Hz) frequency bands over a "hand-cup interaction" observation task, this study investigates the topological transition from the action observation network (AON) to the mentalizing network (MZN), and estimates their functional relevance for intention identification from other's different action kinematics. Sequential brain microstates were extracted based on event-related potentials (ERPs), in which significantly differing neuronal responses were found in N170-P200 related to perceptually matching kinematic profiles and P400-700 involved in goal inference. Inter-electrode weighted phase lag index analysis on the ERP microstates revealed a shift of hub centrality salient in α frequency band, from the AON dominated by left-lateral frontal-premotor-temporal and temporal-parietooccipital synchronizations to the MZN consisting of more bilateral frontal-parietal and temporal-parietal synchronizations. As compared with usual actions, intention identification of unintelligible actions induces weaker synchronizations in the AON but dramatically increased connectivity in right frontal-temporal-parietal regions of the MZN, indicating a spatiotemporally complementary effect between the functional network configurations involved in mirror and mentalizing processes. Perceptual processing in observing usual/unintelligible actions decreases/increases requirements for intention inference, which would induce less/greater functional network reorganization on the way to mentalization. From the comparison, our study suggests that the adaptive topological changes from the AON to the MZN indicate implicit causal association between the mirror and mentalizing systems for decoding others' intentionality.

Inferior parietal lobule projections to anterior inferotemporal cortex (area TE) in macaque monkey.

PubMed

Zhong, Yong-Mei; Rockland, Kathleen S

2003-05-01

Parietal cortical areas have generally been considered as part of the dorsal stream and, as such, only indirectly connected with inferotemporal cortex. In this report we demonstrate, by using the anterograde tracer BDA, that much of the inferior parietal lobule (IPL) has direct connections to anterior-ventral TE (TEav) around the anterior middle temporal sulcus (amts). Connections from area PG terminate in layers 1 and 5 as well as 4; and those from area PF, target layer 6 of TEav, with a small secondary focus in layer 4 of anterior-dorsal TE. Connections from areas PG and PF are relatively sparse; but those from the mid-IPL region (approximately area PFG), which terminate in layer 4, are light to moderate. In confirmation of these results, injections of retrograde tracers in TEav produce labeled neurons in the IPL. These are most numerous in layer 3 at the border of areas PG and PFG, but also occur in layer 5/6. These laminar patterns are more complex than the classical 'feedforward' or 'feedback' patterns associated with early sensory areas. Branched collaterals are common; and three of seven reconstructed axons branched to both TEav and to the lateral bank of the occipito-temporal sulcus, itself a major source of inputs to TEav. The existence of connections from the IPL preferentially to TEav and the amts provides another example where direct 'bypass' connections operate in parallel with multiple indirect routes. It provides further evidence for the differential connectivity of subdivisions within anterior TE and is consistent with recent evidence from functional magnetic resonance imaging studies that the region around the amts may be part of a network involved in three- dimensional shape, which is distributed across both 'what' and 'where' processing streams.

Spatial working memory in neurofibromatosis 1: Altered neural activity and functional connectivity.

PubMed

Ibrahim, Amira F A; Montojo, Caroline A; Haut, Kristen M; Karlsgodt, Katherine H; Hansen, Laura; Congdon, Eliza; Rosser, Tena; Bilder, Robert M; Silva, Alcino J; Bearden, Carrie E

2017-01-01

Neurofibromatosis Type 1 (NF1) is a genetic disorder that disrupts central nervous system development and neuronal function. Cognitively, NF1 is characterized by difficulties with executive control and visuospatial abilities. Little is known about the neural substrates underlying these deficits. The current study utilized Blood-Oxygen-Level-Dependent (BOLD) functional MRI (fMRI) to explore the neural correlates of spatial working memory (WM) deficits in patients with NF1. BOLD images were acquired from 23 adults with NF1 (age M  = 32.69; 61% male) and 25 matched healthy controls (age M  = 33.08; 64% male) during an in-scanner visuo-spatial WM task. Whole brain functional and psycho-physiological interaction analyses were utilized to investigate neural activity and functional connectivity, respectively, during visuo-spatial WM performance. Participants also completed behavioral measures of spatial reasoning and verbal WM. Relative to healthy controls, participants with NF1 showed reduced recruitment of key components of WM circuitry, the left dorsolateral prefrontal cortex and right parietal cortex. In addition, healthy controls exhibited greater simultaneous deactivation between the posterior cingulate cortex (PCC) and temporal regions than NF1 patients. In contrast, NF1 patients showed greater PCC and bilateral parietal connectivity with visual cortices as well as between the PCC and the cerebellum. In NF1 participants, increased functional coupling of the PCC with frontal and parietal regions was associated with better spatial reasoning and WM performance, respectively; these relationships were not observed in controls. Dysfunctional engagement of WM circuitry, and aberrant functional connectivity of 'task-negative' regions in NF1 patients may underlie spatial WM difficulties characteristic of the disorder.

What Can Psychiatric Disorders Tell Us about Neural Processing of the Self?

PubMed

Zhao, Weihua; Luo, Lizhu; Li, Qin; Kendrick, Keith M

2013-01-01

Many psychiatric disorders are associated with abnormal self-processing. While these disorders also have a wide-range of complex, and often heterogeneous sets of symptoms involving different cognitive, emotional, and motor domains, an impaired sense of self can contribute to many of these. Research investigating self-processing in healthy subjects has facilitated identification of changes in specific neural circuits which may cause altered self-processing in psychiatric disorders. While there is evidence for altered self-processing in many psychiatric disorders, here we will focus on four of the most studied ones, schizophrenia, autism spectrum disorder (ASD), major depression, and borderline personality disorder (BPD). We review evidence for dysfunction in two different neural systems implicated in self-processing, namely the cortical midline system (CMS) and the mirror neuron system (MNS), as well as contributions from altered inter-hemispheric connectivity (IHC). We conclude that while abnormalities in frontal-parietal activity and/or connectivity in the CMS are common to all four disorders there is more disruption of integration between frontal and parietal regions resulting in a shift toward parietal control in schizophrenia and ASD which may contribute to the greater severity and delusional aspects of their symptoms. Abnormalities in the MNS and in IHC are also particularly evident in schizophrenia and ASD and may lead to disturbances in sense of agency and the physical self in these two disorders. A better future understanding of how changes in the neural systems sub-serving self-processing contribute to different aspects of symptom abnormality in psychiatric disorders will require that more studies carry out detailed individual assessments of altered self-processing in conjunction with measurements of neural functioning.

NOS1 ex1f-VNTR polymorphism influences prefrontal brain oxygenation during a working memory task.

