Selective modulation of intracortical inhibition by low-intensity Theta Burst Stimulation.

PubMed

McAllister, S M; Rothwell, J C; Ridding, M C

2009-04-01

Theta Burst Stimulation (TBS) is a repetitive transcranial magnetic stimulation paradigm which has effects on both excitatory and inhibitory intracortical pathways when applied at an intensity of 80% of active motor threshold. As intracortical inhibitory pathways have a lower threshold for activation than excitatory pathways, we sought to determine whether it was possible to selectively target cortical inhibitory circuitry by reducing the intensity of TBS to 70% of active motor threshold. Motor evoked potentials (MEPs), short latency intracortical facilitation (SICF), intracortical facilitation (ICF) and short interval intracortical inhibition (SICI) were measured at baseline, 5-20 and 20-35 min following continuous (cTBS) and intermittent (iTBS) low-intensity TBS in nine healthy subjects. Low-intensity cTBS significantly reduced SICI 5-20 min following stimulation, whilst having no effect on MEPs, SICF or ICF. Low-intensity iTBS had no effect on SICI, MEPs, SICF or ICF. It is possible to selectively target intracortical inhibitory networks for modulation by low-intensity TBS, however, responses may critically depend upon the particular paradigm chosen. These findings have important implications for the treatment of neurological disorders where abnormal levels of intracortical inhibition are present, such as Parkinson's disease and focal hand dystonia and requires further investigation.

The Contribution of Primary Motor Cortex Is Essential for Probabilistic Implicit Sequence Learning: Evidence from Theta Burst Magnetic Stimulation

ERIC Educational Resources Information Center

Wilkinson, Leonora; Teo, James T.; Obeso, Ignacio; Rothwell, John C.; Jahanshahi, Marjan

2010-01-01

Theta burst transcranial magnetic stimulation (TBS) is considered to produce plastic changes in human motor cortex. Here, we examined the inhibitory and excitatory effects of TBS on implicit sequence learning using a probabilistic serial reaction time paradigm. We investigated the involvement of several cortical regions associated with implicit…

Inhibition of Pre-Supplementary Motor Area by Continuous Theta Burst Stimulation Leads to More Cautious Decision-making and More Efficient Sensory Evidence Integration.

PubMed

Tosun, Tuğçe; Berkay, Dilara; Sack, Alexander T; Çakmak, Yusuf Ö; Balcı, Fuat

2017-08-01

Decisions are made based on the integration of available evidence. The noise in evidence accumulation leads to a particular speed-accuracy tradeoff in decision-making, which can be modulated and optimized by adaptive decision threshold setting. Given the effect of pre-SMA activity on striatal excitability, we hypothesized that the inhibition of pre-SMA would lead to higher decision thresholds and an increased accuracy bias. We used offline continuous theta burst stimulation to assess the effect of transient inhibition of the right pre-SMA on the decision processes in a free-response two-alternative forced-choice task within the drift diffusion model framework. Participants became more cautious and set higher decision thresholds following right pre-SMA inhibition compared with inhibition of the control site (vertex). Increased decision thresholds were accompanied by an accuracy bias with no effects on post-error choice behavior. Participants also exhibited higher drift rates as a result of pre-SMA inhibition compared with the vertex inhibition. These results, in line with the striatal theory of speed-accuracy tradeoff, provide evidence for the functional role of pre-SMA activity in decision threshold modulation. Our results also suggest that pre-SMA might be a part of the brain network associated with the sensory evidence integration.

Transient Beneficial Effects of Excitatory Theta Burst Stimulation in a Patient with Phonological Agraphia after Left Supramarginal Gyrus Infarction

ERIC Educational Resources Information Center

Nardone, Raffaele; De Blasi, Pierpaolo; Zuccoli, Giulio; Tezzon, Frediano; Golaszewski, Stefan; Trinka, Eugen

2012-01-01

We report a patient showing isolated phonological agraphia after an ischemic stroke involving the left supramarginal gyrus (SMG). In this patient, we investigated the effects of focal repetitive transcranial magnetic stimulation (rTMS) given as theta burst stimulation (TBS) over the left SMG, corresponding to the Brodmann area (BA) 40. The patient…

Theta burst magnetic stimulation over the pre-supplementary motor area improves motor inhibition.

PubMed

Obeso, Ignacio; Wilkinson, Leonora; Teo, James T; Talelli, Penelope; Rothwell, John C; Jahanshahi, Marjan

Stopping an ongoing motor response or resolving conflict induced by conflicting stimuli are associated with activation of a right-lateralized network of inferior frontal gyrus (IFG), pre-supplementary motor area (pre-SMA) and subthalamic nucleus (STN). However, the roles of the right IFG and pre-SMA in stopping a movement and in conflict resolution remain unclear. We used continuous theta burst stimulation (cTBS) to examine the involvement of the right IFG and pre-SMA in inhibition and conflict resolution using the conditional stop signal task. We measured stop signal reaction time (SSRT, measure of reactive inhibition), response delay effect (RDE, measure of proactive action restraint) and conflict induced slowing (CIS, measure of conflict resolution). Stimulation over the pre-SMA resulted in significantly shorter SSRTs (improved inhibition) compared to sham cTBS. This effect was not observed for CIS, RDE, or any other measures. cTBS over the right IFG had no effect on SSRT, CIS, RDE or on any other measure. The improvement of SSRT with cTBS over the pre-SMA suggests its critical contribution to stopping ongoing movements. Copyright © 2017 Elsevier Inc. All rights reserved.

Intermittent theta-burst stimulation induces correlated changes in cortical and corticospinal excitability in healthy older subjects.

PubMed

Gedankien, Tamara; Fried, Peter J; Pascual-Leone, Alvaro; Shafi, Mouhsin M

2017-12-01

We studied the correlation between motor evoked potentials (MEPs) and early TMS-evoked EEG potentials (TEPs) from single-pulse TMS before and after intermittent Theta Burst Stimulation (iTBS) to the left primary motor cortex (M1) in 17 healthy older participants. TMS was targeted to the hand region of M1 using a MRI-guided navigated brain stimulation system and a figure-of-eight biphasic coil. MEPs were recorded from the right first dorsal interosseous muscle using surface EMG. TEPs were extracted from a 61-channel EEG recording. Participants received 90 single TMS pulses at 120% of resting motor threshold before and after iTBS. Across all participants, the change in N15-P30 TEP and MEP amplitudes were significantly correlated (r=0.69; p<0.01). Average TEP responses did not change significantly after iTBS, whereas MEP amplitudes showed a significant increase. Changes in corticospinal reactivity and cortical reactivity induced by iTBS are related. However, the effect of iTBS on TEPs, unlike MEPs, is not straightforward. Our findings help elucidate the relationship between changes in cortical and corticospinal excitability in healthy older individuals. Going forward, TEPs may be used to evaluate the effects of theta-burst stimulation in non-motor brain regions. Copyright © 2017 International Federation of Clinical Neurophysiology. Published by Elsevier B.V. All rights reserved.

Visual-spatial memory may be enhanced with theta burst deep brain stimulation of the fornix: a preliminary investigation with four cases.

PubMed

Miller, Jonathan P; Sweet, Jennifer A; Bailey, Christopher M; Munyon, Charles N; Luders, Hans O; Fastenau, Philip S

2015-07-01

Memory loss after brain injury can be a source of considerable morbidity, but there are presently few therapeutic options for restoring memory function. We have previously demonstrated that burst stimulation of the fornix is able to significantly improve memory in a rodent model of traumatic brain injury. The present study is a preliminary investigation with a small group of cases to explore whether theta burst stimulation of the fornix might improve memory in humans. Four individuals undergoing stereo-electroencephalography evaluation for drug-resistant epilepsy were enrolled. All participants were implanted with an electrode into the proximal fornix and dorsal hippocampal commissure on the language dominant (n = 3) or language non-dominant (n = 1) side, and stimulation of this electrode reliably produced a diffuse evoked potential in the head and body of the ipsilateral hippocampus. Each participant underwent testing of verbal memory (Rey Auditory-Verbal Learning Test), visual-spatial memory (Medical College of Georgia Complex Figure Test), and visual confrontational naming (Boston Naming Test Short Form) once per day over at least two consecutive days using novel test forms each day. For 50% of the trials, the fornix electrode was continuously stimulated using a burst pattern (200 Hz in 100 ms trains, five trains per second, 100 µs, 7 mA) and was compared with sham stimulation. Participants and examiners were blinded to whether stimulation was active or not, and the order of stimulation was randomized. The small sample size precluded use of inferential statistics; therefore, data were analysed using descriptive statistics and graphic analysis. Burst stimulation of the fornix was not perceived by any of the participants but was associated with a robust reversible improvement in immediate and delayed performance on the Medical College of Georgia Complex Figure Test. There were no apparent differences on either Rey Auditory-Verbal Learning Test or Boston Naming

Modulating Mimetic Preference with Theta Burst Stimulation of the Inferior Parietal Cortex

PubMed Central

Ticini, Luca F.; Urgesi, Cosimo; Kotz, Sonja A.

2017-01-01

We like an object more when we see someone else reaching for it. To what extent is action observation causally linked to object valuation? In this study, we set out to answer to this question by applying continuous theta burst stimulation (cTBS) over the left inferior parietal lobule (IPL). Previous studies pointed to this region as critical in the representation of others' actions and in tool manipulation. However, it is unclear to what extent IPL's involvement simply reflects action observation, rather than a casual role in objects' valuation. To clarify this issue, we measured cTBS-dependent modulations of participants' “mimetic preference ratings”, i.e., the difference between the ratings of pairs of familiar objects that were (vs. were not) reached out for by other individuals. Our result shows that cTBS increased mimetic preference ratings for tools, when compared to a control condition without stimulation. This effect was selective for items that were reached for or manipulated by another individual, whilst it was not detected in non-tool objects. Although preliminary, this finding suggests that the automatic and covert simulation of an observed action, even when there is no intention to act on an object, influences explicit affective judgments for objects. This work supports embodied cognition theories by substantiating that our subjective preference is grounded in action. PMID:29250021

Cerebellar theta burst stimulation modulates short latency afferent inhibition in Alzheimer's disease patients

PubMed Central

Di Lorenzo, Francesco; Martorana, Alessandro; Ponzo, Viviana; Bonnì, Sonia; D'Angelo, Egidio; Caltagirone, Carlo; Koch, Giacomo

2013-01-01

The dysfunction of cholinergic neurons is a typical hallmark in Alzheimer's disease (AD). Previous findings demonstrated that high density of cholinergic receptors is found in the thalamus and the cerebellum compared with the cerebral cortex and the hippocampus. We aimed at investigating whether activation of the cerebello-thalamo-cortical pathway by means of cerebellar theta burst stimulation (TBS) could modulate central cholinergic functions evaluated in vivo by using the neurophysiological determination of Short-Latency Afferent Inhibition (SLAI). We tested the SLAI circuit before and after administration of cerebellar continuous TBS (cTBS) in 12 AD patients and in 12 healthy age-matched control subjects (HS). We also investigated potential changes of intracortical circuits of the contralateral primary motor cortex (M1) by assessing short intracortical inhibition (SICI) and intracortical facilitation (ICF). SLAI was decreased in AD patients compared to HS. Cerebellar cTBS partially restored SLAI in AD patients at later inter-stimulus intervals (ISIs), but did not modify SLAI in HS. SICI and ICF did not differ in the two groups and were not modulated by cerebellar cTBS. These results demonstrate that cerebellar magnetic stimulation is likely to affect mechanisms of cortical cholinergic activity, suggesting that the cerebellum may have a direct influence on the cholinergic dysfunction in AD. PMID:23423358

Theta Oscillations During Active Sleep Synchronize The Developing Rubro-Hippocampal Sensorimotor Network

PubMed Central

Rio-Bermudez, Carlos Del; Kim, Jangjin; Sokoloff, Greta; Blumberg, Mark S.

2017-01-01

Summary Neuronal oscillations comprise a fundamental mechanism by which distant neural structures establish and express functional connectivity. Long-range functional connectivity between the hippocampus and other forebrain structures is enabled by theta oscillations. Here we show for the first time that the infant rat red nucleus (RN)—a brainstem sensorimotor structure— exhibits theta (4-7 Hz) oscillations restricted primarily to periods of active (REM) sleep. At postnatal day (P) 8, theta is expressed as brief bursts immediately following myoclonic twitches; by P12, theta oscillations are expressed continuously across bouts of active sleep. Simultaneous recordings from the hippocampus and RN at P12 show that theta oscillations in both structures are coherent, co-modulated, and mutually interactive during active sleep. Critically, at P12, inactivation of the medial septum eliminates theta in both structures. The developmental emergence of theta-dependent functional coupling between the hippocampus and RN parallels that between the hippocampus and prefrontal cortex. Accordingly, disruptions in the early expression of theta could underlie the cognitive and sensorimotor deficits associated with neurodevelopmental disorders such as autism and schizophrenia. PMID:28479324

Theta-burst microstimulation in the human entorhinal area improves memory specificity.

PubMed

Titiz, Ali S; Hill, Michael R H; Mankin, Emily A; M Aghajan, Zahra; Eliashiv, Dawn; Tchemodanov, Natalia; Maoz, Uri; Stern, John; Tran, Michelle E; Schuette, Peter; Behnke, Eric; Suthana, Nanthia A; Fried, Itzhak

2017-10-24

The hippocampus is critical for episodic memory, and synaptic changes induced by long-term potentiation (LTP) are thought to underlie memory formation. In rodents, hippocampal LTP may be induced through electrical stimulation of the perforant path. To test whether similar techniques could improve episodic memory in humans, we implemented a microstimulation technique that allowed delivery of low-current electrical stimulation via 100 μm -diameter microelectrodes. As thirteen neurosurgical patients performed a person recognition task, microstimulation was applied in a theta-burst pattern, shown to optimally induce LTP. Microstimulation in the right entorhinal area during learning significantly improved subsequent memory specificity for novel portraits; participants were able both to recognize previously-viewed photos and reject similar lures. These results suggest that microstimulation with physiologic level currents-a radical departure from commonly used deep brain stimulation protocols-is sufficient to modulate human behavior and provides an avenue for refined interrogation of the circuits involved in human memory.

Continuous and intermittent transcranial magnetic theta burst stimulation modify tactile learning performance and cortical protein expression in the rat differently.

PubMed

Mix, Annika; Benali, Alia; Eysel, Ulf T; Funke, Klaus

2010-11-01

Repetitive transcranial magnetic stimulation (rTMS) can modulate cortical excitability in a stimulus-frequency-dependent manner. Two kinds of theta burst stimulation (TBS) [intermittent TBS (iTBS) and continuous TBS (cTBS)] modulate human cortical excitability differently, with iTBS increasing it and cTBS decreasing it. In rats, we recently showed that this is accompanied by changes in the cortical expression of proteins related to the activity of inhibitory neurons. Expression levels of the calcium-binding protein parvalbumin (PV) and of the 67-kDa isoform of glutamic acid decarboxylase (GAD67) were strongly reduced following iTBS, but not cTBS, whereas both increased expression of the 65-kDa isoform of glutamic acid decarboxylase. In the present study, to investigate possible functional consequences, we applied iTBS and cTBS to rats learning a tactile discrimination task. Conscious rats received either verum or sham rTMS prior to the task. Finally, to investigate how rTMS and learning effects interact, protein expression was determined for cortical areas directly involved in the task and for those either not, or indirectly, involved. We found that iTBS, but not cTBS, improved learning and strongly reduced cortical PV and GAD67 expression. However, the combination of learning and iTBS prevented this effect in those cortical areas involved in the task, but not in unrelated areas. We conclude that the improved learning found following iTBS is a result of the interaction of two effects, possibly in a homeostatic manner: a general weakening of inhibition mediated by the fast-spiking interneurons, and re-established activity in those neurons specifically involved in the learning task, leading to enhanced contrast between learning-induced and background activity. © 2010 The Authors. European Journal of Neuroscience © 2010 Federation of European Neuroscience Societies and Blackwell Publishing Ltd.

Probing changes in corticospinal excitability following theta burst stimulation of the human primary motor cortex.

PubMed

Goldsworthy, Mitchell R; Vallence, Ann-Maree; Hodyl, Nicolette A; Semmler, John G; Pitcher, Julia B; Ridding, Michael C

2016-01-01

To determine whether the intensity of transcranial magnetic stimulation (TMS) used to probe changes in corticospinal excitability influences the measured plasticity response to theta burst stimulation (TBS) of the human primary motor cortex. Motor evoked potential (MEP) input/output (I/O) curves were recorded before and following continuous TBS (cTBS) (Experiment 1; n=18) and intermittent TBS (iTBS) (Experiment 2; n=18). The magnitude and consistency of MEP depression induced by cTBS was greatest when probed using stimulus intensities at or above 150% of resting motor threshold (RMT). In contrast, facilitation of MEPs following iTBS was strongest and most consistent at 110% of RMT. The plasticity response to both cTBS and iTBS is influenced by the stimulus intensity used to probe the induced changes in corticospinal excitability. The results highlight the importance of the test stimulus intensity used to assess TBS-induced changes in corticospinal excitability when interpreting neuroplasticity data, and suggest that a number of test intensities may be required to reliably probe the plasticity response. Copyright © 2015 International Federation of Clinical Neurophysiology. Published by Elsevier Ireland Ltd. All rights reserved.

Bilateral somatosensory evoked potentials following intermittent theta-burst repetitive transcranial magnetic stimulation.

PubMed

Premji, Azra; Ziluk, Angela; Nelson, Aimee J

2010-08-05

Intermittent theta-burst stimulation (iTBS) is a form of repetitive transcranial magnetic stimulation that may alter cortical excitability in the primary somatosensory cortex (SI). The present study investigated the effects of iTBS on subcortical and early cortical somatosensory evoked potentials (SEPs) recorded over left, iTBS stimulated SI and the right-hemisphere non-stimulated SI. SEPs were recorded before and at 5, 15, and 25 minutes following iTBS. Compared to pre-iTBS, the amplitude of cortical potential N20/P25 was significantly increased for 5 minutes from non-stimulated SI and for 15 to 25 minutes from stimulated SI. Subcortical potentials recorded bilaterally remained unaltered following iTBS. We conclude that iTBS increases the cortical excitability of SI bilaterally and does not alter thalamocortical afferent input to SI. ITBS may provide one avenue to induce cortical plasticity in the somatosensory cortex.

Human hippocampal theta power indicates movement onset and distance travelled

PubMed Central

Bird, Chris M.; Gollwitzer, Stephanie; Rodionov, Roman; Diehl, Beate; McEvoy, Andrew W.; Walker, Matthew C.; Burgess, Neil

2017-01-01

Theta frequency oscillations in the 6- to 10-Hz range dominate the rodent hippocampal local field potential during translational movement, suggesting that theta encodes self-motion. Increases in theta power have also been identified in the human hippocampus during both real and virtual movement but appear as transient bursts in distinct high- and low-frequency bands, and it is not yet clear how these bursts relate to the sustained oscillation observed in rodents. Here, we examine depth electrode recordings from the temporal lobe of 13 presurgical epilepsy patients performing a self-paced spatial memory task in a virtual environment. In contrast to previous studies, we focus on movement-onset periods that incorporate both initial acceleration and an immediately preceding stationary interval associated with prominent theta oscillations in the rodent hippocampal formation. We demonstrate that movement-onset periods are associated with a significant increase in both low (2–5 Hz)- and high (6–9 Hz)-frequency theta power in the human hippocampus. Similar increases in low- and high-frequency theta power are seen across lateral temporal lobe recording sites and persist throughout the remainder of movement in both regions. In addition, we show that movement-related theta power is greater both before and during longer paths, directly implicating human hippocampal theta in the encoding of translational movement. These findings strengthen the connection between studies of theta-band activity in rodents and humans and offer additional insight into the neural mechanisms of spatial navigation. PMID:29078334

Multiple blocks of intermittent and continuous theta-burst stimulation applied via transcranial magnetic stimulation differently affect sensory responses in rat barrel cortex

PubMed Central

Thimm, Andreas; Funke, Klaus

2015-01-01

Cortical sensory processing varies with cortical state and the balance of inhibition to excitation. Repetitive transcranial magnetic stimulation (rTMS) has been shown to modulate human cortical excitability. In a rat model, we recently showed that intermittent theta-burst stimulation (iTBS) applied to the corpus callosum, to activate primarily supragranular cortical pyramidal cells but fewer subcortical neurons, strongly reduced the cortical expression of parvalbumin (PV), indicating reduced activity of fast-spiking interneurons. Here, we used the well-studied rodent barrel cortex system to test how iTBS and continuous TBS (cTBS) modulate sensory responses evoked by either single or double stimuli applied to the principal (PW) and/or adjacent whisker (AW) in urethane-anaesthetized rats. Compared to sham stimulation, iTBS but not cTBS particularly enhanced late (>18 ms) response components of multi-unit spiking and local field potential responses in layer 4 but not the very early response (<18 ms). Similarly, only iTBS diminished the suppression of the second response evoked by paired PW or AW–PW stimulation at 20 ms intervals. The effects increased with each of the five iTBS blocks applied. With cTBS a mild effect similar to that of iTBS was first evident after 4–5 stimulation blocks. Enhanced cortical c-Fos and zif268 expression but reduced PV and GAD67 expression was found only after iTBS, indicating increased cortical activity due to lowered inhibition. We conclude that iTBS but less cTBS may primarily weaken a late recurrent-type cortical inhibition mediated via a subset of PV+ interneurons, enabling stronger late response components believed to contribute to the perception of sensory events. PMID:25504571

Inter- and Intra-individual variability following intermittent theta burst stimulation: implications for rehabilitation and recovery.

PubMed

Hinder, Mark R; Goss, Emily L; Fujiyama, Hakuei; Canty, Alison J; Garry, Michael I; Rodger, Jennifer; Summers, Jeffery J

2014-01-01

The continued refinement of non-invasive brain stimulation (NBS) techniques is indicative of promising clinical and rehabilitative interventions that are able to modulate cortical excitability. Intermittent theta burst stimulation (iTBS) is one such technique that can increase cortical excitability, purportedly via LTP-like mechanisms. While iTBS may have the capacity to promote recovery after neurological injury, and to combat cognitive and motor decline, recent reports observed highly variable effects across individuals, questioning the efficacy of iTBS as a clinical tool. The aim of this study was to examine intra-individual reliability and inter-individual variability in responses to iTBS. Thirty healthy participants completed two experimental sessions of the iTBS protocol 1-3 weeks apart. Motor evoked potentials in response to single pulse TMS were used to assess corticospinal excitability prior to, and up to 36 min following, iTBS. At the group level, iTBS evoked statistically significant increases in motor cortical excitability across both sessions (P < 0.001), with 22 out of 30 participants exhibiting increases in excitability in both sessions. A strong intraclass correlation demonstrated that both the direction, and magnitude of the plastic changes were reliable at the individual level. Overall, our results suggest that iTBS is capable of inducing relatively robust and consistent effects within and between young individuals. As such, the capacity for iTBS to be exploited in clinical and rehabilitative interventions should continue to be explored. Copyright © 2014 Elsevier Inc. All rights reserved.

Improvement of tactile perception and enhancement of cortical excitability through intermittent theta burst rTMS over human primary somatosensory cortex.

PubMed

Ragert, Patrick; Franzkowiak, Stephanie; Schwenkreis, Peter; Tegenthoff, Martin; Dinse, Hubert R

2008-01-01

Adopting the patterns of theta burst stimulation (TBS) used in brain-slice preparations, a novel and rapid method of conditioning the human brain has recently been introduced. Using short bursts of high-frequency (50 Hz) repetitive transcranial magnetic stimulation (rTMS) has been shown to induce lasting changes in brain physiology of the motor cortex. In the present study, we tested whether a few minutes of intermittent theta burst stimulation (iTBS) over left primary somatosensory cortex (SI) evokes excitability changes within the stimulated brain area and whether such changes are accompanied by changes in tactile discrimination behavior. As a measure of altered perception we assessed tactile discrimination thresholds on the right and left index fingers (d2) before and after iTBS. We found an improved discrimination performance on the right d2 that was present for at least 30 min after termination of iTBS. Similar improvements were found for the ring finger, while left d2 remained unaffected in all cases. As a control, iTBS over the tibialis anterior muscle representation within primary motor cortex had no effects on tactile discrimination. Recording somatosensory evoked potentials over left SI after median nerve stimulation revealed a reduction in paired-pulse inhibition after iTBS that was associated but not correlated with improved discrimination performance. No excitability changes could be found for SI contralateral to iTBS. Testing the performance of simple motor tasks revealed no alterations after iTBS was applied over left SI. Our results demonstrate that iTBS protocols resembling those used in slice preparations for the induction of long-term potentiation are also effective in driving lasting improvements of the perception of touch in human subjects together with an enhancement of cortical excitability.

Effects of intermittent theta burst stimulation on spasticity after stroke.

PubMed

Kim, Dae Hyun; Shin, Ji Cheol; Jung, Seungsoo; Jung, Tae-Min; Kim, Deog Young

2015-07-08

Spasticity is a common cause of long-term disability in poststroke hemiplegic patients. We investigated whether intermittent theta burst stimulation (iTBS) could reduce upper-limb spasticity after a stroke. Fifteen hemiplegic stroke patients were recruited for a double-blind sham-controlled cross-over design study. A single session of iTBS or sham stimulation was delivered on the motor hotspot of the affected flexor carpi radialis muscle in a random and counterbalanced order with a 1-week interval. Modified Ashworth scale (MAS), modified Tardieu scale (MTS), H-wave/M-wave amplitude ratio, peak torque (PT), peak torque angle (PTA), work of affected wrist flexor, and rectified integrated electromyographic activity of the flexor carpi radialis muscle were measured before, immediately after, 30 min after, and 1 week after iTBS or sham stimulation. Repeated-measures analysis of variance showed a significant interaction between time and intervention for the MAS, MTS, PT, PTA, and rectified integrated electromyographic activity (P<0.05), indicating that these parameters were significantly improved by iTBS compared with sham stimulation. However, the H-wave/M-wave amplitude ratio and work were not affected. MAS and MTS significantly improved for at least 30 min after iTBS, but the other parameters only improved immediately after iTBS (P<0.05). In conclusion, iTBS on the affected hemisphere may help to reduce poststroke spasticity transiently.

Single session intermittent theta-burst stimulation on the left premotor cortex does not alleviate freezing of gait in Parkinson's disease.

PubMed

Tard, Céline; Devanne, Hervé; Defebvre, Luc; Delval, Arnaud

2016-08-15

To investigate the efficiency of intermittent theta-burst stimulation (iTBS) to alleviate the symptoms of freezing of gait (FoG) in Parkinson's disease (PD). We performed a cross-over, sham-controlled study of patients with severe PD, bilateral motor signs and debilitating, severe FoG, that was levodopa-sensitive but not controlled by optimal dopatherapy. We applied iTBS to the left premotor cortex and measured FoG, gait initiation and continuous gait, before and immediately after the iTBS session. All patients received sham and true iTBS with a one-week interval and in randomized order. 15 patients were included in the study. Recordings were performed under usual medication and all patients always showed unresponsive freezing. The pre- and post-stimulation gait trajectories did not differ in terms of the mean trajectory completion time or the percent time with FoG. The percent time with FoG was 6% greater after sham stimulation and 3% lower after iTBS (p>0.05). Visual cueing modified gait initiation and continuous gait but these latter were not influenced by rTMS. The present study provides Class I evidence that iTBS of the left premotor cortex does not alleviate FoG in PD. Copyright © 2016 Elsevier Ireland Ltd. All rights reserved.

Impact of Prefrontal Theta Burst Stimulation on Clinical Neuropsychological Tasks.

PubMed

Viejo-Sobera, Raquel; Redolar-Ripoll, Diego; Boixadós, Mercè; Palaus, Marc; Valero-Cabré, Antoni; Marron, Elena M

2017-01-01

Theta burst stimulation (TBS) protocols hold high promise in neuropsychological rehabilitation. Nevertheless, their ability to either decrease (continuous, cTBS) or increase (intermittent, iTBS) cortical excitability in areas other than the primary motor cortex, and their consistency modulating human behaviors with clinically relevant tasks remain to be fully established. The behavioral effects of TBS over the dorsolateral prefrontal cortex (dlPFC) are particularly interesting given its involvement in working memory (WM) and executive functions (EF), often impaired following frontal brain damage. We aimed to explore the ability of cTBS and iTBS to modulate WM and EF in healthy individuals, assessed with clinical neuropsychological tests (Digits Backward, 3-back task, Stroop Test, and Tower of Hanoi). To this end, 36 participants were assessed using the four tests 1 week prior to stimulation and immediately following a single session of either cTBS, iTBS, or sham TBS, delivered to the left dlPFC. No significant differences were found across stimulation conditions in any of the clinical tasks. Nonetheless, in some of them, active stimulation induced significant pre/post performance modulations, which were not found for the sham condition. More specifically, sham stimulation yielded improvements in the 3-back task and the Color, Color-Word, and Interference Score of the Stroop Test, an effect likely caused by task practice. Both, iTBS and cTBS, produced improvements in Digits Backward and impairments in 3-back task accuracy. Moreover, iTBS increased Interference Score in the Stroop Test in spite of the improved word reading and impaired color naming, whereas cTBS decreased the time required to complete the Tower of Hanoi. Differing from TBS outcomes reported for cortico-spinal measures on the primary motor cortex, our analyses did not reveal any of the expected performance differences across stimulation protocols. However, if one considers independently pre

Impact of Prefrontal Theta Burst Stimulation on Clinical Neuropsychological Tasks

PubMed Central

Viejo-Sobera, Raquel; Redolar-Ripoll, Diego; Boixadós, Mercè; Palaus, Marc; Valero-Cabré, Antoni; Marron, Elena M.

2017-01-01

Theta burst stimulation (TBS) protocols hold high promise in neuropsychological rehabilitation. Nevertheless, their ability to either decrease (continuous, cTBS) or increase (intermittent, iTBS) cortical excitability in areas other than the primary motor cortex, and their consistency modulating human behaviors with clinically relevant tasks remain to be fully established. The behavioral effects of TBS over the dorsolateral prefrontal cortex (dlPFC) are particularly interesting given its involvement in working memory (WM) and executive functions (EF), often impaired following frontal brain damage. We aimed to explore the ability of cTBS and iTBS to modulate WM and EF in healthy individuals, assessed with clinical neuropsychological tests (Digits Backward, 3-back task, Stroop Test, and Tower of Hanoi). To this end, 36 participants were assessed using the four tests 1 week prior to stimulation and immediately following a single session of either cTBS, iTBS, or sham TBS, delivered to the left dlPFC. No significant differences were found across stimulation conditions in any of the clinical tasks. Nonetheless, in some of them, active stimulation induced significant pre/post performance modulations, which were not found for the sham condition. More specifically, sham stimulation yielded improvements in the 3-back task and the Color, Color-Word, and Interference Score of the Stroop Test, an effect likely caused by task practice. Both, iTBS and cTBS, produced improvements in Digits Backward and impairments in 3-back task accuracy. Moreover, iTBS increased Interference Score in the Stroop Test in spite of the improved word reading and impaired color naming, whereas cTBS decreased the time required to complete the Tower of Hanoi. Differing from TBS outcomes reported for cortico-spinal measures on the primary motor cortex, our analyses did not reveal any of the expected performance differences across stimulation protocols. However, if one considers independently pre

Interhemispheric Plasticity following Intermittent Theta Burst Stimulation in Chronic Poststroke Aphasia

PubMed Central

Griffis, Joseph C.; Nenert, Rodolphe; Allendorfer, Jane B.; Szaflarski, Jerzy P.

2016-01-01

The effects of noninvasive neurostimulation on brain structure and function in chronic poststroke aphasia are poorly understood. We investigated the effects of intermittent theta burst stimulation (iTBS) applied to residual language-responsive cortex in chronic patients using functional and anatomical MRI data acquired before and after iTBS. Lateralization index (LI) analyses, along with comparisons of inferior frontal gyrus (IFG) activation and connectivity during covert verb generation, were used to assess changes in cortical language function. Voxel-based morphometry (VBM) was used to assess effects on regional grey matter (GM). LI analyses revealed a leftward shift in IFG activity after treatment. While left IFG activation increased, right IFG activation decreased. Changes in right to left IFG connectivity during covert verb generation also decreased after iTBS. Behavioral correlations revealed a negative relationship between changes in right IFG activation and improvements in fluency. While anatomical analyses did not reveal statistically significant changes in grey matter volume, the fMRI results provide evidence for changes in right and left IFG function after iTBS. The negative relationship between post-iTBS changes in right IFG activity during covert verb generation and improvements in fluency suggests that iTBS applied to residual left-hemispheric language areas may reduce contralateral responses related to language production and facilitate recruitment of residual language areas after stroke. PMID:26881111

Interhemispheric Plasticity following Intermittent Theta Burst Stimulation in Chronic Poststroke Aphasia.

PubMed

Griffis, Joseph C; Nenert, Rodolphe; Allendorfer, Jane B; Szaflarski, Jerzy P

2016-01-01

The effects of noninvasive neurostimulation on brain structure and function in chronic poststroke aphasia are poorly understood. We investigated the effects of intermittent theta burst stimulation (iTBS) applied to residual language-responsive cortex in chronic patients using functional and anatomical MRI data acquired before and after iTBS. Lateralization index (LI) analyses, along with comparisons of inferior frontal gyrus (IFG) activation and connectivity during covert verb generation, were used to assess changes in cortical language function. Voxel-based morphometry (VBM) was used to assess effects on regional grey matter (GM). LI analyses revealed a leftward shift in IFG activity after treatment. While left IFG activation increased, right IFG activation decreased. Changes in right to left IFG connectivity during covert verb generation also decreased after iTBS. Behavioral correlations revealed a negative relationship between changes in right IFG activation and improvements in fluency. While anatomical analyses did not reveal statistically significant changes in grey matter volume, the fMRI results provide evidence for changes in right and left IFG function after iTBS. The negative relationship between post-iTBS changes in right IFG activity during covert verb generation and improvements in fluency suggests that iTBS applied to residual left-hemispheric language areas may reduce contralateral responses related to language production and facilitate recruitment of residual language areas after stroke.

Effects of intermittent theta burst stimulation on spasticity after spinal cord injury.

PubMed

Nardone, Raffaele; Langthaler, Patrick B; Orioli, Andrea; Höller, Peter; Höller, Yvonne; Frey, Vanessa N; Brigo, Francesco; Trinka, Eugen

2017-01-01

Spasticity is a common disorder in patients with spinal cord injury (SCI). The aim of this study was to investigate whether intermittent theta burst stimulation (iTBS), a safe, non-invasive and well-tolerated protocol of excitatory repetitive transcranial magnetic stimulation (rTMS), is effective in modulating spasticity in SCI patients. In this randomized, double-blind, crossover, sham-controlled study, ten subjects with incomplete cervical or thoracic SCI received 10 days of daily sessions of real or sham iTBS. The H/M amplitude ratio of the Soleus H reflex, the amplitude of the motor evoked potentials (MEPs) at rest and during background contraction, as well as Modified Ashworth Scale (MAS) and the Spinal Cord Injury Assessment Tool for Spasticity (SCAT) were compared before and after the stimulation protocols. Patients receiving real iTBS showed significant increased resting and active MEPs amplitude and a significant reduction of the H/M amplitude ratio. In these patients also the MAS and SCAT scores were significantly reduced after treatment. These changes persisted up to 1 week after the end of the iTBS treatment, and were not observed under the sham-TBS condition. These findings suggest that iTBS may be a promising therapeutic tool for the spasticity in SCI patients.

Associative Recognition Memory Awareness Improved by Theta-Burst Stimulation of Frontopolar Cortex

PubMed Central

Ryals, Anthony J.; Rogers, Lynn M.; Gross, Evan Z.; Polnaszek, Kelly L.; Voss, Joel L.