PubMed

Kopf, Juliane; Schecklmann, Martin; Hahn, Tim; Dresler, Thomas; Dieler, Alica C; Herrmann, Martin J; Fallgatter, Andreas J; Reif, Andreas

2011-08-15

Nitric oxide (NO) synthase produces NO, which serves as first and second messenger in neurons, where the protein is encoded by the NOS1 gene. A functional variable number of tandem repeats (VNTR) polymorphism in the promoter region of the alternative first exon 1f of NOS1 is associated with various functions of human behavior, for example increased impulsivity, while another, non-functional variant was linked to decreased verbal working memory and a heightened risk for schizophrenia. We therefore investigated the influence of NOS1 ex 1f-VNTR on working memory function as reflected by both behavioral measures and prefrontal oxygenation. We hypothesized that homozygous short allele carriers exhibit altered brain oxygenation in task-related areas, namely the dorsolateral and ventrolateral prefrontal cortex and the parietal cortex. To this end, 56 healthy subjects were stratified into a homozygous long allele group and a homozygous short allele group comparable for age, sex and intelligence. All subjects completed a letter n-back task (one-, two-, and three-back), while concentration changes of oxygenated (O(2)Hb) hemoglobin in the prefrontal cortex were measured with functional near-infrared spectroscopy (fNIRS). We found load-associated O(2)Hb increases in the prefrontal and parts of the parietal cortex. Significant load-associated oxygenation differences between the two genotype groups could be shown for the dorsolateral prefrontal cortex and the parietal cortex. Specifically, short allele carriers showed a significantly larger increase in oxygenation in all three n-back tasks. This suggests a potential compensatory mechanism, with task-related brain regions being more active in short allele carriers to compensate for reduced NOS1 expression. Copyright © 2011 Elsevier Inc. All rights reserved.

Can responses to basic non-numerical visual features explain neural numerosity responses?

PubMed

Harvey, Ben M; Dumoulin, Serge O

2017-04-01

Humans and many animals can distinguish between stimuli that differ in numerosity, the number of objects in a set. Human and macaque parietal lobes contain neurons that respond to changes in stimulus numerosity. However, basic non-numerical visual features can affect neural responses to and perception of numerosity, and visual features often co-vary with numerosity. Therefore, it is debated whether numerosity or co-varying low-level visual features underlie neural and behavioral responses to numerosity. To test the hypothesis that non-numerical visual features underlie neural numerosity responses in a human parietal numerosity map, we analyze responses to a group of numerosity stimulus configurations that have the same numerosity progression but vary considerably in their non-numerical visual features. Using ultra-high-field (7T) fMRI, we measure responses to these stimulus configurations in an area of posterior parietal cortex whose responses are believed to reflect numerosity-selective activity. We describe an fMRI analysis method to distinguish between alternative models of neural response functions, following a population receptive field (pRF) modeling approach. For each stimulus configuration, we first quantify the relationships between numerosity and several non-numerical visual features that have been proposed to underlie performance in numerosity discrimination tasks. We then determine how well responses to these non-numerical visual features predict the observed fMRI responses, and compare this to the predictions of responses to numerosity. We demonstrate that a numerosity response model predicts observed responses more accurately than models of responses to simple non-numerical visual features. As such, neural responses in cognitive processing need not reflect simpler properties of early sensory inputs. Copyright © 2017 Elsevier Inc. All rights reserved.

Spatiotemporal Computations of an Excitable and Plastic Brain: Neuronal Plasticity Leads to Noise-Robust and Noise-Constructive Computations

PubMed Central

Toutounji, Hazem; Pipa, Gordon

2014-01-01

It is a long-established fact that neuronal plasticity occupies the central role in generating neural function and computation. Nevertheless, no unifying account exists of how neurons in a recurrent cortical network learn to compute on temporally and spatially extended stimuli. However, these stimuli constitute the norm, rather than the exception, of the brain's input. Here, we introduce a geometric theory of learning spatiotemporal computations through neuronal plasticity. To that end, we rigorously formulate the problem of neural representations as a relation in space between stimulus-induced neural activity and the asymptotic dynamics of excitable cortical networks. Backed up by computer simulations and numerical analysis, we show that two canonical and widely spread forms of neuronal plasticity, that is, spike-timing-dependent synaptic plasticity and intrinsic plasticity, are both necessary for creating neural representations, such that these computations become realizable. Interestingly, the effects of these forms of plasticity on the emerging neural code relate to properties necessary for both combating and utilizing noise. The neural dynamics also exhibits features of the most likely stimulus in the network's spontaneous activity. These properties of the spatiotemporal neural code resulting from plasticity, having their grounding in nature, further consolidate the biological relevance of our findings. PMID:24651447

Cracking the barcode of fullerene-like cortical microcolumns.

PubMed

Tozzi, Arturo; Peters, James F; Ori, Ottorino

2017-03-22

Artificial neural systems and nervous graph theoretical analysis rely upon the stance that the neural code is embodied in logic circuits, e.g., spatio-temporal sequences of ON/OFF spiking neurons. Nevertheless, this assumption does not fully explain complex brain functions. Here we show how nervous activity, other than logic circuits, could instead depend on topological transformations and symmetry constraints occurring at the micro-level of the cortical microcolumn, i.e., the embryological, anatomical and functional basic unit of the brain. Tubular microcolumns can be flattened in fullerene-like two-dimensional lattices, equipped with about 80 nodes standing for pyramidal neurons where neural computations take place. We show how the countless possible combinations of activated neurons embedded in the lattice resemble a barcode. Despite the fact that further experimental verification is required in order to validate our claim, different assemblies of firing neurons might have the appearance of diverse codes, each one responsible for a single mental activity. A two-dimensional fullerene-like lattice, grounded on simple topological changes standing for pyramidal neurons' activation, not just displays analogies with the real microcolumn's microcircuitry and the neural connectome, but also the potential for the manufacture of plastic, robust and fast artificial networks in robotic forms of full-fledged neural systems. Copyright © 2017 Elsevier B.V. All rights reserved.

Neurons in the barrel cortex turn into processing whisker and odor signals: a cellular mechanism for the storage and retrieval of associative signals

PubMed Central

Wang, Dangui; Zhao, Jun; Gao, Zilong; Chen, Na; Wen, Bo; Lu, Wei; Lei, Zhuofan; Chen, Changfeng; Liu, Yahui; Feng, Jing; Wang, Jin-Hui

2015-01-01

Associative learning and memory are essential to logical thinking and cognition. How the neurons are recruited as associative memory cells to encode multiple input signals for their associated storage and distinguishable retrieval remains unclear. We studied this issue in the barrel cortex by in vivo two-photon calcium imaging, electrophysiology, and neural tracing in our mouse model that the simultaneous whisker and olfaction stimulations led to odorant-induced whisker motion. After this cross-modal reflex arose, the barrel and piriform cortices connected. More than 40% of barrel cortical neurons became to encode odor signal alongside whisker signal. Some of these neurons expressed distinct activity patterns in response to acquired odor signal and innate whisker signal, and others encoded similar pattern in response to these signals. In the meantime, certain barrel cortical astrocytes encoded odorant and whisker signals. After associative learning, the neurons and astrocytes in the sensory cortices are able to store the newly learnt signal (cross-modal memory) besides the innate signal (native-modal memory). Such associative memory cells distinguish the differences of these signals by programming different codes and signify the historical associations of these signals by similar codes in information retrievals. PMID:26347609

Beyond Molecular Codes: Simple Rules to Wire Complex Brains

PubMed Central

Hassan, Bassem A.; Hiesinger, P. Robin

2015-01-01

Summary Molecular codes, like postal zip codes, are generally considered a robust way to ensure the specificity of neuronal target selection. However, a code capable of unambiguously generating complex neural circuits is difficult to conceive. Here, we re-examine the notion of molecular codes in the light of developmental algorithms. We explore how molecules and mechanisms that have been considered part of a code may alternatively implement simple pattern formation rules sufficient to ensure wiring specificity in neural circuits. This analysis delineates a pattern-based framework for circuit construction that may contribute to our understanding of brain wiring. PMID:26451480

Lentiviral infection of rhesus macaques causes long-term injury to cortical and hippocampal projections of prostaglandin-expressing cholinergic basal forebrain neurons.

PubMed

Depboylu, Candan; Weihe, Eberhard; Eiden, Lee E

2012-01-01

The simian immunodeficiency virus (SIV) macaque model resembles human immunodeficiency virus-acquired immunodeficiency syndrome (AIDS) and associated brain dysfunction. Altered expression of synaptic markers and transmitters in neuro-AIDS has been reported, but limited data exist for the cholinergic system and lipid mediators such as prostaglandins. Here, we analyzed cholinergic basal forebrain neurons with their telencephalic projections and the rate-limiting enzymes for prostaglandin synthesis, cyclooxygenase isotypes 1 and 2 (COX1 and COX2) in the brains of SIV-infected macaques with or without encephalitis and antiretroviral therapy and uninfected controls.Cyclooxygenase isotype 1, but not COX2, was coexpressed with markers of cholinergic phenotype, that is, choline acetyltransferase and vesicular acetylcholine transporter (VAChT), in basal forebrain neurons of monkey, as well as human, brain. Cyclooxygenase isotype 1 was decreased in basal forebrain neurons in macaques with AIDS versus uninfected and asymptomatic SIV-infected macaques. The VAChT-positive fiber density was reduced in frontal, parietal, and hippocampal-entorhinal cortex. Although brain SIV burden and associated COX1- and COX2-positive mononuclear and endothelial inflammatory reactions were mostly reversed in AIDS-diseased macaques that received 6-chloro-2',3'-dideoxyguanosine treatment, decreased VAChT-positive terminal density and reduced cholinergic COX1 expression were not. Thus, COX1 expression is a feature of primate cholinergic basal forebrain neurons; it may be functionally important and a critical biomarker of cholinergic dysregulation accompanying lentiviral encephalopathy. These results further imply that insufficiently prompt initiation of antiretroviral therapy in lentiviral infection may lead to neurostructurally unremarkable but neurochemically prominent irreversible brain damage.

Coding of Border Ownership in Monkey Visual Cortex

PubMed Central

Zhou, Hong; Friedman, Howard S.; von der Heydt, Rüdiger

2016-01-01

Areas V1 and V2 of the visual cortex have traditionally been conceived as stages of local feature representations. We investigated whether neural responses carry information about how local features belong to objects. Single-cell activity was recorded in areas V1, V2, and V4 of awake behaving monkeys. Displays were used in which the same local feature (contrast edge or line) could be presented as part of different figures. For example, the same light–dark edge could be the left side of a dark square or the right side of a light square. Each display was also presented with reversed contrast. We found significant modulation of responses as a function of the side of the figure in >50% of neurons of V2 and V4 and in 18% of neurons of the top layers of V1. Thus, besides the local contrast border information, neurons were found to encode the side to which the border belongs (“border ownership coding”). A majority of these neurons coded border ownership and the local polarity of luminance–chromaticity contrast. The others were insensitive to contrast polarity. Another 20% of the neurons of V2 and V4, and 48% of top layer V1, coded local contrast polarity, but not border ownership. The border ownership-related response differences emerged soon (<25 msec) after the response onset. In V2 and V4, the differences were found to be nearly independent of figure size up to the limit set by the size of our display (21°). Displays that differed only far outside the conventional receptive field could produce markedly different responses. When tested with more complex displays in which figure-ground cues were varied, some neurons produced invariant border ownership signals, others failed to signal border ownership for some of the displays, but neurons that reversed signals were rare. The influence of visual stimulation far from the receptive field center indicates mechanisms of global context integration. The short latencies and incomplete cue invariance suggest that the border-ownership effect is generated within the visual cortex rather than projected down from higher levels. PMID:10964965

Coding and Decoding with Adapting Neurons: A Population Approach to the Peri-Stimulus Time Histogram

PubMed Central

Naud, Richard; Gerstner, Wulfram

2012-01-01

The response of a neuron to a time-dependent stimulus, as measured in a Peri-Stimulus-Time-Histogram (PSTH), exhibits an intricate temporal structure that reflects potential temporal coding principles. Here we analyze the encoding and decoding of PSTHs for spiking neurons with arbitrary refractoriness and adaptation. As a modeling framework, we use the spike response model, also known as the generalized linear neuron model. Because of refractoriness, the effect of the most recent spike on the spiking probability a few milliseconds later is very strong. The influence of the last spike needs therefore to be described with high precision, while the rest of the neuronal spiking history merely introduces an average self-inhibition or adaptation that depends on the expected number of past spikes but not on the exact spike timings. Based on these insights, we derive a ‘quasi-renewal equation’ which is shown to yield an excellent description of the firing rate of adapting neurons. We explore the domain of validity of the quasi-renewal equation and compare it with other rate equations for populations of spiking neurons. The problem of decoding the stimulus from the population response (or PSTH) is addressed analogously. We find that for small levels of activity and weak adaptation, a simple accumulator of the past activity is sufficient to decode the original input, but when refractory effects become large decoding becomes a non-linear function of the past activity. The results presented here can be applied to the mean-field analysis of coupled neuron networks, but also to arbitrary point processes with negative self-interaction. PMID:23055914

Coding of vocalizations by single neurons in ventrolateral prefrontal cortex.