2016-01-01

Neuroimaging and lesion studies have implicated specific prefrontal cortex locations in subjective memory awareness. Based on this evidence, a rostrocaudal organization has been proposed whereby increasingly anterior prefrontal regions are increasingly involved in memory awareness. We used theta-burst transcranial magnetic stimulation (TBS) to temporarily modulate dorsolateral versus frontopolar prefrontal cortex to test for distinct causal roles in memory awareness. In three sessions, participants received TBS bilaterally to frontopolar cortex, dorsolateral prefrontal cortex, or a control location prior to performing an associative-recognition task involving judgments of memory awareness. Objective memory performance (i.e., accuracy) did not differ based on stimulation location. In contrast, frontopolar stimulation significantly influenced several measures of memory awareness. During study, judgments of learning were more accurate such that lower ratings were given to items that were subsequently forgotten selectively following frontopolar TBS. Confidence ratings during test were also higher for correct trials following frontopolar TBS. Finally, trial-by-trial correspondence between overt performance and subjective awareness during study demonstrated a linear increase across control, dorsolateral, and frontopolar TBS locations, supporting a rostrocaudal hierarchy of prefrontal contributions to memory awareness. These findings indicate that frontopolar cortex contributes causally to memory awareness, which was improved selectively by anatomically targeted TBS. PMID:25577574

Resting state morphology predicts the effect of theta burst stimulation in false belief reasoning.

PubMed

Hartwright, Charlotte E; Hardwick, Robert M; Apperly, Ian A; Hansen, Peter C

2016-10-01

When required to represent a perspective that conflicts with one's own, functional magnetic resonance imaging (fMRI) suggests that the right ventrolateral prefrontal cortex (rvlPFC) supports the inhibition of that conflicting self-perspective. The present task dissociated inhibition of self-perspective from other executive control processes by contrasting belief reasoning-a cognitive state where the presence of conflicting perspectives was manipulated-with a conative desire state wherein no systematic conflict existed. Linear modeling was used to examine the effect of continuous theta burst stimulation (cTBS) to rvlPFC on participants' reaction times in belief and desire reasoning. It was anticipated that cTBS applied to rvlPFC would affect belief but not desire reasoning, by modulating activity in the Ventral Attention System (VAS). We further anticipated that this effect would be mediated by functional connectivity within this network, which was identified using resting state fMRI and an unbiased model-free approach. Simple reaction-time analysis failed to detect an effect of cTBS. However, by additionally modeling individual measures from within the stimulated network, the hypothesized effect of cTBS to belief (but, importantly, not desire) reasoning was demonstrated. Structural morphology within the stimulated region, rvlPFC, and right temporoparietal junction were demonstrated to underlie this effect. These data provide evidence that inconsistencies found with cTBS can be mediated by the composition of the functional network that is being stimulated. We suggest that the common claim that this network constitutes the VAS explains the effect of cTBS to this network on false belief reasoning. Hum Brain Mapp 37:3502-3514, 2016. © 2016 Wiley Periodicals, Inc. © 2016 Wiley Periodicals, Inc.

Effects of High Frequency Repeated Transcranial Magnetic Stimulation and Continuous Theta Burst Stimulation on Gambling Reinforcement, Delay Discounting, and Stroop Interference in Men with Pathological Gambling.

PubMed

Zack, Martin; Cho, Sang Soo; Parlee, Jennifer; Jacobs, Mark; Li, Crystal; Boileau, Isabelle; Strafella, Antonio

Repeated transcranial magnetic stimulation (rTMS) can reduce cravings and improve cognitive function in substance dependent individuals. Whether these benefits extend to individuals with pathological gambling (PG) is unclear. High-frequency rTMS of the medial prefrontal cortex (PFC) and continuous theta burst stimulation (cTBS) of the right dorsolateral PFC can reduce impulsive choice in healthy volunteers. This study aimed to assess the effects of these two protocols on gambling reinforcement and related responses in otherwise healthy men with PG. Participants (n = 9) underwent active or sham treatments at weekly intervals in a repeated-measures, Latin square design. Subjective and physiological responses were assessed before and after a 15-min slot machine game on each session. Delay discounting and Stroop tasks measured post-game impulsive choice and attentional control. Multivariate analysis of covariance, controlling for winnings on the slot machine under each treatment, found that rTMS reduced the post-game increase in Desire to Gamble; cTBS reduced amphetamine-like effects, and decreased diastolic blood pressure. Treatment had no significant univariate effects on bet size or speed of play in the game; however, a multivariate effect for the two indices suggested that treatment decreased behavioral activation. Neither treatment reduced impulsive choice, while both treatments increased Stroop interference. rTMS and cTBS can reduce gambling reinforcement in non-comorbid men with PG. Separate processes appear to mediate gambling reinforcement and betting behavior as against delay discounting and Stroop interference. Interventions that modify risky as opposed to temporal aspects of decision making may better predict therapeutic response in PG. Copyright © 2016 Elsevier Inc. All rights reserved.

Long lasting effects of daily theta burst rTMS sessions in the human amblyopic cortex.

PubMed

Clavagnier, Simon; Thompson, Benjamin; Hess, Robert F

2013-11-01

It has been reported that a single session of 1 Hz or 10 Hz repetitive transcranial magnetic stimulation (rTMS) of the visual cortex can temporarily improve contrast sensitivity in adults with amblyopia. More recently, continuous theta burst stimulation (cTBS) of the visual cortex has been found to improve contrast sensitivity in observers with normal vision. The aims of this study were to assess whether cTBS of the visual cortex could improve contrast sensitivity in adults with amblyopia and whether repeated sessions of cTBS would lead to more pronounced and/or longer lasting effects. cTBS was delivered to the visual cortex while patients viewed a high contrast stimulus with their non-amblyopic eye. This manipulation was designed to bias the effects of cTBS toward inputs from the amblyopic eye. Contrast sensitivity was measured before and after stimulation. The effects of one cTBS session were measured in five patients and the effects of five consecutive daily sessions were measured in four patients. Three patients were available for follow-up at varying intervals after the final session. cTBS improved amblyopic eye contrast sensitivity to high spatial frequencies (P < 0.05) and there was a cumulative improvement across sessions with asymptotic improvement occurring after 2 daily sessions of stimulation. The contrast sensitivity improvements were stable over a period of up to 78 days. These initial results in a small number of patients indicate the cTBS may allow for enduring visual function improvements in adults with amblyopia. Copyright © 2013 Elsevier Inc. All rights reserved.

Improvement of language functions in a chronic non-fluent post-stroke aphasic patient following bilateral sequential theta burst magnetic stimulation.

PubMed

Vuksanović, Jasmina; Jelić, Milan B; Milanović, Sladjan D; Kačar, Katarina; Konstantinović, Ljubica; Filipović, Saša R

2015-01-01

In chronic non-fluent aphasia patients, inhibition of the intact right hemisphere (RH), by transcranial magnetic stimulation (TMS) or similar methods, can induce improvement in language functions. The supposed mechanism behind this improvement is a release of preserved left hemisphere (LH) language networks from RH transcallosal inhibition. Direct stimulation of the damaged LH can sometimes bring similar results too. Therefore, we developed a novel treatment approach that combined direct LH (Broca's area (BA)) stimulation, by intermittent theta burst stimulation (TBS), with homologue RH area's inhibition, by continuous TBS. We present the results of application of 15 daily sessions of the described treatment approach in a right-handed patient with chronic post-stroke non-fluent aphasia. The intervention appeared to improve several language functions, but most notably propositional speech, semantic fluency, short-term verbal memory, and verbal learning. Bilateral TBS modulation of activation of the language-related areas of both hemispheres seems to be a feasible and promising way to induce recovery in chronic aphasic patients. Due to potentially cumulative physiological effects of bilateral stimulation, the improvements may be even greater than following unilateral interventions.

Galactic dual population models of gamma-ray bursts

NASA Technical Reports Server (NTRS)

Higdon, J. C.; Lingenfelter, R. E.

1994-01-01

We investigate in more detail the properties of two-population models for gamma-ray bursts in the galactic disk and halo. We calculate the gamma-ray burst statistical properties, mean value of (V/V(sub max)), mean value of cos Theta, and mean value of (sin(exp 2) b), as functions of the detection flux threshold for bursts coming from both Galactic disk and massive halo populations. We consider halo models inferred from the observational constraints on the large-scale Galactic structure and we compare the expected values of mean value of (V/V(sub max)), mean value of cos Theta, and mean value of (sin(exp 2) b), with those measured by Burst and Transient Source Experiment (BATSE) and other detectors. We find that the measured values are consistent with solely Galactic populations having a range of halo distributions, mixed with local disk distributions, which can account for as much as approximately 25% of the observed BATSE bursts. M31 does not contribute to these modeled bursts. We also demonstrate, contrary to recent arguments, that the size-frequency distributions of dual population models are quite consistent with the BATSE observations.

Intermittent theta-burst transcranial magnetic stimulation for treatment of Parkinson disease.

PubMed

Benninger, D H; Berman, B D; Houdayer, E; Pal, N; Luckenbaugh, D A; Schneider, L; Miranda, S; Hallett, M

2011-02-15

To investigate the safety and efficacy of intermittent theta-burst stimulation (iTBS) in the treatment of motor symptoms in Parkinson disease (PD). Progression of PD is characterized by the emergence of motor deficits, which eventually respond less to dopaminergic therapy and pose a therapeutic challenge. Repetitive transcranial magnetic stimulation (rTMS) has shown promising results in improving gait, a major cause of disability, and may provide a therapeutic alternative. iTBS is a novel type of rTMS that may be more efficacious than conventional rTMS. In this randomized, double-blind, sham-controlled study, we investigated safety and efficacy of iTBS of the motor and dorsolateral prefrontal cortices in 8 sessions over 2 weeks (evidence Class I). Assessment of safety and clinical efficacy over a 1-month period included timed tests of gait and bradykinesia, Unified Parkinson's Disease Rating Scale (UPDRS), and additional clinical, neuropsychological, and neurophysiologic measures. We investigated 26 patients with mild to moderate PD: 13 received iTBS and 13 sham stimulation. We found beneficial effects of iTBS on mood, but no improvement of gait, bradykinesia, UPDRS, and other measures. EEG/EMG monitoring recorded no pathologic increase of cortical excitability or epileptic activity. Few reported discomfort or pain and one experienced tinnitus during real stimulation. iTBS of the motor and prefrontal cortices appears safe and improves mood, but failed to improve motor performance and functional status in PD. This study provides Class I evidence that iTBS was not effective for gait, upper extremity bradykinesia, or other motor symptoms in PD.

Theta-rhythmic drive between medial septum and hippocampus in slow-wave sleep and microarousal: a Granger causality analysis.

PubMed

Kang, D; Ding, M; Topchiy, I; Shifflett, L; Kocsis, B

2015-11-01

Medial septum (MS) plays a critical role in controlling the electrical activity of the hippocampus (HIPP). In particular, theta-rhythmic burst firing of MS neurons is thought to drive lasting HIPP theta oscillations in rats during waking motor activity and REM sleep. Less is known about MS-HIPP interactions in nontheta states such as non-REM sleep, in which HIPP theta oscillations are absent but theta-rhythmic burst firing in subsets of MS neurons is preserved. The present study used Granger causality (GC) to examine the interaction patterns between MS and HIPP in slow-wave sleep (SWS, a nontheta state) and during its short interruptions called microarousals (a transient theta state). We found that during SWS, while GC revealed a unidirectional MS→HIPP influence over a wide frequency band (2-12 Hz, maximum: ∼8 Hz), there was no theta peak in the hippocampal power spectra, indicating a lack of theta activity in HIPP. In contrast, during microarousals, theta peaks were seen in both MS and HIPP power spectra and were accompanied by bidirectional GC with MS→HIPP and HIPP→MS theta drives being of equal magnitude. Thus GC in a nontheta state (SWS) vs. a theta state (microarousal) primarily differed in the level of HIPP→MS. The present findings suggest a modification of our understanding of the role of MS as the theta generator in two regards. First, a MS→HIPP theta drive does not necessarily induce theta field oscillations in the hippocampus, as found in SWS. Second, HIPP theta oscillations entail bidirectional theta-rhythmic interactions between MS and HIPP. Copyright © 2015 the American Physiological Society.

Targeted transcranial theta-burst stimulation alters fronto-insular network and prefrontal GABA.

PubMed

Iwabuchi, Sarina J; Raschke, Felix; Auer, Dorothee P; Liddle, Peter F; Lankappa, Sudheer T; Palaniyappan, Lena

2017-02-01

Repetitive transcranial magnetic stimulation (rTMS) has been used worldwide to treat depression. However, the exact physiological effects are not well understood. Pathophysiology of depression involves crucial limbic structures (e.g. insula), and it is still not clear if these structures can be modulated through neurostimulation of surface regions (e.g. dorsolateral prefrontal cortex, DLPFC), and whether rTMS-induced excitatory/inhibitory transmission alterations relate to fronto-limbic connectivity changes. Therefore, we sought proof-of-concept for neuromodulation of insula via prefrontal intermittent theta-burst stimulation (iTBS), and how these effects relate to GABAergic and glutamatergic systems. In 27 healthy controls, we employed a single-blind crossover randomised-controlled trial comparing placebo and real iTBS using resting-state functional MRI and magnetic resonance spectroscopy. Granger causal analysis was seeded from right anterior insula (rAI) to locate individualized left DLPFC rTMS targets. Effective connectivity coefficients within rAI and DLPFC were calculated, and levels of GABA/Glx, GABA/Cr and Glx/Cr in DLPFC and anterior cingulate voxels were also measured. ITBS significantly dampened fronto-insular connectivity and reduced GABA/Glx in both voxels. GABA/Glx had a significant mediating effect on iTBS-induced changes in DLPFC-to-rAI connectivity. We demonstrate modulation of the rAI using targeted iTBS through alterations of excitatory/inhibitory interactions, which may underlie therapeutic effects of rTMS, offering promise for rTMS treatment optimization. Copyright © 2016 Elsevier Inc. All rights reserved.

Effects of theta burst stimulation on motor cortex excitability in Parkinson's disease.

PubMed

Zamir, Orit; Gunraj, Carolyn; Ni, Zhen; Mazzella, Filomena; Chen, Robert

2012-04-01

Long-term potentiation (LTP)-like plasticity induced by paired associative stimulation (PAS) is impaired in Parkinson's disease (PD). Intermittent theta burst stimulation (iTBS) is another rTMS protocol that produces LTP-like effects and increases cortical excitability but its effects are independent of afferent input. The aim of the present study was to examine the effects of iTBS on cortical excitability in PD. iTBS was applied to the motor cortex in 10 healthy subjects and 12 PD patients ON and OFF dopaminergic medications. Motor evoked potential (MEP) before and for 60 min after iTBS were used to examine the changes in cortical excitability induced by iTBS. Paired-pulse TMS was used to test whether intracortical circuits, including short interval intracortical inhibition, intracortical facilitation, short and long latency afferent inhibition, were modulated by iTBS. After iTBS, the control, PD ON and OFF groups had similar increases in MEP amplitude compared to baseline over the course of 60 min. Changes in intracortical circuits induced by iTBS were also similar for the different groups. iTBS produced similar effects on cortical excitability for PD patients and controls. Spike-timing dependent heterosynaptic LTP-like plasticity induced by PAS may be more impaired in PD than frequency dependent homosynaptic LTP-like plasticity induced by iTBS. Copyright © 2011 International Federation of Clinical Neurophysiology. Published by Elsevier Ireland Ltd. All rights reserved.

Frontal and parietal theta burst TMS impairs working memory for visual-spatial conjunctions

PubMed Central

Morgan, Helen M.; Jackson, Margaret C.; van Koningsbruggen, Martijn G.; Shapiro, Kimron L.; Linden, David E.J.

2013-01-01

In tasks that selectively probe visual or spatial working memory (WM) frontal and posterior cortical areas show a segregation, with dorsal areas preferentially involved in spatial (e.g. location) WM and ventral areas in visual (e.g. object identity) WM. In a previous fMRI study [1], we showed that right parietal cortex (PC) was more active during WM for orientation, whereas left inferior frontal gyrus (IFG) was more active during colour WM. During WM for colour-orientation conjunctions, activity in these areas was intermediate to the level of activity for the single task preferred and non-preferred information. To examine whether these specialised areas play a critical role in coordinating visual and spatial WM to perform a conjunction task, we used theta burst transcranial magnetic stimulation (TMS) to induce a functional deficit. Compared to sham stimulation, TMS to right PC or left IFG selectively impaired WM for conjunctions but not single features. This is consistent with findings from visual search paradigms, in which frontal and parietal TMS selectively affects search for conjunctions compared to single features, and with combined TMS and functional imaging work suggesting that parietal and frontal regions are functionally coupled in tasks requiring integration of visual and spatial information. Our results thus elucidate mechanisms by which the brain coordinates spatially segregated processing streams and have implications beyond the field of working memory. PMID:22483548

Intermittent theta-burst transcranial magnetic stimulation for treatment of Parkinson disease

PubMed Central

Berman, B.D.; Houdayer, E.; Pal, N.; Luckenbaugh, D.A.; Schneider, L.; Miranda, S.; Hallett, M.

2011-01-01

Objective: To investigate the safety and efficacy of intermittent theta-burst stimulation (iTBS) in the treatment of motor symptoms in Parkinson disease (PD). Background: Progression of PD is characterized by the emergence of motor deficits, which eventually respond less to dopaminergic therapy and pose a therapeutic challenge. Repetitive transcranial magnetic stimulation (rTMS) has shown promising results in improving gait, a major cause of disability, and may provide a therapeutic alternative. iTBS is a novel type of rTMS that may be more efficacious than conventional rTMS. Methods: In this randomized, double-blind, sham-controlled study, we investigated safety and efficacy of iTBS of the motor and dorsolateral prefrontal cortices in 8 sessions over 2 weeks (evidence Class I). Assessment of safety and clinical efficacy over a 1-month period included timed tests of gait and bradykinesia, Unified Parkinson's Disease Rating Scale (UPDRS), and additional clinical, neuropsychological, and neurophysiologic measures. Results: We investigated 26 patients with mild to moderate PD: 13 received iTBS and 13 sham stimulation. We found beneficial effects of iTBS on mood, but no improvement of gait, bradykinesia, UPDRS, and other measures. EEG/EMG monitoring recorded no pathologic increase of cortical excitability or epileptic activity. Few reported discomfort or pain and one experienced tinnitus during real stimulation. Conclusion: iTBS of the motor and prefrontal cortices appears safe and improves mood, but failed to improve motor performance and functional status in PD. Classification of evidence: This study provides Class I evidence that iTBS was not effective for gait, upper extremity bradykinesia, or other motor symptoms in PD. PMID:21321333

Bilateral theta-burst magnetic stimulation influence on event-related brain potentials.

PubMed

Pinto, Nuno; Duarte, Marta; Gonçalves, Helena; Silva, Ricardo; Gama, Jorge; Pato, Maria Vaz

2018-01-01

Theta-burst stimulation (TBS) can be a non-invasive technique to modulate cognitive functions, with promising therapeutic potential, but with some contradictory results. Event related potentials are used as a marker of brain deterioration and can be used to evaluate TBS-related cognitive performance, but its use remains scant. This study aimed to study bilateral inhibitory and excitatory TBS effects upon neurocognitive performance of young healthy volunteers, using the auditory P300' results. Using a double-blind sham-controlled study, 51 healthy volunteers were randomly assigned to five different groups, two submitted to either excitatory (iTBS) or inhibitory (cTBS) stimulation over the left dorsolateral pre-frontal cortex (DLPFC), two other actively stimulated the right DLPFC and finally a sham stimulation group. An oddball based auditory P300 was performed just before a single session of iTBS, cTBS or sham stimulation and repeated immediately after. P300 mean latency comparison between the pre- and post-TBS stimulation stages revealed significantly faster post stimulation latencies only when iTBS was performed on the left hemisphere (p = 0.003). Right and left hemisphere cTBS significantly delayed P300 latency (right p = 0.026; left p = 0.000). Multiple comparisons for N200 showed slower latencies after iTBS over the right hemisphere. No significant difference was found in amplitude variation. TBS appears to effectively influence neural networking involved in P300 formation, but effects seem distinct for iTBS vs cTBS and for the right or the left hemisphere. P300 evoked potentials can be an effective and practical tool to evaluate transcranial magnetic stimulation related outcomes.

Current direction-dependent modulation of human hand motor function by intermittent theta burst stimulation (iTBS).

PubMed

Shirota, Yuichiro; Dhaka, Suman; Paulus, Walter; Sommer, Martin

2017-05-22

Transcranial magnetic stimulation (TMS) with different current directions can activate different sets of neurons. Current direction can also affect the results of repetitive TMS. To test the influence of uni-directional intermittent theta burst stimulation (iTBS) using different current directions, namely posteroanterior (PA) and anteroposterior (AP), on motor behaviour. In a cross-over design, PA- and AP-iTBS was applied over the left primary motor cortex in 19 healthy, right-handed volunteers. Performance of a finger-tapping task was recorded before and 0, 10, 20, and 30min after the iTBS. The task was conducted with the right and left hands separately at each time point. As a control, AP-iTBS with reduced intensity was applied to 14 participants in a separate session (AP weak condition). The finger-tapping count with the left hand was decreased after PA-iTBS. Neither AP- nor AP weak -iTBS altered the performance. Current direction had a significant impact on the after-effects of iTBS. Copyright © 2017 Elsevier B.V. All rights reserved.

Does a single session of theta-burst transcranial magnetic stimulation of inferior temporal cortex affect tinnitus perception?

PubMed

Poreisz, Csaba; Paulus, Walter; Moser, Tobias; Lang, Nicolas

2009-05-29

Cortical excitability changes as well as imbalances in excitatory and inhibitory circuits play a distinct pathophysiological role in chronic tinnitus. Repetitive transcranial magnetic stimulation (rTMS) over the temporoparietal cortex was recently introduced to modulate tinnitus perception. In the current study, the effect of theta-burst stimulation (TBS), a novel rTMS paradigm was investigated in chronic tinnitus. Twenty patients with chronic tinnitus completed the study. Tinnitus severity and loudness were monitored using a tinnitus questionnaire (TQ) and a visual analogue scale (VAS) before each session. Patients received 600 pulses of continuous TBS (cTBS), intermittent TBS (iTBS) and intermediate TBS (imTBS) over left inferior temporal cortex with an intensity of 80% of the individual active or resting motor threshold. Changes in subjective tinnitus perception were measured with a numerical rating scale (NRS). TBS applied to inferior temporal cortex appeared to be safe. Although half of the patients reported a slight attenuation of tinnitus perception, group analysis resulted in no significant difference when comparing the three specific types of TBS. Converting the NRS into the VAS allowed us to compare the time-course of aftereffects. Only cTBS resulted in a significant short-lasting improvement of the symptoms. In addition there was no significant difference when comparing the responder and non-responder groups regarding their anamnestic and audiological data. The TQ score correlated significantly with the VAS, lower loudness indicating less tinnitus distress. TBS does not offer a promising outcome for patients with tinnitus in the presented study.

Facilitation of speech repetition accuracy by theta burst stimulation of the left posterior inferior frontal gyrus.

PubMed

Restle, Julia; Murakami, Takenobu; Ziemann, Ulf

2012-07-01

The posterior part of the inferior frontal gyrus (pIFG) in the left hemisphere is thought to form part of the putative human mirror neuron system and is assigned a key role in mapping sensory perception onto motor action. Accordingly, the pIFG is involved in motor imitation of the observed actions of others but it is not known to what extent speech repetition of auditory-presented sentences is also a function of the pIFG. Here we applied fMRI-guided facilitating intermittent theta burst transcranial magnetic stimulation (iTBS), or depressant continuous TBS (cTBS), or intermediate TBS (imTBS) over the left pIFG of healthy subjects and compared speech repetition accuracy of foreign Japanese sentences before and after TBS. We found that repetition accuracy improved after iTBS and, to a lesser extent, after imTBS, but remained unchanged after cTBS. In a control experiment, iTBS was applied over the left middle occipital gyrus (MOG), a region not involved in sensorimotor processing of auditory-presented speech. Repetition accuracy remained unchanged after iTBS of MOG. We argue that the stimulation type and stimulation site specific facilitating effect of iTBS over left pIFG on speech repetition accuracy indicates a causal role of the human left-hemispheric pIFG in the translation of phonological perception to motor articulatory output for repetition of speech. This effect may prove useful in rehabilitation strategies that combine repetitive speech training with iTBS of the left pIFG in speech disorders, such as aphasia after cerebral stroke. Copyright © 2012 Elsevier Ltd. All rights reserved.

Intermittent theta-burst transcranial magnetic stimulation for autism spectrum disorder: an open-label pilot study.

PubMed

Abujadi, Caio; Croarkin, Paul E; Bellini, Bianca B; Brentani, Helena; Marcolin, Marco A

2017-12-11

Theta-burst stimulation (TBS) modulates synaptic plasticity more efficiently than standard repetitive transcranial magnetic stimulation delivery and may be a promising modality for neuropsychiatric disorders such as autism spectrum disorder (ASD). At present there are few effective interventions for prefrontal cortex dysfunction in ASD. We report on an open-label, pilot study of intermittent TBS (iTBS) to target executive function deficits and restricted, repetitive behaviors in male children and adolescents with ASD. Ten right-handed, male participants, aged 9-17 years with ASD were enrolled in an open-label trial of iTBS treatment. Fifteen sessions of neuronavigated iTBS at 100% motor threshold targeting the right dorsolateral prefrontal cortex were delivered over 3 weeks. Parent report scores on the Repetitive Behavior Scale Revised and the Yale-Brown Obsessive Compulsive Scale demonstrated improvements with iTBS treatment. Participants demonstrated improvements in perseverative errors on the Wisconsin Card Sorting Test and total time for the Stroop test. The iTBS treatments were well tolerated with no serious adverse effects. These preliminary results suggest that further controlled interventional studies of iTBS for ASD are warranted.

Priming theta burst stimulation enhances motor cortex plasticity in young but not old adults.

PubMed

Opie, George M; Vosnakis, Eleni; Ridding, Michael C; Ziemann, Ulf; Semmler, John G

Primary motor cortex neuroplasticity is reduced in old adults, which may contribute to the motor deficits commonly observed in the elderly. Previous research in young subjects suggests that the neuroplastic response can be enhanced using non-invasive brain stimulation (NIBS), with a larger plastic response observed following priming with both long-term potentiation (LTP) and depression (LTD)-like protocols. However, it is not known if priming stimulation can also modulate plasticity in older adults. To investigate if priming NIBS can be used to modulate motor cortical plasticity in old subjects. In 16 young (22.3 ± 1.0 years) and 16 old (70.2 ± 1.7 years) subjects, we investigated the response to intermittent theta burst stimulation (iTBS; LTP-like) when applied 10 min after sham stimulation, continuous TBS (cTBS; LTD-like) or an identical block of iTBS. Corticospinal plasticity was assessed by recording changes in motor evoked potential (MEP) amplitude. In young subjects, priming with cTBS (cTBS + iTBS) resulted in larger MEPs than priming with either iTBS (iTBS + iTBS; P = 0.001) or sham (sham + iTBS; P < 0.0001), while larger MEPs were seen following iTBS + iTBS than sham + iTBS (P < 0.0001). In old subjects, the response to iTBS + iTBS was not different to sham + iTBS (P > 0.9), whereas the response to cTBS + iTBS was reduced relative to iTBS + iTBS (P = 0.02) and sham + iTBS (P = 0.04). Priming TBS is ineffective for modifying M1 plasticity in older adults, which may limit the therapeutic use of priming stimulation in neurological conditions common in the elderly. Copyright © 2017 Elsevier Inc. All rights reserved.

Frontal and parietal theta burst TMS impairs working memory for visual-spatial conjunctions.

PubMed

Morgan, Helen M; Jackson, Margaret C; van Koningsbruggen, Martijn G; Shapiro, Kimron L; Linden, David E J

2013-03-01

In tasks that selectively probe visual or spatial working memory (WM) frontal and posterior cortical areas show a segregation, with dorsal areas preferentially involved in spatial (e.g. location) WM and ventral areas in visual (e.g. object identity) WM. In a previous fMRI study [1], we showed that right parietal cortex (PC) was more active during WM for orientation, whereas left inferior frontal gyrus (IFG) was more active during colour WM. During WM for colour-orientation conjunctions, activity in these areas was intermediate to the level of activity for the single task preferred and non-preferred information. To examine whether these specialised areas play a critical role in coordinating visual and spatial WM to perform a conjunction task, we used theta burst transcranial magnetic stimulation (TMS) to induce a functional deficit. Compared to sham stimulation, TMS to right PC or left IFG selectively impaired WM for conjunctions but not single features. This is consistent with findings from visual search paradigms, in which frontal and parietal TMS selectively affects search for conjunctions compared to single features, and with combined TMS and functional imaging work suggesting that parietal and frontal regions are functionally coupled in tasks requiring integration of visual and spatial information. Our results thus elucidate mechanisms by which the brain coordinates spatially segregated processing streams and have implications beyond the field of working memory. Copyright © 2013 Elsevier Inc. All rights reserved.

Plasticity Induced by Intermittent Theta Burst Stimulation in Bilateral Motor Cortices Is Not Altered in Older Adults

PubMed Central

Dickins, Daina S. E.; Sale, Martin V.

2015-01-01

Numerous studies have reported that plasticity induced in the motor cortex by transcranial magnetic stimulation (TMS) is attenuated in older adults. Those investigations, however, have focused solely on the stimulated hemisphere. Compared to young adults, older adults exhibit more widespread activity across bilateral motor cortices during the performance of unilateral motor tasks, suggesting that the manifestation of plasticity might also be altered. To address this question, twenty young (<35 years old) and older adults (>65 years) underwent intermittent theta burst stimulation (iTBS) whilst attending to the hand targeted by the plasticity-inducing procedure. The amplitude of motor evoked potentials (MEPs) elicited by single pulse TMS was used to quantify cortical excitability before and after iTBS. Individual responses to iTBS were highly variable, with half the participants showing an unexpected decrease in cortical excitability. Contrary to predictions, however, there were no age-related differences in the magnitude or manifestation of plasticity across bilateral motor cortices. The findings suggest that advancing age does not influence the capacity for, or manifestation of, plasticity induced by iTBS. PMID:26064691

The theta burst transcranial magnetic stimulation over the right PFC affects electroencephalogram oscillation during emotional processing.

PubMed

Cao, Dan; Li, Yingjie; Niznikiewicz, Margaret A; Tang, Yingying; Wang, Jijun

2018-03-02

Prefrontal cortex (PFC) plays an important role in emotional processing and therefore is one of the most frequently targeted regions for non-invasive brain stimulation such as repetitive transcranial magnetic stimulation (rTMS) in clinical trials, especially in the treatment of emotional disorders. As an approach to enhance the effectiveness of rTMS, continuous theta burst stimulation (cTBS) has been demonstrated to be efficient and safe. However, it is unclear how cTBS affects brain processes related to emotion. In particular, psychophysiological studies on the underlying neural mechanisms are sparse. In the current study, we investigated how the cTBS influences emotional processing when applied over the right PFC. Participants performed an emotion recognition Go/NoGo task, which asked them to select a GO response to either happy or fearful faces after the cTBS or after sham stimulation, while 64-channel electroencephalogram (EEG) was recorded. EEG oscillation was examined using event-related spectral perturbation (ERSP) in a time-interval between 170 and 310ms after face stimuli onset. In the sham group, we found a significant difference in the alpha band between response to happy and fearful stimuli but that effect did not exist in the cTBS group. The alpha band activity at the scalp was reduced suggesting the excitatory effect at the brain level. The beta and gamma band activity was not sensitive to cTBS intervention. The results of the current study demonstrate that cTBS does affect emotion processing and the effect is reflected in changes in EEG oscillations in the alpha band specifically. The results confirm the role of prefrontal cortex in emotion processing. We also suggest that this pattern of cTBS results elucidates mechanisms by which mood improvement in depressive disorders is achieved using cTBS intervention. Copyright © 2017 Elsevier Inc. All rights reserved.

Discrimination of speech and non-speech sounds following theta-burst stimulation of the motor cortex

PubMed Central

Rogers, Jack C.; Möttönen, Riikka; Boyles, Rowan; Watkins, Kate E.

2014-01-01

Perceiving speech engages parts of the motor system involved in speech production. The role of the motor cortex in speech perception has been demonstrated using low-frequency repetitive transcranial magnetic stimulation (rTMS) to suppress motor excitability in the lip representation and disrupt discrimination of lip-articulated speech sounds (Möttönen and Watkins, 2009). Another form of rTMS, continuous theta-burst stimulation (cTBS), can produce longer-lasting disruptive effects following a brief train of stimulation. We investigated the effects of cTBS on motor excitability and discrimination of speech and non-speech sounds. cTBS was applied for 40 s over either the hand or the lip representation of motor cortex. Motor-evoked potentials recorded from the lip and hand muscles in response to single pulses of TMS revealed no measurable change in motor excitability due to cTBS. This failure to replicate previous findings may reflect the unreliability of measurements of motor excitability related to inter-individual variability. We also measured the effects of cTBS on a listener’s ability to discriminate: (1) lip-articulated speech sounds from sounds not articulated by the lips (“ba” vs. “da”); (2) two speech sounds not articulated by the lips (“ga” vs. “da”); and (3) non-speech sounds produced by the hands (“claps” vs. “clicks”). Discrimination of lip-articulated speech sounds was impaired between 20 and 35 min after cTBS over the lip motor representation. Specifically, discrimination of across-category ba–da sounds presented with an 800-ms inter-stimulus interval was reduced to chance level performance. This effect was absent for speech sounds that do not require the lips for articulation and non-speech sounds. Stimulation over the hand motor representation did not affect discrimination of speech or non-speech sounds. These findings show that stimulation of the lip motor representation disrupts discrimination of speech sounds in an

Discrimination of speech and non-speech sounds following theta-burst stimulation of the motor cortex.

PubMed

Rogers, Jack C; Möttönen, Riikka; Boyles, Rowan; Watkins, Kate E

2014-01-01

Perceiving speech engages parts of the motor system involved in speech production. The role of the motor cortex in speech perception has been demonstrated using low-frequency repetitive transcranial magnetic stimulation (rTMS) to suppress motor excitability in the lip representation and disrupt discrimination of lip-articulated speech sounds (Möttönen and Watkins, 2009). Another form of rTMS, continuous theta-burst stimulation (cTBS), can produce longer-lasting disruptive effects following a brief train of stimulation. We investigated the effects of cTBS on motor excitability and discrimination of speech and non-speech sounds. cTBS was applied for 40 s over either the hand or the lip representation of motor cortex. Motor-evoked potentials recorded from the lip and hand muscles in response to single pulses of TMS revealed no measurable change in motor excitability due to cTBS. This failure to replicate previous findings may reflect the unreliability of measurements of motor excitability related to inter-individual variability. We also measured the effects of cTBS on a listener's ability to discriminate: (1) lip-articulated speech sounds from sounds not articulated by the lips ("ba" vs. "da"); (2) two speech sounds not articulated by the lips ("ga" vs. "da"); and (3) non-speech sounds produced by the hands ("claps" vs. "clicks"). Discrimination of lip-articulated speech sounds was impaired between 20 and 35 min after cTBS over the lip motor representation. Specifically, discrimination of across-category ba-da sounds presented with an 800-ms inter-stimulus interval was reduced to chance level performance. This effect was absent for speech sounds that do not require the lips for articulation and non-speech sounds. Stimulation over the hand motor representation did not affect discrimination of speech or non-speech sounds. These findings show that stimulation of the lip motor representation disrupts discrimination of speech sounds in an articulatory feature

Short theta burst stimulation to left frontal cortex prior to encoding enhances subsequent recognition memory

PubMed Central

Demeter, Elise; Mirdamadi, Jasmine L.; Meehan, Sean K.; Taylor, Stephan F.

2016-01-01

Deep semantic encoding of verbal stimuli can aid in later successful retrieval of those stimuli from long-term episodic memory. Evidence from numerous neuropsychological and neuroimaging experiments demonstrate regions in left prefrontal cortex, including left dorsolateral prefrontal cortex (DLPFC), are important for processes related to encoding. Here, we investigated the relationship between left DLPFC activity during encoding and successful subsequent memory with transcranial magnetic stimulation (TMS). In a pair of experiments using a 2-session within-subjects design, we stimulated either left DLPFC or a control region (Vertex) with a single 2-s train of short theta burst stimulation (sTBS) during a semantic encoding task and then gave participants a recognition memory test. We found that subsequent memory was enhanced on the day left DLPFC was stimulated, relative to the day Vertex was stimulated, and that DLPFC stimulation also increased participants’ confidence in their decisions during the recognition task. We also explored the time course of how long the effects of sTBS persisted. Our data suggest 2 s of sTBS to left DLPFC is capable of enhancing subsequent memory for items encoded up to 15 s following stimulation. Collectively, these data demonstrate sTBS is capable of enhancing long-term memory and provide evidence that TBS protocols are a potentially powerful tool for modulating cognitive function. PMID:27098772

The facilitatory effects of intermittent theta burst stimulation on corticospinal excitability are enhanced by nicotine.

PubMed

Swayne, Orlando B C; Teo, James T H; Greenwood, Richard J; Rothwell, John C

2009-08-01

Intermittent theta burst stimulation (iTBS) is increasingly widely used as a means of facilitating corticospinal excitability in the human primary motor cortex. This form of facilitatory plasticity within the stimulated cortex may occur by induction of long term potentiation (LTP). In animal models, agonists of nicotinic acetylcholine receptors have been shown to modulate or induce LTP; we thus sought to test whether nicotine may modulate the effects of iTBS on corticospinal excitability in humans. A double-blind placebo-controlled cross-over design study was conducted with 10 healthy subjects. iTBS was delivered 60min after subjects took either 4mg nicotine or placebo lozenges, and motor-evoked potentials (MEPs) were then recorded for 40min after the end of stimulation. In the placebo arm, iTBS produced an increase in the amplitudes of MEPs which lasted for 5min. In the nicotine arm, iTBS produced a more pronounced facilitation of MEPs that was still present at 40min. In a control experiment, nicotine alone had no effect on MEP amplitudes when given in the absence of iTBS. These data indicate that the effects of iTBS can be enhanced and prolonged by nicotine. These results are consistent with animal models demonstrating nicotinic modulation of facilitatory plasticity, and will be of interest to investigators seeking to enhance artificially induced changes in cortical excitability.

Agonist contraction during intermittent theta burst stimulation enhances motor cortical plasticity of the wrist flexors.

PubMed

Mirdamadi, J L; Suzuki, L Y; Meehan, S K

2015-03-30

Differences in cortical control across the different muscles of the upper limb may mitigate the efficacy of TMS interventions targeting a specific muscle. The current study sought to determine whether weak concurrent contraction during TMS could enhance the efficacy of intermittent theta burst stimulation (iTBS) in the forearm flexors. Motor evoked potentials (MEP) were elicited from the flexor (FCR) and extensor carpi radialis (ECR) motor cortical hotspots before and after iTBS over the FCR cortical hotspot. During iTBS the FCR was either relaxed (iTBS-Relax) or tonically contracted to 10% of maximum voluntary force (iTBS-Contract). iTBS-Relax failed to produce consistent potentiation of MEPFCR amplitude. Individuals with a relatively lower RMTFCR compared RMTECR demonstrated MEPFCR facilitation post-iTBS-Relax. Individuals with relatively higher RMTFCR demonstrated less facilitation and even suppression of MEPFCR amplitude. iTBS-Contract facilitated MEPFCR amplitude but only for MEPFCR evoked from the ECR hotspot. Interactions between overlapping cortical representations determine the efficacy of iTBS. Tonic contraction increases the efficacy of iTBS by enhancing the volume of the cortical representation. However, metaplastic effects may attenuate the enhancement of MEP gain at the motor cortical hotspot. The use of TMS as an adjunct to physical therapy should account for inter-muscle interactions when targeting muscles of the forearm. Copyright © 2015 Elsevier Ireland Ltd. All rights reserved.

Accelerated intermittent theta burst stimulation treatment in medication-resistant major depression: A fast road to remission?

PubMed

Duprat, Romain; Desmyter, Stefanie; Rudi, De Raedt; van Heeringen, Kees; Van den Abbeele, Dirk; Tandt, Hannelore; Bakic, Jasmina; Pourtois, Gilles; Dedoncker, Josefien; Vervaet, Myriam; Van Autreve, Sara; Lemmens, Gilbert M D; Baeken, Chris

2016-08-01

Although accelerated repetitive Transcranial Magnetic Stimulation (rTMS) paradigms and intermittent Theta-burst Stimulation (iTBS) may have the potency to result in superior clinical outcomes in Treatment Resistant Depression (TRD), accelerated iTBS treatment has not yet been studied. In this registered randomized double-blind sham-controlled crossover study, spread over four successive days, 50 TRD patients received 20 iTBS sessions applied to the left dorsolateral prefrontal cortex (DLPFC). The accelerated iTBS treatment procedure was found to be safe and resulted in immediate statistically significant decreases in depressive symptoms regardless of order/type of stimulation (real/sham). While only 28% of the patients showed a 50% reduction of their initial Hamilton Depression Rating Scale score at the end of the two-week procedure, this response rate increased to 38% when assessed two weeks after the end of the sham-controlled iTBS protocol, indicating delayed clinical effects. Importantly, 30% of the responders were considered in clinical remission. We found no demographic predictors for response. Our findings indicate that only four days of accelerated iTBS treatment applied to the left DLPFC in TRD may lead to meaningful clinical responses within two weeks post stimulation. Copyright © 2016 Elsevier B.V. All rights reserved.

Damage detection and locating using tone burst and continuous excitation modulation method

NASA Astrophysics Data System (ADS)

Li, Zheng; Wang, Zhi; Xiao, Li; Qu, Wenzhong

2014-03-01

Among structural health monitoring techniques, nonlinear ultrasonic spectroscopy methods are found to be effective diagnostic approach to detecting nonlinear damage such as fatigue crack, due to their sensitivity to incipient structural changes. In this paper, a nonlinear ultrasonic modulation method was developed to detect and locate a fatigue crack on an aluminum plate. The method is different with nonlinear wave modulation method which recognizes the modulation of low-frequency vibration and high-frequency ultrasonic wave; it recognizes the modulation of tone burst and high-frequency ultrasonic wave. In the experiment, a Hanning window modulated sinusoidal tone burst and a continuous sinusoidal excitation were simultaneously imposed on the PZT array which was bonded on the surface of an aluminum plate. The modulations of tone burst and continuous sinusoidal excitation was observed in different actuator-sensor paths, indicating the presence and location of fatigue crack. The results of experiments show that the proposed method is capable of detecting and locating the fatigue crack successfully.

Intermittent Theta Burst Stimulation Increases Reward Responsiveness in Individuals with Higher Hedonic Capacity.

PubMed

Duprat, Romain; De Raedt, Rudi; Wu, Guo-Rong; Baeken, Chris

2016-01-01

Repetitive transcranial magnetic stimulation over the left dorsolateral prefrontal cortex (DLPFC) has been documented to influence striatal and orbitofrontal dopaminergic activity implicated in reward processing. However, the exact neuropsychological mechanisms of how DLPFC stimulation may affect the reward system and how trait hedonic capacity may interact with the effects remains to be elucidated. In this sham-controlled study in healthy individuals, we investigated the effects of a single session of neuronavigated intermittent theta burst stimulation (iTBS) on reward responsiveness, as well as the influence of trait hedonic capacity. We used a randomized crossover single session iTBS design with an interval of 1 week. We assessed reward responsiveness using a rewarded probabilistic learning task and measured individual trait hedonic capacity (the ability to experience pleasure) with the temporal experience of pleasure scale questionnaire. As expected, the participants developed a response bias toward the most rewarded stimulus (rich stimulus). Reaction time and accuracy for the rich stimulus were respectively shorter and higher as compared to the less rewarded stimulus (lean stimulus). Active or sham stimulation did not seem to influence the outcome. However, when taking into account individual trait hedonic capacity, we found an early significant increase in the response bias only after active iTBS. The higher the individual's trait hedonic capacity, the more the response bias toward the rich stimulus increased after the active stimulation. When taking into account trait hedonic capacity, one active iTBS session over the left DLPFC improved reward responsiveness in healthy male participants with higher hedonic capacity. This suggests that individual differences in hedonic capacity may influence the effects of iTBS on the reward system.

The effect of stimulation interval on plasticity following repeated blocks of intermittent theta burst stimulation.

PubMed

Tse, Nga Yan; Goldsworthy, Mitchell R; Ridding, Michael C; Coxon, James P; Fitzgerald, Paul B; Fornito, Alex; Rogasch, Nigel C

2018-06-04

This study assessed the effect of interval duration on the direction and magnitude of changes in cortical excitability and inhibition when applying repeated blocks of intermittent theta burst stimulation (iTBS) over motor cortex. 15 participants received three different iTBS conditions on separate days: single iTBS; repeated iTBS with a 5 minute interval (iTBS-5-iTBS); and with a 15 minute interval (iTBS-15-iTBS). Changes in cortical excitability and short-interval cortical inhibition (SICI) were assessed via motor-evoked potentials (MEPs) before and up to 60 mins following stimulation. iTBS-15-iTBS increased MEP amplitude for up to 60 mins post stimulation, whereas iTBS-5-iTBS decreased MEP amplitude. In contrast, MEP amplitude was not altered by single iTBS. Despite the group level findings, only 53% of individuals showed facilitated MEPs following iTBS-15-iTBS, and only 40% inhibited MEPs following iTBS-5-iTBS. Modulation of SICI did not differ between conditions. These results suggest interval duration between spaced iTBS plays an important role in determining the direction of plasticity on excitatory, but not inhibitory circuits in human motor cortex. While repeated iTBS can increase the magnitude of MEP facilitation/inhibition in some individuals compared to single iTBS, the response to repeated iTBS appears variable between individuals in this small sample.

Remote effects of intermittent theta burst stimulation of the human pharyngeal motor system.

PubMed

Mistry, Satish; Michou, Emilia; Rothwell, John; Hamdy, Shaheen

2012-08-01

Intermittent theta burst stimulation (iTBS) is a novel, non-invasive form of brain stimulation capable of facilitating excitability of the human primary motor cortex with therapeutic potential in the treatment of neurological conditions, such as multiple sclerosis. The objectives of this study were to evaluate the effects of iTBS on cortical properties in the human pharyngeal motor system. Transcranial magnetic stimulation (TMS)-evoked pharyngeal motor responses were recorded via a swallowed intra-luminal catheter and used to assess motor cortical pathways to the pharynx in both hemispheres before and for up to 90 min after iTBS in 15 healthy adults (nine male/six female, 22-59 years old). Active/sham iTBS comprised 600 intermittent repetitive TMS pulses, delivered in a double-blind pseudo-randomised order over each hemisphere on separate days at least 1 week apart. Abductor pollicis brevis (APB) recordings were used as control. Hemispheric interventional data were compared with sham using repeated-measures anova. iTBS was delivered at an average intensity of 43±1% of stimulator output. Compared with sham, iTBS to the hemisphere with stronger pharyngeal projections induced increased responses only in the contralateral weaker projection 60-90 min post-iTBS (maximum 54±19%, P≤0.007), with no change in stronger hemisphere responses. By contrast, iTBS to weaker projections had no significant effects (P=0.39) on either hemisphere. APB responses similarly did not change significantly (P=0.78) across all study arms. We conclude that iTBS can induce remote changes in corticobulbar excitability. While further studies will clarify the extent of these changes, iTBS holds promise as a potential treatment for dysphagia after unilateral brain damage. © 2012 The Authors. European Journal of Neuroscience © 2012 Federation of European Neuroscience Societies and Blackwell Publishing Ltd.

Remote effects of intermittent theta burst stimulation of the human pharyngeal motor system

PubMed Central

Mistry, Satish; Michou, Emilia; Rothwell, John; Hamdy, Shaheen

2015-01-01

Intermittent theta burst stimulation (iTBS) is a novel, non-invasive form of brain stimulation capable of facilitating excitability of the human primary motor cortex with therapeutic potential in the treatment of neurological conditions, such as multiple sclerosis. The objectives of this study were to evaluate the effects of iTBS on cortical properties in the human pharyngeal motor system. Transcranial magnetic stimulation (TMS)-evoked pharyngeal motor responses were recorded via a swallowed intra-luminal catheter and used to assess motor cortical pathways to the pharynx in both hemispheres before and for up to 90 min after iTBS in 15 healthy adults (nine male/six female, 22–59 years old). Active/sham iTBS comprised 600 intermittent repetitive TMS pulses, delivered in a double-blind pseudo-randomised order over each hemisphere on separate days at least 1 week apart. Abductor pollicis brevis (APB) recordings were used as control. Hemispheric interventional data were compared with sham using repeated-measures anova. iTBS was delivered at an average intensity of 43 ± 1% of stimulator output. Compared with sham, iTBS to the hemisphere with stronger pharyngeal projections induced increased responses only in the contralateral weaker projection 60–90 min post-iTBS (maximum 54 ± 19%, P ≤ 0.007), with no change in stronger hemisphere responses. By contrast, iTBS to weaker projections had no significant effects (P = 0.39) on either hemisphere. APB responses similarly did not change significantly (P = 0.78) across all study arms. We conclude that iTBS can induce remote changes in corticobulbar excitability. While further studies will clarify the extent of these changes, iTBS holds promise as a potential treatment for dysphagia after unilateral brain damage. PMID:22640033

Investigating the Neural Basis of Theta Burst Stimulation to Premotor Cortex on Emotional Vocalization Perception: A Combined TMS-fMRI Study

PubMed Central

Agnew, Zarinah K.; Banissy, Michael J.; McGettigan, Carolyn; Walsh, Vincent; Scott, Sophie K.

2018-01-01

Previous studies have established a role for premotor cortex in the processing of auditory emotional vocalizations. Inhibitory continuous theta burst transcranial magnetic stimulation (cTBS) applied to right premotor cortex selectively increases the reaction time to a same-different task, implying a causal role for right ventral premotor cortex (PMv) in the processing of emotional sounds. However, little is known about the functional networks to which PMv contribute across the cortical hemispheres. In light of these data, the present study aimed to investigate how and where in the brain cTBS affects activity during the processing of auditory emotional vocalizations. Using functional neuroimaging, we report that inhibitory cTBS applied to the right premotor cortex (compared to vertex control site) results in three distinct response profiles: following stimulation of PMv, widespread frontoparietal cortices, including a site close to the target site, and parahippocampal gyrus displayed an increase in activity, whereas the reverse response profile was apparent in a set of midline structures and right IFG. A third response profile was seen in left supramarginal gyrus in which activity was greater post-stimulation at both stimulation sites. Finally, whilst previous studies have shown a condition specific behavioral effect following cTBS to premotor cortex, we did not find a condition specific neural change in BOLD response. These data demonstrate a complex relationship between cTBS and activity in widespread neural networks and are discussed in relation to both emotional processing and the neural basis of cTBS. PMID:29867402

STAR FORMATION IN ULTRA-FAINT DWARFS: CONTINUOUS OR SINGLE-AGE BURSTS?

DOE Office of Scientific and Technical Information (OSTI.GOV)

Webster, David; Bland-Hawthorn, Joss; Sutherland, Ralph, E-mail: d.webster@physics.usyd.edu.au

2015-01-30

We model the chemical evolution of six ultra-faint dwarfs (UFDs): Bootes I, Canes Venatici II, Coma Berenices, Hercules, Leo IV, and Ursa Major I based on their recently determined star formation histories. We show that two single-age bursts cannot explain the observed [α/Fe] versus [Fe/H] distribution in these galaxies and that some self-enrichment is required within the first burst. An alternative scenario is modeled, in which star formation is continuous except for short interruptions when one or more supernovae temporarily blow the dense gas out from the center of the system. This model allows for self-enrichment and can reproduce themore » chemical abundances of the UFDs in which the second burst is only a trace population. We conclude that the most likely star formation history is one or two extended periods of star formation, with the first burst lasting for at least 100 Myr. As found in earlier work, the observed properties of UFDs can be explained by formation at a low mass (M{sub vir}∼10{sup 7} M{sub ⊙}), rather than being stripped remnants of much larger systems.« less

A distinctive subpopulation of medial septal slow-firing neurons promote hippocampal activation and theta oscillations

PubMed Central

Lin, Shih-Chieh; Nicolelis, Miguel A. L.

2011-01-01

The medial septum-vertical limb of the diagonal band of Broca (MSvDB) is important for normal hippocampal functions and theta oscillations. Although many previous studies have focused on understanding how MSVDB neurons fire rhythmic bursts to pace hippocampal theta oscillations, a significant portion of MSVDB neurons are slow-firing and thus do not pace theta oscillations. The function of these MSVDB neurons, especially their role in modulating hippocampal activity, remains unknown. We recorded MSVDB neuronal ensembles in behaving rats, and identified a distinct physiologically homogeneous subpopulation of slow-firing neurons (overall firing <4 Hz) that shared three features: 1) much higher firing rate during rapid eye movement sleep than during slow-wave (SW) sleep; 2) temporary activation associated with transient arousals during SW sleep; 3) brief responses (latency 15∼30 ms) to auditory stimuli. Analysis of the fine temporal relationship of their spiking and theta oscillations showed that unlike the theta-pacing neurons, the firing of these “pro-arousal” neurons follows theta oscillations. However, their activity precedes short-term increases in hippocampal oscillation power in the theta and gamma range lasting for a few seconds. Together, these results suggest that these pro-arousal slow-firing MSvDB neurons may function collectively to promote hippocampal activation. PMID:21865435

Accelerated Intermittent Theta Burst Stimulation for Suicide Risk in Therapy-Resistant Depressed Patients: A Randomized, Sham-Controlled Trial.

PubMed

Desmyter, Stefanie; Duprat, Romain; Baeken, Chris; Van Autreve, Sara; Audenaert, Kurt; van Heeringen, Kees

2016-01-01

Objectives: We aimed to examine the effects and safety of accelerated intermittent Theta Burst Stimulation (iTBS) on suicide risk in a group of treatment-resistant unipolar depressed patients, using an extensive suicide assessment scale. Methods: In 50 therapy-resistant, antidepressant-free depressed patients, an intensive protocol of accelerated iTBS was applied over the left dorsolateral prefrontal cortex (DLPFC) in a randomized, sham-controlled crossover design. Patients received 20 iTBS sessions over 4 days. Suicide risk was assessed using the Beck Scale of Suicide ideation (BSI). Results: The iTBS protocol was safe and well tolerated. We observed a significant decrease of the BSI score over time, unrelated to active or sham stimulation and unrelated to depression-response. No worsening of suicidal ideation was observed. The effects of accelerated iTBS on mood and depression severity are reported in Duprat et al. (2016). The decrease in suicide risk lasted up to 1 month after baseline, even in depression non-responders. Conclusions: This accelerated iTBS protocol was safe. The observed significant decrease in suicide risk was unrelated to active or sham stimulation and unrelated to depression response. Further sham-controlled research in suicidal depressed patients is necessary. (Clinicaltrials.gov identifier: NCT01832805).

A Neocortical Delta Rhythm Facilitates Reciprocal Interlaminar Interactions via Nested Theta Rhythms

PubMed Central

Carracedo, Lucy M.; Kjeldsen, Henrik; Cunnington, Leonie; Jenkins, Alastair; Schofield, Ian; Cunningham, Mark O.; Davies, Ceri H.; Traub, Roger D.

2013-01-01

Delta oscillations (1–4 Hz) associate with deep sleep and are implicated in memory consolidation and replay of cortical responses elicited during wake states. A potent local generator has been characterized in thalamus, and local generators in neocortex have been suggested. Here we demonstrate that isolated rat neocortex generates delta rhythms in conditions mimicking the neuromodulatory state during deep sleep (low cholinergic and dopaminergic tone). The rhythm originated in an NMDA receptor-driven network of intrinsic bursting (IB) neurons in layer 5, activating a source of GABAB receptor-mediated inhibition. In contrast, regular spiking (RS) neurons in layer 5 generated theta-frequency outputs. In layer 2/3 principal cells, outputs from IB cells associated with IPSPs, whereas those from layer 5 RS neurons related to nested bursts of theta-frequency EPSPs. Both interlaminar spike and field correlations revealed a sequence of events whereby sparse spiking in layer 2/3 was partially reflected back from layer 5 on each delta period. We suggest that these reciprocal, interlaminar interactions may represent a “Helmholtz machine”-like process to control synaptic rescaling during deep sleep. PMID:23804097

Frontoparietal regions may become hypoactive after intermittent theta burst stimulation over the contralateral homologous cortex in humans.

PubMed

He, Xiaofei; Lan, Yue; Xu, Guangqing; Mao, Yurong; Chen, Zhenghong; Huang, Dongfeng; Pei, Zhong

2013-12-01

Brain injury to the dorsal frontoparietal networks, including the posterior parietal cortex (PPC) and dorsolateral prefrontal cortex (DLPFC), commonly cause spatial neglect. However, the interaction of these different regions in spatial attention is unclear. The aim of the present study was to investigate whether hyperexcitable neural networks can cause an abnormal interhemispheric inhibition. The Attention Network Test was used to test subjects following intermittent theta burst stimulation (iTBS) to the left or right frontoparietal networks. During the Attention Network Test task, all subjects tolerated each conditioning iTBS without any obvious iTBS-related side effects. Subjects receiving real-right-PPC iTBS showed significant enhancement in both alerting and orienting efficiency compared with those receiving either sham-right-PPC iTBS or real-left-PPC iTBS. Moreover, subjects exposed to the real-right-DLPFC iTBS exhibited significant improvement in both alerting and executive control efficiency, compared with those exposed to either the sham-right-DLPFC or real-left-DLPFC conditioning. Interestingly, compared with subjects exposed to the sham-left-PPC stimuli, subjects exposed to the real-left-PPC iTBS had a significant deficit in the orienting index. The present study indicates that iTBS over the contralateral homologous cortex may induce the hypoactivity of the right PPC through interhemispheric competition in spatial orienting attention.

Characterizing Oscillatory Bursts in Single-Trial EEG Data

NASA Technical Reports Server (NTRS)

Knuth, K. H.; Shah, A. S.; Lakatos, P.; Schroeder, C. E.

2004-01-01

Oscillatory bursts in numerous bands ranging from low (theta) to high frequencies (e.g., gamma) undoubtedly play an important role in cortical dynamics. Largely because of the inadequacy of existing analytic techniques. however, oscillatory bursts and their role in cortical processing remains poorly understood. To study oscillatory bursts effectively one must be able to isolate them and characterize them in the single trial. We describe a series of straightforward analysis techniques that produce useful indices of burst characteristics. First, stimulus-evoked responses are estimated using Differentially Variable Component Analysis (dVCA), and are subtracted from the single-trial. The single-trial characteristics of the evoked responses are stored to identify possible correlations with burst activity. Time-frequency (T-F), or wavelet, analyses are then applied to the single trial residuals. While T-F plots have been used in recent studies to identify and isolate bursts, we go further by fitting each burst in the T-F plot with a two-dimensional Gaussian. This provides a set of burst characteristics, such as, center time. burst duration, center frequency. frequency dispersion. and amplitude, all of which contribute to the accurate characterization of the individual burst. The burst phase can also be estimated. Burst characteristics can be quantified with several standard techniques (e.g.. histogramming and clustering), as well as Bayesian techniques (e.g., blocking) to allow a more parametric description analysis of the characteristics of oscillatory bursts, and the relationships of specific parameters to cortical excitability and stimulus integration.

The Impact of Single Session Intermittent Theta-Burst Stimulation over the Dorsolateral Prefrontal Cortex and Posterior Superior Temporal Sulcus on Adults with Autism Spectrum Disorder

PubMed Central

Ni, Hsing-Chang; Hung, June; Wu, Chen-Te; Wu, Yu-Yu; Chang, Chee-Jen; Chen, Rou-Shayn; Huang, Ying-Zu

2017-01-01

Intermittent theta burst stimulation (iTBS), a patterned repetitive transcranial magnetic stimulation, was applied over the posterior superior temporal sulcus (pSTS) or dorsolateral prefrontal cortex (DLPFC) to explore its impact in adults with autism spectrum disorder (ASD). Among 25 adults with ASD, 19 (mean age: 20.8 years) completed the randomized, sham-controlled, crossover trial. Every participant received iTBS over the bilateral DLPFC, bilateral pSTS and inion (as a sham control stimulation) in a randomized order with a 1-week interval. Neuropsychological functions were assessed using the Conners' Continuous Performance Test (CCPT) and the Wisconsin Card Sorting Test (WCST). Behavioral outcomes were measured using the Yale-Brown Obsessive Compulsive Scale (Y-BOCS) and the Social Responsiveness Scale (SRS). In comparison to that in the sham stimulation, the reaction time in the CCPT significantly decreased following single DLPFC session (p = 0.04, effect size = 0.71) while there were no significant differences in the CCPT and WCST following single pSTS session. Besides, the results in behavioral outcomes were inconsistent and had discrepancy between reports of parents and patients. In conclusion, a single session of iTBS over the bilateral DLPFC may alter the neuropsychological function in adults with ASD. The impacts of multiple-sessions iTBS over the DLPFC or pSTS deserve further investigations. PMID:28536500

The physiological basis of the effects of intermittent theta burst stimulation of the human motor cortex.

PubMed

Di Lazzaro, V; Pilato, F; Dileone, M; Profice, P; Oliviero, A; Mazzone, P; Insola, A; Ranieri, F; Meglio, M; Tonali, P A; Rothwell, J C

2008-08-15

Theta burst stimulation (TBS) is a form of repetitive transcranial magnetic stimulation (TMS). When applied to motor cortex it leads to after-effects on corticospinal and corticocortical excitability that may reflect LTP/LTD-like synaptic effects. An inhibitory form of TBS (continuous, cTBS) suppresses MEPs, and spinal epidural recordings show this is due to suppression of the I1 volley evoked by TMS. Here we investigate whether the excitatory form of TBS (intermittent, iTBS) affects the same I-wave circuitry. We recorded corticospinal volleys evoked by single pulse TMS of the motor cortex before and after iTBS in three conscious patients who had an electrode implanted in the cervical epidural space for the control of pain. As in healthy subjects, iTBS increased MEPs, and this was accompanied by a significant increase in the amplitude of later I-waves, but not the I1 wave. In two of the patients we tested the excitability of the contralateral cortex and found a significant suppression of the late I-waves. The extent of the changes varied between the three patients, as did their age. To investigate whether age might be a significant contributor to the variability we examined the effect of iTBS on MEPs in 18 healthy subjects. iTBS facilitated MEPs evoked by TMS of the conditioned hemisphere and suppressed MEPs evoked by stimulation of the contralateral hemisphere. There was a slight but non-significant decline in MEP facilitation with age, suggesting that interindividual variability was more important than age in explaining our data. In a subgroup of 10 subjects we found that iTBS had no effect on the duration of the ipsilateral silent period suggesting that the reduction in contralateral MEPs was not due to an increase in ongoing transcallosal inhibition. In conclusion, iTBS affects the excitability of excitatory synaptic inputs to pyramidal tract neurones that are recruited by a TMS pulse, both in the stimulated hemisphere and in the contralateral hemisphere

Decreased rhythmic GABAergic septal activity and memory-associated theta oscillations after hippocampal amyloid-beta pathology in the rat.

PubMed

Villette, Vincent; Poindessous-Jazat, Frédérique; Simon, Axelle; Léna, Clément; Roullot, Elodie; Bellessort, Brice; Epelbaum, Jacques; Dutar, Patrick; Stéphan, Aline

2010-08-18

The memory deficits associated with Alzheimer's disease result to a great extent from hippocampal network dysfunction. The coordination of this network relies on theta (symbol) oscillations generated in the medial septum. Here, we investigated in rats the impact of hippocampal amyloid beta (Abeta) injections on the physiological and cognitive functions that depend on the septohippocampal system. Hippocampal Abeta injections progressively impaired behavioral performances, the associated hippocampal theta power, and theta frequency response in a visuospatial recognition test. These alterations were associated with a specific reduction in the firing of the identified rhythmic bursting GABAergic neurons responsible for the propagation of the theta rhythm to the hippocampus, but without loss of medial septal neurons. Such results indicate that hippocampal Abeta treatment leads to a specific functional depression of inhibitory projection neurons of the medial septum, resulting in the functional impairment of the temporal network.

Theta EEG dynamics of the error-related negativity.

PubMed

Trujillo, Logan T; Allen, John J B

2007-03-01

The error-related negativity (ERN) is a response-locked brain potential (ERP) occurring 80-100ms following response errors. This report contrasts three views of the genesis of the ERN, testing the classic view that time-locked phasic bursts give rise to the ERN against the view that the ERN arises from a pure phase-resetting of ongoing theta (4-7Hz) EEG activity and the view that the ERN is generated - at least in part - by a phase-resetting and amplitude enhancement of ongoing theta EEG activity. Time-domain ERP analyses were augmented with time-frequency investigations of phase-locked and non-phase-locked spectral power, and inter-trial phase coherence (ITPC) computed from individual EEG trials, examining time courses and scalp topographies. Simulations based on the assumptions of the classic, pure phase-resetting, and phase-resetting plus enhancement views, using parameters from each subject's empirical data, were used to contrast the time-frequency findings that could be expected if one or more of these hypotheses adequately modeled the data. Error responses produced larger amplitude activity than correct responses in time-domain ERPs immediately following responses, as expected. Time-frequency analyses revealed that significant error-related post-response increases in total spectral power (phase- and non-phase-locked), phase-locked power, and ITPC were primarily restricted to the theta range, with this effect located over midfrontocentral sites, with a temporal distribution from approximately 150-200ms prior to the button press and persisting up to 400ms post-button press. The increase in non-phase-locked power (total power minus phase-locked power) was larger than phase-locked power, indicating that the bulk of the theta event-related dynamics were not phase-locked to response. Results of the simulations revealed a good fit for data simulated according to the phase-locking with amplitude enhancement perspective, and a poor fit for data simulated according to

Effects of intermittent theta-burst stimulation on practice-related changes in fast finger movements in healthy subjects.

PubMed

Agostino, Rocco; Iezzi, Ennio; Dinapoli, Loredana; Suppa, Antonio; Conte, Antonella; Berardelli, Alfredo

2008-08-01

In this paper we investigated the effects of intermittent theta-burst stimulation (iTBS) applied to the primary motor cortex on practice-related changes in motor performance. Seventeen healthy subjects underwent two experimental sessions, one testing real iTBS and the other testing sham iTBS. Before and after both iTBS sessions, the subjects practiced fast right index-finger abductions for a few minutes. As measures of cortical excitability we calculated resting motor threshold and motor-evoked potential amplitude. As measures of practice-related changes we evaluated the mean movement amplitude, peak velocity and peak acceleration values for each block. When subjects practiced the movement task, the three variables measuring practice-related changes improved to a similar extent during real and sham iTBS whereas cortical excitability increased only during real iTBS. In a further group of five healthy subjects we investigated the effect of real and sham iTBS on changes in motor performance after a longer task practice and found no significant changes in motor performance and retention after real and sham iTBS. From our results overall we conclude that in healthy subjects iTBS applied to the primary motor cortex leaves practice-related changes in an index finger abduction task unaffected. We suggest that iTBS delivered over the primary motor cortex is insufficient to alter motor performance because early motor learning probably engages a wide cortical and subcortical network.

Boosting the LTP-like plasticity effect of intermittent theta-burst stimulation using gamma transcranial alternating current stimulation.

PubMed

Guerra, Andrea; Suppa, Antonio; Bologna, Matteo; D'Onofrio, Valentina; Bianchini, Edoardo; Brown, Peter; Di Lazzaro, Vincenzo; Berardelli, Alfredo

2018-03-24

Transcranial Alternating Current Stimulation (tACS) consists in delivering electric current to the brain using an oscillatory pattern that may entrain the rhythmic activity of cortical neurons. When delivered at gamma frequency, tACS modulates motor performance and GABA-A-ergic interneuron activity. Since interneuronal discharges play a crucial role in brain plasticity phenomena, here we co-stimulated the primary motor cortex (M1) in healthy subjects by means of tACS during intermittent theta-burst stimulation (iTBS), a transcranial magnetic stimulation paradigm known to induce long-term potentiation (LTP)-like plasticity. We measured and compared motor evoked potentials before and after gamma, beta and sham tACS-iTBS. While we delivered gamma-tACS, we also measured short-interval intracortical inhibition (SICI) to detect any changes in GABA-A-ergic neurotransmission. Gamma, but not beta and sham tACS, significantly boosted and prolonged the iTBS-induced after-effects. Interestingly, the extent of the gamma tACS-iTBS after-effects correlated directly with SICI changes. Overall, our findings point to a link between gamma oscillations, interneuronal GABA-A-ergic activity and LTP-like plasticity in the human M1. Gamma tACS-iTBS co-stimulation might represent a new strategy to enhance and prolong responses to plasticity-inducing protocols, thereby lending itself to future applications in the neurorehabilitation setting. Copyright © 2018 Elsevier Inc. All rights reserved.

Theta and gamma coordination of hippocampal networks during waking and rapid eye movement sleep.

PubMed

Montgomery, Sean M; Sirota, Anton; Buzsáki, György

2008-06-25

Rapid eye movement (REM) sleep has been considered a paradoxical state because, despite the high behavioral threshold to arousing perturbations, gross physiological patterns in the forebrain resemble those of waking states. To understand how intrahippocampal networks interact during REM sleep, we used 96 site silicon probes to record from different hippocampal subregions and compared the patterns of activity during waking exploration and REM sleep. Dentate/CA3 theta and gamma synchrony was significantly higher during REM sleep compared with active waking. In contrast, gamma power in CA1 and CA3-CA1 gamma coherence showed significant decreases in REM sleep. Changes in unit firing rhythmicity and unit-field coherence specified the local generation of these patterns. Although these patterns of hippocampal network coordination characterized the more common tonic periods of REM sleep (approximately 95% of total REM), we also detected large phasic bursts of local field potential power in the dentate molecular layer that were accompanied by transient increases in the firing of dentate and CA1 neurons. In contrast to tonic REM periods, phasic REM epochs were characterized by higher theta and gamma synchrony among the dentate, CA3, and CA1 regions. These data suggest enhanced dentate processing, but limited CA3-CA1 coordination during tonic REM sleep. In contrast, phasic bursts of activity during REM sleep may provide windows of opportunity to synchronize the hippocampal trisynaptic loop and increase output to cortical targets. We hypothesize that tonic REM sleep may support off-line mnemonic processing, whereas phasic bursts of activity during REM may promote memory consolidation.

Reversed Effects of Intermittent Theta Burst Stimulation following Motor Training That Vary as a Function of Training-Induced Changes in Corticospinal Excitability

PubMed Central

Stöckel, Tino; Summers, Jeffery J.; Hinder, Mark R.

2015-01-01

Intermittent theta burst stimulation (iTBS) has the potential to enhance corticospinal excitability (CSE) and subsequent motor learning. However, the effects of iTBS following motor learning are unknown. The purpose of the present study was to explore the effect of iTBS on CSE and performance following motor learning. Therefore twenty-four healthy participants practiced a ballistic motor task for a total of 150 movements. iTBS was subsequently applied to the trained motor cortex (STIM group) or the vertex (SHAM group). Performance and CSE were assessed before motor learning and before and after iTBS. Training significantly increased performance and CSE in both groups. In STIM group participants, subsequent iTBS significantly reduced motor performance with smaller reductions in CSE. CSE changes as a result of motor learning were negatively correlated with both the CSE changes and performance changes as a result of iTBS. No significant effects of iTBS were found for SHAM group participants. We conclude that iTBS has the potential to degrade prior motor learning as a function of training-induced CSE changes. That means the expected LTP-like effects of iTBS are reversed following motor learning. PMID:26167305

Reversed Effects of Intermittent Theta Burst Stimulation following Motor Training That Vary as a Function of Training-Induced Changes in Corticospinal Excitability.

PubMed

Stöckel, Tino; Summers, Jeffery J; Hinder, Mark R

2015-01-01

Intermittent theta burst stimulation (iTBS) has the potential to enhance corticospinal excitability (CSE) and subsequent motor learning. However, the effects of iTBS following motor learning are unknown. The purpose of the present study was to explore the effect of iTBS on CSE and performance following motor learning. Therefore twenty-four healthy participants practiced a ballistic motor task for a total of 150 movements. iTBS was subsequently applied to the trained motor cortex (STIM group) or the vertex (SHAM group). Performance and CSE were assessed before motor learning and before and after iTBS. Training significantly increased performance and CSE in both groups. In STIM group participants, subsequent iTBS significantly reduced motor performance with smaller reductions in CSE. CSE changes as a result of motor learning were negatively correlated with both the CSE changes and performance changes as a result of iTBS. No significant effects of iTBS were found for SHAM group participants. We conclude that iTBS has the potential to degrade prior motor learning as a function of training-induced CSE changes. That means the expected LTP-like effects of iTBS are reversed following motor learning.