PubMed

Plakke, Bethany; Diltz, Mark D; Romanski, Lizabeth M

2013-11-01

Neuronal activity in single prefrontal neurons has been correlated with behavioral responses, rules, task variables and stimulus features. In the non-human primate, neurons recorded in ventrolateral prefrontal cortex (VLPFC) have been found to respond to species-specific vocalizations. Previous studies have found multisensory neurons which respond to simultaneously presented faces and vocalizations in this region. Behavioral data suggests that face and vocal information are inextricably linked in animals and humans and therefore may also be tightly linked in the coding of communication calls in prefrontal neurons. In this study we therefore examined the role of VLPFC in encoding vocalization call type information. Specifically, we examined previously recorded single unit responses from the VLPFC in awake, behaving rhesus macaques in response to 3 types of species-specific vocalizations made by 3 individual callers. Analysis of responses by vocalization call type and caller identity showed that ∼19% of cells had a main effect of call type with fewer cells encoding caller. Classification performance of VLPFC neurons was ∼42% averaged across the population. When assessed at discrete time bins, classification performance reached 70 percent for coos in the first 300 ms and remained above chance for the duration of the response period, though performance was lower for other call types. In light of the sub-optimal classification performance of the majority of VLPFC neurons when only vocal information is present, and the recent evidence that most VLPFC neurons are multisensory, the potential enhancement of classification with the addition of accompanying face information is discussed and additional studies recommended. Behavioral and neuronal evidence has shown a considerable benefit in recognition and memory performance when faces and voices are presented simultaneously. In the natural environment both facial and vocalization information is present simultaneously and neural systems no doubt evolved to integrate multisensory stimuli during recognition. This article is part of a Special Issue entitled "Communication Sounds and the Brain: New Directions and Perspectives". Copyright © 2013 Elsevier B.V. All rights reserved.

Surfing a spike wave down the ventral stream.

PubMed

VanRullen, Rufin; Thorpe, Simon J

2002-10-01

Numerous theories of neural processing, often motivated by experimental observations, have explored the computational properties of neural codes based on the absolute or relative timing of spikes in spike trains. Spiking neuron models and theories however, as well as their experimental counterparts, have generally been limited to the simulation or observation of isolated neurons, isolated spike trains, or reduced neural populations. Such theories would therefore seem inappropriate to capture the properties of a neural code relying on temporal spike patterns distributed across large neuronal populations. Here we report a range of computer simulations and theoretical considerations that were designed to explore the possibilities of one such code and its relevance for visual processing. In a unified framework where the relation between stimulus saliency and spike relative timing plays the central role, we describe how the ventral stream of the visual system could process natural input scenes and extract meaningful information, both rapidly and reliably. The first wave of spikes generated in the retina in response to a visual stimulation carries information explicitly in its spatio-temporal structure: the most salient information is represented by the first spikes over the population. This spike wave, propagating through a hierarchy of visual areas, is regenerated at each processing stage, where its temporal structure can be modified by (i). the selectivity of the cortical neurons, (ii). lateral interactions and (iii). top-down attentional influences from higher order cortical areas. The resulting model could account for the remarkable efficiency and rapidity of processing observed in the primate visual system.

Activity of striatal neurons reflects social action and own reward.

PubMed

Báez-Mendoza, Raymundo; Harris, Christopher J; Schultz, Wolfram

2013-10-08

Social interactions provide agents with the opportunity to earn higher benefits than when acting alone and contribute to evolutionary stable strategies. A basic requirement for engaging in beneficial social interactions is to recognize the actor whose movement results in reward. Despite the recent interest in the neural basis of social interactions, the neurophysiological mechanisms identifying the actor in social reward situations are unknown. A brain structure well suited for exploring this issue is the striatum, which plays a role in movement, reward, and goal-directed behavior. In humans, the striatum is involved in social processes related to reward inequity, donations to charity, and observational learning. We studied the neurophysiology of social action for reward in rhesus monkeys performing a reward-giving task. The behavioral data showed that the animals distinguished between their own and the conspecific's reward and knew which individual acted. Striatal neurons coded primarily own reward but rarely other's reward. Importantly, the activations occurred preferentially, and in approximately similar fractions, when either the own or the conspecific's action was followed by own reward. Other striatal neurons showed social action coding without reward. Some of the social action coding disappeared when the conspecific's role was simulated by a computer, confirming a social rather than observational relationship. These findings demonstrate a role of striatal neurons in identifying the social actor and own reward in a social setting. These processes may provide basic building blocks underlying the brain's function in social interactions.

Bitter Taste Stimuli Induce Differential Neural Codes in Mouse Brain

PubMed Central

Wilson, David M.; Boughter, John D.; Lemon, Christian H.

2012-01-01

A growing literature suggests taste stimuli commonly classified as “bitter” induce heterogeneous neural and perceptual responses. Here, the central processing of bitter stimuli was studied in mice with genetically controlled bitter taste profiles. Using these mice removed genetic heterogeneity as a factor influencing gustatory neural codes for bitter stimuli. Electrophysiological activity (spikes) was recorded from single neurons in the nucleus tractus solitarius during oral delivery of taste solutions (26 total), including concentration series of the bitter tastants quinine, denatonium benzoate, cycloheximide, and sucrose octaacetate (SOA), presented to the whole mouth for 5 s. Seventy-nine neurons were sampled; in many cases multiple cells (2 to 5) were recorded from a mouse. Results showed bitter stimuli induced variable gustatory activity. For example, although some neurons responded robustly to quinine and cycloheximide, others displayed concentration-dependent activity (p<0.05) to quinine but not cycloheximide. Differential activity to bitter stimuli was observed across multiple neurons recorded from one animal in several mice. Across all cells, quinine and denatonium induced correlated spatial responses that differed (p<0.05) from those to cycloheximide and SOA. Modeling spatiotemporal neural ensemble activity revealed responses to quinine/denatonium and cycloheximide/SOA diverged during only an early, at least 1 s wide period of the taste response. Our findings highlight how temporal features of sensory processing contribute differences among bitter taste codes and build on data suggesting heterogeneity among “bitter” stimuli, data that challenge a strict monoguesia model for the bitter quality. PMID:22844505

An ancient neurotrophin receptor code; a single Runx/Cbfβ complex determines somatosensory neuron fate specification in zebrafish

PubMed Central

Condon, Logan; Raible, David W.

2017-01-01

In terrestrial vertebrates such as birds and mammals, neurotrophin receptor expression is considered fundamental for the specification of distinct somatosensory neuron types where TrkA, TrkB and TrkC specify nociceptors, mechanoceptors and proprioceptors/mechanoceptors, respectively. In turn, Runx transcription factors promote neuronal fate specification by regulating neurotrophin receptor and sensory receptor expression where Runx1 mediates TrkA+ nociceptor diversification while Runx3 promotes a TrkC+ proprioceptive/mechanoceptive fate. Here, we report in zebrafish larvae that orthologs of the neurotrophin receptors in contrast to terrestrial vertebrates mark overlapping and distinct subsets of nociceptors suggesting that TrkA, TrkB and TrkC do not intrinsically promote nociceptor, mechanoceptor and proprioceptor/mechanoceptor neuronal fates, respectively. While we find that zebrafish Runx3 regulates nociceptors in contrast to terrestrial vertebrates, it shares a conserved regulatory mechanism found in terrestrial vertebrate proprioceptors/mechanoceptors in which it promotes TrkC expression and suppresses TrkB expression. We find that Cbfβ, which enhances Runx protein stability and affinity for DNA, serves as an obligate cofactor for Runx in neuronal fate determination. High levels of Runx can compensate for the loss of Cbfβ, indicating that in this context Cbfβ serves solely as a signal amplifier of Runx activity. Our data suggests an alteration/expansion of the neurotrophin receptor code of sensory neurons between larval teleost fish and terrestrial vertebrates, while the essential roles of Runx/Cbfβ in sensory neuron cell fate determination while also expanded are conserved. PMID:28708822

An ancient neurotrophin receptor code; a single Runx/Cbfβ complex determines somatosensory neuron fate specification in zebrafish.

PubMed

Gau, Philia; Curtright, Andrew; Condon, Logan; Raible, David W; Dhaka, Ajay

2017-07-01

In terrestrial vertebrates such as birds and mammals, neurotrophin receptor expression is considered fundamental for the specification of distinct somatosensory neuron types where TrkA, TrkB and TrkC specify nociceptors, mechanoceptors and proprioceptors/mechanoceptors, respectively. In turn, Runx transcription factors promote neuronal fate specification by regulating neurotrophin receptor and sensory receptor expression where Runx1 mediates TrkA+ nociceptor diversification while Runx3 promotes a TrkC+ proprioceptive/mechanoceptive fate. Here, we report in zebrafish larvae that orthologs of the neurotrophin receptors in contrast to terrestrial vertebrates mark overlapping and distinct subsets of nociceptors suggesting that TrkA, TrkB and TrkC do not intrinsically promote nociceptor, mechanoceptor and proprioceptor/mechanoceptor neuronal fates, respectively. While we find that zebrafish Runx3 regulates nociceptors in contrast to terrestrial vertebrates, it shares a conserved regulatory mechanism found in terrestrial vertebrate proprioceptors/mechanoceptors in which it promotes TrkC expression and suppresses TrkB expression. We find that Cbfβ, which enhances Runx protein stability and affinity for DNA, serves as an obligate cofactor for Runx in neuronal fate determination. High levels of Runx can compensate for the loss of Cbfβ, indicating that in this context Cbfβ serves solely as a signal amplifier of Runx activity. Our data suggests an alteration/expansion of the neurotrophin receptor code of sensory neurons between larval teleost fish and terrestrial vertebrates, while the essential roles of Runx/Cbfβ in sensory neuron cell fate determination while also expanded are conserved.

Neural coding of syntactic structure in learned vocalizations in the songbird.

PubMed

Fujimoto, Hisataka; Hasegawa, Taku; Watanabe, Dai

2011-07-06

Although vocal signals including human languages are composed of a finite number of acoustic elements, complex and diverse vocal patterns can be created from combinations of these elements, linked together by syntactic rules. To enable such syntactic vocal behaviors, neural systems must extract the sequence patterns from auditory information and establish syntactic rules to generate motor commands for vocal organs. However, the neural basis of syntactic processing of learned vocal signals remains largely unknown. Here we report that the basal ganglia projecting premotor neurons (HVC(X) neurons) in Bengalese finches represent syntactic rules that generate variable song sequences. When vocalizing an alternative transition segment between song elements called syllables, sparse burst spikes of HVC(X) neurons code the identity of a specific syllable type or a specific transition direction among the alternative trajectories. When vocalizing a variable repetition sequence of the same syllable, HVC(X) neurons not only signal the initiation and termination of the repetition sequence but also indicate the progress and state-of-completeness of the repetition. These different types of syntactic information are frequently integrated within the activity of single HVC(X) neurons, suggesting that syntactic attributes of the individual neurons are not programmed as a basic cellular subtype in advance but acquired in the course of vocal learning and maturation. Furthermore, some auditory-vocal mirroring type HVC(X) neurons display transition selectivity in the auditory phase, much as they do in the vocal phase, suggesting that these songbirds may extract syntactic rules from auditory experience and apply them to form their own vocal behaviors.

Effects of glutamic acid analogues on identifiable giant neurones, sensitive to beta-hydroxy-L-glutamic acid, of an African giant snail (Achatina fulica Férussac).

PubMed Central

Nakajima, T.; Nomoto, K.; Ohfune, Y.; Shiratori, Y.; Takemoto, T.; Takeuchi, H.; Watanabe, K.

1985-01-01

The effects of the seven glutamic acid analogues, alpha-kainic acid, alpha-allo-kainic acid, domoic acid, erythro-L-tricholomic acid, DL-ibotenic acid, L-quisqualic acid and allo-gamma-hydroxy-L-glutamic acid were examined on six identifiable giant neurones of an African giant snail (Achatina fulica Férussac). The neurones studied were: PON (periodically oscillating neurone), d-RPLN (dorsal-right parietal large neurone), VIN (visceral intermittently firing neurone), RAPN (right anterior pallial neurone), FAN (frequently autoactive neurone) and v-RCDN (ventral-right cerebral distinct neurone). Of these, d-RPLN and RAPN were excited by the two isomers (erythro- and threo-) of beta-hydroxy-L-glutamic acid (L-BHGA), whereas PON, VIN, FAN and v-RCDN were inhibited. L-Glutamic acid (L-Glu) had virtually no effect on these neurones. alpha-Kainic acid and domoic acid showed marked excitatory effects, similar to those of L-BHGA, on d-RPLN and RAPN. Their effective potency quotients (EPQs), relative to the more effective isomer of L-BHGA were: 0.3 for both substances on d-RPLN, and 1 for alpha-kainic acid and 3-1 for domoic acid on RAPN. alpha-Kainic acid also had excitatory effects on FAN and v-RCDN (EPQ for both: 0.3), which were inhibited by L-BHGA but excited by gamma-aminobutyric acid (GABA). Erythro-L-tricholomic acid showed marked effects, similar to those of L-BHGA, on VIN (EPQ: 0.3) and RAPN (EPQ: 3-1), but produced weaker effects on PON and d-RPLN (EPQ: 0.1). DL-Ibotenic acid produced marked effects, similar to those of L-BHGA, on PON, VIN (EPQ for both: 1) and RAPN (EPQ: 1-0.3), but had weak effects on d-RPLN (EPQ: less than 0.1) and FAN (EPQ: 0.1). It had excitatory effects on v-RCDN (EPQ: 0.1). This neurone was inhibited by L-BHGA but excited by GABA. L-Quisqualic acid showed the same effects as L-BHGA on all of the neurones examined (EPQ range 30-0.1). It was the most potent of the compounds tested on RAPN (EPQ: 30-10), FAN (EPQ: 30) and v-RCDN (EPQ: 3). alpha-Allo-kainic acid and allo-gamma-hydroxy-L-glutamic acid had no obvious effect on any of the neurones examined. As described above, the responses of the neurones examined to these substances varied widely. However, L-quisqualic acid generally had effects on the neurones similar to those of L-BHGA; the L-BHGA-excited neurones were also excited by alpha-kainic acid and domoic acid. PMID:2866005

The Rhythm Aftereffect: Support for Time Sensitive Neurons with Broad Overlapping Tuning Curves

ERIC Educational Resources Information Center

Becker, Mark W.; Rasmussen, Ian P.