A theta rhythm in macaque visual cortex and its attentional modulation

PubMed Central

Spyropoulos, Georgios; Fries, Pascal

2018-01-01

Theta rhythms govern rodent sniffing and whisking, and human language processing. Human psychophysics suggests a role for theta also in visual attention. However, little is known about theta in visual areas and its attentional modulation. We used electrocorticography (ECoG) to record local field potentials (LFPs) simultaneously from areas V1, V2, V4, and TEO of two macaque monkeys performing a selective visual attention task. We found a ≈4-Hz theta rhythm within both the V1–V2 and the V4–TEO region, and theta synchronization between them, with a predominantly feedforward directed influence. ECoG coverage of large parts of these regions revealed a surprising spatial correspondence between theta and visually induced gamma. Furthermore, gamma power was modulated with theta phase. Selective attention to the respective visual stimulus strongly reduced these theta-rhythmic processes, leading to an unusually strong attention effect for V1. Microsaccades (MSs) were partly locked to theta. However, neuronal theta rhythms tended to be even more pronounced for epochs devoid of MSs. Thus, we find an MS-independent theta rhythm specific to visually driven parts of V1–V2, which rhythmically modulates local gamma and entrains V4–TEO, and which is strongly reduced by attention. We propose that the less theta-rhythmic and thereby more continuous processing of the attended stimulus serves the exploitation of this behaviorally most relevant information. The theta-rhythmic and thereby intermittent processing of the unattended stimulus likely reflects the ecologically important exploration of less relevant sources of information. PMID:29848632

Ketamine blocks bursting in the lateral habenula to rapidly relieve depression.

PubMed

Yang, Yan; Cui, Yihui; Sang, Kangning; Dong, Yiyan; Ni, Zheyi; Ma, Shuangshuang; Hu, Hailan

2018-02-14

The N-methyl-d-aspartate receptor (NMDAR) antagonist ketamine has attracted enormous interest in mental health research owing to its rapid antidepressant actions, but its mechanism of action has remained elusive. Here we show that blockade of NMDAR-dependent bursting activity in the 'anti-reward center', the lateral habenula (LHb), mediates the rapid antidepressant actions of ketamine in rat and mouse models of depression. LHb neurons show a significant increase in burst activity and theta-band synchronization in depressive-like animals, which is reversed by ketamine. Burst-evoking photostimulation of LHb drives behavioural despair and anhedonia. Pharmacology and modelling experiments reveal that LHb bursting requires both NMDARs and low-voltage-sensitive T-type calcium channels (T-VSCCs). Furthermore, local blockade of NMDAR or T-VSCCs in the LHb is sufficient to induce rapid antidepressant effects. Our results suggest a simple model whereby ketamine quickly elevates mood by blocking NMDAR-dependent bursting activity of LHb neurons to disinhibit downstream monoaminergic reward centres, and provide a framework for developing new rapid-acting antidepressants.

The effect of single and repeated prefrontal intermittent theta burst stimulation on cortical reactivity and working memory.

PubMed

Chung, Sung Wook; Rogasch, Nigel C; Hoy, Kate E; Fitzgerald, Paul B

With an increasing interest in the use of theta burst stimulation (TBS) as a cognitive enhancer and a potential therapeutic tool for psychiatric disorders, there is a need to identify optimal parameters of TBS in the prefrontal cortex. This study examined the effect of two blocks of prefrontal intermittent TBS (iTBS) on cortical reactivity and working memory performance, compared to one block of iTBS and sham stimulation. We hypothesized that greater cortical effects would be obtained with two blocks of iTBS. Eighteen healthy participants attended three experimental sessions and received either sham, one block or two blocks of iTBS with a 15-min interval. Concurrent transcranial magnetic stimulation with electroencephalography (TMS-EEG) was used to assess the change in cortical reactivity via TMS-evoked potentials. Working memory performance was assessed using the N-back task. Cluster-based permutation statistics and two-way ANOVAs were used for neurophysiological and behavioural data, respectively. Both single and two blocks of iTBS resulted in a significant increase in the amplitude of TMS-evoked N100 and P200. No significant differences were observed between active conditions in either neurophysiological changes or working memory performance, and both failed to improve working memory performance relative to sham. Two blocks of iTBS did not result in stronger measured effects as compared to one block of iTBS. Future studies are needed to identify the optimal stimulation pattern in order to achieve a desired effect. It is also important to establish the best approach in quantifying neuromodulatory effects targeting the prefrontal cortex. Copyright © 2018 Elsevier Inc. All rights reserved.

Modulation of inhibitory activity markers by intermittent theta-burst stimulation in rat cortex is NMDA-receptor dependent.

PubMed

Labedi, Adnan; Benali, Alia; Mix, Annika; Neubacher, Ute; Funke, Klaus

2014-01-01

Intermittent theta-burst stimulation (iTBS) applied via transcranial magnetic stimulation has been shown to increase cortical excitability in humans. In the rat brain it strongly reduced the number of neurons expressing the 67-kD isoform of the GABA-synthesizing enzyme glutamic acid decarboxylase (GAD67) and those expressing the calcium-binding proteins parvalbumin (PV) and calbindin (CB), specific markers of fast-spiking (FS) and non-FS inhibitory interneurons, respectively, an indication of modified cortical inhibition. Since iTBS effects in humans have been shown to be NMDA receptor sensitive, we wondered whether the iTBS-induced changes in the molecular phenotype of interneurons may be also sensitive to glutamatergic synaptic transmission mediated by NMDA receptors. In a sham-controlled fashion, five iTBS-blocks of 600 stimuli were applied to rats either lightly anesthetized by only urethane or by an additional low (subnarcotic) or high dose of the NMDA receptor antagonist ketamine before immunohistochemical analysis. iTBS reduced the number of neurons expressing GAD67, PV and CB. Except for CB, a low dose of ketamine partially prevented these effects while a higher dose almost completely abolished the iTBS effects. Our findings indicate that iTBS modulates the molecular, and likely also the electric, activity of cortical inhibitory interneurons and that the modulation of FS-type but less that of non-FS-type neurons is mediated by NMDA receptors. A combination of iTBS with pharmacological interventions affecting distinct receptor subtypes may thus offer options to enhance its selectivity in modulating the activity of distinct cell types and preventing others from being modulated. Copyright © 2014 Elsevier Inc. All rights reserved.

Behavioural Inhibition System (BIS) sensitivity differentiates EEG theta responses during goal conflict in a continuous monitoring task.

PubMed

Moore, Roger A; Mills, Matthew; Marshman, Paul; Corr, Philip J

2012-08-01

Previous research has revealed that EEG theta oscillations are affected during goal conflict processing. This is consistent with the behavioural inhibition system (BIS) theory of anxiety (Gray & McNaughton, 2000). However, studies have not attempted to relate these BIS-related theta effects to BIS personality measures. Confirmation of such an association would provide further support for BIS theory, especially as it relates to trait differences. EEG was measured (32 electrodes) from extreme groups (low/high trait BIS) engaged in a target detection task. Goal conflicts were introduced throughout the task. Results show that the two groups did not differ in behavioural performance. The major EEG result was that a stepwise discriminant analysis indicated discrimination by 6 variables derived from coherence and power, with 5 of the 6 in the theta range as predicted by BIS theory and one in the beta range. Also, across the whole sample, EEG theta coherence increased at a variety of regions during primary goal conflict and showed a general increase during response execution; EEG theta power, in contrast, was primarily reactive to response execution. This is the first study to reveal a three-way relationship between the induction of goal conflict, the induction of theta power and coherence, and differentiation by psychometrically-defined low/high BIS status. Copyright © 2012 Elsevier B.V. All rights reserved.

Rapid fading of optical afterglows as evidence for beaming in gamma-ray bursts

NASA Astrophysics Data System (ADS)

Huang, Y. F.; Dai, Z. G.; Lu, T.

2000-03-01

Based on the refined dynamical model proposed by us earlier for beamed gamma -ray burst ejecta, we carry out detailed numerical procedure to study those gamma -ray bursts with rapidly fading afterglows (i.e., ~ t-2). It is found that optical afterglows from GRB 970228, 980326, 980519, 990123, 990510 and 991208 can be satisfactorily fitted if the gamma -ray burst ejecta are highly collimated, with a universal initial half opening angle theta_0 ~ 0.1. The obvious light curve break observed in GRB 990123 is due to the relativistic-Newtonian transition of the beamed ejecta, and the rapidly fading optical afterglows come from synchrotron emissions during the mildly relativistic and non-relativistic phases. We strongly suggest that the rapid fading of afterglows currently observed in some gamma -ray bursts is evidence for beaming in these cases.

Effect of 30 Hz theta burst transcranial magnetic stimulation on the primary motor cortex in children and adolescents

PubMed Central

Pedapati, Ernest V.; Gilbert, Donald L.; Horn, Paul S.; Huddleston, David A.; Laue, Cameron S.; Shahana, Nasrin; Wu, Steve W.

2015-01-01

Fourteen healthy children (13.8 ± 2.2 years, range 10–16; M:F = 5:9) received 30 Hz intermittent theta burst transcranial magnetic stimulation (iTBS) with a stimulation intensity of 70% of resting motor threshold (RMT) with a total of 300 (iTBS300) pulses. All volunteers were free of neurologic, psychiatric and serious medical illnesses, not taking any neuropsychiatric medications, and did not have any contraindications to transcranial magnetic stimulation. Changes in the mean amplitudes of motor-evoked potentials from baseline following iTBS were expressed as a ratio and assessed from 1 to 10 min (BLOCK1) and 1–30 min (BLOCK2) using repeated-measures analysis of variance. All 14 subjects completed iTBS300 over the dominant primary motor cortex (M1) without any clinically reported adverse events. ITBS300 produced significant M1 facilitation [F(5, 65) = 3.165, p = 0.01] at BLOCK1 and trend level M1 facilitation at BLOCK2 [F(10, 129) = 1.69, p = 0.089]. Although iTBS300 (stimulation duration of 92 s at 70% RMT) delivered over M1 in typically developed children was well-tolerated and produced on average significant facilitatory changes in cortical excitability, the post-iTBS300 neurophysiologic response was variable in our small sample. ITBS300-induced changes may represent a potential neuroplastic biomarker in healthy children and those with neuro-genetic or neuro-psychiatric disorders. However, a larger sample size is needed to address safety and concerns of response variability. PMID:25762919

Learning alters theta amplitude, theta-gamma coupling and neuronal synchronization in inferotemporal cortex.

PubMed

Kendrick, Keith M; Zhan, Yang; Fischer, Hanno; Nicol, Alister U; Zhang, Xuejuan; Feng, Jianfeng

2011-06-09

How oscillatory brain rhythms alone, or in combination, influence cortical information processing to support learning has yet to be fully established. Local field potential and multi-unit neuronal activity recordings were made from 64-electrode arrays in the inferotemporal cortex of conscious sheep during and after visual discrimination learning of face or object pairs. A neural network model has been developed to simulate and aid functional interpretation of learning-evoked changes. Following learning the amplitude of theta (4-8 Hz), but not gamma (30-70 Hz) oscillations was increased, as was the ratio of theta to gamma. Over 75% of electrodes showed significant coupling between theta phase and gamma amplitude (theta-nested gamma). The strength of this coupling was also increased following learning and this was not simply a consequence of increased theta amplitude. Actual discrimination performance was significantly correlated with theta and theta-gamma coupling changes. Neuronal activity was phase-locked with theta but learning had no effect on firing rates or the magnitude or latencies of visual evoked potentials during stimuli. The neural network model developed showed that a combination of fast and slow inhibitory interneurons could generate theta-nested gamma. By increasing N-methyl-D-aspartate receptor sensitivity in the model similar changes were produced as in inferotemporal cortex after learning. The model showed that these changes could potentiate the firing of downstream neurons by a temporal desynchronization of excitatory neuron output without increasing the firing frequencies of the latter. This desynchronization effect was confirmed in IT neuronal activity following learning and its magnitude was correlated with discrimination performance. Face discrimination learning produces significant increases in both theta amplitude and the strength of theta-gamma coupling in the inferotemporal cortex which are correlated with behavioral performance. A network

Learning alters theta amplitude, theta-gamma coupling and neuronal synchronization in inferotemporal cortex

PubMed Central

2011-01-01

Background How oscillatory brain rhythms alone, or in combination, influence cortical information processing to support learning has yet to be fully established. Local field potential and multi-unit neuronal activity recordings were made from 64-electrode arrays in the inferotemporal cortex of conscious sheep during and after visual discrimination learning of face or object pairs. A neural network model has been developed to simulate and aid functional interpretation of learning-evoked changes. Results Following learning the amplitude of theta (4-8 Hz), but not gamma (30-70 Hz) oscillations was increased, as was the ratio of theta to gamma. Over 75% of electrodes showed significant coupling between theta phase and gamma amplitude (theta-nested gamma). The strength of this coupling was also increased following learning and this was not simply a consequence of increased theta amplitude. Actual discrimination performance was significantly correlated with theta and theta-gamma coupling changes. Neuronal activity was phase-locked with theta but learning had no effect on firing rates or the magnitude or latencies of visual evoked potentials during stimuli. The neural network model developed showed that a combination of fast and slow inhibitory interneurons could generate theta-nested gamma. By increasing N-methyl-D-aspartate receptor sensitivity in the model similar changes were produced as in inferotemporal cortex after learning. The model showed that these changes could potentiate the firing of downstream neurons by a temporal desynchronization of excitatory neuron output without increasing the firing frequencies of the latter. This desynchronization effect was confirmed in IT neuronal activity following learning and its magnitude was correlated with discrimination performance. Conclusions Face discrimination learning produces significant increases in both theta amplitude and the strength of theta-gamma coupling in the inferotemporal cortex which are correlated with

Adaptive [theta]-methods for pricing American options

NASA Astrophysics Data System (ADS)

Khaliq, Abdul Q. M.; Voss, David A.; Kazmi, Kamran

2008-12-01

We develop adaptive [theta]-methods for solving the Black-Scholes PDE for American options. By adding a small, continuous term, the Black-Scholes PDE becomes an advection-diffusion-reaction equation on a fixed spatial domain. Standard implementation of [theta]-methods would require a Newton-type iterative procedure at each time step thereby increasing the computational complexity of the methods. Our linearly implicit approach avoids such complications. We establish a general framework under which [theta]-methods satisfy a discrete version of the positivity constraint characteristic of American options, and numerically demonstrate the sensitivity of the constraint. The positivity results are established for the single-asset and independent two-asset models. In addition, we have incorporated and analyzed an adaptive time-step control strategy to increase the computational efficiency. Numerical experiments are presented for one- and two-asset American options, using adaptive exponential splitting for two-asset problems. The approach is compared with an iterative solution of the two-asset problem in terms of computational efficiency.

rTMS of the dorsomedial prefrontal cortex for major depression: safety, tolerability, effectiveness, and outcome predictors for 10 Hz versus intermittent theta-burst stimulation.

PubMed

Bakker, Nathan; Shahab, Saba; Giacobbe, Peter; Blumberger, Daniel M; Daskalakis, Zafiris J; Kennedy, Sidney H; Downar, Jonathan

2015-01-01

Conventional rTMS protocols for major depression commonly employ stimulation sessions lasting >30 min. However, recent studies have sought to improve costs, capacities, and outcomes by employing briefer protocols such as theta burst stimulation (iTBS). To compare safety, effectiveness, and outcome predictors for DMPFC-rTMS with 10 Hz (30 min) versus iTBS (6 min) protocols, in a large, naturalistic, retrospective case series. A chart review identified 185 patients with a medication-resistant major depressive episode who underwent 20-30 sessions of DMPFC-rTMS (10 Hz, n = 98; iTBS, n = 87) at a single Canadian clinic from 2011 to 2014. Clinical characteristics of 10 Hz and iTBS patients did not differ prior to treatment, aside from significantly higher age in iTBS patients. A total 7912 runs of DMPFC-rTMS (10 Hz, 4274; iTBS, 3638) were administered, without any seizures or other serious adverse events, and no significant differences in rates of premature discontinuation between groups. Dichotomous outcomes did not differ significantly between groups (Response/remission rates: Beck Depression Inventory-II: 10 Hz, 40.6%/29.2%; iTBS, 43.0%/31.0%. 17-item Hamilton Rating Scale for Depression: 10 Hz, 50.6%/38.5%; iTBS, 48.5%/27.9%). On continuous outcomes, there was no significant difference between groups in pre-treatment or post-treatment scores, or percent improvement on either measure. Mixed-effects modeling revealed no significant group-by-time interaction on either measure. Both 10 Hz and iTBS DMPFC-rTMS appear safe and tolerable at 120% resting motor threshold. The effectiveness of 6 min iTBS and 30 min 10 Hz protocols appears comparable. Randomized trials comparing 10 Hz to iTBS may be warranted. Copyright © 2015 The Authors. Published by Elsevier Inc. All rights reserved.

Theta Burst Stimulation in the Rehabilitation of the Upper Limb: A Semirandomized, Placebo-Controlled Trial in Chronic Stroke Patients

PubMed Central

Talelli, Penelope; Wallace, Amanda; Dileone, Michelle; Hoad, Damon; Cheeran, Binith; Oliver, Rupert; VandenBos, Mehdi; Hammerbeck, Ulrike; Barratt, Karen; Gillini, Cecilia; Musumeci, Gabriella; Boudrias, Marie-Hélène; Cloud, Geoffrey C.; Ball, Joanna; Marsden, Jonathan F.; Ward, Nicholas S.; Di Lazzaro, Vincenzo; Greenwood, Richard G.; Rothwell, John C.

2013-01-01

Background Noninvasive cortical stimulation could represent an add-on treatment to enhance motor recovery after stroke. However, its clinical value, including anticipated size and duration of the treatment effects, remains largely unknown. Objective The authors designed a small semi-randomized clinical trial to explore whether long-lasting clinically important gains can be achieved by adding theta burst stimulation (TBS), a form of repetitive transcranial magnetic stimulation (TMS), to a rehabilitation program for the hand. Methods A total of 41 chronic stroke patients received excitatory TBS to the ipsilesional hemisphere or inhibitory TBS to the contralesional hemisphere in 2 centers; each active group was compared with a group receiving sham TBS. TBS was followed by physical therapy for 10 working days. Patients and therapists were blinded to the type of TBS. Primary outcome measures (9-hole Peg Test [9HPT], Jebsen Taylor Test [JTT], and grip and pinch-grip dynamometry) were assessed 4, 30, and 90 days post treatment. The clinically important difference was defined as 10% of the maximum score. Results There were no differences between the active treatment and sham groups in any of the outcome measures. All patients achieved small sustainable improvements—9HPT, 5% of maximum (confidence interval [CI] = 3%-7%); JTT, 5.7% (CI = 3%-8%); and grip strength, 6% (CI = 2%-10%)—all below the defined clinically important level. Conclusions Cortical stimulation did not augment the gains from a late rehabilitation program. The effect size anticipated by the authors was overestimated. These results can improve the design of future work on therapeutic uses of TMS. PMID:22412171

Transcranial Magnetic Stimulation with Intermittent Theta Burst Stimulation Alters Corticospinal Output in Patients with Chronic Incomplete Spinal Cord Injury.

PubMed

Fassett, Hunter J; Turco, Claudia V; El-Sayes, Jenin; Lulic, Tea; Baker, Steve; Richardson, Brian; Nelson, Aimee J

2017-01-01

Intermittent theta burst stimulation (iTBS) is intended primarily to alter corticospinal excitability, creating an attractive opportunity to alter neural output following incomplete spinal cord injury (SCI). This study is the first to assess the effects of iTBS in SCI. Eight individuals with chronic incomplete SCI were studied. Sham or real iTBS was delivered (to each participant) over primary motor and somatosensory cortices in separate sessions. Motor-evoked potential (MEP) recruitment curves were obtained from the flexor carpi radialis muscle before and after iTBS. Results indicate similar responses for iTBS to both motor and somatosensory cortex and reduced MEPs in 56.25% and increased MEPs in 25% of instances. Sham stimulation exceeded real iTBS effects in the remaining 18.25%. It is our opinion that observing short-term neuroplasticity in corticospinal output in chronic SCI is an important advance and should be tested in future studies as an opportunity to improve function in this population. We emphasize the need to re-consider the importance of the direction of MEP change following a single session of iTBS since the relationship between MEP direction and motor function is unknown and multiple sessions of iTBS may yield very different directional results. Furthermore, we highlight the importance of including sham control in the experimental design. The fundamental point from this pilot research is that a single session of iTBS is often capable of creating short-term change in SCI. Future sham-controlled randomized trials may consider repeat iTBS sessions to promote long-term changes in corticospinal excitability.

Phase-locking of bursting neuronal firing to dominant LFP frequency components.

PubMed

Constantinou, Maria; Elijah, Daniel H; Squirrell, Daniel; Gigg, John; Montemurro, Marcelo A

2015-10-01

Neuronal firing in the hippocampal formation relative to the phase of local field potentials (LFP) has a key role in memory processing and spatial navigation. Firing can be in either tonic or burst mode. Although bursting neurons are common in the hippocampal formation, the characteristics of their locking to LFP phase are not completely understood. We investigated phase-locking properties of bursting neurons using simulations generated by a dual compartmental model of a pyramidal neuron adapted to match the bursting activity in the subiculum of a rat. The model was driven with stochastic input signals containing a power spectral profile consistent with physiologically relevant frequencies observed in LFP. The single spikes and spike bursts fired by the model were locked to a preferred phase of the predominant frequency band where there was a peak in the power of the driving signal. Moreover, the preferred phase of locking shifted with increasing burst size, providing evidence that LFP phase can be encoded by burst size. We also provide initial support for the model results by analysing example data of spontaneous LFP and spiking activity recorded from the subiculum of a single urethane-anaesthetised rat. Subicular neurons fired single spikes, two-spike bursts and larger bursts that locked to a preferred phase of either dominant slow oscillations or theta rhythms within the LFP, according to the model prediction. Both power-modulated phase-locking and gradual shift in the preferred phase of locking as a function of burst size suggest that neurons can use bursts to encode timing information contained in LFP phase into a spike-count code. Copyright © 2015 The Authors. Published by Elsevier Ireland Ltd.. All rights reserved.

A Nontriggered Burst Supplement to the BATSE Gamma-Ray Burst Catalogs

NASA Technical Reports Server (NTRS)

Kommers, Jefferson M.; Lewin, Walter H. G.; Kouveliotou, Chryssa; vanParadijs, Jan; Pendleton, Geoffrey N.; Meegan, Charles A.; Fishman, Gerald J.

2001-01-01

The Burst and Transient Source Experiment (BATSE) on the Compton Gamma Ray Observatory detects gamma-ray bursts (GRBs) with a real-time burst detection (or "trigger") system running onboard the spacecraft. Under some circumstances, however, a GRB may not activate the on-board burst trigger. For example, the burst may be too faint to exceed the on-board detection threshold, or it may occur while the on-board burst trigger is disabled for technical reasons. This paper describes a catalog of 873 "nontriggered" GRBs that were detected in a search of the archival continuous data from BATSE recorded between 1991 December 9.0 and 1997 December 17.0. For each burst, the catalog gives an estimated source direction, duration, peak flux, and fluence. Similar data are presented for 50 additional bursts of unknown origin that were detected in the 25-50 keV range; these events may represent the low-energy "tail" of the GRB spectral distribution. This catalog increases the number of GRBs detected with BATSE by 48% during the time period covered by the search.

A Non-Triggered Burst Supplement to the BATSE Gamma-Ray Burst Catalogs

NASA Technical Reports Server (NTRS)

Kommers, J.; Lewin, W. H.; Kouveliotou, C.; vanParadijs, J.; Pendleton, G. N.; Meegan, C. A.; Fishman, G. J.

1998-01-01

The Burst and Transient Source Experiment (BATSE) on the Compton Gamma Ray Observatory detects gamma-ray bursts (GRBs) with a real-time burst detection (or "trigger") system running onboard the spacecraft. Under some circumstances, however, a GRB may not activate the onboard burst trigger. For example, the burst may be too faint to exceed the onboard detection threshold, or it may occur while the onboard burst trigger is disabled for technical reasons. This paper is a catalog of such "non-triggered" GRBs that were detected in a search of the archival continuous data from BATSE. It lists 873 non-triggered bursts that were recorded between 1991 December 9.0 and 1997 December 17.0. For each burst, the catalog gives an estimated source direction, duration, peak flux, and fluence. Similar data are presented for 50 additional bursts of unknown origin that were detected in the 25-50 keV range; these events may represent the low-energy "tail" of the GRB spectral distribution. This catalog increases the number of GRBs detected with BATSE by 48% during the time period covered by the search.

Effects of Intermittent Theta Burst Stimulation on Manual Dexterity and Motor Imagery in Patients with Multiple Sclerosis: A Quasi-Experimental Controlled Study.

PubMed

Azin, Mahdieh; Zangiabadi, Nasser; Iranmanesh, Farhad; Baneshi, Mohammad Reza; Banihashem, Seyedshahab

2016-10-01

Intermittent theta burst stimulation (iTBS) is a repetitive transcranial magnetic stimulation (rTMS) protocol that influences cortical excitability and motor function recovery. This study aimed to investigate the effects of iTBS on manual dexterity and hand motor imagery in multiple sclerosis (MS) patients. Thirty-six MS patients were non-randomly assigned into sham (control) or iTBS groups. Then, iTBS was delivered to the primary motor cortex for ten days over two consecutive weeks. The patients' manual dexterity was assessed using the nine-hole peg test (9HPT) and the Box and Block Test (BBT), while the hand motor imagery was assessed with the hand mental rotation task (HMRT). iTBS group showed a reduction in the time required to complete the 9HPT (mean difference = -3.05, P = 0.002), and an increase in the number of blocks transferred in one minute in the BBT (mean difference = 8.9, P = 0.001) when compared to the control group. Furthermore, there was no significant difference between the two groups in terms of the reaction time (P = 0.761) and response accuracy rate (P = 0.482) in the HMRT. When iTBS was applied over the primary motor cortex, it significantly improved manual dexterity, but had no significant effect on the hand motor imagery ability in MS patients.

Effects of Intermittent Theta Burst Stimulation on Manual Dexterity and Motor Imagery in Patients with Multiple Sclerosis: A Quasi-Experimental Controlled Study

PubMed Central

Azin, Mahdieh; Zangiabadi, Nasser; Iranmanesh, Farhad; Baneshi, Mohammad Reza; Banihashem, Seyedshahab

2016-01-01

Background Intermittent theta burst stimulation (iTBS) is a repetitive transcranial magnetic stimulation (rTMS) protocol that influences cortical excitability and motor function recovery. Objectives This study aimed to investigate the effects of iTBS on manual dexterity and hand motor imagery in multiple sclerosis (MS) patients. Methods Thirty-six MS patients were non-randomly assigned into sham (control) or iTBS groups. Then, iTBS was delivered to the primary motor cortex for ten days over two consecutive weeks. The patients’ manual dexterity was assessed using the nine-hole peg test (9HPT) and the Box and Block Test (BBT), while the hand motor imagery was assessed with the hand mental rotation task (HMRT). Results iTBS group showed a reduction in the time required to complete the 9HPT (mean difference = -3.05, P = 0.002), and an increase in the number of blocks transferred in one minute in the BBT (mean difference = 8.9, P = 0.001) when compared to the control group. Furthermore, there was no significant difference between the two groups in terms of the reaction time (P = 0.761) and response accuracy rate (P = 0.482) in the HMRT. Conclusions When iTBS was applied over the primary motor cortex, it significantly improved manual dexterity, but had no significant effect on the hand motor imagery ability in MS patients. PMID:28180015

Interaction of motor training and intermittent theta burst stimulation in modulating motor cortical plasticity: influence of BDNF Val66Met polymorphism.

PubMed

Lee, Mina; Kim, Song E; Kim, Won Sup; Lee, Jungyeun; Yoo, Hye Kyung; Park, Kee-Duk; Choi, Kyoung-Gyu; Jeong, Seon-Yong; Kim, Byung Gon; Lee, Hyang Woon

2013-01-01

Cortical physiology in human motor cortex is influenced by behavioral motor training (MT) as well as repetitive transcranial magnetic stimulation protocol such as intermittent theta burst stimulation (iTBS). This study aimed to test whether MT and iTBS can interact with each other to produce additive changes in motor cortical physiology. We hypothesized that potential interaction between MT and iTBS would be dependent on BDNF Val66Met polymorphism, which is known to affect neuroplasticity in the human motor cortex. Eighty two healthy volunteers were genotyped for BDNF polymorphism. Thirty subjects were assigned for MT alone, 23 for iTBS alone, and 29 for MT + iTBS paradigms. TMS indices for cortical excitability and motor map areas were measured prior to and after each paradigm. MT alone significantly increased the motor cortical excitability and expanded the motor map areas. The iTBS alone paradigm also enhanced excitability and increased the motor map areas to a slightly greater extent than MT alone. A combination of MT and iTBS resulted in the largest increases in the cortical excitability, and the representational motor map expansion of MT + iTBS was significantly greater than MT or iTBS alone only in Val/Val genotype. As a result, the additive interaction between MT and iTBS was highly dependent on BDNF Val66Met polymorphism. Our results may have clinical relevance in designing rehabilitative strategies that combine therapeutic cortical stimulation and physical exercise for patients with motor disabilities.

Transcranial Magnetic Stimulation with Intermittent Theta Burst Stimulation Alters Corticospinal Output in Patients with Chronic Incomplete Spinal Cord Injury

PubMed Central

Fassett, Hunter J.; Turco, Claudia V.; El-Sayes, Jenin; Lulic, Tea; Baker, Steve; Richardson, Brian; Nelson, Aimee J.

2017-01-01

Intermittent theta burst stimulation (iTBS) is intended primarily to alter corticospinal excitability, creating an attractive opportunity to alter neural output following incomplete spinal cord injury (SCI). This study is the first to assess the effects of iTBS in SCI. Eight individuals with chronic incomplete SCI were studied. Sham or real iTBS was delivered (to each participant) over primary motor and somatosensory cortices in separate sessions. Motor-evoked potential (MEP) recruitment curves were obtained from the flexor carpi radialis muscle before and after iTBS. Results indicate similar responses for iTBS to both motor and somatosensory cortex and reduced MEPs in 56.25% and increased MEPs in 25% of instances. Sham stimulation exceeded real iTBS effects in the remaining 18.25%. It is our opinion that observing short-term neuroplasticity in corticospinal output in chronic SCI is an important advance and should be tested in future studies as an opportunity to improve function in this population. We emphasize the need to re-consider the importance of the direction of MEP change following a single session of iTBS since the relationship between MEP direction and motor function is unknown and multiple sessions of iTBS may yield very different directional results. Furthermore, we highlight the importance of including sham control in the experimental design. The fundamental point from this pilot research is that a single session of iTBS is often capable of creating short-term change in SCI. Future sham-controlled randomized trials may consider repeat iTBS sessions to promote long-term changes in corticospinal excitability. PMID:28824536

Impact of different intensities of intermittent theta burst stimulation on the cortical properties during TMS-EEG and working memory performance.

PubMed

Chung, Sung Wook; Rogasch, Nigel C; Hoy, Kate E; Sullivan, Caley M; Cash, Robin F H; Fitzgerald, Paul B

2018-02-01

Intermittent theta burst stimulation (iTBS) is a noninvasive brain stimulation technique capable of increasing cortical excitability beyond the stimulation period. Due to the rapid induction of modulatory effects, prefrontal application of iTBS is gaining popularity as a therapeutic tool for psychiatric disorders such as depression. In an attempt to increase efficacy, higher than conventional intensities are currently being applied. The assumption that this increases neuromodulatory may be mechanistically false for iTBS. This study examined the influence of intensity on the neurophysiological and behavioural effects of iTBS in the prefrontal cortex. Sixteen healthy participants received iTBS over prefrontal cortex at either 50, 75 or 100% resting motor threshold in separate sessions. Single-pulse TMS and concurrent electroencephalography (EEG) was used to assess changes in cortical reactivity measured as TMS-evoked potentials and oscillations. The n-back task was used to assess changes in working memory performance. The data can be summarised as an inverse U-shape relationship between intensity and iTBS plastic effects, where 75% iTBS yielded the largest neurophysiological changes. Improvement in reaction time in the 3-back task was supported by the change in alpha power, however, comparison between conditions revealed no significant differences. The assumption that higher intensity results in greater neuromodulatory effects may be false, at least in healthy individuals, and should be carefully considered for clinical populations. Neurophysiological changes associated with working memory following iTBS suggest functional relevance. However, the effects of different intensities on behavioural performance remain elusive in the present healthy sample. © 2017 Wiley Periodicals, Inc.

Intermittent Theta-Burst Stimulation of the Right Dorsolateral Prefrontal Cortex to Promote Metaphor Comprehension in Parkinson Disease: A Case Study.

PubMed

Tremblay, Christina; Monetta, Laura; Langlois, Mélanie; Schneider, Cyril

2016-01-01

This single-case research-designed study explored whether intermittent theta-burst stimulation (iTBS) of the right dorsolateral prefrontal cortex (DLPFC) could improve metaphor comprehension in people with Parkinson disease (PD) and language impairments. A right-handed participant with PD diagnosed 9 years ago, receiving long-term treatment with levodopa, and with metaphor comprehension impairment was recruited to undergo 10 sessions of sham stimulation (in 2wk), a washout period (6wk), and then 10 sessions of iTBS (in 2wk). Clinical scores of metaphor comprehension and motor evaluation (Unified Parkinson Disease Rating Scale part III) and transcranial magnetic stimulation to test the excitability of the primary motor cortex (M1) were used at baseline, postsham, post-iTBS, and at 3 follow-ups (8, 14, and 20wk post-iTBS). Metaphor comprehension was improved after iTBS, and the highest scores were obtained 8 weeks later (P=.01). This improvement was correlated with the increase of the right M1 excitability (r=-.86, P=.03) and with the decrease of transcallosal inhibition latency from the left to the right hemisphere (r=-.88, P=.02). Sham yielded no effect (P>.05). Administration of iTBS over the right DLPFC improved metaphor comprehension likely by a long-term influence on brain synaptic plasticity, including improvement of interhemispheric dialogue. More studies are warranted to confirm these findings in larger samples of participants with PD. Copyright © 2016 American Congress of Rehabilitation Medicine. Published by Elsevier Inc. All rights reserved.

Impaired Midline Theta Power and Connectivity During Proactive Cognitive Control in Schizophrenia.

PubMed

Ryman, Sephira G; Cavanagh, James F; Wertz, Christopher J; Shaff, Nicholas A; Dodd, Andrew B; Stevens, Brigitte; Ling, Josef; Yeo, Ronald A; Hanlon, Faith M; Bustillo, Juan; Stromberg, Shannon F; Lin, Denise S; Abrams, Swala; Mayer, Andrew R

2018-05-25

Disrupted proactive cognitive control, a form of early selection and active goal maintenance, is hypothesized to underlie the broad cognitive deficits observed in patients with schizophrenia (SPs). Current research suggests that the disrupted activation within and connectivity between regions of the cognitive control network contribute to disrupted proactive cognitive control; however, no study has examined these mechanisms using an AX Continuous Performance Test task in schizophrenia. Twenty-six SPs (17 male subjects; mean age 34.46 ± 8.77 years) and 28 healthy control participants (HCs; 16 male subjects; mean age 31.43 ± 7.23 years) underwent an electroencephalogram while performing the AX Continuous Performance Test. To examine the extent of activation and level of connectivity within the cognitive control network, power, intertrial phase clustering, and intersite phase clustering metrics were calculated and analyzed. SPs exhibited expected general decrements in behavioral performance relative to HCs and a more selective deficit in conditions requiring proactive cognitive control. Additionally, SPs exhibited deficits in midline theta power and connectivity during proactive cognitive control trials. Specifically, HCs exhibited significantly greater theta power for B cues relative to A cues, whereas SPs exhibited no significant differences between A- and B-cue theta power. Additionally, differential theta connectivity patterns were observed in SPs and HCs. Behavioral measures of proactive cognitive control predicted functional outcomes in SPs. This study suggests that low-frequency midline theta activity is selectively disrupted during proactive cognitive control in SPs. The disrupted midline theta activity may reflect a failure of SPs to proactively recruit cognitive control processes. Copyright © 2018 Society of Biological Psychiatry. Published by Elsevier Inc. All rights reserved.