2007-01-01

Ivry [Ivry, R. B. (1996). The representation of temporal information in perception and motor control. Current Opinion in Neurobiology, 6, 851-857.] proposed that explicit coding of brief time intervals is accomplished by neurons that are tuned to a preferred temporal interval and have broad overlapping tuning curves. This proposal is analogous to…

Translating working memory into action: behavioral and neural evidence for using motor representations in encoding visuo-spatial sequences.

PubMed

Langner, Robert; Sternkopf, Melanie A; Kellermann, Tanja S; Grefkes, Christian; Kurth, Florian; Schneider, Frank; Zilles, Karl; Eickhoff, Simon B

2014-07-01

The neurobiological organization of action-oriented working memory is not well understood. To elucidate the neural correlates of translating visuo-spatial stimulus sequences into delayed (memory-guided) sequential actions, we measured brain activity using functional magnetic resonance imaging while participants encoded sequences of four to seven dots appearing on fingers of a left or right schematic hand. After variable delays, sequences were to be reproduced with the corresponding fingers. Recall became less accurate with longer sequences and was initiated faster after long delays. Across both hands, encoding and recall activated bilateral prefrontal, premotor, superior and inferior parietal regions as well as the basal ganglia, whereas hand-specific activity was found (albeit to a lesser degree during encoding) in contralateral premotor, sensorimotor, and superior parietal cortex. Activation differences after long versus short delays were restricted to motor-related regions, indicating that rehearsal during long delays might have facilitated the conversion of the memorandum into concrete motor programs at recall. Furthermore, basal ganglia activity during encoding selectively predicted correct recall. Taken together, the results suggest that to-be-reproduced visuo-spatial sequences are encoded as prospective action representations (motor intentions), possibly in addition to retrospective sensory codes. Overall, our study supports and extends multi-component models of working memory, highlighting the notion that sensory input can be coded in multiple ways depending on what the memorandum is to be used for. Copyright © 2013 Wiley Periodicals, Inc.

Temporal coding in a silicon network of integrate-and-fire neurons.

PubMed

Liu, Shih-Chii; Douglas, Rodney

2004-09-01

Spatio-temporal processing of spike trains by neuronal networks depends on a variety of mechanisms distributed across synapses, dendrites, and somata. In natural systems, the spike trains and the processing mechanisms cohere though their common physical instantiation. This coherence is lost when the natural system is encoded for simulation on a general purpose computer. By contrast, analog VLSI circuits are, like neurons, inherently related by their real-time physics, and so, could provide a useful substrate for exploring neuronlike event-based processing. Here, we describe a hybrid analog-digital VLSI chip comprising a set of integrate-and-fire neurons and short-term dynamical synapses that can be configured into simple network architectures with some properties of neocortical neuronal circuits. We show that, despite considerable fabrication variance in the properties of individual neurons, the chip offers a viable substrate for exploring real-time spike-based processing in networks of neurons.

Signal, noise, and variation in neural and sensory-motor latency

PubMed Central

Lee, Joonyeol; Joshua, Mati; Medina, Javier F.; Lisberger, Stephen G.

2016-01-01

Analysis of the neural code for sensory-motor latency in smooth pursuit eye movements reveals general principles of neural variation and the specific origin of motor latency. The trial-by-trial variation in neural latency in MT comprises: a shared component expressed as neuron-neuron latency correlations; and an independent component that is local to each neuron. The independent component arises heavily from fluctuations in the underlying probability of spiking with an unexpectedly small contribution from the stochastic nature of spiking itself. The shared component causes the latency of single neuron responses in MT to be weakly predictive of the behavioral latency of pursuit. Neural latency deeper in the motor system is more strongly predictive of behavioral latency. A model reproduces both the variance of behavioral latency and the neuron-behavior latency correlations in MT if it includes realistic neural latency variation, neuron-neuron latency correlations in MT, and noisy gain control downstream from MT. PMID:26971946

Hippocampal “Time Cells”: Time versus Path Integration

PubMed Central

Kraus, Benjamin J.; Robinson, Robert J.; White, John A.; Eichenbaum, Howard; Hasselmo, Michael E.

2014-01-01

SUMMARY Recent studies have reported the existence of hippocampal “time cells,” neurons that fire at particular moments during periods when behavior and location are relatively constant. However, an alternative explanation of apparent time coding is that hippocampal neurons “path integrate” to encode the distance an animal has traveled. Here, we examined hippocampal neuronal firing patterns as rats ran in place on a treadmill, thus “clamping” behavior and location, while we varied the treadmill speed to distinguish time elapsed from distance traveled. Hippocampal neurons were strongly influenced by time and distance, and less so by minor variations in location. Furthermore, the activity of different neurons reflected integration over time and distance to varying extents, with most neurons strongly influenced by both factors and some significantly influenced by only time or distance. Thus, hippocampal neuronal networks captured both the organization of time and distance in a situation where these dimensions dominated an ongoing experience. PMID:23707613

DeepNeuron: an open deep learning toolbox for neuron tracing.

PubMed

Zhou, Zhi; Kuo, Hsien-Chi; Peng, Hanchuan; Long, Fuhui

2018-06-06

Reconstructing three-dimensional (3D) morphology of neurons is essential for understanding brain structures and functions. Over the past decades, a number of neuron tracing tools including manual, semiautomatic, and fully automatic approaches have been developed to extract and analyze 3D neuronal structures. Nevertheless, most of them were developed based on coding certain rules to extract and connect structural components of a neuron, showing limited performance on complicated neuron morphology. Recently, deep learning outperforms many other machine learning methods in a wide range of image analysis and computer vision tasks. Here we developed a new Open Source toolbox, DeepNeuron, which uses deep learning networks to learn features and rules from data and trace neuron morphology in light microscopy images. DeepNeuron provides a family of modules to solve basic yet challenging problems in neuron tracing. These problems include but not limited to: (1) detecting neuron signal under different image conditions, (2) connecting neuronal signals into tree(s), (3) pruning and refining tree morphology, (4) quantifying the quality of morphology, and (5) classifying dendrites and axons in real time. We have tested DeepNeuron using light microscopy images including bright-field and confocal images of human and mouse brain, on which DeepNeuron demonstrates robustness and accuracy in neuron tracing.

Dual coding with STDP in a spiking recurrent neural network model of the hippocampus.

PubMed

Bush, Daniel; Philippides, Andrew; Husbands, Phil; O'Shea, Michael

2010-07-01

The firing rate of single neurons in the mammalian hippocampus has been demonstrated to encode for a range of spatial and non-spatial stimuli. It has also been demonstrated that phase of firing, with respect to the theta oscillation that dominates the hippocampal EEG during stereotype learning behaviour, correlates with an animal's spatial location. These findings have led to the hypothesis that the hippocampus operates using a dual (rate and temporal) coding system. To investigate the phenomenon of dual coding in the hippocampus, we examine a spiking recurrent network model with theta coded neural dynamics and an STDP rule that mediates rate-coded Hebbian learning when pre- and post-synaptic firing is stochastic. We demonstrate that this plasticity rule can generate both symmetric and asymmetric connections between neurons that fire at concurrent or successive theta phase, respectively, and subsequently produce both pattern completion and sequence prediction from partial cues. This unifies previously disparate auto- and hetero-associative network models of hippocampal function and provides them with a firmer basis in modern neurobiology. Furthermore, the encoding and reactivation of activity in mutually exciting Hebbian cell assemblies demonstrated here is believed to represent a fundamental mechanism of cognitive processing in the brain.

Dissociating Neural Correlates of Meaningful Emblems from Meaningless Gestures in Deaf Signers and Hearing Non-Signers

PubMed Central

Husain, Fatima T.; Patkin, Debra J.; Kim, Jieun; Braun, Allen R.; Horwitz, Barry

2012-01-01

Emblems are meaningful, culturally-specific hand gestures that are analogous to words. In this fMRI study, we contrasted the processing of emblematic gestures with meaningless gestures by pre-lingually Deaf and hearing participants. Deaf participants, who used American Sign Language, activated bilateral auditory processing and associative areas in the temporal cortex to a greater extent than the hearing participants while processing both types of gestures relative to rest. The hearing non-signers activated a diverse set of regions, including those implicated in the mirror neuron system, such as premotor cortex (BA 6) and inferior parietal lobule (BA 40) for the same contrast. Further, when contrasting the processing of meaningful to meaningless gestures (both relative to rest), the Deaf participants, but not the hearing, showed greater response in the left angular and supramarginal gyri, regions that play important roles in linguistic processing. These results suggest that whereas the signers interpreted emblems to be comparable to words, the non-signers treated emblems as similar to pictorial descriptions of the world and engaged the mirror neuron system. PMID:22968047

Neuronal bases of structural coherence in contemporary dance observation.

PubMed

Bachrach, Asaf; Jola, Corinne; Pallier, Christophe

2016-01-01

The neuronal processes underlying dance observation have been the focus of an increasing number of brain imaging studies over the past decade. However, the existing literature mainly dealt with effects of motor and visual expertise, whereas the neural and cognitive mechanisms that underlie the interpretation of dance choreographies remained unexplored. Hence, much attention has been given to the action observation network (AON) whereas the role of other potentially relevant neuro-cognitive mechanisms such as mentalizing (theory of mind) or language (narrative comprehension) in dance understanding is yet to be elucidated. We report the results of an fMRI study where the structural coherence of short contemporary dance choreographies was manipulated parametrically using the same taped movement material. Our participants were all trained dancers. The whole-brain analysis argues that the interpretation of structurally coherent dance phrases involves a subpart (superior parietal) of the AON as well as mentalizing regions in the dorsomedial prefrontal cortex. An ROI analysis based on a similar study using linguistic materials (Pallier et al., 2011) suggests that structural processing in language and dance might share certain neural mechanisms. Copyright © 2015 Elsevier Inc. All rights reserved.

Reduced functional connectivity between V1 and inferior frontal cortex associated with visuomotor performance in autism

PubMed Central

Villalobos, Michele E.; Mizuno, Akiko; Dahl, Branelle C.; Kemmotsu, Nobuko; Müller, Ralph-Axel

2010-01-01

Some recent evidence has suggested abnormalities of the dorsal stream and possibly the mirror neuron system in autism, which may be responsible for impairments of joint attention, imitation, and secondarily for language delays. The current study investigates functional connectivity along the dorsal stream in autism, examining interregional blood oxygenation level dependent (BOLD) signal cross-correlation during visuomotor coordination. Eight high-functioning autistic men and 8 handedness and age-matched controls were included. Visually prompted button presses were performed with the preferred hand. For each subject, functional connectivity was computed in terms of BOLD signal correlation with the mean time series in bilateral visual area 17. Our hypothesis of reduced dorsal stream connectivity in autism was only in part confirmed. Functional connectivity with superior parietal areas was not significantly reduced. However, the autism group showed significantly reduced connectivity with bilateral inferior frontal area 44, which is compatible with the hypothesis of mirror neuron defects in autism. More generally, our findings suggest that dorsal stream connectivity in autism may not be fully functional. PMID:15808991

Reduced functional connectivity between V1 and inferior frontal cortex associated with visuomotor performance in autism.

PubMed

Villalobos, Michele E; Mizuno, Akiko; Dahl, Branelle C; Kemmotsu, Nobuko; Müller, Ralph-Axel

2005-04-15

Some recent evidence has suggested abnormalities of the dorsal stream and possibly the mirror neuron system in autism, which may be responsible for impairments of joint attention, imitation, and secondarily for language delays. The current study investigates functional connectivity along the dorsal stream in autism, examining interregional blood oxygenation level dependent (BOLD) signal cross-correlation during visuomotor coordination. Eight high-functioning autistic men and eight handedness and age-matched controls were included. Visually prompted button presses were performed with the preferred hand. For each subject, functional connectivity was computed in terms of BOLD signal correlation with the mean time series in bilateral visual area 17. Our hypothesis of reduced dorsal stream connectivity in autism was only in part confirmed. Functional connectivity with superior parietal areas was not significantly reduced. However, the autism group showed significantly reduced connectivity with bilateral inferior frontal area 44, which is compatible with the hypothesis of mirror neuron defects in autism. More generally, our findings suggest that dorsal stream connectivity in autism may not be fully functional.

The evolution of neocortex in primates

PubMed Central

Kaas, Jon H.

2013-01-01

We can learn about the evolution of neocortex in primates through comparative studies of cortical organization in primates and those mammals that are the closest living relatives of primates, in conjunction with brain features revealed by the skull endocasts of fossil archaic primates. Such studies suggest that early primates had acquired a number of features of neocortex that now distinguish modern primates. Most notably, early primates had an array of new visual areas, and those visual areas widely shared with other mammals had been modified. Posterior parietal cortex was greatly expanded with sensorimotor modules for reaching, grasping, and personal defense. Motor cortex had become more specialized for hand use, and the functions of primary motor cortex were enhanced by the addition and development of premotor and cingulate motor areas. Cortical architecture became more varied, and cortical neuron populations became denser overall than in nonprimate ancestors. Primary visual cortex had the densest population of neurons, and this became more pronounced in the anthropoid radiation. Within the primate clade, considerable variability in cortical size, numbers of areas, and architecture evolved. PMID:22230624

The evolution of neocortex in primates.