Cortical theta wanes for language.

PubMed

Hermes, Dora; Miller, Kai J; Vansteensel, Mariska J; Edwards, Erik; Ferrier, Cyrille H; Bleichner, Martin G; van Rijen, Peter C; Aarnoutse, Erik J; Ramsey, Nick F

2014-01-15

The role of low frequency oscillations in language areas is not yet understood. Using ECoG in six human subjects, we studied whether different language regions show prominent power changes in a specific rhythm, in similar manner as the alpha rhythm shows the most prominent power changes in visual areas. Broca's area and temporal language areas were localized in individual subjects using fMRI. In these areas, the theta rhythm showed the most pronounced power changes and theta power decreased significantly during verb generation. To better understand the role of this language-related theta decrease, we then studied the interaction between low frequencies and local neuronal activity reflected in high frequencies. Amplitude-amplitude correlations showed that theta power correlated negatively with high frequency activity, specifically across verb generation trials. Phase-amplitude coupling showed that during control trials, high frequency power was coupled to theta phase, but this coupling decreased significantly during verb generation trials. These results suggest a dynamic interaction between the neuronal mechanisms underlying the theta rhythm and local neuronal activity in language areas. As visual areas show a pronounced alpha rhythm that may reflect pulsed inhibition, language regions show a pronounced theta rhythm with highly similar features. © 2013.

Hippocampal theta, gamma, and theta-gamma coupling: effects of aging, environmental change, and cholinergic activation

PubMed Central

Jacobson, Tara K.; Howe, Matthew D.; Schmidt, Brandy; Hinman, James R.; Escabí, Monty A.

2013-01-01

Hippocampal theta and gamma oscillations coordinate the timing of multiple inputs to hippocampal neurons and have been linked to information processing and the dynamics of encoding and retrieval. One major influence on hippocampal rhythmicity is from cholinergic afferents. In both humans and rodents, aging is linked to impairments in hippocampus-dependent function along with degradation of cholinergic function. Cholinomimetics can reverse some age-related memory impairments and modulate oscillations in the hippocampus. Therefore, one would expect corresponding changes in these oscillations and possible rescue with the cholinomimetic physostigmine. Hippocampal activity was recorded while animals explored a familiar or a novel maze configuration. Reexposure to a familiar situation resulted in minimal aging effects or changes in theta or gamma oscillations. In contrast, exploration of a novel maze configuration increased theta power; this was greater in adult than old animals, although the deficit was reversed with physostigmine. In contrast to the theta results, the effects of novelty, age, and/or physostigmine on gamma were relatively weak. Unrelated to the behavioral situation were an age-related decrease in the degree of theta-gamma coupling and the fact that physostigmine lowered the frequency of theta in both adult and old animals. The results indicate that age-related changes in gamma and theta modulation of gamma, while reflecting aging changes in hippocampal circuitry, seem less related to aging changes in information processing. In contrast, the data support a role for theta and the cholinergic system in encoding and that hippocampal aging is related to impaired encoding of new information. PMID:23303862

Intermittent Theta-Burst Transcranial Magnetic Stimulation Alters Electrical Properties of Fast-Spiking Neocortical Interneurons in an Age-Dependent Fashion

PubMed Central

Hoppenrath, Kathrin; Härtig, Wolfgang; Funke, Klaus

2016-01-01

Modulation of human cortical excitability by repetitive transcranial magnetic stimulation (rTMS) appears to be in part related to changed activity of inhibitory systems. Our own studies showed that intermittent theta-burst stimulation (iTBS) applied via rTMS to rat cortex primarily affects the parvalbumin-expressing (PV) fast-spiking interneurons (FSIs), evident via a strongly reduced PV expression. We further found the iTBS effect on PV to be age-dependent since no reduction in PV could be induced before the perineuronal nets (PNNs) of FSIs start to grow around postnatal day (PD) 30. To elucidate possible iTBS-induced changes in the electrical properties of FSIs and cortical network activity during cortical critical period, we performed ex vivo—in vitro whole-cell patch clamp recordings from pre-labeled FSIs in the current study. FSIs of verum iTBS-treated rats displayed a higher excitability than sham-treated controls at PD29–38, evident as higher rates of induced action potential firing at low current injections (100–200 pA) and a more depolarized resting membrane potential. This effect was absent in younger (PD26–28) and older animals (PD40–62). Slices of verum iTBS-treated rats further showed higher rates of spontaneous excitatory postsynaptic currents (sEPSCs). Based on these and previous findings we conclude that FSIs are particularly sensitive to TBS during early cortical development, when FSIs show an activity-driven step of maturation which is paralleled by intense growth of the PNNs and subsequent closure of the cortical critical period. Although to be proven further, rTMS may be a possible early intervention to compensate for hypo-activity related mal-development of cortical neuronal circuits. PMID:27065812

Intermittent Theta-Burst Transcranial Magnetic Stimulation Alters Electrical Properties of Fast-Spiking Neocortical Interneurons in an Age-Dependent Fashion.

PubMed

Hoppenrath, Kathrin; Härtig, Wolfgang; Funke, Klaus

2016-01-01

Modulation of human cortical excitability by repetitive transcranial magnetic stimulation (rTMS) appears to be in part related to changed activity of inhibitory systems. Our own studies showed that intermittent theta-burst stimulation (iTBS) applied via rTMS to rat cortex primarily affects the parvalbumin-expressing (PV) fast-spiking interneurons (FSIs), evident via a strongly reduced PV expression. We further found the iTBS effect on PV to be age-dependent since no reduction in PV could be induced before the perineuronal nets (PNNs) of FSIs start to grow around postnatal day (PD) 30. To elucidate possible iTBS-induced changes in the electrical properties of FSIs and cortical network activity during cortical critical period, we performed ex vivo-in vitro whole-cell patch clamp recordings from pre-labeled FSIs in the current study. FSIs of verum iTBS-treated rats displayed a higher excitability than sham-treated controls at PD29-38, evident as higher rates of induced action potential firing at low current injections (100-200 pA) and a more depolarized resting membrane potential. This effect was absent in younger (PD26-28) and older animals (PD40-62). Slices of verum iTBS-treated rats further showed higher rates of spontaneous excitatory postsynaptic currents (sEPSCs). Based on these and previous findings we conclude that FSIs are particularly sensitive to TBS during early cortical development, when FSIs show an activity-driven step of maturation which is paralleled by intense growth of the PNNs and subsequent closure of the cortical critical period. Although to be proven further, rTMS may be a possible early intervention to compensate for hypo-activity related mal-development of cortical neuronal circuits.

Interaction of Motor Training and Intermittent Theta Burst Stimulation in Modulating Motor Cortical Plasticity: Influence of BDNF Val66Met Polymorphism

PubMed Central

Lee, Mina; Kim, Song E.; Kim, Won Sup; Lee, Jungyeun; Yoo, Hye Kyung; Park, Kee-Duk; Choi, Kyoung-Gyu; Jeong, Seon-Yong; Kim, Byung Gon; Lee, Hyang Woon

2013-01-01

Cortical physiology in human motor cortex is influenced by behavioral motor training (MT) as well as repetitive transcranial magnetic stimulation protocol such as intermittent theta burst stimulation (iTBS). This study aimed to test whether MT and iTBS can interact with each other to produce additive changes in motor cortical physiology. We hypothesized that potential interaction between MT and iTBS would be dependent on BDNF Val66Met polymorphism, which is known to affect neuroplasticity in the human motor cortex. Eighty two healthy volunteers were genotyped for BDNF polymorphism. Thirty subjects were assigned for MT alone, 23 for iTBS alone, and 29 for MT + iTBS paradigms. TMS indices for cortical excitability and motor map areas were measured prior to and after each paradigm. MT alone significantly increased the motor cortical excitability and expanded the motor map areas. The iTBS alone paradigm also enhanced excitability and increased the motor map areas to a slightly greater extent than MT alone. A combination of MT and iTBS resulted in the largest increases in the cortical excitability, and the representational motor map expansion of MT + iTBS was significantly greater than MT or iTBS alone only in Val/Val genotype. As a result, the additive interaction between MT and iTBS was highly dependent on BDNF Val66Met polymorphism. Our results may have clinical relevance in designing rehabilitative strategies that combine therapeutic cortical stimulation and physical exercise for patients with motor disabilities. PMID:23451258

Alterations of the amplitude of low-frequency fluctuation in healthy subjects with theta-burst stimulation of the cortex of the suprahyoid muscles.

PubMed

Ruan, Xiuhang; Xu, Guangqing; Gao, Cuihua; Liu, Lingling; Liu, Yanli; Jiang, Lisheng; Chen, Xin; Yu, Shaode; Jiang, Xinqing; Lan, Yue; Wei, Xinhua

2017-12-04

Theta burst stimulation (TBS) has emerged as a promising tool for the treatment of swallowing disorders; however, the short-term after-effects of brain activation induced by TBS remain unknown. Here, we measured the changes in spontaneous brain activation using the amplitude of low-frequency fluctuation (ALFF) approach in subjects who underwent different TBS protocols. Sixty right-handed healthy participants (male, n=30; female, n=30; mean age=23.5y) were recruited in this study and randomly assigned to three groups that underwent three different TBS protocols. In group 1, continuous TBS (cTBS) was positioned on the left hemisphere of the suprahyoid muscle cortex. For group 2, intermittent TBS (iTBS) was placed on the left hemisphere of the suprahyoid muscle cortex. Group 3 underwent combined cTBS/iTBS protocols in which iTBS on the right hemisphere was performed immediately after completing cTBS on the left suprahyoid muscle cortex. Compared to pre-TBS, post-cTBS showed decreased ALFF in the anterior cingulate gyrus (BA 32); post-iTBS induced an increase in ALFF in the bilateral precuneus (BA 7); and post-cTBS/iTBS induced a decrease in ALFF in the brainstem, and resulted in increased ALFF in the middle cingulate gyrus (BA 24) as well as the left precentral gyrus (BA 6). Compared the effect of post-TBS protocols, increased ALFF was found in left posterior cerebellum lobe and left inferior parietal lobule (BA 40) (post-cTBS vs post-iTBS), and decreased ALFF exhibited in paracentral lobule (BA 4) (post-iTBS vs post-cTBS/iTBS). These findings indicate that multiple brain areas involved in swallowing regulation after stimulation of TBS over the suprahyoid muscles. cTBS induces decreased after-effects while iTBS results in increased after-effects on spontaneous brain activation. Moreover, iTBS can eliminate the after-effects of cTBS applied on the contralateral swallowing cortex and alter the activity of contralateral motor cortex and brainstem. Our findings provide a

Induced theta oscillations as biomarkers for alcoholism.

PubMed

Andrew, Colin; Fein, George

2010-03-01

Studies have suggested that non-phase-locked event-related oscillations (ERO) in target stimulus processing might provide biomarkers of alcoholism. This study investigates the discriminatory power of non-phase-locked oscillations in a group of long-term abstinent alcoholics (LTAAs) and non-alcoholic controls (NACs). EEGs were recorded from 48 LTAAs and 48 age and gender comparable NACs during rest with eyes open (EO) and during the performance of a three-condition visual target detection task. The data were analyzed to extract resting power, ERP amplitude and non-phase-locked ERO power measures. Data were analyzed using MANCOVA to determine the discriminatory power of induced theta ERO vs. resting theta power vs. P300 ERP measures in differentiating the LTAA and NAC groups. Both groups showed significantly more theta power in the pre-stimulus reference period of the task vs. the resting EO condition. The resting theta power did not discriminate the groups, while the LTAAs showed significantly less pre-stimulus theta power vs. the NACs. The LTAAs showed a significantly larger theta event-related synchronization (ERS) to the target stimulus vs. the NACs, even after accounting for pre-stimulus theta power levels. ERS to non-target stimuli showed smaller induced oscillations vs. target stimuli with no group differences. Alcohol use variables, a family history of alcohol problems, and the duration of alcohol abstinence were not associated with any theta power measures. While reference theta power in the task and induced theta oscillations to target stimuli both discriminate LTAAs and NACs, induced theta oscillations better discriminate the groups. Induced theta power measures are also more powerful and independent group discriminators than the P3b amplitude. Induced frontal theta oscillations promise to provide biomarkers of alcoholism that complement the well-established P300 ERP discriminators.

Theta rhythm-like bidirectional cycling dynamics of living neuronal networks in vitro.

PubMed

Gladkov, Arseniy; Grinchuk, Oleg; Pigareva, Yana; Mukhina, Irina; Kazantsev, Victor; Pimashkin, Alexey

2018-01-01

The phenomena of synchronization, rhythmogenesis and coherence observed in brain networks are believed to be a dynamic substrate for cognitive functions such as learning and memory. However, researchers are still debating whether the rhythmic activity emerges from the network morphology that developed during neurogenesis or as a result of neuronal dynamics achieved under certain conditions. In the present study, we observed self-organized spiking activity that converged to long, complex and rhythmically repeated superbursts in neural networks formed by mature hippocampal cultures with a high cellular density. The superburst lasted for tens of seconds and consisted of hundreds of short (50-100 ms) small bursts with a high spiking rate of 139.0 ± 78.6 Hz that is associated with high-frequency oscillations in the hippocampus. In turn, the bursting frequency represents a theta rhythm (11.2 ± 1.5 Hz). The distribution of spikes within the bursts was non-random, representing a set of well-defined spatio-temporal base patterns or motifs. The long superburst was classified into two types. Each type was associated with a unique direction of spike propagation and, hence, was encoded by a binary sequence with random switching between the two "functional" states. The precisely structured bidirectional rhythmic activity that developed in self-organizing cultured networks was quite similar to the activity observed in the in vivo experiments.

Traveling Theta Waves in the Human Hippocampus

PubMed Central

Zhang, Honghui

2015-01-01

The hippocampal theta oscillation is strongly correlated with behaviors such as memory and spatial navigation, but we do not understand its specific functional role. One hint of theta's function came from the discovery in rodents that theta oscillations are traveling waves that allow parts of the hippocampus to simultaneously exhibit separate oscillatory phases. Because hippocampal theta oscillations in humans have different properties compared with rodents, we examined these signals directly using multielectrode recordings from neurosurgical patients. Our findings confirm that human hippocampal theta oscillations are traveling waves, but also show that these oscillations appear at a broader range of frequencies compared with rodents. Human traveling waves showed a distinctive pattern of spatial propagation such that there is a consistent phase spread across the hippocampus regardless of the oscillations' frequency. This suggests that traveling theta oscillations are important functionally in humans because they coordinate phase coding throughout the hippocampus in a consistent manner. SIGNIFICANCE STATEMENT We show for the first time in humans that hippocampal theta oscillations are traveling waves, moving along the length of the hippocampus in a posterior–anterior direction. The existence of these traveling theta waves is important for understanding hippocampal neural coding because they cause neurons at separate positions in the hippocampus to experience different theta phases simultaneously. The theta phase that a neuron measures is a key factor in how that cell represents behavioral information. Therefore, the existence of traveling theta waves indicates that, to fully understand how a hippocampal neuron represents information, it is vital to also account for that cell's location in addition to conventional measures of neural activity. PMID:26354915

Bilateral primary motor cortex circuitry is modulated due to theta burst stimulation to left dorsal premotor cortex and bimanual training.

PubMed

Neva, Jason L; Vesia, Michael; Singh, Amaya M; Staines, W Richard

2015-08-27

Motor preparatory and execution activity is enhanced after a single session of bimanual visuomotor training (BMT). Recently, we have shown that increased primary motor cortex (M1) excitability occurs when BMT involves simultaneous activation of homologous muscles and these effects are enhanced when BMT is preceded by intermittent theta burst stimulation (iTBS) to the left dorsal premotor cortex (lPMd). The neural mechanisms underlying these modulations are unclear, but may include interhemispheric interactions between homologous M1s and connectivity with premotor regions. The purpose of this study was to investigate the possible intracortical and interhemispheric modulations of the extensor carpi radials (ECR) representation in M1 bilaterally due to: (1) BMT, (2) iTBS to lPMd, and (3) iTBS to lPMd followed by BMT. This study tests three related hypotheses: (1) BMT will enhance excitability within and between M1 bilaterally, (2) iTBS to lPMd will primarily enhance left M1 (lM1) excitability, and (3) the combination of these interventions will cause a greater enhancement of bilateral M1 excitability. We used single and paired-pulse transcranial magnetic stimulation (TMS) to quantify M1 circuitry bilaterally. The results demonstrate the neural mechanisms underlying the early markers of rapid functional plasticity associated with BMT and iTBS to lPMd primarily relate to modulations of long-interval inhibitory (i.e. GABAB-mediated) circuitry within and between M1s. This work provides novel insight into the underlying neural mechanisms involved in M1 excitability changes associated with BMT and iTBS to lPMd. Critically, this work may inform rehabilitation training and stimulation techniques that modulate cortical plasticity after brain injury. Copyright © 2015. Published by Elsevier B.V.

Dose-Dependent Effects of Theta Burst rTMS on Cortical Excitability and Resting-State Connectivity of the Human Motor System

PubMed Central

Nettekoven, Charlotte; Volz, Lukas J.; Kutscha, Martha; Pool, Eva-Maria; Rehme, Anne K.; Eickhoff, Simon B.; Fink, Gereon R.

2014-01-01

Theta burst stimulation (TBS), a specific protocol of repetitive transcranial magnetic stimulation (rTMS), induces changes in cortical excitability that last beyond stimulation. TBS-induced aftereffects, however, vary between subjects, and the mechanisms underlying these aftereffects to date remain poorly understood. Therefore, the purpose of this study was to investigate whether increasing the number of pulses of intermittent TBS (iTBS) (1) increases cortical excitability as measured by motor-evoked potentials (MEPs) and (2) alters functional connectivity measured using resting-state fMRI, in a dose-dependent manner. Sixteen healthy, human subjects received three serially applied iTBS blocks of 600 pulses over the primary motor cortex (M1 stimulation) and the parieto-occipital vertex (sham stimulation) to test for dose-dependent iTBS effects on cortical excitability and functional connectivity (four sessions in total). iTBS over M1 increased MEP amplitudes compared with sham stimulation after each stimulation block. Although the increase in MEP amplitudes did not differ between the first and second block of M1 stimulation, we observed a significant increase after three blocks (1800 pulses). Furthermore, iTBS enhanced resting-state functional connectivity between the stimulated M1 and premotor regions in both hemispheres. Functional connectivity between M1 and ipsilateral dorsal premotor cortex further increased dose-dependently after 1800 pulses of iTBS over M1. However, no correlation between changes in MEP amplitudes and functional connectivity was detected. In summary, our data show that increasing the number of iTBS stimulation blocks results in dose-dependent effects at the local level (cortical excitability) as well as at a systems level (functional connectivity) with a dose-dependent enhancement of dorsal premotor cortex-M1 connectivity. PMID:24828639

Modulation of left primary motor cortex excitability after bimanual training and intermittent theta burst stimulation to left dorsal premotor cortex.

PubMed

Neva, Jason L; Vesia, Michael; Singh, Amaya M; Staines, W Richard

2014-03-15

Bimanual visuomotor movement training (BMT) enhances the excitability of human preparatory premotor and primary motor (M1) cortices compared to unimanual movement. This occurs when BMT involves mirror symmetrical movements of both upper-limbs (in-phase) but not with non-symmetrical movements (anti-phase). The neural mechanisms mediating the effect of BMT is unclear, but may involve interhemispheric connections between homologous M1 representations as well as the dorsal premotor cortices (PMd). The purpose of this study is to assess how intermittent theta burst stimulation (iTBS) of the left PMd affects left M1 excitability, and the possible combined effects of iTBS to left PMd applied before a single session of BMT. Left M1 excitability was quantified using transcranial magnetic stimulation (TMS) in terms of both the amplitudes and spatial extent of motor evoked potentials (MEPs) for the extensor carpi radialis (ECR) before and multiple time points following (1) BMT, (2) iTBS to left PMd or (3) iTBS to left PMd and BMT. Although there was not a greater increase in either specific measure of M1 excitability due to the combination of the interventions, iTBS applied before BMT showed that both the spatial extent and global MEP amplitude for the ECR became larger in parallel, whereas the spatial extent was enhanced with BMT alone and global MEP amplitude was enhanced with iTBS to left PMd alone. These results suggest that the modulation of rapid functional M1 excitability associated with BMT and iTBS of the left PMd could operate under related early markers of neuro-plastic mechanisms, which may be expressed in concurrent and distinct patterns of M1 excitability. Critically, this work may guide rehabilitation training and stimulation techniques that modulate cortical excitability after brain injury. Copyright © 2013 Elsevier B.V. All rights reserved.

Dose-dependent effects of theta burst rTMS on cortical excitability and resting-state connectivity of the human motor system.

PubMed

Nettekoven, Charlotte; Volz, Lukas J; Kutscha, Martha; Pool, Eva-Maria; Rehme, Anne K; Eickhoff, Simon B; Fink, Gereon R; Grefkes, Christian

2014-05-14

Theta burst stimulation (TBS), a specific protocol of repetitive transcranial magnetic stimulation (rTMS), induces changes in cortical excitability that last beyond stimulation. TBS-induced aftereffects, however, vary between subjects, and the mechanisms underlying these aftereffects to date remain poorly understood. Therefore, the purpose of this study was to investigate whether increasing the number of pulses of intermittent TBS (iTBS) (1) increases cortical excitability as measured by motor-evoked potentials (MEPs) and (2) alters functional connectivity measured using resting-state fMRI, in a dose-dependent manner. Sixteen healthy, human subjects received three serially applied iTBS blocks of 600 pulses over the primary motor cortex (M1 stimulation) and the parieto-occipital vertex (sham stimulation) to test for dose-dependent iTBS effects on cortical excitability and functional connectivity (four sessions in total). iTBS over M1 increased MEP amplitudes compared with sham stimulation after each stimulation block. Although the increase in MEP amplitudes did not differ between the first and second block of M1 stimulation, we observed a significant increase after three blocks (1800 pulses). Furthermore, iTBS enhanced resting-state functional connectivity between the stimulated M1 and premotor regions in both hemispheres. Functional connectivity between M1 and ipsilateral dorsal premotor cortex further increased dose-dependently after 1800 pulses of iTBS over M1. However, no correlation between changes in MEP amplitudes and functional connectivity was detected. In summary, our data show that increasing the number of iTBS stimulation blocks results in dose-dependent effects at the local level (cortical excitability) as well as at a systems level (functional connectivity) with a dose-dependent enhancement of dorsal premotor cortex-M1 connectivity. Copyright © 2014 the authors 0270-6474/14/346849-11$15.00/0.

Enhanced motor skill acquisition in the non-dominant upper extremity using intermittent theta burst stimulation and transcranial direct current stimulation.

PubMed

Butts, Raymond J; Kolar, Melissa B; Newman-Norlund, Roger D

2014-01-01

Individuals suffering from motor impairments often require physical therapy (PT) to help improve their level of function. Previous investigations suggest that both intermittent theta burst stimulation (iTBS) and bihemispheric transcranial direct current stimulation (tDCS) may increase the speed and extent of motor learning/relearning. The purpose of the current study was to explore the feasibility and effectiveness of a novel, non-invasive brain stimulation approach that combined an iTBS primer, and bihemispheric stimulation coupled with motor training. We hypothesized that individuals exposed to this novel treatment would make greater functional improvements than individuals undergoing sham stimulation when tested immediately following, 24-h, and 7-days post-training. A total of 26 right-handed, healthy young adults were randomly assigned to either a treatment (n = 15) or control group (n = 12). iTBS (20 trains of 10 pulse triplets each delivered at 80% active motor threshold (AMT) / 50 Hz over 191.84 s) and bihemispheric tDCS (1.0 ma for 20 min) were used as a primer to, and in conjunction with, 20 min of motor training, respectively. Our primary outcome measure was performance on the Jebsen-Taylor Hand Function (JTHF) test. Participants tolerated the combined iTBS/bihemispheric stimulation treatment without complaint. While performance gains in the sham and stimulation group were not significant immediately after training, they were nearly significant 24-h post training (p = 0.055), and were significant at 7-days post training (p < 0.05). These results suggest that the combined iTBS/bihemispheric stimulation protocol is both feasible and effective. Future research should examine the mechanistic explanation of this approach as well as the potential of using this approach in clinical populations.

Characterizing the roles of alpha and theta oscillations in multisensory attention.

PubMed

Keller, Arielle S; Payne, Lisa; Sekuler, Robert

2017-05-01

Cortical alpha oscillations (8-13Hz) appear to play a role in suppressing distractions when just one sensory modality is being attended, but do they also contribute when attention is distributed over multiple sensory modalities? For an answer, we examined cortical oscillations in human subjects who were dividing attention between auditory and visual sequences. In Experiment 1, subjects performed an oddball task with auditory, visual, or simultaneous audiovisual sequences in separate blocks, while the electroencephalogram was recorded using high-density scalp electrodes. Alpha oscillations were present continuously over posterior regions while subjects were attending to auditory sequences. This supports the idea that the brain suppresses processing of visual input in order to advantage auditory processing. During a divided-attention audiovisual condition, an oddball (a rare, unusual stimulus) occurred in either the auditory or the visual domain, requiring that attention be divided between the two modalities. Fronto-central theta band (4-7Hz) activity was strongest in this audiovisual condition, when subjects monitored auditory and visual sequences simultaneously. Theta oscillations have been associated with both attention and with short-term memory. Experiment 2 sought to distinguish these possible roles of fronto-central theta activity during multisensory divided attention. Using a modified version of the oddball task from Experiment 1, Experiment 2 showed that differences in theta power among conditions were independent of short-term memory load. Ruling out theta's association with short-term memory, we conclude that fronto-central theta activity is likely a marker of multisensory divided attention. Copyright © 2017 Elsevier Ltd. All rights reserved.

Reduction in cortical parvalbumin expression due to intermittent theta-burst stimulation correlates with maturation of the perineuronal nets in young rats.

PubMed

Mix, Annika; Hoppenrath, Kathrin; Funke, Klaus

2015-01-01

We recently showed that intermittent theta-burst stimulation (iTBS) using transcranial magnetic stimulation strongly reduces the number of rat neocortical interneurons expressing glutamic acid decarboxylase 67 kDa (GAD67) and parvalbumin (PV), indicating changed activity of fast-spiking (FS) interneurons. In advance of in vitro studies intended to characterize changes in electrical properties of FS interneurons under these conditions, we tested whether the iTBS effect is age-dependent. Conscious Sprague-Dawley rats aged between 28 and 90 days received three blocks of iTBS at 15 min intervals. We found that iTBS-related reduction in PV+ cells was absent up to an age of 32 days, then gradually increased, and approached a maximum of about 40% reduction at an age of about 40 days. The relative number of cells expressing PV (PV+, 8-9%) did not change with age in sham-controls and also the increase in cortical c-Fos expression induced by iTBS was not principally age-dependent. However, a prominent growth of the perineuronal nets, typically surrounding the PV+ cells, exactly paralleled the increase in the iTBS effect. Based on these findings, we conclude that the functional development of the inhibitory network of PV+ interneurons with regard to intracortical synaptic connectivity is not sufficiently matured in rats younger than 35 d to enable activity-dependent modifications during iTBS. Outgrowth of the perineuronal nets and associated maturation of excitatory cortical inputs, as is characteristic for the critical cortical period, may take place before PV+ interneurons can be sufficiently activated via repetitive transcranial magnetic stimulation, allowing plastic changes of molecular phenotype and likely also synaptic plasticity. © 2014 Wiley Periodicals, Inc.

Three-dimensional ideal theta(1)/theta(2) angular transformer and its uses in fiber optics.

PubMed

Ning, X

1988-10-01

A 3-D ideal theta(1)/theta(2) angular transformer in nonimaging optics is introduced. The axially symmetric transformer, combining a portion of a hyperbolic concentrator with two lenses, transforms an input limited Lambertian over an angle theta(1) to an output limited Lambertian over an angle theta(2) without losing throughput. This is the first known transformer with such ideal properties. Results of computer simulations of a transformer with planospherical lenses are presented. Because of its ideal angular transforming property, the transformer offers an excellent solution for power launching and fiber-fiber coupling in optical fiber systems. In principle, the theoretical maximum coupling efficiency based on radiance conservation can be achieved with this transformer. Several conceptual designs of source-fiber and fiber-fiber couplers using the transformer are given.

BATSE Observations of the Large-Scale Isotropy of Gamma-Ray Bursts

NASA Technical Reports Server (NTRS)

Briggs, Michael S.; Paciesas, William S.; Pendleton, Geoffrey N.; Meegan, Charles A.; Fishman, Gerald J.; Horack, John M.; Brock, Martin N.; Kouveliotou, Chryssa; Hartmann, Dieter H.; Hakkila, Jon

1996-01-01

We use dipole and quadrupole statistics to test the large-scale isotropy of the first 1005 gamma-ray bursts observed by the Burst and Transient Source Experiment (BATSE). In addition to the entire sample of 1005 gamma-ray bursts, many subsets are examined. We use a variety of dipole and quadrupole statistics to search for Galactic and other predicted anisotropies and for anisotropies in a coordinate-system independent manner. We find the gamma-ray burst locations to be consistent with isotropy, e.g., for the total sample the observed Galactic dipole moment (cos theta) differs from the value predicted for isotropy by 0.9 sigma and the observed Galactic quadrupole moment (sin(exp 2) b - 1/3) by 0.3 sigma. We estimate for various models the anisotropies that could have been detected. If one-half of the locations were within 86 deg of the Galactic center, or within 28 deg of the Galactic plane, the ensuing dipole or quadrupole moment would have typically been detected at the 99% confidence level. We compare the observations with the dipole and quadrupole moments of various Galactic models. Several Galactic gamma-ray bursts models have moments within 2 sigma of the observations; most of the Galactic models proposed to date are no longer in acceptable agreement with the data. Although a spherical dark matter halo distribution could be consistent with the data, the required core radius is larger than the core radius of the dark matter halo used to explain the Galaxy's rotation curve. Gamma-ray bursts are much more isotropic than any observed Galactic population, strongly favoring but not requiring an origin at cosmological distances.

Theta oscillations promote temporal sequence learning.

PubMed

Crivelli-Decker, Jordan; Hsieh, Liang-Tien; Clarke, Alex; Ranganath, Charan

2018-05-17

Many theoretical models suggest that neural oscillations play a role in learning or retrieval of temporal sequences, but the extent to which oscillations support sequence representation remains unclear. To address this question, we used scalp electroencephalography (EEG) to examine oscillatory activity over learning of different object sequences. Participants made semantic decisions on each object as they were presented in a continuous stream. For three "Consistent" sequences, the order of the objects was always fixed. Activity during Consistent sequences was compared to "Random" sequences that consisted of the same objects presented in a different order on each repetition. Over the course of learning, participants made faster semantic decisions to objects in Consistent, as compared to objects in Random sequences. Thus, participants were able to use sequence knowledge to predict upcoming items in Consistent sequences. EEG analyses revealed decreased oscillatory power in the theta (4-7 Hz) band at frontal sites following decisions about objects in Consistent sequences, as compared with objects in Random sequences. The theta power difference between Consistent and Random only emerged in the second half of the task, as participants were more effectively able to predict items in Consistent sequences. Moreover, we found increases in parieto-occipital alpha (10-13 Hz) and beta (14-28 Hz) power during the pre-response period for objects in Consistent sequences, relative to objects in Random sequences. Linear mixed effects modeling revealed that single trial theta oscillations were related to reaction time for future objects in a sequence, whereas beta and alpha oscillations were only predictive of reaction time on the current trial. These results indicate that theta and alpha/beta activity preferentially relate to future and current events, respectively. More generally our findings highlight the importance of band-specific neural oscillations in the learning of

Intermittent Theta Burst Over M1 May Increase Peak Power of a Wingate Anaerobic Test and Prevent the Reduction of Voluntary Activation Measured with Transcranial Magnetic Stimulation

PubMed Central

Giboin, Louis-Solal; Thumm, Patrick; Bertschinger, Raphael; Gruber, Markus

2016-01-01

Despite the potential of repetitive transcranial magnetic stimulation (rTMS) to improve performances in patients suffering from motor neuronal afflictions, its effect on motor performance enhancement in healthy subjects during a specific sport task is still unknown. We hypothesized that after an intermittent theta burst (iTBS) treatment, performance during the Wingate Anaerobic Test (WAnT) will increase and supraspinal fatigue following the exercise will be lower in comparison to a control treatment. Ten subjects participated in two randomized experiments consisting of a WAnT 5 min after either an iTBS or a control treatment. We determined voluntary activation (VA) of the right knee extensors with TMS (VATMS) and with peripheral nerve stimulation (VAPNS) of the femoral nerve, before and after the WAnT. T-tests were applied to the WAnT results and a two way within subject ANOVA was applied to VA results. The iTBS treatment increased the peak power and the maximum pedalling cadence and suppressed the reduction of VATMS following the WAnT compared to the control treatment. No behavioral changes related to fatigue (mean power and fatigue index) were observed. These results indicate for the first time that iTBS could be used as a potential intervention to improve anaerobic performance in a sport specific task. PMID:27486391

Intermittent Theta Burst Over M1 May Increase Peak Power of a Wingate Anaerobic Test and Prevent the Reduction of Voluntary Activation Measured with Transcranial Magnetic Stimulation.

PubMed

Giboin, Louis-Solal; Thumm, Patrick; Bertschinger, Raphael; Gruber, Markus

2016-01-01

Despite the potential of repetitive transcranial magnetic stimulation (rTMS) to improve performances in patients suffering from motor neuronal afflictions, its effect on motor performance enhancement in healthy subjects during a specific sport task is still unknown. We hypothesized that after an intermittent theta burst (iTBS) treatment, performance during the Wingate Anaerobic Test (WAnT) will increase and supraspinal fatigue following the exercise will be lower in comparison to a control treatment. Ten subjects participated in two randomized experiments consisting of a WAnT 5 min after either an iTBS or a control treatment. We determined voluntary activation (VA) of the right knee extensors with TMS (VATMS) and with peripheral nerve stimulation (VAPNS) of the femoral nerve, before and after the WAnT. T-tests were applied to the WAnT results and a two way within subject ANOVA was applied to VA results. The iTBS treatment increased the peak power and the maximum pedalling cadence and suppressed the reduction of VATMS following the WAnT compared to the control treatment. No behavioral changes related to fatigue (mean power and fatigue index) were observed. These results indicate for the first time that iTBS could be used as a potential intervention to improve anaerobic performance in a sport specific task.

Theta-frequency phase-locking of single anterior cingulate cortex neurons and synchronization with the medial thalamus are modulated by visceral noxious stimulation in rats.

PubMed

Wang, J; Cao, B; Yu, T R; Jelfs, B; Yan, J; Chan, R H M; Li, Y

2015-07-09

The rodent anterior cingulate cortex (ACC) is critical for visceral pain and pain-related aversive response in chronic visceral hypersensitive (VH) state. Long-term potentiation (LTP), induced by theta burst stimulation (TBS) in the medial thalamus (MT)-ACC pathway, is blocked in VH rats. However, the neuronal intrinsic firing characteristics and the MT-ACC connectivity have not been investigated in visceral pain. Using repetitive distension of the colon and rectum (rCRD) as a sensitization paradigm, we have identified that the spontaneous firing rates of ACC neurons and the CRD-stimulated neuronal firings were increased after repetitive visceral noxious stimulation. This correlates with increases in visceral pain responses (visceromotor responses, VMRs). Two multichannel arrays of electrodes were implanted in the MT and ACC. Recordings were performed in free-moving rats before and after repeated CRD treatment. Power spectral density analysis showed that the local field potential (LFP) recorded in the ACC displayed increases in theta band power (4-10 Hz) that were modulated by rCRD. Neural spike activity in the ACC becomes synchronized with ongoing theta oscillations of LFP. Furthermore, cross correlation analysis showed augmented synchronization of thalamo-ACC theta band LFPs, which was consistent with an increase of neuronal communication between the two regions. In conclusion, these results reveal theta oscillations and theta-frequency phase-locking as prominent features of neural activity in the ACC and a candidate neural mechanism underlying acute visceral pain. Copyright © 2015 The Authors. Published by Elsevier Ltd.. All rights reserved.