PubMed

Kaas, Jon H

2012-01-01

We can learn about the evolution of neocortex in primates through comparative studies of cortical organization in primates and those mammals that are the closest living relatives of primates, in conjunction with brain features revealed by the skull endocasts of fossil archaic primates. Such studies suggest that early primates had acquired a number of features of neocortex that now distinguish modern primates. Most notably, early primates had an array of new visual areas, and those visual areas widely shared with other mammals had been modified. Posterior parietal cortex was greatly expanded with sensorimotor modules for reaching, grasping, and personal defense. Motor cortex had become more specialized for hand use, and the functions of primary motor cortex were enhanced by the addition and development of premotor and cingulate motor areas. Cortical architecture became more varied, and cortical neuron populations became denser overall than in nonprimate ancestors. Primary visual cortex had the densest population of neurons, and this became more pronounced in the anthropoid radiation. Within the primate clade, considerable variability in cortical size, numbers of areas, and architecture evolved. Copyright © 2012 Elsevier B.V. All rights reserved.

Histological evidence for drug diffusion across the cerebral meninges into the underlying neocortex in rats.

PubMed

Ludvig, Nandor; Sheffield, Lynette G; Tang, Hai M; Baptiste, Shirn L; Devinsky, Orrin; Kuzniecky, Ruben I

2008-01-10

Transmeningeal pharmacotherapy has been proposed to treat neurological disorders with localized pathology, such as intractable focal epilepsy. As a step toward understanding the diffusion and intracortical spread of transmeningeally delivered drugs, the present study used histological methods to determine the extent to which a marker compound, N-methyl-D-aspartate (NMDA), can diffuse into the neocortex through the meninges. Rats were implanted with bilateral parietal cortical epidural cups filled with 50 mM NMDA on the right side and artificial cerebrospinal fluid (ACSF) in the contralateral side. After 24 h, the histological effects of these treatments were evaluated using cresyl violet (Nissl) staining. The epidural NMDA exposure caused neuronal loss that in most animals extended from the pial surface through layer V. The area indicated by this neuronal loss was localized to the neocortical region underlying the epidural cup. These results suggest that NMDA-like, water soluble, small molecules can diffuse through the subdural/subarachnoid space into the underlying neocortex and spread in a limited fashion, close to the meningeal penetration site.

Neuronal migration disorders in microcephalic osteodysplastic primordial dwarfism type I/III.

PubMed

Juric-Sekhar, Gordana; Kapur, Raj P; Glass, Ian A; Murray, Mitzi L; Parnell, Shawn E; Hevner, Robert F

2011-04-01

Microcephalic osteodysplastic primordial dwarfism (MOPD) is a rare microlissencephaly syndrome, with at least two distinct phenotypic and genetic types. MOPD type II is caused by pericentrin mutations, while types I and III appear to represent a distinct entity (MOPD I/III) with variably penetrant phenotypes and unknown genetic basis. The neuropathology of MOPD I/III is little understood, especially in comparison to other forms of lissencephaly. Here, we report postmortem brain findings in an 11-month-old female infant with MOPD I/III. The cerebral cortex was diffusely pachygyric, with a right parietal porencephalic lesion. Histologically, the cortex was abnormally thick and disorganized. Distinct malformations were observed in different cerebral lobes, as characterized using layer-specific neuronal markers. Frontal cortex was severely disorganized and coated with extensive leptomeningeal glioneuronal heterotopia. Temporal cortex had a relatively normal 6-layered pattern, despite cortical thickening. Occipital cortex was variably affected. The corpus callosum was extremely hypoplastic. Brainstem and cerebellar malformations were also present, as well as old necrotic foci. Findings in this case suggest that the cortical malformation in MOPD I/III is distinct from other forms of pachygyria-lissencephaly.

From speech to thought: the neuronal basis of cognitive units in non-experimental, real-life communication investigated using ECoG

PubMed Central

Derix, Johanna; Iljina, Olga; Weiske, Johanna; Schulze-Bonhage, Andreas; Aertsen, Ad; Ball, Tonio

2014-01-01

Exchange of thoughts by means of expressive speech is fundamental to human communication. However, the neuronal basis of real-life communication in general, and of verbal exchange of ideas in particular, has rarely been studied until now. Here, our aim was to establish an approach for exploring the neuronal processes related to cognitive “idea” units (IUs) in conditions of non-experimental speech production. We investigated whether such units corresponding to single, coherent chunks of speech with syntactically-defined borders, are useful to unravel the neuronal mechanisms underlying real-world human cognition. To this aim, we employed simultaneous electrocorticography (ECoG) and video recordings obtained in pre-neurosurgical diagnostics of epilepsy patients. We transcribed non-experimental, daily hospital conversations, identified IUs in transcriptions of the patients' speech, classified the obtained IUs according to a previously-proposed taxonomy focusing on memory content, and investigated the underlying neuronal activity. In each of our three subjects, we were able to collect a large number of IUs which could be assigned to different functional IU subclasses with a high inter-rater agreement. Robust IU-onset-related changes in spectral magnitude could be observed in high gamma frequencies (70–150 Hz) on the inferior lateral convexity and in the superior temporal cortex regardless of the IU content. A comparison of the topography of these responses with mouth motor and speech areas identified by electrocortical stimulation showed that IUs might be of use for extraoperative mapping of eloquent cortex (average sensitivity: 44.4%, average specificity: 91.1%). High gamma responses specific to memory-related IU subclasses were observed in the inferior parietal and prefrontal regions. IU-based analysis of ECoG recordings during non-experimental communication thus elicits topographically- and functionally-specific effects. We conclude that segmentation of spontaneous real-world speech in linguistically-motivated units is a promising strategy for elucidating the neuronal basis of mental processing during non-experimental communication. PMID:24982625

Absolute Depth Sensitivity in Cat Primary Visual Cortex under Natural Viewing Conditions.

PubMed

Pigarev, Ivan N; Levichkina, Ekaterina V

2016-01-01

Mechanisms of 3D perception, investigated in many laboratories, have defined depth either relative to the fixation plane or to other objects in the visual scene. It is obvious that for efficient perception of the 3D world, additional mechanisms of depth constancy could operate in the visual system to provide information about absolute distance. Neurons with properties reflecting some features of depth constancy have been described in the parietal and extrastriate occipital cortical areas. It has also been shown that, for some neurons in the visual area V1, responses to stimuli of constant angular size differ at close and remote distances. The present study was designed to investigate whether, in natural free gaze viewing conditions, neurons tuned to absolute depths can be found in the primary visual cortex (area V1). Single-unit extracellular activity was recorded from the visual cortex of waking cats sitting on a trolley in front of a large screen. The trolley was slowly approaching the visual scene, which consisted of stationary sinusoidal gratings of optimal orientation rear-projected over the whole surface of the screen. Each neuron was tested with two gratings, with spatial frequency of one grating being twice as high as that of the other. Assuming that a cell is tuned to a spatial frequency, its maximum response to the grating with a spatial frequency twice as high should be shifted to a distance half way closer to the screen in order to attain the same size of retinal projection. For hypothetical neurons selective to absolute depth, location of the maximum response should remain at the same distance irrespective of the type of stimulus. It was found that about 20% of neurons in our experimental paradigm demonstrated sensitivity to particular distances independently of the spatial frequencies of the gratings. We interpret these findings as an indication of the use of absolute depth information in the primary visual cortex.