Study of CP(N-1) theta-vacua by cluster simulation of SU(N) quantum spin ladders.

PubMed

Beard, B B; Pepe, M; Riederer, S; Wiese, U-J

2005-01-14

D-theory provides an alternative lattice regularization of the 2D CP(N-1) quantum field theory in which continuous classical fields emerge from the dimensional reduction of discrete SU(N) quantum spins. Spin ladders consisting of n transversely coupled spin chains lead to a CP(N-1) model with a vacuum angle theta=npi. In D-theory no sign problem arises and an efficient cluster algorithm is used to investigate theta-vacuum effects. At theta=pi there is a first order phase transition with spontaneous breaking of charge conjugation symmetry for CP(N-1) models with N>2.

Harnessing the power of theta: natural manipulations of cognitive performance during hippocampal theta-contingent eyeblink conditioning

PubMed Central

Hoffmann, Loren C.; Cicchese, Joseph J.; Berry, Stephen D.

2015-01-01

Neurobiological oscillations are regarded as essential to normal information processing, including coordination and timing of cells and assemblies within structures as well as in long feedback loops of distributed neural systems. The hippocampal theta rhythm is a 3–12 Hz oscillatory potential observed during cognitive processes ranging from spatial navigation to associative learning. The lower range, 3–7 Hz, can occur during immobility and depends upon the integrity of cholinergic forebrain systems. Several studies have shown that the amount of pre-training theta in the rabbit strongly predicts the acquisition rate of classical eyeblink conditioning and that impairment of this system substantially slows the rate of learning. Our lab has used a brain-computer interface (BCI) that delivers eyeblink conditioning trials contingent upon the explicit presence or absence of hippocampal theta. A behavioral benefit of theta-contingent training has been demonstrated in both delay and trace forms of the paradigm with a two- to four-fold increase in learning speed. This behavioral effect is accompanied by enhanced amplitude and synchrony of hippocampal local field potential (LFP)s, multi-unit excitation, and single-unit response patterns that depend on theta state. Additionally, training in the presence of hippocampal theta has led to increases in the salience of tone-induced unit firing patterns in the medial prefrontal cortex, followed by persistent multi-unit activity during the trace interval. In cerebellum, rhythmicity and precise synchrony of stimulus time-locked LFPs with those of hippocampus occur preferentially under the theta condition. Here we review these findings, integrate them into current models of hippocampal-dependent learning and suggest how improvement in our understanding of neurobiological oscillations is critical for theories of medial temporal lobe processes underlying intact and pathological learning. PMID:25918501

Harnessing the power of theta: natural manipulations of cognitive performance during hippocampal theta-contingent eyeblink conditioning.

PubMed

Hoffmann, Loren C; Cicchese, Joseph J; Berry, Stephen D

2015-01-01

Neurobiological oscillations are regarded as essential to normal information processing, including coordination and timing of cells and assemblies within structures as well as in long feedback loops of distributed neural systems. The hippocampal theta rhythm is a 3-12 Hz oscillatory potential observed during cognitive processes ranging from spatial navigation to associative learning. The lower range, 3-7 Hz, can occur during immobility and depends upon the integrity of cholinergic forebrain systems. Several studies have shown that the amount of pre-training theta in the rabbit strongly predicts the acquisition rate of classical eyeblink conditioning and that impairment of this system substantially slows the rate of learning. Our lab has used a brain-computer interface (BCI) that delivers eyeblink conditioning trials contingent upon the explicit presence or absence of hippocampal theta. A behavioral benefit of theta-contingent training has been demonstrated in both delay and trace forms of the paradigm with a two- to four-fold increase in learning speed. This behavioral effect is accompanied by enhanced amplitude and synchrony of hippocampal local field potential (LFP)s, multi-unit excitation, and single-unit response patterns that depend on theta state. Additionally, training in the presence of hippocampal theta has led to increases in the salience of tone-induced unit firing patterns in the medial prefrontal cortex, followed by persistent multi-unit activity during the trace interval. In cerebellum, rhythmicity and precise synchrony of stimulus time-locked LFPs with those of hippocampus occur preferentially under the theta condition. Here we review these findings, integrate them into current models of hippocampal-dependent learning and suggest how improvement in our understanding of neurobiological oscillations is critical for theories of medial temporal lobe processes underlying intact and pathological learning.

Heterogeneity in Short Gamma-Ray Bursts

NASA Technical Reports Server (NTRS)

Norris, Jay P.; Gehrels Neil; Scargle, Jeffrey D.

2011-01-01

We analyze the Swift/BAT sample of short gamma-ray bursts, using an objective Bayesian Block procedure to extract temporal descriptors of the bursts' initial pulse complexes (IPCs). The sample comprises 12 and 41 bursts with and without extended emission (EE) components, respectively. IPCs of non-EE bursts are dominated by single pulse structures, while EE bursts tend to have two or more pulse structures. The medians of characteristic timescales - durations, pulse structure widths, and peak intervals - for EE bursts are factors of approx 2-3 longer than for non-EE bursts. A trend previously reported by Hakkila and colleagues unifying long and short bursts - the anti-correlation of pulse intensity and width - continues in the two short burst groups, with non-EE bursts extending to more intense, narrower pulses. In addition we find that preceding and succeeding pulse intensities are anti-correlated with pulse interval. We also examine the short burst X-ray afterglows as observed by the Swift/XRT. The median flux of the initial XRT detections for EE bursts (approx 6 X 10(exp -10) erg / sq cm/ s) is approx > 20 x brighter than for non-EE bursts, and the median X-ray afterglow duration for EE bursts (approx 60,000 s) is approx 30 x longer than for non-EE bursts. The tendency for EE bursts toward longer prompt-emission timescales and higher initial X-ray afterglow fluxes implies larger energy injections powering the afterglows. The longer-lasting X-ray afterglows of EE bursts may suggest that a significant fraction explode into more dense environments than non-EE bursts, or that the sometimes-dominant EE component efficiently p()wers the afterglow. Combined, these results favor different progenitors for EE and non-EE short bursts.

Cholinergic Blockade Reduces Theta-Gamma Phase Amplitude Coupling and Speed Modulation of Theta Frequency Consistent with Behavioral Effects on Encoding

PubMed Central

Gillet, Shea N.; Climer, Jason R.; Hasselmo, Michael E.

2013-01-01

Large-scale neural activation dynamics in the hippocampal-entorhinal circuit local field potential, observable as theta and gamma rhythms and coupling between these rhythms, is predictive of encoding success. Behavioral studies show that systemic administration of muscarinic acetylcholine receptor antagonists selectively impairs encoding, suggesting that they may also disrupt the coupling between the theta and gamma bands. Here, we tested the hypothesis that muscarinic antagonists selectively disrupt coupling between theta and gamma. Specifically, we characterized the effects of systemically administered scopolamine on movement-induced theta and gamma rhythms recorded in the superficial layers of the medial entorhinal cortex (MEC) of freely moving rats. We report the novel result that gamma power at the peak of theta was most reduced following muscarinic blockade, significantly shifting the phase of maximal gamma power to occur at later phases of theta. We also characterize the existence of multiple distinct gamma bands in the superficial layers of the MEC. Further, we observed that theta frequency was significantly less modulated by movement speed following muscarinic blockade. Finally, the slope relating speed to theta frequency, a correlate of familiarity with a testing enclosure, increased significantly less between the preinjection and recovery trials when scopolamine was administered during the intervening injection session than when saline was administered, suggesting that scopolamine reduced encoding of the testing enclosure. These data are consistent with computational models suggesting that encoding and retrieval occur during the peak and trough of theta, respectively, and support the theory that acetylcholine regulates the balance between encoding versus retrieval. PMID:24336727

Heterogeneity in Short Gamma-Ray Bursts

NASA Astrophysics Data System (ADS)

Norris, Jay P.; Gehrels, Neil; Scargle, Jeffrey D.

2011-07-01

We analyze the Swift/BAT sample of short gamma-ray bursts, using an objective Bayesian Block procedure to extract temporal descriptors of the bursts' initial pulse complexes (IPCs). The sample is comprised of 12 and 41 bursts with and without extended emission (EE) components, respectively. IPCs of non-EE bursts are dominated by single pulse structures, while EE bursts tend to have two or more pulse structures. The medians of characteristic timescales—durations, pulse structure widths, and peak intervals—for EE bursts are factors of ~2-3 longer than for non-EE bursts. A trend previously reported by Hakkila and colleagues unifying long and short bursts—the anti-correlation of pulse intensity and width—continues in the two short burst groups, with non-EE bursts extending to more intense, narrower pulses. In addition, we find that preceding and succeeding pulse intensities are anti-correlated with pulse interval. We also examine the short burst X-ray afterglows as observed by the Swift/X-Ray Telescope (XRT). The median flux of the initial XRT detections for EE bursts (~6×10-10 erg cm-2 s-1) is gsim20× brighter than for non-EE bursts, and the median X-ray afterglow duration for EE bursts (~60,000 s) is ~30× longer than for non-EE bursts. The tendency for EE bursts toward longer prompt-emission timescales and higher initial X-ray afterglow fluxes implies larger energy injections powering the afterglows. The longer-lasting X-ray afterglows of EE bursts may suggest that a significant fraction explode into denser environments than non-EE bursts, or that the sometimes-dominant EE component efficiently powers the afterglow. Combined, these results favor different progenitors for EE and non-EE short bursts.

Better than sleep: theta neurofeedback training accelerates memory consolidation.

PubMed

Reiner, Miriam; Rozengurt, Roman; Barnea, Anat

2014-01-01

Consistent empirical results showed that both night and day sleep enhanced memory consolidation. In this study we explore processes of consolidation of memory during awake hours. Since theta oscillations have been shown to play a central role in exchange of information, we hypothesized that elevated theta during awake hours will enhance memory consolidation. We used a neurofeedback protocol, to enhance the relative power of theta or beta oscillations. Participants trained on a tapping task, were divided into three groups: neurofeedback theta; neurofeedback beta; control. We found a significant improvement in performance in the theta group, relative to the beta and control groups, immediately after neurofeedback. Performance was further improved after night sleep in all groups, with a significant advantage favoring the theta group. Theta power during training was correlated with the level of improvement, indicating a clear relationship between memory consolidation, and theta neurofeedback. Copyright © 2013 Elsevier B.V. All rights reserved.

Characterizing the roles of alpha and theta oscillations in multisensory attention

PubMed Central

Keller, Arielle S.; Payne, Lisa; Sekuler, Robert

2017-01-01

Cortical alpha oscillations (8–13 Hz) appear to play a role in suppressing distractions when just one sensory modality is being attended, but do they also contribute when attention is distributed over multiple sensory modalities? For an answer, we examined cortical oscillations in human subjects who were dividing attention between auditory and visual sequences. In Experiment 1, subjects performed an oddball task with auditory, visual, or simultaneous audiovisual sequences in separate blocks, while the electroencephalogram was recorded using high-density scalp electrodes. Alpha oscillations were present continuously over posterior regions while subjects were attending to auditory sequences. This supports the idea that the brain suppresses processing of visual input in order to advantage auditory processing. During a divided-attention audiovisual condition, an oddball (a rare, unusual stimulus) occurred in either the auditory or the visual domain, requiring that attention be divided between the two modalities. Fronto-central theta band (4–7 Hz) activity was strongest in this audiovisual condition, when subjects monitored auditory and visual sequences simultaneously. Theta oscillations have been associated with both attention and with short-term memory. Experiment 2 sought to distinguish these possible roles of fronto-central theta activity during multisensory divided attention. Using a modified version of the oddball task from Experiment 1, Experiment 2 showed that differences in theta power among conditions were independent of short-term memory load. Ruling out theta’s association with short-term memory, we conclude that fronto-central theta activity is likely a marker of multisensory divided attention. PMID:28259771

Gamma-Ray Bursts in the Swift Era

NASA Technical Reports Server (NTRS)

Gehrels, Neil; Ramirez-Ruiz, E.; Fox, D. B.

2010-01-01

With its rapid-response capability and multiwavelength complement of instruments, the Swift satellite has transformed our physical understanding of gamma-ray bursts. Providing high-quality observations of hundreds of bursts, and facilitating a wide range of follow-up observations within seconds of each event, Swift has revealed an unforeseen richness in observed burst properties, shed light on the nature of short-duration bursts, and helped realize the promise of gamma-ray bursts as probes of the processes and environments of star formation out to the earliest cosmic epochs. These advances have opened new perspectives on the nature and properties of burst central engines, interactions with the burst environment from microparsec to gigaparsec scales, and the possibilities for non-photonic signatures. Our understanding of these extreme cosmic sources has thus advanced substantially; yet more than forty years after their discovery, gamma-ray bursts continue to present major challenges on both observational and theoretical fronts.

Improvement of spasticity following intermittent theta burst stimulation in multiple sclerosis is associated with modulation of resting-state functional connectivity of the primary motor cortices.

PubMed

Boutière, Clémence; Rey, Caroline; Zaaraoui, Wafaa; Le Troter, Arnaud; Rico, Audrey; Crespy, Lydie; Achard, Sophie; Reuter, Françoise; Pariollaud, Fanelly; Wirsich, Jonathan; Asquinazi, Patrick; Confort-Gouny, Sylviane; Soulier, Elisabeth; Guye, Maxime; Pelletier, Jean; Ranjeva, Jean-Philippe; Audoin, Bertrand

2017-05-01

Intermittent theta burst stimulation (iTBS) of the primary motor cortex improves transiently lower limbs spasticity in multiple sclerosis (MS). However, the cerebral mechanisms underlying this effect have never been investigated. To assess whether modulation of spasticity induced by iTBS is underlined by functional reorganization of the primary motor cortices. A total of 17 patients with MS suffering from lower limbs spasticity were randomized to receive real iTBS or sham iTBS during the first half of a 5-week indoor rehabilitation programme. Spasticity was assessed using the Modified Ashworth Scale and the Visual Analogue Scale at baseline, after the stimulation session and at the end of the rehabilitation programme. Resting-state functional magnetic resonance imaging (fMRI) was performed at the three time points, and brain functional networks topology was analysed using graph-theoretical approach. At the end of stimulation, improvement of spasticity was greater in real iTBS group than in sham iTBS group ( p = 0.026). iTBS had a significant effect on the balance of the connectivity degree between the stimulated and the homologous primary motor cortex ( p = 0.005). Changes in inter-hemispheric balance were correlated with improvement of spasticity (rho = 0.56, p = 0.015). This longitudinal resting-state fMRI study evidences that functional reorganization of the primary motor cortices may underlie the effect of iTBS on spasticity in MS.

Progressive Fracture of [0/90/ + or - Theta]s Composite Structure Under Uniform Pressure Load

NASA Technical Reports Server (NTRS)

Gotsis, Pascalis K.; Chamis, Christos C.; Gotsis, Christos K.; Mouratidis, Ericos

2007-01-01

S-Glass/epoxy [0/90/plus or minus theta]s for theta =45 deg., 60 deg., and 75 deg. laminated fiber-reinforced composite stiffened plate was simulated to investigated for damage and fracture progression under uniform pressure. An integrated computer code was augmented for the simulation of the damage initiation, growth, accumulation, and propagation to fracture and to structural collapse. Results show in detail the damage progression sequence and structural fracture resistance during different degradation stages. Damage through the thickness of the laminate initiated first at [0/90/plus or minus 45]s at 15.168 MPa (2200 psi), followed by [0/90/plus or minus 60]s at 16.96 MPa (2460 psi) and finally by [0/90/plus or minus 75]s at 19.3 MPa (2800 psi). After damage initiation happened the cracks propagate rapidly to structural fracture.

Reproducibility of Single-Pulse, Paired-Pulse, and Intermittent Theta-Burst TMS Measures in Healthy Aging, Type-2 Diabetes, and Alzheimer’s Disease

PubMed Central

Fried, Peter J.; Jannati, Ali; Davila-Pérez, Paula; Pascual-Leone, Alvaro

2017-01-01

Background: Transcranial magnetic stimulation (TMS) can be used to assess neurophysiology and the mechanisms of cortical brain plasticity in humans in vivo. As the use of these measures in specific populations (e.g., Alzheimer’s disease; AD) increases, it is critical to understand their reproducibility (i.e., test–retest reliability) in the populations of interest. Objective: Reproducibility of TMS measures was evaluated in older adults, including healthy, AD, and Type-2 diabetes mellitus (T2DM) groups. Methods: Participants received two identical neurophysiological assessments within a year including motor thresholds, baseline motor evoked potentials (MEPs), short- and long-interval intracortical inhibition (SICI, LICI) and intracortical facilitation (ICF), and MEP changes following intermittent theta-burst stimulation (iTBS). Cronbach’s α coefficients were calculated to assess reproducibility. Multiple linear regression analyses were used to investigate factors related to intraindividual variability. Results: Reproducibility was highest for motor thresholds, followed by baseline MEPs, SICI and LICI, and was lowest for ICF and iTBS aftereffects. The AD group tended to show higher reproducibility than T2DM or controls. Intraindividual variability of baseline MEPs was related to age and variability of RMT, while the intraindividual variability in post-iTBS measures was related to baseline MEP variability, intervisit duration, and Brain-derived neurotrophic factor (BDNF) polymorphism. Conclusion: Increased reproducibility in AD may reflect pathophysiological declines in the efficacy of neuroplastic mechanisms. Reproducibility of iTBS aftereffects can be improved by keeping baseline MEPs consistent, controlling for BDNF genotype, and waiting at least a week between visits. Significance: These findings provide the first direct assessment of reproducibility of TMS measures in older clinical populations. Reproducibility coefficients may be used to adjust effect

EEG theta waves and psychological phenomena: a review and analysis.

PubMed

Schacter, D L

1977-03-01

In this paper, studies which have explored the relation between EEG theta waves and psychological phenomena in normal human subjects are reviewed. It is noted that increases in theta activity occur in conjunction with several kinds of psychological processes. The importance of ocnsidering properties of theta activity, such as amplitude, rhythmicity and scalp topography when analyzing the relation between theta and psychological processes is emphasized. Although there is some evidence for a relationship between theta and psychological processes, it is concluded that the degree to which properties of theta activity are systematically related to specific psychological processes is not yet known.

Laboratory-induced learned helplessness attenuates approach motivation as indexed by posterior versus frontal theta activity.

PubMed

Reznik, Samantha J; Nusslock, Robin; Pornpattananangkul, Narun; Abramson, Lyn Y; Coan, James A; Harmon-Jones, Eddie

2017-08-01

Research suggests that midline posterior versus frontal electroencephalographic (EEG) theta activity (PFTA) may reflect a novel neurophysiological index of approach motivation. Elevated PFTA has been associated with approach-related tendencies both at rest and during laboratory tasks designed to enhance approach motivation. PFTA is sensitive to changes in dopamine signaling within the fronto-striatal neural circuit, which is centrally involved in approach motivation, reward processing, and goal-directed behavior. To date, however, no studies have examined PFTA during a laboratory task designed to reduce approach motivation or goal-directed behavior. Considerable animal and human research supports the hypothesis put forth by the learned helplessness theory that exposure to uncontrollable aversive stimuli decreases approach motivation by inducing a state of perceived uncontrollability. Accordingly, the present study examined the effect of perceived uncontrollability (i.e., learned helplessness) on PFTA. EEG data were collected from 74 participants (mean age = 19.21 years; 40 females) exposed to either Controllable (n = 26) or Uncontrollable (n = 25) aversive noise bursts, or a No-Noise Condition (n = 23). In line with prediction, individuals exposed to uncontrollable aversive noise bursts displayed a significant decrease in PFTA, reflecting reduced approach motivation, relative to both individuals exposed to controllable noise bursts or the No-Noise Condition. There was no relationship between perceived uncontrollability and frontal EEG alpha asymmetry, another commonly used neurophysiological index of approach motivation. Results have implications for understanding the neurophysiology of approach motivation and establishing PFTA as a neurophysiological index of approach-related tendencies.

Bright x-ray flares in gamma-ray burst afterglows.

PubMed

Burrows, D N; Romano, P; Falcone, A; Kobayashi, S; Zhang, B; Moretti, A; O'brien, P T; Goad, M R; Campana, S; Page, K L; Angelini, L; Barthelmy, S; Beardmore, A P; Capalbi, M; Chincarini, G; Cummings, J; Cusumano, G; Fox, D; Giommi, P; Hill, J E; Kennea, J A; Krimm, H; Mangano, V; Marshall, F; Mészáros, P; Morris, D C; Nousek, J A; Osborne, J P; Pagani, C; Perri, M; Tagliaferri, G; Wells, A A; Woosley, S; Gehrels, N

2005-09-16

Gamma-ray burst (GRB) afterglows have provided important clues to the nature of these massive explosive events, providing direct information on the nearby environment and indirect information on the central engine that powers the burst. We report the discovery of two bright x-ray flares in GRB afterglows, including a giant flare comparable in total energy to the burst itself, each peaking minutes after the burst. These strong, rapid x-ray flares imply that the central engines of the bursts have long periods of activity, with strong internal shocks continuing for hundreds of seconds after the gamma-ray emission has ended.

Introducing Argonne’s Theta Supercomputer

DOE Office of Scientific and Technical Information (OSTI.GOV)

None

Theta, the Argonne Leadership Computing Facility’s (ALCF) new Intel-Cray supercomputer, is officially open to the research community. Theta’s massively parallel, many-core architecture puts the ALCF on the path to Aurora, the facility’s future Intel-Cray system. Capable of nearly 10 quadrillion calculations per second, Theta enables researchers to break new ground in scientific investigations that range from modeling the inner workings of the brain to developing new materials for renewable energy applications.

Distinct slow and fast cortical theta dynamics in episodic memory retrieval.

PubMed

Pastötter, Bernhard; Bäuml, Karl-Heinz T

2014-07-01

Brain oscillations in the theta frequency band (3-8 Hz) have been shown to be critically involved in human episodic memory retrieval. In prior work, both positive and negative relationships between cortical theta power and retrieval success have been reported. This study examined the hypothesis that slow and fast cortical theta oscillations at the edges of the traditional theta frequency band are differentially related to retrieval success. Scalp EEG was recorded in healthy human participants as they performed a cued-recall episodic memory task. Slow (~3 Hz) and fast (~7 Hz) theta oscillations at retrieval were examined as a function of whether an item was recalled or not and as a function of the items' output position at test. Recall success typically declines with output position, due to increases in interference level. The results showed that slow theta power was positively related but fast theta power was negatively related to retrieval success. Concurrent positive and negative episodic memory effects for slow and fast theta oscillations were dissociable in time and space, showing different time courses and different spatial locations on the scalp. Moreover, fast theta power increased from early to late output positions, whereas slow theta power was unaffected by items' output position. Together with prior work, the results suggest that slow and fast theta oscillations have distinct functional roles in episodic memory retrieval, with slow theta oscillations being related to processes of recollection and conscious awareness, and fast theta oscillations being linked to processes of interference and interference resolution. Copyright © 2014 Elsevier Inc. All rights reserved.

Modulation of Effects of Intermittent Theta Burst Stimulation Applied Over Primary Motor Cortex (M1) by Conditioning Stimulation of the Opposite M1

PubMed Central

Ragert, Patrick; Camus, Mickael; Vandermeeren, Yves; Dimyan, Michael A.; Cohen, Leonardo G.

2009-01-01

The excitability of the human primary motor cortex (M1) as tested with transcranial magnetic stimulation (TMS) depends on its previous history of neural activity. Homeostatic plasticity might be one important physiological mechanism for the regulation of corticospinal excitability and synaptic plasticity. Although homeostatic plasticity has been demonstrated locally within M1, it is not known whether priming M1 could result in similar homeostatic effects in the homologous M1 of the opposite hemisphere. Here, we sought to determine whether down-regulating excitability (priming) in the right (R) M1 with 1-Hz repetitive transcranial magnetic stimulation (rTMS) changes the excitability-enhancing effect of intermittent theta burst stimulation (iTBS) applied over the homologous left (L) M1. Subjects were randomly allocated to one of four experimental groups in a sham-controlled parallel design with real or sham R M1 1-Hz TMS stimulation always preceding L M1 iTBS or sham by about 10 min. The primary outcome measure was corticospinal excitability in the L M1, as measured by recruitment curves (RCs). Secondary outcome measures included pinch force, simple reaction time, and tapping speed assessed in the right hand. The main finding of this study was that preconditioning R M1 with 1-Hz rTMS significantly decreased the excitability-enhancing effects of subsequent L M1 iTBS on RCs. Application of 1-Hz rTMS over R M1 alone and iTBS over L M1 alone resulted in increased RC in L M1 relative to sham interventions. The present findings are consistent with the hypothesis that homeostatic mechanisms operating across hemispheric boundaries contribute to regulate motor cortical function in the primary motor cortex. PMID:19474173

Flexible theta sequence compression mediated via phase precessing interneurons

PubMed Central

Chadwick, Angus; van Rossum, Mark CW; Nolan, Matthew F

2016-01-01

Encoding of behavioral episodes as spike sequences during hippocampal theta oscillations provides a neural substrate for computations on events extended across time and space. However, the mechanisms underlying the numerous and diverse experimentally observed properties of theta sequences remain poorly understood. Here we account for theta sequences using a novel model constrained by the septo-hippocampal circuitry. We show that when spontaneously active interneurons integrate spatial signals and theta frequency pacemaker inputs, they generate phase precessing action potentials that can coordinate theta sequences in place cell populations. We reveal novel constraints on sequence generation, predict cellular properties and neural dynamics that characterize sequence compression, identify circuit organization principles for high capacity sequential representation, and show that theta sequences can be used as substrates for association of conditioned stimuli with recent and upcoming events. Our results suggest mechanisms for flexible sequence compression that are suited to associative learning across an animal’s lifespan. DOI: http://dx.doi.org/10.7554/eLife.20349.001 PMID:27929374

Theta power is reduced in healthy cognitive aging.

PubMed

Cummins, Tarrant D R; Finnigan, Simon

2007-10-01

The effects of healthy cognitive aging on electroencephalographic (EEG) theta (4.9-6.8 Hz) power were examined during performance of a modified Sternberg, S., 1966. High-speed scanning in human memory. Science 153, 652-654.) word recognition task. In a sample of fourteen young (mean age 21.9 years, range=18-27) and fourteen older (mean age 68.4 years, range=60-80) participants, theta power was found to be significantly lower in older adults during both the retention and recognition intervals. This theta power difference was greatest at the fronto-central midline electrode and occurred in parallel with a small, non-significant decrease in recognition accuracy in the older sample. A significant decrease in older adults' mean theta power was also observed in resting EEG, however, it was of substantially smaller magnitude than the task-related theta difference. It is proposed that a neurophysiological measure(s), such as task-specific frontal midline theta (fmtheta) power, may be a more sensitive marker of cognitive aging than task performance measures. Furthermore, as recent research indicates that fmtheta is generated primarily in the anterior cingulate cortex, the current findings support evidence that the function of brain networks incorporating this structure may be affected in cognitive aging.

Impaired theta-gamma coupling during working memory performance in schizophrenia.

PubMed

Barr, Mera S; Rajji, Tarek K; Zomorrodi, Reza; Radhu, Natasha; George, Tony P; Blumberger, Daniel M; Daskalakis, Zafiris J

2017-11-01

Working memory deficits represent a core feature of schizophrenia. These deficits have been associated with dysfunctional dorsolateral prefrontal cortex (DLPFC) cortical oscillations. Theta-gamma coupling describes the modulation of gamma oscillations by theta phasic activity that has been directly associated with the ordering of information during working memory performance. Evaluating theta-gamma coupling may provide greater insight into the neural mechanisms mediating working memory deficits in this disorder. Thirty-eight patients diagnosed with schizophrenia or schizoaffective disorder and 38 healthy controls performed the verbal N-Back task administered at 4 levels, while EEG was recorded. Theta (4-7Hz)-gamma (30-50Hz) coupling was calculated for target and non-target correct trials for each working memory load. The relationship between theta-gamma coupling and accuracy was determined. Theta-gamma coupling was significantly and selectively impaired during correct responses to target letters among schizophrenia patients compared to healthy controls. A significant and positive relationship was found between theta-gamma coupling and 3-Back accuracy in controls, while this relationship was not observed in patients. These findings suggest that impaired theta-gamma coupling contribute to working memory dysfunction in schizophrenia. Future work is needed to evaluate the predictive utility of theta-gamma coupling as a neurophysiological marker for functional outcomes in this disorder. Copyright © 2017. Published by Elsevier B.V.

Interpretation of the Theta+ as an isotensor pentaquark with weakly decaying partners

DOE Office of Scientific and Technical Information (OSTI.GOV)

Simon Capstick; Philip R. Page; Winston Roberts

2003-09-25

The {Theta}{sup +}(1540), recently observed at LEPS, DIANA and CLAS, is hypothesized to be an isotensor resonance. This implies the existence of a multiplet where the {Theta}{sup ++}, {Theta}{sup +} and {Theta}{sup 0} have isospin-violating strong decays, and the {Theta}{sup +++} and {Theta}{sup -} have weak decays and so are long-lived. Production mechanisms for these states are discussed. The J{sup P} assignment of the {Theta} is most likely 1/2{sup -} or 3/2{sup -} or 5/2{sup -}.

Cortical processes associated with continuous balance control as revealed by EEG spectral power.

PubMed

Hülsdünker, T; Mierau, A; Neeb, C; Kleinöder, H; Strüder, H K

2015-04-10

Balance is a crucial component in numerous every day activities such as locomotion. Previous research has reported distinct changes in cortical theta activity during transient balance instability. However, there remains little understanding of the neural mechanisms underlying continuous balance control. This study aimed to investigate cortical theta activity during varying difficulties of continuous balance tasks, as well as examining the relationship between theta activity and balance performance. 37 subjects completed nine balance tasks with different levels of surface stability and base of support. Throughout the balancing task, electroencephalogram (EEG) was recorded from 32 scalp locations. ICA-based artifact rejection was applied and spectral power was analyzed in the theta frequency band. Theta power increased in the frontal, central, and parietal regions of the cortex when balance tasks became more challenging. In addition, fronto-central and centro-parietal theta power correlated with balance performance. This study demonstrates the involvement of the cerebral cortex in maintaining upright posture during continuous balance tasks. Specifically, the results emphasize the important role of frontal and parietal theta oscillations in balance control. Copyright © 2015 Elsevier Ireland Ltd. All rights reserved.

Expected reward modulates encoding-related theta activity before an event.

PubMed

Gruber, Matthias J; Watrous, Andrew J; Ekstrom, Arne D; Ranganath, Charan; Otten, Leun J

2013-01-01

Oscillatory brain activity in the theta frequency range (4-8 Hz) before the onset of an event has been shown to affect the likelihood of successfully encoding the event into memory. Recent work has also indicated that frontal theta activity might be modulated by reward, but it is not clear how reward expectancy, anticipatory theta activity, and memory formation might be related. Here, we used scalp electroencephalography (EEG) to assess the relationship between these factors. EEG was recorded from healthy adults while they memorized a series of words. Each word was preceded by a cue that indicated whether a high or low monetary reward would be earned if the word was successfully remembered in a later recognition test. Frontal theta power between the presentation of the reward cue and the onset of a word was predictive of later memory for the word, but only in the high reward condition. No theta differences were observed before word onset following low reward cues. The magnitude of prestimulus encoding-related theta activity in the high reward condition was correlated with the number of high reward words that were later confidently recognized. These findings provide strong evidence for a link between reward expectancy, theta activity, and memory encoding. Theta activity before event onset seems to be especially important for the encoding of motivationally significant stimuli. One possibility is that dopaminergic activity during reward anticipation mediates frontal theta activity related to memory. Copyright © 2012 Elsevier Inc. All rights reserved.

Measuring Theta_13 at Daya Bay

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lau, Kwong

2014-03-14

We measured the neutrino mixing angle, theta13, presumably related to the preponderance of matter over antimatter in our universe with high precision. We determined theta13 by measuring the disappearance of neutrinos from a group of six nuclear reactors. The target, located inside a mountain at about 2 km from the reactors, is 80 tons of liquid scintillator doped with trace amount of Gadolinium to increase its neutron detection efficiency. The neutrino flux is measured by the inverse beta-decay reaction where the final-state particles are detected by the liquid scintillator. The measured value of theta13, based on data collected over 3more » years, is large, around 8 degrees, rendering the measurement of the parameter related to matter-antimatter asymmetry in future long baseline neutrino experiments easier.« less

Dissociation between dorsal and ventral hippocampal theta oscillations during decision-making.

PubMed

Schmidt, Brandy; Hinman, James R; Jacobson, Tara K; Szkudlarek, Emily; Argraves, Melissa; Escabí, Monty A; Markus, Etan J

2013-04-03

Hippocampal theta oscillations are postulated to support mnemonic processes in humans and rodents. Theta oscillations facilitate encoding and spatial navigation, but to date, it has been difficult to dissociate the effects of volitional movement from the cognitive demands of a task. Therefore, we examined whether volitional movement or cognitive demands exerted a greater modulating factor over theta oscillations during decision-making. Given the anatomical, electrophysiological, and functional dissociations along the dorsal-ventral axis, theta oscillations were simultaneously recorded in the dorsal and ventral hippocampus in rats trained to switch between place and motor-response strategies. Stark differences in theta characteristics were found between the dorsal and ventral hippocampus in frequency, power, and coherence. Theta power increased in the dorsal, but decreased in the ventral hippocampus, during the decision-making epoch. Interestingly, the relationship between running speed and theta power was uncoupled during the decision-making epoch, a phenomenon limited to the dorsal hippocampus. Theta frequency increased in both the dorsal and ventral hippocampus during the decision epoch, although this effect was greater in the dorsal hippocampus. Despite these differences, ventral hippocampal theta was responsive to the navigation task; theta frequency, power, and coherence were all affected by cognitive demands. Theta coherence increased within the dorsal hippocampus during the decision-making epoch on all three tasks. However, coherence selectively increased throughout the hippocampus (dorsal to ventral) on the task with new hippocampal learning. Interestingly, most results were consistent across tasks, regardless of hippocampal-dependent learning. These data indicate increased integration and cooperation throughout the hippocampus during information processing.

How long does a burst burst?

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhang, Bin-Bin; Connaughton, Valerie; Briggs, Michael S.

2014-05-20

Several gamma-ray bursts (GRBs) last much longer (∼hours) in γ-rays than typical long GRBs (∼minutes), and it has recently been proposed that these 'ultra-long GRBs' may form a distinct population, probably with a different (e.g., blue supergiant) progenitor than typical GRBs. However, Swift observations suggest that many GRBs have extended central engine activities manifested as flares and internal plateaus in X-rays. We perform a comprehensive study on a large sample of Swift GRBs with X-Ray Telescope observations to investigate GRB central engine activity duration and to determine whether ultra-long GRBs are unusual events. We define burst duration t {sub burst}more » based on both γ-ray and X-ray light curves rather than using γ-ray observations alone. We find that t {sub burst} can be reliably measured in 343 GRBs. Within this 'good' sample, 21.9% GRBs have t {sub burst} ≳ 10{sup 3} s and 11.5% GRBs have t {sub burst} ≳ 10{sup 4} s. There is an apparent bimodal distribution of t {sub burst} in this sample. However, when we consider an 'undetermined' sample (304 GRBs) with t {sub burst} possibly falling in the gap between GRB duration T {sub 90} and the first X-ray observational time, as well as a selection effect against t {sub burst} falling into the first Swift orbital 'dead zone' due to observation constraints, the intrinsic underlying t {sub burst} distribution is consistent with being a single component distribution. We found that the existing evidence for a separate ultra-long GRB population is inconclusive, and further multi-wavelength observations are needed to draw a firmer conclusion. We also discuss the theoretical implications of our results. In particular, the central engine activity duration of GRBs is generally much longer than the γ-ray T {sub 90} duration and it does not even correlate with T {sub 90}. It would be premature to make a direct connection between T {sub 90} and the size of the progenitor star.« less

The central responsiveness of the acute cerveau isolé rat.

PubMed

User, P; Gottesmann, C

1982-01-01

The electrophysiological patterns of the frontal cortex and dorsal hippocampus were studied in the acute cerveau isolé rat. Central and peripheral stimulations were performed in order to modulate these patterns. The results showed that the permanent alternation of high amplitude spindle bursts and low voltage activity in the anterior neocortex of the acute cerveau isolé was influenced neither by olfactory nor by posterior hypothalamic stimulation. In contrast, these two kinds of stimulation easily modulated the continuous low frequency theta rhythm, recorded in the dorsal hippocampus, in terms of amplitude and in overall frequency. This modulation of the theta rhythm in the acute cerveau isolé rat mimics the changes observed when the normal rat comes from the intermediate stage of sleep (as characterized in the the acute intercollicular transected rat by high amplitude spindle bursts at frontal cortex level and low frequency theta activity in the dorsal hippocampus) to rapid sleep. These results further suggest that, during the intermediate stage (as in the cerveau isolé preparation), the hippocampus montonous theta activity appears through a brainstem disinhibitory process releasing the forebrain limbic pacemaker(s). During the following rapid sleep phase, the theta rhythm would be modulated by pontine activity influences acting on the theta generators.

Theta synchronization networks emerge during human object-place memory encoding.

PubMed

Sato, Naoyuki; Yamaguchi, Yoko

2007-03-26

Recent rodent hippocampus studies have suggested that theta rhythm-dependent neural dynamics ('theta phase precession') is essential for an on-line memory formation. A computational study indicated that the phase precession enables a human object-place association memory with voluntary eye movements, although it is still an open question whether the human brain uses the dynamics. Here we elucidated subsequent memory-correlated activities in human scalp electroencephalography in an object-place association memory designed according the former computational study. Our results successfully demonstrated that subsequent memory recall is characterized by an increase in theta power and coherence, and further, that multiple theta synchronization networks emerge. These findings suggest the human theta dynamics in common with rodents in episodic memory formation.

Optimization of pencil beam f-theta lens for high-accuracy metrology

NASA Astrophysics Data System (ADS)

Peng, Chuanqian; He, Yumei; Wang, Jie

2018-01-01

Pencil beam deflectometric profilers are common instruments for high-accuracy surface slope metrology of x-ray mirrors in synchrotron facilities. An f-theta optical system is a key optical component of the deflectometric profilers and is used to perform the linear angle-to-position conversion. Traditional optimization procedures of the f-theta systems are not directly related to the angle-to-position conversion relation and are performed with stops of large size and a fixed working distance, which means they may not be suitable for the design of f-theta systems working with a small-sized pencil beam within a working distance range for ultra-high-accuracy metrology. If an f-theta system is not well-designed, aberrations of the f-theta system will introduce many systematic errors into the measurement. A least-squares' fitting procedure was used to optimize the configuration parameters of an f-theta system. Simulations using ZEMAX software showed that the optimized f-theta system significantly suppressed the angle-to-position conversion errors caused by aberrations. Any pencil-beam f-theta optical system can be optimized with the help of this optimization method.

Comparison of numerical techniques for the evaluation of the Doppler broadening functions psi(x,theta) and chi(x,theta)

NASA Technical Reports Server (NTRS)

Canright, R. B., Jr.; Semler, T. T.

1972-01-01

Several approximations to the Doppler broadening functions psi(x, theta) and chi(x, theta) are compared with respect to accuracy and speed of evaluation. A technique, due to A. M. Turning (1943), is shown to be at least as accurate as direct numerical quadrature and somewhat faster than Gaussian quadrature. FORTRAN 4 listings are included.

Hippocampal theta activity in the acute cerveau isolé cat.

PubMed

Gottesmann, C; Zernicki, B; Gandolfo, G

1981-01-01

In three cerveau isole cats, cortical and hippocampal EEG activity were recorded. In the cortical records, spindles alternated with low-voltage activity, whereas theta activity dominated in the hippocampus. The amount and frequency of theta were similar to those described previously for the pretrigeminal cat. In confirmation of previous results on rats, although cortical EEG activity differs in cerveau isole cat and pretrigeminal cat, both preparations show domination of theta activity in the hippocampus. It is concluded that the mesencephalic transection eliminates inhibitory effects from the lower brainstem on generators of the theta rhythm.

Theta synchronizes the activity of medial prefrontal neurons during learning

PubMed Central

Paz, Rony; Bauer, Elizabeth P.; Paré, Denis

2008-01-01

Memory consolidation is thought to involve the gradual transfer of transient hippocampal-dependent traces to distributed neocortical sites via the rhinal cortices. Recently, medial prefrontal (mPFC) neurons were shown to facilitate this process when their activity becomes synchronized. However, the mechanisms underlying this enhanced synchrony remain unclear. Because the hippocampus projects to the mPFC, we tested whether theta oscillations contribute to synchronize mPFC neurons during learning. Thus, we obtained field (LFP) and unit recordings from multiple mPFC sites during the acquisition of a trace-conditioning task, where a visual conditioned stimulus (CS) predicted reward delivery. In quiet waking, the activity of mPFC neurons was modulated by theta oscillations. During conditioning, CS presentation caused an increase in mPFC theta power that augmented as the CS gained predictive value for reward delivery. This increased theta power coincided with a transient theta phase locking at distributed mPFC sites, an effect that was also manifest in the timing of mPFC unit activity. Overall, these results show that theta oscillations contribute to synchronize neuronal activity at distributed mPFC sites, suggesting that the hippocampus, by generating a stronger theta source during learning, can synchronize mPFC activity, in turn facilitating rhinal transfer of its activity to the neocortex. PMID:18612069

Improved dichotomous search frequency offset estimator for burst-mode continuous phase modulation

NASA Astrophysics Data System (ADS)

Zhai, Wen-Chao; Li, Zan; Si, Jiang-Bo; Bai, Jun

2015-11-01

A data-aided technique for carrier frequency offset estimation with continuous phase modulation (CPM) in burst-mode transmission is presented. The proposed technique first exploits a special pilot sequence, or training sequence, to form a sinusoidal waveform. Then, an improved dichotomous search frequency offset estimator is introduced to determine the frequency offset using the sinusoid. Theoretical analysis and simulation results indicate that our estimator is noteworthy in the following aspects. First, the estimator can operate independently of timing recovery. Second, it has relatively low outlier, i.e., the minimum signal-to-noise ratio (SNR) required to guarantee estimation accuracy. Finally, the most important property is that our estimator is complexity-reduced compared to the existing dichotomous search methods: it eliminates the need for fast Fourier transform (FFT) and modulation removal, and exhibits faster convergence rate without accuracy degradation. Project supported by the National Natural Science Foundation of China (Grant No. 61301179), the Doctorial Programs Foundation of the Ministry of Education, China (Grant No. 20110203110011), and the Programme of Introducing Talents of Discipline to Universities, China (Grant No. B08038).

Gamma Ray Burst Discoveries with the Swift Mission

NASA Technical Reports Server (NTRS)

Gehrels, Neil

2008-01-01

Gamma-ray bursts (GRBs) are among the most fascinating occurrences in the universe. They are powerful explosions, visible to high redshift, and thought to be the signature of black hole formation. The Swift Observatory has been detecting 100 bursts per year for 3 years and has greatly stimulated the field with new findings. Observations are made of the X-ray and optical afterglow from - 1 minute after the burst, continuing for days. Evidence is building that the long and short duration subcategories of GRBs have very different origins: massive star core collapse to a black hole for long bursts and binary neutron star coalescence to a black hole for short bursts. The similarity to Type I1 and Ia supernovae originating from young and old stellar progenitors is striking. Bursts are providing a new tool to study the high redshift universe. Swift has detected several events at z>5 and one at z=6.3 giving metallicity measurements and other data on galaxies at previously inaccessible distances. The talk will present the latest results from Swift in GRB astronomy.

Gamma Ray Burst Discoveries with the Swift Mission

NASA Technical Reports Server (NTRS)

Gehrels, Neil

2008-01-01

Gamma-ray bursts (GRBs) are among the most fascinating occurrences in the universe. They are powerful explosions, visible to high redshift, and thought to be the signature of black hole formation. The Swift Observatory has been detecting 100 bursts per year for 3 years and has greatly stimulated the field with new findings. Observations are made of the X-ray and optical afterglow from approximately 1 minute after the burst, continuing for days. Evidence is building that the long and short duration subcategories of GRBs have very different origins: massive star core collapse to a black hole for long bursts and binary neutron star coalescence to a black hole for short bursts. The similarity to Type II and Ia supernovae originating from young and old stellar progenitors is striking. Bursts are providing a new tool to study the high redshift universe. Swift has detected several events at z greater than 5 and one at z=6.3 giving metallicity measurements and other data on galaxies at previously inaccessible distances. The talk will present the latest results from Swift in GRB astronomy.

Gamma Ray Burst Discoveries with the Swift Mission

NASA Technical Reports Server (NTRS)

Gehrels, Neil

2009-01-01

Gamma-ray bursts (GRBs) are among the most fascinating occurrences in the universe. They are powerful explosions, visible to high redshift, and thought to be the signature of black hole formation. The Swift Observatory has been detecting 100 bursts per year for 4 years and has greatly stimulated the field with new findings. Observations are made of the X-ray and optical afterglow from approximately 1 minute after the burst, continuing for days. Evidence is building that the long and short duration subcategories of GRBs have very different origins: massive star core collapse to a black hole for long bursts and binary neutron star coalescence to a black hole for short bursts. The similarity to Type II and Ia supernovae originating from young and old stellar progenitors is striking. Bursts are providing a new tool to study the high redshift universe. Swift has detected several events at z>5 and one at z=6.7 giving metallicity measurements and other data on galaxies at previously inaccessible distances. The talk will present the latest results from Swift in GRB astronomy.

Experimental search for radiative decays of the pentaquark baryon {Theta}{sup +}(1540)

DOE Office of Scientific and Technical Information (OSTI.GOV)

Barmin, V. V.; Asratyan, A. E.; Borisov, V. S.

2010-07-15

The data on the reactions K{sup +}Xe {sup {yields}}K{sup 0{gamma}}X and K{sup +}Xe {sup {yields}}K{sup +{gamma}}X, obtained with the bubble chamber DIANA, have been analyzed for possible radiative decays of the {Theta}{sup +}(1540) baryon: {Theta}{sup +} {sup {yields}}K{sup 0}p{gamma} and {Theta}{sup +} {sup {yields}}K{sup +}n{gamma}. No signals have been observed, and we derive the upper limits {Gamma}({Theta}{sup +} {sup {yields}}K{sup 0}p{gamma})/{Gamma}({Theta}{sup +} {sup {yields}}K{sup 0}p) < 0.032 and {Gamma}({Theta}{sup +} {sup {yields}}K{sup +}n{gamma})/{Gamma}({Theta}{sup +} {sup {yields}}K{sup +}n{gamma}) < 0.041 which, using our previous measurement of {Gamma}({Theta}{sup +} {sup {yields}}KN) = 0.39 {+-} 0.10 MeV, translate to {Gamma}({Theta}{sup +} {sup {yields}}K{supmore » 0}p{gamma}) < 8 keV and {Gamma}({Theta}{sup +} {sup {yields}}K{sup +}n{gamma}) < 11 keV at 90% confidence level. We have also measured the cross sections of K{sup +}-induced reactions involving emission of a neutral pion: {sigma}(K{sup +}n {sup {yields}}K{sup 0}p{pi}{sup 0}) = 68 {+-} 18 {mu}b and {sigma}(K{sup +}N {sup {yields}}K{sup +}N{pi}{sup 0}) = 30 {+-} 8 {mu}b for incident K{sup +} momentum of 640 MeV.« less

Septal serotonin depletion in rats facilitates working memory in the radial arm maze and increases hippocampal high-frequency theta activity.

PubMed

López-Vázquez, Miguel Ángel; López-Loeza, Elisa; Lajud Ávila, Naima; Gutiérrez-Guzmán, Blanca Erika; Hernández-Pérez, J Jesús; Reyes, Yoana Estrada; Olvera-Cortés, María Esther

2014-07-05

Hippocampal theta activity, which is strongly modulated by the septal medial/Broca׳s diagonal band neurons, has been linked to information processing of the hippocampus. Serotonin from the medial raphe nuclei desynchronises hippocampal theta activity, whereas inactivation or a lesion of this nucleus induces continuous and persistent theta activity in the hippocampus. Hippocampal serotonin depletion produces an increased expression of high-frequency theta activity concurrent with the facilitation of place learning in the Morris maze. The medial septum-diagonal band of Broca complex (MS/DBB) has been proposed as a key structure in the serotonin modulation of theta activity. We addressed whether serotonin depletion of the MS/DBB induces changes in the characteristics of hippocampal theta activity and whether the depletion is associated with learning in a working memory spatial task in the radial arm maze. Sprague Dawley rats were depleted of 5HT with the infusion of 5,7-dihydroxytriptamine (5,7-DHT) in MS/DBB and were subsequently trained in the standard test (win-shift) in the radial arm, while the CA1 EEG activity was simultaneously recorded through telemetry. The MS/DBB serotonin depletion induced a low level of expression of low-frequency (4.5-6.5Hz) and a higher expression of high-frequency (6.5-9.5Hz) theta activity concomitant to a minor number of errors committed by rats on the working memory test. Thus, the depletion of serotonin in the MS/DBB caused a facilitator effect on working memory and a predominance of high-frequency theta activity. Copyright © 2014 Elsevier B.V. All rights reserved.

Atmospheric, long baseline, and reactor neutrino data constraints on theta_{13}.

PubMed

Roa, J E; Latimer, D C; Ernst, D J

2009-08-07

An atmospheric neutrino oscillation tool that uses full three-neutrino oscillation probabilities and a full three-neutrino treatment of the Mikheyev-Smirnov-Wolfenstein effect, together with an analysis of the K2K, MINOS, and CHOOZ data, is used to examine the bounds on theta_{13}. The recent, more finely binned, Super-K atmospheric data are employed. For L/E_{nu} greater, similar 10;{4} km/GeV, we previously found significant linear in theta_{13} terms. This analysis finds theta_{13} bounded from above by the atmospheric data while bounded from below by CHOOZ. The origin of this result arises from data in the previously mentioned very long baseline region; here, matter effects conspire with terms linear in theta_{13} to produce asymmetric bounds on theta_{13}. Assuming CP conservation, we find theta_{13} = -0.07_{-0.11};{+0.18} (90% C.L.).

Automatic burst detection for the EEG of the preterm infant.

PubMed

Jennekens, Ward; Ruijs, Loes S; Lommen, Charlotte M L; Niemarkt, Hendrik J; Pasman, Jaco W; van Kranen-Mastenbroek, Vivianne H J M; Wijn, Pieter F F; van Pul, Carola; Andriessen, Peter

2011-10-01

To aid with prognosis and stratification of clinical treatment for preterm infants, a method for automated detection of bursts, interburst-intervals (IBIs) and continuous patterns in the electroencephalogram (EEG) is developed. Results are evaluated for preterm infants with normal neurological follow-up at 2 years. The detection algorithm (MATLAB®) for burst, IBI and continuous pattern is based on selection by amplitude, time span, number of channels and numbers of active electrodes. Annotations of two neurophysiologists were used to determine threshold values. The training set consisted of EEG recordings of four preterm infants with postmenstrual age (PMA, gestational age + postnatal age) of 29-34 weeks. Optimal threshold values were based on overall highest sensitivity. For evaluation, both observers verified detections in an independent dataset of four EEG recordings with comparable PMA. Algorithm performance was assessed by calculation of sensitivity and positive predictive value. The results of algorithm evaluation are as follows: sensitivity values of 90% ± 6%, 80% ± 9% and 97% ± 5% for burst, IBI and continuous patterns, respectively. Corresponding positive predictive values were 88% ± 8%, 96% ± 3% and 85% ± 15%, respectively. In conclusion, the algorithm showed high sensitivity and positive predictive values for bursts, IBIs and continuous patterns in preterm EEG. Computer-assisted analysis of EEG may allow objective and reproducible analysis for clinical treatment.

Frontal Theta Dynamics during Response Conflict in Long-Term Mindfulness Meditators

PubMed Central

Jo, Han-Gue; Malinowski, Peter; Schmidt, Stefan

2017-01-01

Mindfulness meditators often show greater efficiency in resolving response conflicts than non-meditators. However, the neural mechanisms underlying the improved behavioral efficiency are unclear. Here, we investigated frontal theta dynamics—a neural mechanism involved in cognitive control processes—in long-term mindfulness meditators. The dynamics of EEG theta oscillations (4–8 Hz) recorded over the medial frontal cortex (MFC) were examined in terms of their power (MFC theta power) and their functional connectivity with other brain areas (the MFC-centered theta network). Using a flanker-type paradigm, EEG data were obtained from 22 long-term mindfulness meditators and compared to those from 23 matched controls without meditation experience. Meditators showed more efficient cognitive control after conflicts, evidenced by fewer error responses irrespective of response timing. Furthermore, meditators exhibited enhanced conflict modulations of the MFC-centered theta network shortly before the response, in particular for the functional connection between the MFC and the motor cortex. In contrast, MFC theta power was comparable between groups. These results suggest that the higher behavioral efficiency after conflicts in mindfulness meditators could be a function of increased engagement to control the motor system in association with the MFC-centered theta network. PMID:28638334

Enhancing early consolidation of human episodic memory by theta EEG neurofeedback.

PubMed

Rozengurt, Roman; Shtoots, Limor; Sheriff, Aviv; Sadka, Ofir; Levy, Daniel A

2017-11-01

Consolidation of newly formed memories is readily disrupted, but can it be enhanced? Given the prominent role of hippocampal theta oscillations in memory formation and retrieval, we hypothesized that upregulating theta power during early stages of consolidation might benefit memory stability and persistence. We used EEG neurofeedback to enable participants to selectively increase theta power in their EEG spectra following episodic memory encoding, while other participants engaged in low beta-focused neurofeedback or passively viewed a neutral nature movie. Free recall assessments immediately following the interventions, 24h later and 7d later all indicated benefit to memory of theta neurofeedback, relative to low beta neurofeedback or passive movie-viewing control conditions. The degree of benefit to memory was correlated with the extent of theta power modulation, but not with other spectral changes. Theta enhancement may provide optimal conditions for stabilization of new hippocampus-dependent memories. Copyright © 2017 Elsevier Inc. All rights reserved.

Synaptic correlates of increased cognitive vulnerability with aging: peripheral immune challenge and aging interact to disrupt theta-burst late-phase long-term potentiation in hippocampal area CA1.

PubMed

Chapman, Timothy R; Barrientos, Ruth M; Ahrendsen, Jared T; Maier, Steven F; Patterson, Susan L

2010-06-02

Variability in cognitive functioning increases markedly with age, as does cognitive vulnerability to physiological and psychological challenges. Exploring the basis of this vulnerability may provide important insights into the mechanisms underlying aging-associated cognitive decline. As we have previously reported, the cognitive abilities of aging (24-month-old) F344 x BN rats are generally good, but are more vulnerable to the consequences of a peripheral immune challenge (an intraperitoneal injection of live Escherichia coli) than those of their younger (3-month-old) counterparts. Four days after the injection, the aging, but not the young rats show profound memory deficits, specific to the consolidation of hippocampus-dependent memory processes. Here, we have extended these observations, using hippocampal slices to examine for the first time the combined effects of aging and a recent infection on several forms of synaptic plasticity. We have found that the specific deficit in long-lasting memory observed in the aged animals after infection is mirrored by a specific deficit in a form of long-lasting synaptic plasticity. The late-phase long-term potentiation induced in area CA1 using theta-burst stimulation is particularly compromised by the combined effects of aging and infection-a deficit that can be ameliorated by intra-cisterna magna administration of the naturally occurring antiinflammatory cytokine IL-1Ra (interleukin-1 receptor antagonist). These data support the idea that the combination of aging and a negative life event such as an infection might produce selective, early-stage failures of synaptic plasticity in the hippocampus, with corresponding selective deficits in memory.

Theta variation and spatiotemporal scaling along the septotemporal axis of the hippocampus

PubMed Central

Long, Lauren L.; Bunce, Jamie G.; Chrobak, James J.

2015-01-01

Hippocampal theta has been related to locomotor speed, attention, anxiety, sensorimotor integration and memory among other emergent phenomena. One difficulty in understanding the function of theta is that the hippocampus (HPC) modulates voluntary behavior at the same time that it processes sensory input. Both functions are correlated with characteristic changes in theta indices. The current review highlights a series of studies examining theta local field potential (LFP) signals across the septotemporal or longitudinal axis of the HPC. While the theta signal is coherent throughout the entirety of the HPC, the amplitude, but not the frequency, of theta varies significantly across its three-dimensional expanse. We suggest that the theta signal offers a rich vein of information about how distributed neuronal ensembles support emergent function. Further, we speculate that emergent function across the long axis varies with respect to spatiotemporal scale. Thus, septal HPC processes details of the proximal spatiotemporal environment while more temporal aspects process larger spaces and wider time-scales. The degree to which emergent functions are supported by the synchronization of theta across the septotemporal axis is an open question. Our working model is that theta synchrony serves to bind ensembles representing varying resolutions of spatiotemporal information at interdependent septotemporal areas of the HPC. Such synchrony and cooperative interactions along the septotemporal axis likely support memory formation and subsequent consolidation and retrieval. PMID:25852496

Aged rats show dominant modulation of lower frequency hippocampal theta rhythm during running.

PubMed

Li, Jia-Yi; Kuo, Terry B J; Yang, Cheryl C H

2016-10-01

Aging causes considerable decline in both physiological and mental functions, particularly cognitive function. The hippocampal theta rhythm (4-12Hz) is related to both cognition and locomotion. Aging-related findings of the frequency and amplitude of hippocampal theta oscillations are inconsistent and occasionally contradictory. This inconsistency may be due to the effects of the sleep/wake state and different frequency subbands being overlooked. We assumed that aged rats have lower responses of the hippocampal theta rhythm during running, which is mainly due to the dominant modulation of theta frequency subbands related to cognition. By simultaneously recording electroencephalography, physical activity (PA), and the heart rate (HR), this experiment explored the theta oscillations before, during, and after treadmill running at a constant speed in 8-week-old (adult) and 60-week-old (middle-aged) rats. Compared with adult rats, the middle-aged rats exhibited lower theta activity in all frequency ranges before running. Running increased the theta frequency (Frq, 4-12Hz), total activity of the whole theta band (total power, TP), activity of the middle theta frequency (MT, 6.5-9.5Hz), and PA in both age groups. However, the middle-aged rats still showed fewer changes in these parameters during the whole running process. After the waking baseline values were substracted, middle-aged rats showed significantly fewer differences in ΔFrq, ΔTP, and ΔMT but significantly more differences in low-frequency theta activity (4.0-6.5Hz) and HR than the adult rats did. Therefore, the decreasing activity and response of the whole theta band in the middle-aged rats resulted in dominant modulation of the middle to lower frequency (4.0-9.5Hz) theta rhythm. The different alterations in the theta rhythm during treadmill running in the two groups may reflect that learning decline with age. Copyright © 2016 Elsevier Inc. All rights reserved.

Beam heated linear theta-pinch device for producing hot plasmas

DOEpatents

Bohachevsky, Ihor O.

1981-01-01

A device for producing hot plasmas comprising a single turn theta-pinch coil, a fast discharge capacitor bank connected to the coil, a fuel element disposed along the center axis of the coil, a predetermined gas disposed within the theta-pinch coil, and a high power photon, electron or ion beam generator concentrically aligned to the theta-pinch coil. Discharge of the capacitor bank generates a cylindrical plasma sheath within the theta-pinch coil which heats the outer layer of the fuel element to form a fuel element plasma layer. The beam deposits energy in either the cylindrical plasma sheath or the fuel element plasma layer to assist the implosion of the fuel element to produce a hot plasma.

Characteristics of shock-associated fast-drift kilometric radio bursts

NASA Technical Reports Server (NTRS)

Macdowall, R. J.; Kundu, M. R.; Stone, R. G.

1987-01-01

The existence of a class of fast-drift, shock-associated (SA), kilometric radio bursts which occur at the time of metric type II emission and which are not entirely the kilometric continuation of metric type III bursts has been reported previously (Cane et al., 1981). In this paper unambiguous SA event criteria are established for the purpose of statistically comparing SA events with conventional kilometric type III bursts. Applying these criteria to all long-duration, fast-drift bursts observed by the ISEE-3 spacecraft during a 28-month interval, it is found that more than 70 percent of the events satisfying the criteria are associated with the radio signatures of coronal shocks. If a given event is associated with a metric type II or type IV burst, it is 13 times more likely to satisfy the SA criteria than an event associated only with metric type III activity.

Theta oscillations locked to intended actions rhythmically modulate perception.

PubMed

Tomassini, Alice; Ambrogioni, Luca; Medendorp, W Pieter; Maris, Eric

2017-07-07

Ongoing brain oscillations are known to influence perception, and to be reset by exogenous stimulations. Voluntary action is also accompanied by prominent rhythmic activity, and recent behavioral evidence suggests that this might be coupled with perception. Here, we reveal the neurophysiological underpinnings of this sensorimotor coupling in humans. We link the trial-by-trial dynamics of EEG oscillatory activity during movement preparation to the corresponding dynamics in perception, for two unrelated visual and motor tasks. The phase of theta oscillations (~4 Hz) predicts perceptual performance, even >1 s before movement. Moreover, theta oscillations are phase-locked to the onset of the movement. Remarkably, the alignment of theta phase and its perceptual relevance unfold with similar non-monotonic profiles, suggesting their relatedness. The present work shows that perception and movement initiation are automatically synchronized since the early stages of motor planning through neuronal oscillatory activity in the theta range.

Pre-stimulus thalamic theta power predicts human memory formation.

PubMed

Sweeney-Reed, Catherine M; Zaehle, Tino; Voges, Jürgen; Schmitt, Friedhelm C; Buentjen, Lars; Kopitzki, Klaus; Richardson-Klavehn, Alan; Hinrichs, Hermann; Heinze, Hans-Jochen; Knight, Robert T; Rugg, Michael D

2016-09-01

Pre-stimulus theta (4-8Hz) power in the hippocampus and neocortex predicts whether a memory for a subsequent event will be formed. Anatomical studies reveal thalamus-hippocampal connectivity, and lesion, neuroimaging, and electrophysiological studies show that memory processing involves the dorsomedial (DMTN) and anterior thalamic nuclei (ATN). The small size and deep location of these nuclei have limited real-time study of their activity, however, and it is unknown whether pre-stimulus theta power predictive of successful memory formation is also found in these subcortical structures. We recorded human electrophysiological data from the DMTN and ATN of 7 patients receiving deep brain stimulation for refractory epilepsy. We found that greater pre-stimulus theta power in the right DMTN was associated with successful memory encoding, predicting both behavioral outcome and post-stimulus correlates of successful memory formation. In particular, significant correlations were observed between right DMTN theta power and both frontal theta and right ATN gamma (32-50Hz) phase alignment, and frontal-ATN theta-gamma cross-frequency coupling. We draw the following primary conclusions. Our results provide direct electrophysiological evidence in humans of a role for the DMTN as well as the ATN in memory formation. Furthermore, prediction of subsequent memory performance by pre-stimulus thalamic oscillations provides evidence that post-stimulus differences in thalamic activity that index successful and unsuccessful encoding reflect brain processes specifically underpinning memory formation. Finally, the findings broaden the understanding of brain states that facilitate memory encoding to include subcortical as well as cortical structures. Copyright © 2016 Elsevier Inc. All rights reserved.

Burst-by-burst laser frequency monitor

NASA Technical Reports Server (NTRS)

Esproles, Carlos (Inventor)

1994-01-01

The invention is a system for real-time frequency monitoring and display of an RF burst where the burst frequency is analyzed and displayed on a burst-by-burst basis in order to allow for frequency control. Although the invention was made for monitoring the laser frequency of a LIDAR system, it has other applications where realtime monitoring is required. The novelty of the invention resides in the use of a counter that is reset at the beginning of each unit time of monitoring and then gated for a unit of time. The invention also has an LED bar graph for displaying the measure of frequency at the end of each unit time in either a bar length mode or a moving dot mode. In the latter mode, the operator makes necessary adjustments to maintain the dot at the center of the bar graph.

Non-Equilibrium Thermodynamics of Transcriptional Bursts

NASA Astrophysics Data System (ADS)

Hernández-Lemus, Enrique

Gene transcription or Gene Expression (GE) is the process which transforms the information encoded in DNA into a functional RNA message. It is known that GE can occur in bursts or pulses. Transcription is irregular, with strong periods of activity, interspersed by long periods of inactivity. If we consider the average behavior over millions of cells, this process appears to be continuous. But at the individual cell level, there is considerable variability, and for most genes, very little activity at any one time. Some have claimed that GE bursting can account for the high variability in gene expression occurring between cells in isogenic populations. This variability has a big impact on cell behavior and thus on phenotypic conditions and disease. In view of these facts, the development of a thermodynamic framework to study gene expression and transcriptional regulation to integrate the vast amount of molecular biophysical GE data is appealing. Application of such thermodynamic formalism is useful to observe various dissipative phenomena in GE regulatory dynamics. In this chapter we will examine at some detail the complex phenomena of transcriptional bursts (specially of a certain class of anomalous bursts) in the context of a non-equilibrium thermodynamics formalism and will make some initial comments on the relevance of some irreversible processes that may be connected to anomalous transcriptional bursts.

Magnetar Bursts

NASA Technical Reports Server (NTRS)

Kouveliotou, Chryssa

2014-01-01

The Fermi/Gamma-ray Burst Monitor (GBM) was launched in June 2008. During the last five years the instrument has observed several hundreds of bursts from 8 confirmed magnetars and 19 events from unconfirmed sources. I will discuss the results of the GBM magnetar burst catalog, expand on the different properties of their diverse source population, and compare these results with the bursting activity of past sources. I will then conclude with thoughts of how these properties fit the magnetar theoretical models.

Bursts of seizures in long-term recordings of human focal epilepsy

PubMed Central

Karoly, Philippa J.; Nurse, Ewan S.; Freestone, Dean R.; Ung, Hoameng; Cook, Mark J.; Boston, Ray

2017-01-01

Summary Objective We report on temporally clustered seizures detected from continuous long-term ambulatory human electroencephalographic data. The objective was to investigate short-term seizure clustering, which we have termed bursting, and consider implications for patient care, seizure prediction, and evaluating therapies. Methods Chronic ambulatory intracranial EEG data collected for the purpose of seizure prediction were annotated to identify seizure events. A detection algorithm was used to identify bursts of events. Burst events were compared to non-burst events to evaluate event dispersion, duration and dynamics. Results Bursts of seizures were present in six of fifteen patients, and detections were consistent over long term monitoring (> 2 years). Seizures within bursts are highly overdispersed compared to non-burst seizures. There was a complicated relationship between bursts and clinical seizures, although bursts were associated with multi-modal distributions of seizure duration, and poorer predictive outcomes. For three subjects, bursts demonstrated distinctive pre-ictal dynamics compared to clinical seizures. Significance We have previously hypothesized that there are distinct physiological pathways underlying short and long duration seizures. Here we show that burst seizures fall almost exclusively within the short population of seizure durations; however, a short duration was not sufficient to induce or imply bursting. We can therefore conclude that in addition to distinct mechanisms underlying seizure duration, there are separate factors regulating bursts of seizures. We show that bursts were a robust phenomenon in our patient cohort, which were consistent with overdispersed seizure rates, suggesting long-memory dynamics. PMID:28084639

Oscillatory frontal theta responses are increased upon bisensory stimulation.

PubMed

Sakowitz, O W; Schürmann, M; Başar, E

2000-05-01

To investigate the functional correlation of oscillatory EEG components with the interaction of sensory modalities following simultaneous audio-visual stimulation. In an experimental study (15 subjects) we compared auditory evoked potentials (AEPs) and visual evoked potentials (VEPs) to bimodal evoked potentials (BEPs; simultaneous auditory and visual stimulation). BEPs were assumed to be brain responses to complex stimuli as a marker for intermodal associative functioning. Frequency domain analysis of these EPs showed marked theta-range components in response to bimodal stimulation. These theta components could not be explained by linear addition of the unimodal responses in the time domain. Considering topography the increased theta-response showed a remarkable frontality in proximity to multimodal association cortices. Referring to methodology we try to demonstrate that, even if various behavioral correlates of brain oscillations exist, common patterns can be extracted by means of a systems-theoretical approach. Serving as an example of functionally relevant brain oscillations, theta responses could be interpreted as an indicator of associative information processing.

Burst Firing in Bee Gustatory Neurons Prevents Adaptation.

PubMed

Miriyala, Ashwin; Kessler, Sébastien; Rind, F Claire; Wright, Geraldine A

2018-05-01

Animals detect changes in the environment using modality-specific, peripheral sensory neurons. The insect gustatory system encodes tastant identity and concentration through the independent firing of gustatory receptor neurons (GRNs) that spike rapidly at stimulus onset and quickly adapt. Here, we show the first evidence that concentrated sugar evokes a temporally structured burst pattern of spiking involving two GRNs within the gustatory sensilla of bumblebees. Bursts of spikes resulted when a sucrose-activated GRN was inhibited by another GRN at a frequency of ∼22 Hz during the first 1 s of stimulation. Pharmacological blockade of gap junctions abolished bursting, indicating that bee GRNs have electrical synapses that produce a temporal pattern of spikes when one GRN is activated by a sugar ligand. Bursting permitted bee GRNs to maintain a high rate of spiking and to exhibit the slowest rate of adaptation of any insect species. Feeding bout duration correlated with coherent bursting; only sugar concentrations that produced bursting evoked the bumblebee's feeding reflex. Volume of solution imbibed was a direct function of time in contact with food. We propose that gap junctions among GRNs enable a sustained rate of GRN spiking that is necessary to drive continuous feeding by the bee proboscis. Copyright © 2018 Elsevier Ltd. All rights reserved.

Enhancement of motor learning by focal intermittent theta burst stimulation (iTBS) of either the primary motor (M1) or somatosensory area (S1) in healthy human subjects.

PubMed

Platz, Thomas; Adler-Wiebe, Marija; Roschka, Sybille; Lotze, Martin

2018-01-01

Motor rehabilitation after brain damage relies on motor re-learning as induced by specific training. Non-invasive brain stimulation (NIBS) can alter cortical excitability and thereby has a potential to enhance subsequent training-induced learning. Knowledge about any priming effects of NIBS on motor learning in healthy subjects can help to design targeted therapeutic applications in brain-damaged subjects. To examine whether complex motor learning in healthy subjects can be enhanced by intermittent theta burst stimulation (iTBS) to primary motor or sensory cortical areas. Eighteen young healthy subjects trained eight different arm motor tasks (arm ability training, AAT) once a day for 5 days using their left non-dominant arm. Except for day 1 (baseline), training was performed after applying an excitatory form of repetitive transcranial magnetic stimulation (iTBS) to either (I) right M1 or (II) S1, or (III) sham stimulation to the right M1. Subjects were randomly assigned to conditions I, II, or III. A principal component analysis of the motor behaviour data suggested eight independent motor abilities corresponding to the 8 trained tasks. AAT induced substantial motor learning across abilities with generalisation to a non-trained test of finger dexterity (Nine-Hole-Peg-Test, NHPT). Participants receiving iTBS (to either M1 or S1) showed better performance with the AAT tasks over the period of training compared to sham stimulation as well as a bigger improvement with the generalisation task (NHPT) for the trained left hand after training completion. Priming with an excitatory repetitive transcranial magnetic stimulation as iTBS of either M1 or S1 can enhance motor learning across different sensorimotor abilities.

A KCNJ6 gene polymorphism modulates theta oscillations during reward processing.

PubMed

Kamarajan, Chella; Pandey, Ashwini K; Chorlian, David B; Manz, Niklas; Stimus, Arthur T; Edenberg, Howard J; Wetherill, Leah; Schuckit, Marc; Wang, Jen-Chyong; Kuperman, Samuel; Kramer, John; Tischfield, Jay A; Porjesz, Bernice

2017-05-01

Event related oscillations (EROs) are heritable measures of neurocognitive function that have served as useful phenotype in genetic research. A recent family genome-wide association study (GWAS) by the Collaborative Study on the Genetics of Alcoholism (COGA) found that theta EROs during visual target detection were associated at genome-wide levels with several single nucleotide polymorphisms (SNPs), including a synonymous SNP, rs702859, in the KCNJ6 gene that encodes GIRK2, a G-protein inward rectifying potassium channel that regulates excitability of neuronal networks. The present study examined the effect of the KCNJ6 SNP (rs702859), previously associated with theta ERO to targets in a visual oddball task, on theta EROs during reward processing in a monetary gambling task. The participants were 1601 adolescent and young adult offspring within the age-range of 17-25years (800 males and 801 females) from high-dense alcoholism families as well as control families of the COGA prospective study. Theta ERO power (3.5-7.5Hz, 200-500ms post-stimulus) was compared across genotype groups. ERO theta power at central and parietal regions increased as a function of the minor allele (A) dose in the genotype (AA>AG>GG) in both loss and gain conditions. These findings indicate that variations in the KCNJ6 SNP influence magnitude of theta oscillations at posterior loci during the evaluation of loss and gain, reflecting a genetic influence on neuronal circuits involved in reward-processing. Increased theta power as a function of minor allele dose suggests more efficient cognitive processing in those carrying the minor allele of the KCNJ6 SNPs. Future studies are needed to determine the implications of these genetic effects on posterior theta EROs as possible "protective" factors, or as indices of delays in brain maturation (i.e., lack of frontalization). Copyright © 2016 Elsevier B.V. All rights reserved.

The Dynamics of Networks of Identical Theta Neurons.

PubMed

Laing, Carlo R

2018-02-05

We consider finite and infinite all-to-all coupled networks of identical theta neurons. Two types of synaptic interactions are investigated: instantaneous and delayed (via first-order synaptic processing). Extensive use is made of the Watanabe/Strogatz (WS) ansatz for reducing the dimension of networks of identical sinusoidally-coupled oscillators. As well as the degeneracy associated with the constants of motion of the WS ansatz, we also find continuous families of solutions for instantaneously coupled neurons, resulting from the reversibility of the reduced model and the form of the synaptic input. We also investigate a number of similar related models. We conclude that the dynamics of networks of all-to-all coupled identical neurons can be surprisingly complicated.

Theta EEG source localization using LORETA in partial epilepsy patients with and without medication.

PubMed

Clemens, B; Bessenyei, M; Fekete, I; Puskás, S; Kondákor, I; Tóth, M; Hollódy, K

2010-06-01

To investigate and localize the sources of spontaneous, scalp-recorded theta activity in patients with partial epilepsy (PE). Nine patients with beginning, untreated PE (Group 1), 31 patients with already treated PE (Group 2), and 14 healthy persons were investigated by means of spectral analysis and LORETA, low resolution electromagnetic tomography (1 Hz very narrow band analysis, age-adjusted, Z-scored values). The frequency of main interest was 4-8 Hz. Group analysis: Group 1 displayed bilateral theta maxima in the temporal theta area (TTA), parietal theta area (PTA), and frontal theta area (FTA). In Group 2, theta activity increased all over the scalp as compared to the normative mean (Z=0) and also to Group 1. Maximum activity was found in the TTA, PTA, and FTA. However, in the PTA and FTA the centers of the abnormality shifted towards the medial cortex. Individual analysis: all the patients showed preferential activation (maximum Z-values) within one of the three theta areas. EEG activity in the theta band is increased in anatomically meaningful patterns in PE patients, which differs from the anatomical distribution of theta in healthy persons. The findings contribute to our understanding of the sources of theta rhythms and the pathophysiology of PE. Copyright 2010 International Federation of Clinical Neurophysiology. Published by Elsevier Ireland Ltd. All rights reserved.

HUBBLE STAYS ON TRAIL OF FADING GAMMA-RAY BURST FIREBALL

NASA Technical Reports Server (NTRS)

2002-01-01

A Hubble Space Telescope image of the fading fireball from one of the universe's most mysterious phenomena, a gamma-ray burst. Though the visible component has faded to 1/500th its brightness (27.7 magnitude) from the time it was first discovered by ground- based telescopes last March (the actual gamma-ray burst took place on February 28), Hubble continues to clearly see the fireball and discriminated a surrounding nebulosity (at 25th magnitude) which is considered a host galaxy. The continued visibility of the burst, and the rate of its fading, support theories that the light from a gamma-ray burst is an expanding relativistic (moving near the speed of light) fireball, possibly produced by the collision of two dense objects, such as an orbiting pair of neutron stars. If the burst happened nearby, within our own galaxy, the resulting fireball should have had only enough energy to propel it into space for a month. The fact that this fireball is still visible after six months means the explosion was truly titanic and, to match the observed brightness, must have happened at the vast distances of galaxies. The energy released in a burst, which can last from a fraction of a second to a few hundred seconds, is equal to all of the Sun's energy generated over its 10 billion year lifetime. The false-color image was taken Sept. 5, 1997 with the Space Telescope Imaging Spectrograph. Credit: Andrew Fruchter (STScI), Elena Pian (ITSRE-CNR), and NASA

Measurement of theta13 in the double Chooz experiment

NASA Astrophysics Data System (ADS)

Yang, Guang

Neutrino oscillation has been established for over a decade. The mixing angle theta13 is one of the parameters that is most difficult to measure due to its small value. Currently, reactor antineutrino experiments provide the best knowledge of theta13, using the electron antineutrino disappearance phenomenon. The most compelling advantage is the high intensity of the reactor antineutrino rate. The Double Chooz experiment, located on the border of France and Belgium, is such an experiment, which aims to have one of the most precise theta 13 measurements in the world. Double Chooz has a single-detector phase and a double-detector phase. For the single-detector phase, the limit of the theta 13 sensitivity comes mostly from the reactor flux. However, the uncertainty on the reactor flux is highly suppressed in the double-detector phase. Oscillation analyses for the two phases have different strategies but need similar inputs, including background estimation, detection systematics evaluation, energy reconstruction and so on. The Double Chooz detectors are filled with gadolinium (Gd) doped liquid scintillator and use the inverse beta decay (IBD) signal so that for each phase, there are two independent theta13 measurements based on different neutron capturer (Gd or hydrogen). Multiple oscillation analyses are performed to provide the best 13 results. In addition to the 13 measurement, Double Chooz is also an excellent \\playground" to do diverse physics research. For example, a 252Cf calibration source study has been done to understand the spontaneous decay of this radioactive source. Further, Double Chooz also has the ability to do a sterile neutrino search in a certain mass region. Moreover, some new physics ideas can be tested in Double Chooz. In this thesis, the detailed methods to provide precise theta13 measurement will be described and the other physics topics will be introduced.

Method and apparatus for coherent burst ranging

DOEpatents

Wachter, Eric A.; Fisher, Walter G.

1998-01-01

A high resolution ranging method is described utilizing a novel modulated waveform, hereafter referred to as coherent burst modulation. In the coherent burst method, high frequency modulation of an acoustic or electromagnetic transmitter, such as a laser, is performed at a modulation frequency. This modulation frequency is transmitted quasi-continuously in the form of interrupted bursts of radiation. Energy from the transmitter is directed onto a target, interacts with the target, and the returning energy is collected. The encoded burst pattern contained in the collected return signal is detected coherently by a receiver that is tuned so as to be principally sensitive to the modulation frequency. The receiver signal is processed to determine target range using both time-of-flight of the burst envelope and phase shift of the high frequency modulation. This approach effectively decouples the maximum unambiguous range and range resolution relationship of earlier methods, thereby allowing high precision ranging to be conducted at arbitrarily long distances using at least one burst of encoded energy. The use of a receiver tuned to the high frequency modulation contained within the coherent burst vastly improves both sensitivity in the detection of the target return signal and rejection of background interferences, such as ambient acoustic or electromagnetic noise. Simultaneous transmission at several energies (or wavelengths) is possible by encoding each energy with a separate modulation frequency or pattern; electronic demodulation at the receiver allows the return pattern for each energy to be monitored independently. Radial velocity of a target can also be determined by monitoring change in phase shift of the return signal as a function of time.

Method and apparatus for coherent burst ranging

DOEpatents

Wachter, E.A.; Fisher, W.G.

1998-04-28

A high resolution ranging method is described utilizing a novel modulated waveform, hereafter referred to as coherent burst modulation. In the coherent burst method, high frequency modulation of an acoustic or electromagnetic transmitter, such as a laser, is performed at a modulation frequency. This modulation frequency is transmitted quasi-continuously in the form of interrupted bursts of radiation. Energy from the transmitter is directed onto a target, interacts with the target, and the returning energy is collected. The encoded burst pattern contained in the collected return signal is detected coherently by a receiver that is tuned so as to be principally sensitive to the modulation frequency. The receiver signal is processed to determine target range using both time-of-flight of the burst envelope and phase shift of the high frequency modulation. This approach effectively decouples the maximum unambiguous range and range resolution relationship of earlier methods, thereby allowing high precision ranging to be conducted at arbitrarily long distances using at least one burst of encoded energy. The use of a receiver tuned to the high frequency modulation contained within the coherent burst vastly improves both sensitivity in the detection of the target return signal and rejection of background interferences, such as ambient acoustic or electromagnetic noise. Simultaneous transmission at several energies (or wavelengths) is possible by encoding each energy with a separate modulation frequency or pattern; electronic demodulation at the receiver allows the return pattern for each energy to be monitored independently. Radial velocity of a target can also be determined by monitoring change in phase shift of the return signal as a function of time. 12 figs.

Overview of Solar Radio Bursts and their Sources

NASA Astrophysics Data System (ADS)

Golla, Thejappa; MacDowall, Robert J.

2018-06-01

Properties of radio bursts emitted by the Sun at frequencies below tens of MHz are reviewed. In this frequency range, the most prominent radio emissions are those of solar type II, complex type III and solar type IV radio bursts, excited probably by the energetic electron populations accelerated in completely different environments: (1) type II bursts are due to non-relativistic electrons accelerated by the CME driven interplanetary shocks, (2) complex type III bursts are due to near-relativistic electrons accelerated either by the solar flare reconnection process or by the SEP shocks, and (3) type IV bursts are due to relativistic electrons, trapped in the post-eruption arcades behind CMEs; these relativistic electrons probably are accelerated by the continued reconnection processes occurring beneath the CME. These radio bursts, which can serve as the natural plasma probes traversing the heliosphere by providing information about various crucial space plasma parameters, are also an ideal instrument for investigating acceleration mechanisms responsible for the high energy particles. The rich collection of valuable high quality radio and high time resolution in situ wave data from the WAVES experiments of the STEREO A, STEREO B and WIND spacecraft has provided an unique opportunity to study these different radio phenomena and understand the complex physics behind their excitation. We have developed Monte Carlo simulation techniques to estimate the propagation effects on the observed characteristics of these low frequency radio bursts. We will present some of the new results and describe how one can use these radio burst observations for space weather studies. We will also describe some of the non-linear plasma processes detected in the source regions of both solar type III and type II radio bursts. The analysis and simulation techniques used in these studies will be of immense use for future space based radio observations.

Intermediate stage of sleep and acute cerveau isolé preparation in the rat.

PubMed

User, P; Gioanni, H; Gottesmann, C

1980-01-01

The acute cerveau isole rat shows spindle bursts of large amplitude alternating with low voltage activity in the frontal cortex and continuous theta rhythm in the dorsal hippocampus. These patterns closely resemble an "intermediate" stage of sleep-waking cycle, when the forebrain structures seem to be functionally disconnected from the brainstem.

Laminar Profile of Spontaneous and Evoked Theta: Rhythmic Modulation of Cortical Processing During Word Integration

PubMed Central

Halgren, Eric; Kaestner, Erik; Marinkovic, Ksenija; Cash, Sydney S.; Wang, Chunmao; Schomer, Donald L.; Madsen, Joseph R.; Ulbert, Istvan

2015-01-01

Theta may play a central role during language understanding and other extended cognitive processing, providing an envelope for widespread integration of participating cortical areas. We used linear microelectrode arrays in epileptics to define the circuits generating theta in inferotemporal, perirhinal, entorhinal, prefrontal and anterior cingulate cortices. In all locations, theta was generated by excitatory current sinks in middle layers which receive predominantly feedforward inputs, alternating with sinks in superficial layers which receive mainly feedback/associative inputs. Baseline and event-related theta were generated by indistinguishable laminar profiles of transmembrane currents and unit-firing. Word presentation could reset theta phase, permitting theta to contribute to late event-related potentials, even when theta power decreases relative to baseline. Limited recordings during sentence reading are consistent with rhythmic theta activity entrained by a given word modulating the neural background for the following word. These findings show that theta occurs spontaneously, and can be momentarily suppressed, reset and synchronized by words. Theta represents an alternation between feedforward/divergent and associative/convergent processing modes that may temporally organize sustained processing and optimize the timing of memory formation. We suggest that words are initially encoded via a ventral feedforward stream which is lexicosemantic in the anteroventral temporal lobe; its arrival may trigger a widespread theta rhythm which integrates the word within a larger context. PMID:25801916

Theta frequency decreases throughout the hippocampal formation in a focal epilepsy model.

PubMed

Kilias, Antje; Häussler, Ute; Heining, Katharina; Froriep, Ulrich P; Haas, Carola A; Egert, Ulrich

2018-06-01

Mesial temporal lobe epilepsy is characterized by focal, recurrent spontaneous seizures, sclerosis and granule cell dispersion (GCD) in the hippocampal formation. Changes in theta rhythm properties have been correlated with the severity of hippocampal restructuring and were suggested as a cause of memory deficits accompanying epilepsy. For severe sclerosis, it has even been questioned whether theta band oscillations persist. We asked how theta oscillations change with graded restructuring along the longitudinal hippocampal axis and whether these changes correlate with the overall severity of temporal lobe epilepsy. We recorded local field potentials in the medial entorhinal cortex and along the septo-temporal axis of the dentate gyrus at sites with different degrees of GCD in freely behaving epileptic mice. Theta frequency was decreased at all recording positions throughout the dentate gyrus and in the medial entorhinal cortex, irrespective of the extent of GCD or the rate of severe epileptic events. The frequency reduction by up to 1.7 Hz, corresponding to 1/3 octaves within the theta range, was present during rest, exploration and running. Despite the frequency reduction, theta oscillations remained coherent across the hippocampal formation and were modulated by running speed as in controls. The reduction in theta frequency thus is likely not a consequence of the local restructuring but rather a global phenomenon affecting the hippocampal formation as a whole. © 2018 Wiley Periodicals, Inc.

Quantum key based burst confidentiality in optical burst switched networks.

PubMed

Balamurugan, A M; Sivasubramanian, A

2014-01-01

The optical burst switching (OBS) is an emergent result to the technology concern that could achieve a feasible network in future. They are endowed with the ability to meet the bandwidth requirement of those applications that require intensive bandwidth. There are more domains opening up in the OBS that evidently shows their advantages and their capability to face the future network traffic. However, the concept of OBS is still far from perfection facing issues in case of security threat. The transfer of optical switching paradigm to optical burst switching faces serious downfall in the fields of burst aggregation, routing, authentication, dispute resolution, and quality of service (QoS). This paper deals with employing RC4 (stream cipher) to encrypt and decrypt bursts thereby ensuring the confidentiality of the burst. Although the use of AES algorithm has already been proposed for the same issue, by contrasting the two algorithms under the parameters of burst encryption and decryption time, end-to-end delay, it was found that RC4 provided better results. This paper looks to provide a better solution for the confidentiality of the burst in OBS networks.

Quantum Key Based Burst Confidentiality in Optical Burst Switched Networks

PubMed Central

Balamurugan, A. M.; Sivasubramanian, A.

2014-01-01

The optical burst switching (OBS) is an emergent result to the technology concern that could achieve a feasible network in future. They are endowed with the ability to meet the bandwidth requirement of those applications that require intensive bandwidth. There are more domains opening up in the OBS that evidently shows their advantages and their capability to face the future network traffic. However, the concept of OBS is still far from perfection facing issues in case of security threat. The transfer of optical switching paradigm to optical burst switching faces serious downfall in the fields of burst aggregation, routing, authentication, dispute resolution, and quality of service (QoS). This paper deals with employing RC4 (stream cipher) to encrypt and decrypt bursts thereby ensuring the confidentiality of the burst. Although the use of AES algorithm has already been proposed for the same issue, by contrasting the two algorithms under the parameters of burst encryption and decryption time, end-to-end delay, it was found that RC4 provided better results. This paper looks to provide a better solution for the confidentiality of the burst in OBS networks. PMID:24578663

On burst-and-coast swimming performance in fish-like locomotion.

PubMed

Chung, M-H

2009-09-01

Burst-and-coast swimming performance in fish-like locomotion is studied via two-dimensional numerical simulation. The numerical method used is the collocated finite-volume adaptive Cartesian cut-cell method developed previously. The NACA00xx airfoil shape is used as an equilibrium fish-body form. Swimming in a burst-and-coast style is computed assuming that the burst phase is composed of a single tail-beat. Swimming efficiency is evaluated in terms of the mass-specific cost of transport instead of the Froude efficiency. The effects of the Reynolds number (based on the body length and burst time), duty cycle and fineness ratio (the body length over the largest thickness) on swimming performance (momentum capacity and the mass-specific cost of transport) are studied quantitatively. The results lead to a conclusion consistent with previous findings that a larval fish seldom swims in a burst-and-coast style. Given mass and swimming speed, a fish needs the least cost if it swims in a burst-and-coast style with a fineness ratio of 8.33. This energetically optimal fineness ratio is larger than that derived from the simple hydromechanical model proposed in literature. The calculated amount of energy saving in burst-and-coast swimming is comparable with the real-fish estimation in the literature. Finally, the predicted wake-vortex structures of both continuous and burst-and-coast swimming are biologically relevant.

Regular theta-firing neurons in the nucleus incertus during sustained hippocampal activation.

PubMed

Martínez-Bellver, Sergio; Cervera-Ferri, Ana; Martínez-Ricós, Joana; Ruiz-Torner, Amparo; Luque-Garcia, Aina; Luque-Martinez, Aina; Blasco-Serra, Arantxa; Guerrero-Martínez, Juan; Bataller-Mompeán, Manuel; Teruel-Martí, Vicent

2015-04-01

This paper describes the existence of theta-coupled neuronal activity in the nucleus incertus (NI). Theta rhythm is relevant for cognitive processes such as spatial navigation and memory processing, and can be recorded in a number of structures related to the hippocampal activation including the NI. Strong evidence supports the role of this tegmental nucleus in neural circuits integrating behavioural activation with the hippocampal theta rhythm. Theta oscillations have been recorded in the local field potential of the NI, highly coupled to the hippocampal waves, although no rhythmical activity has been reported in neurons of this nucleus. The present work analyses the neuronal activity in the NI in conditions leading to sustained hippocampal theta in the urethane-anaesthetised rat, in order to test whether such activation elicits a differential firing pattern. Wavelet analysis has been used to better define the neuronal activity already described in the nucleus, i.e., non-rhythmical neurons firing at theta frequency (type I neurons) and fast-firing rhythmical neurons (type II). However, the most remarkable finding was that sustained stimulation activated regular-theta neurons (type III), which were almost silent in baseline conditions and have not previously been reported. Thus, we describe the electrophysiological properties of type III neurons, focusing on their coupling to the hippocampal theta. Their spike rate, regularity and phase locking to the oscillations increased at the beginning of the stimulation, suggesting a role in the activation or reset of the oscillation. Further research is needed to address the specific contribution of these neurons to the entire circuit. © 2015 Federation of European Neuroscience Societies and John Wiley & Sons Ltd.

Recent developments in linear theta-pinch research: experiment and theory

DOE Office of Scientific and Technical Information (OSTI.GOV)

McKenna, K.F.; Bartsch, R.R.; Commisso, R.J.

1978-01-01

High energy plasmas offusion interest can be generated in linear theta pinches. However, end losses present a fundamental limitation on the plasma containment time. This paper discusses recent progress in end-loss and end-stoppering experiments and in the theoretical understanding of linear theta-pinch physics.

Burst suppression probability algorithms: state-space methods for tracking EEG burst suppression

NASA Astrophysics Data System (ADS)

Chemali, Jessica; Ching, ShiNung; Purdon, Patrick L.; Solt, Ken; Brown, Emery N.

2013-10-01

Objective. Burst suppression is an electroencephalogram pattern in which bursts of electrical activity alternate with an isoelectric state. This pattern is commonly seen in states of severely reduced brain activity such as profound general anesthesia, anoxic brain injuries, hypothermia and certain developmental disorders. Devising accurate, reliable ways to quantify burst suppression is an important clinical and research problem. Although thresholding and segmentation algorithms readily identify burst suppression periods, analysis algorithms require long intervals of data to characterize burst suppression at a given time and provide no framework for statistical inference. Approach. We introduce the concept of the burst suppression probability (BSP) to define the brain's instantaneous propensity of being in the suppressed state. To conduct dynamic analyses of burst suppression we propose a state-space model in which the observation process is a binomial model and the state equation is a Gaussian random walk. We estimate the model using an approximate expectation maximization algorithm and illustrate its application in the analysis of rodent burst suppression recordings under general anesthesia and a patient during induction of controlled hypothermia. Main result. The BSP algorithms track burst suppression on a second-to-second time scale, and make possible formal statistical comparisons of burst suppression at different times. Significance. The state-space approach suggests a principled and informative way to analyze burst suppression that can be used to monitor, and eventually to control, the brain states of patients in the operating room and in the intensive care unit.

Mid-frontal theta activity is diminished during cognitive control in Parkinson's disease.

PubMed

Singh, Arun; Richardson, Sarah Pirio; Narayanan, Nandakumar; Cavanagh, James F

2018-05-23

Mid-frontal theta activity underlies cognitive control. These 4-8 Hz rhythms are modulated by cortical dopamine and can be abnormal in patients with Parkinson's disease (PD). Here, we investigated mid-frontal theta deficits in PD patients during a task explicitly involving cognitive control. We collected scalp EEG from high-performing PD patients and demographically matched controls during performance of a modified Simon reaction-time task. This task involves cognitive control to adjudicate response conflict and error-related adjustments. Task performance of PD patients was indistinguishable from controls, but PD patients had less mid-frontal theta modulations around cues and responses. Critically, PD patients had attenuated mid-frontal theta activity specifically associated with response conflict and post-error processing. These signals were unaffected by medication or motor scores. Post-error mid-frontal theta activity was correlated with disease duration. Classification of control vs. PD from these data resulted in a specificity of 69% and a sensitivity of 72%. These findings help define the scope of mid-frontal theta aberrations during cognitive control in PD, and may provide insight into the nature of PD-related cognitive dysfunction. Copyright © 2018 Elsevier Ltd. All rights reserved.

Correlation of the Hippocampal theta rhythm to changes in hypothalamic temperature

NASA Technical Reports Server (NTRS)

Saleh, M. A.; Horowitz, J. M.; Hsieh, A. C. L.

1974-01-01

Warming and cooling the preoptic anterior hypothalamic area in awake, loosely restrained rabbits was found to evoke theta rhythm. This is consistent with previous studies indicating that theta rhythm is a nonspecific response evoked by stimulation of several sensory modalities. Several studies have correlated theta rhythm with alertness. A neural pathway involving the hypothalamus, the hippocampus, the septal area, and the reticular formation is proposed. Thus, a role of this pathway may be to alert the animal to changes in its body temperature.

Causal relationships between neurons of the nucleus incertus and the hippocampal theta activity in the rat.

PubMed

Martínez-Bellver, Sergio; Cervera-Ferri, Ana; Luque-García, Aina; Martínez-Ricós, Joana; Valverde-Navarro, Alfonso; Bataller, Manuel; Guerrero, Juan; Teruel-Marti, Vicent

2017-03-01

The nucleus incertus is a key node of the brainstem circuitry involved in hippocampal theta rhythmicity. Synchronisation exists between the nucleus incertus and hippocampal activities during theta periods. By the Granger causality analysis, we demonstrated a directional information flow between theta rhythmical neurons in the nucleus incertus and the hippocampus in theta-on states. The electrical stimulation of the nucleus incertus is also able to evoke a phase reset of the hippocampal theta wave. Our data suggest that the nucleus incertus is a key node of theta generation and the modulation network. In recent years, a body of evidence has shown that the nucleus incertus (NI), in the dorsal tegmental pons, is a key node of the brainstem circuitry involved in hippocampal theta rhythmicity. Ascending reticular brainstem system activation evokes hippocampal theta rhythm with coupled neuronal activity in the NI. In a recent paper, we showed three populations of neurons in the NI with differential firing during hippocampal theta activation. The objective of this work was to better evaluate the causal relationship between the activity of NI neurons and the hippocampus during theta activation in order to further understand the role of the NI in the theta network. A Granger causality analysis was run to determine whether hippocampal theta activity with sensory-evoked theta depends on the neuronal activity of the NI, or vice versa. The analysis showed causal interdependence between the NI and the hippocampus during theta activity, whose directional flow depended on the different neuronal assemblies of the NI. Whereas type I and II NI neurons mainly acted as receptors of hippocampal information, type III neuronal activity was the predominant source of flow between the NI and the hippocampus in theta states. We further determined that the electrical activation of the NI was able to reset hippocampal waves with enhanced theta-band power, depending on the septal area

Structural Organization of the Corpus Callosum Predicts Attentional Shifts after Continuous Theta Burst Stimulation.

PubMed

Chechlacz, Magdalena; Humphreys, Glyn W; Sotiropoulos, Stamatios N; Kennard, Christopher; Cazzoli, Dario

2015-11-18

Repetitive transcranial magnetic stimulation (rTMS) applied over the right posterior parietal cortex (PPC) in healthy participants has been shown to trigger a significant rightward shift in the spatial allocation of visual attention, temporarily mimicking spatial deficits observed in neglect. In contrast, rTMS applied over the left PPC triggers a weaker or null attentional shift. However, large interindividual differences in responses to rTMS have been reported. Studies measuring changes in brain activation suggest that the effects of rTMS may depend on both interhemispheric and intrahemispheric interactions between cortical loci controlling visual attention. Here, we investigated whether variability in the structural organization of human white matter pathways subserving visual attention, as assessed by diffusion magnetic resonance imaging and tractography, could explain interindividual differences in the effects of rTMS. Most participants showed a rightward shift in the allocation of spatial attention after rTMS over the right intraparietal sulcus (IPS), but the size of this effect varied largely across participants. Conversely, rTMS over the left IPS resulted in strikingly opposed individual responses, with some participants responding with rightward and some with leftward attentional shifts. We demonstrate that microstructural and macrostructural variability within the corpus callosum, consistent with differential effects on cross-hemispheric interactions, predicts both the extent and the direction of the response to rTMS. Together, our findings suggest that the corpus callosum may have a dual inhibitory and excitatory function in maintaining the interhemispheric dynamics that underlie the allocation of spatial attention. The posterior parietal cortex (PPC) controls allocation of attention across left versus right visual fields. Damage to this area results in neglect, characterized by a lack of spatial awareness of the side of space contralateral to the brain injury. Transcranial magnetic stimulation over the PPC is used to study cognitive mechanisms of spatial attention and to examine the potential of this technique to treat neglect. However, large individual differences in behavioral responses to stimulation have been reported. We demonstrate that the variability in the structural organization of the corpus callosum accounts for these differences. Our findings suggest novel dual mechanism of the corpus callosum function in spatial attention and have broader implications for the use of stimulation in neglect rehabilitation. Copyright © 2015 the authors 0270-6474/15/3515353-16$15.00/0.

Beta burst dynamics in Parkinson's disease OFF and ON dopaminergic medication.

PubMed

Tinkhauser, Gerd; Pogosyan, Alek; Tan, Huiling; Herz, Damian M; Kühn, Andrea A; Brown, Peter

2017-11-01

Exaggerated basal ganglia beta activity (13-35 Hz) is commonly found in patients with Parkinson's disease and can be suppressed by dopaminergic medication, with the degree of suppression being correlated with the improvement in motor symptoms. Importantly, beta activity is not continuously elevated, but fluctuates to give beta bursts. The percentage number of longer beta bursts in a given interval is positively correlated with clinical impairment in Parkinson's disease patients. Here we determine whether the characteristics of beta bursts are dependent on dopaminergic state. Local field potentials were recorded from the subthalamic nucleus of eight Parkinson's disease patients during temporary lead externalization during surgery for deep brain stimulation. The recordings took place with the patient quietly seated following overnight withdrawal of levodopa and after administration of levodopa. Beta bursts were defined by applying a common amplitude threshold and burst characteristics were compared between the two drug conditions. The amplitude of beta bursts, indicative of the degree of local neural synchronization, progressively increased with burst duration. Treatment with levodopa limited this evolution leading to a relative increase of shorter, lower amplitude bursts. Synchronization, however, was not limited to local neural populations during bursts, but also, when such bursts were cotemporaneous across the hemispheres, was evidenced by bilateral phase synchronization. The probability of beta bursts and the proportion of cotemporaneous bursts were reduced by levodopa. The percentage number of longer beta bursts in a given interval was positively related to motor impairment, while the opposite was true for the percentage number of short duration beta bursts. Importantly, the decrease in burst duration was also correlated with the motor improvement. In conclusion, we demonstrate that long duration beta bursts are associated with an increase in local and

Hippocampal Theta-Gamma Coupling Reflects State-Dependent Information Processing in Decision Making.

PubMed

Amemiya, Seiichiro; Redish, A David

2018-03-20

During decision making, hippocampal activity encodes information sometimes about present and sometimes about potential future plans. The mechanisms underlying this transition remain unknown. Building on the evidence that gamma oscillations at different frequencies (low gamma [LG], 30-55 Hz; high gamma [HG], 60-90 Hz; and epsilon, 100-140 Hz) reflect inputs from different circuits, we identified how changes in those frequencies reflect different information-processing states. Using a unique noradrenergic manipulation by clonidine, which shifted both neural representations and gamma states, we found that future representations depended on gamma components. These changes were identifiable on each cycle of theta as asymmetries in the theta cycle, which arose from changes within the ratio of LG and HG power and the underlying phases of those gamma rhythms within the theta cycle. These changes in asymmetry of the theta cycle reflected changes in representations of present and future on each theta cycle. Copyright © 2018 The Author(s). Published by Elsevier Inc. All rights reserved.

Frontal Theta Links Prediction Errors to Behavioral Adaptation in Reinforcement Learning

PubMed Central

Cavanagh, James F.; Frank, Michael J.; Klein, Theresa J.; Allen, John J.B.

2009-01-01

Investigations into action monitoring have consistently detailed a fronto-central voltage deflection in the Event-Related Potential (ERP) following the presentation of negatively valenced feedback, sometimes termed the Feedback Related Negativity (FRN). The FRN has been proposed to reflect a neural response to prediction errors during reinforcement learning, yet the single trial relationship between neural activity and the quanta of expectation violation remains untested. Although ERP methods are not well suited to single trial analyses, the FRN has been associated with theta band oscillatory perturbations in the medial prefrontal cortex. Medio-frontal theta oscillations have been previously associated with expectation violation and behavioral adaptation and are well suited to single trial analysis. Here, we recorded EEG activity during a probabilistic reinforcement learning task and fit the performance data to an abstract computational model (Q-learning) for calculation of single-trial reward prediction errors. Single-trial theta oscillatory activities following feedback were investigated within the context of expectation (prediction error) and adaptation (subsequent reaction time change). Results indicate that interactive medial and lateral frontal theta activities reflect the degree of negative and positive reward prediction error in the service of behavioral adaptation. These different brain areas use prediction error calculations for different behavioral adaptations: with medial frontal theta reflecting the utilization of prediction errors for reaction time slowing (specifically following errors), but lateral frontal theta reflecting prediction errors leading to working memory-related reaction time speeding for the correct choice. PMID:19969093

Frontal midline theta and the error-related negativity: neurophysiological mechanisms of action regulation.

PubMed

Luu, Phan; Tucker, Don M; Makeig, Scott

2004-08-01

The error-related negativity (ERN) is an event-related potential (ERP) peak occurring between 50 and 100 ms after the commission of a speeded motor response that the subject immediately realizes to be in error. The ERN is believed to index brain processes that monitor action outcomes. Our previous analyses of ERP and EEG data suggested that the ERN is dominated by partial phase-locking of intermittent theta-band EEG activity. In this paper, this possibility is further evaluated. The possibility that the ERN is produced by phase-locking of theta-band EEG activity was examined by analyzing the single-trial EEG traces from a forced-choice speeded response paradigm before and after applying theta-band (4-7 Hz) filtering and by comparing the averaged and single-trial phase-locked (ERP) and non-phase-locked (other) EEG data. Electrical source analyses were used to estimate the brain sources involved in the generation of the ERN. Beginning just before incorrect button presses in a speeded choice response paradigm, midfrontal theta-band activity increased in amplitude and became partially and transiently phase-locked to the subject's motor response, accounting for 57% of ERN peak amplitude. The portion of the theta-EEG activity increase remaining after subtracting the response-locked ERP from each trial was larger and longer lasting after error responses than after correct responses, extending on average 400 ms beyond the ERN peak. Multiple equivalent-dipole source analysis suggested 3 possible equivalent dipole sources of the theta-bandpassed ERN, while the scalp distribution of non-phase-locked theta amplitude suggested the presence of additional frontal theta-EEG sources. These results appear consistent with a body of research that demonstrates a relationship between limbic theta activity and action regulation, including error monitoring and learning.

Hippocampal Non-Theta-Contingent Eyeblink Classical Conditioning: A Model System for Neurobiological Dysfunction

PubMed Central

Cicchese, Joseph J.; Berry, Stephen D.

2016-01-01

Typical information processing is thought to depend on the integrity of neurobiological oscillations that may underlie coordination and timing of cells and assemblies within and between structures. The 3–7 Hz bandwidth of hippocampal theta rhythm is associated with cognitive processes essential to learning and depends on the integrity of cholinergic, GABAergic, and glutamatergic forebrain systems. Since several significant psychiatric disorders appear to result from dysfunction of medial temporal lobe (MTL) neurochemical systems, preclinical studies on animal models may be an important step in defining and treating such syndromes. Many studies have shown that the amount of hippocampal theta in the rabbit strongly predicts the acquisition rate of classical eyeblink conditioning and that impairment of this system substantially slows the rate of learning and attainment of asymptotic performance. Our lab has developed a brain–computer interface that makes eyeblink training trials contingent upon the explicit presence or absence of hippocampal theta. The behavioral benefit of theta-contingent training has been demonstrated in both delay and trace forms of the paradigm with a two- to fourfold increase in learning speed over non-theta states. The non-theta behavioral impairment is accompanied by disruption of the amplitude and synchrony of hippocampal local field potentials, multiple-unit excitation, and single-unit response patterns dependent on theta state. Our findings indicate a significant electrophysiological and behavioral impact of the pretrial state of the hippocampus that suggests an important role for this MTL system in associative learning and a significant deleterious impact in the absence of theta. Here, we focus on the impairments in the non-theta state, integrate them into current models of psychiatric disorders, and suggest how improvement in our understanding of neurobiological oscillations is critical for theories and treatment of psychiatric

Theta Neurofeedback Effects on Motor Memory Consolidation and Performance Accuracy: An Apparent Paradox?

PubMed

Reiner, Miriam; Lev, Dror D; Rosen, Amit

2018-05-15

Previous studies have shown that theta neurofeedback enhances motor memory consolidation on an easy-to-learn finger-tapping task. However, the simplicity of the finger-tapping task precludes evaluating the putative effects of elevated theta on performance accuracy. Mastering a motor sequence is classically assumed to entail faster performance with fewer errors. The speed-accuracy tradeoff (SAT) principle states that as action speed increases, motor performance accuracy decreases. The current study investigated whether theta neurofeedback could improve both performance speed and performance accuracy, or would only enhance performance speed at the cost of reduced accuracy. A more complex task was used to study the effects of parietal elevated theta on 45 healthy volunteers The findings confirmed previous results on the effects of theta neurofeedback on memory consolidation. In contrast to the two control groups, in the theta-neurofeedback group the speed-accuracy tradeoff was reversed. The speed-accuracy tradeoff patterns only stabilized after a night's sleep implying enhancement in terms of both speed and accuracy. Copyright © 2017 IBRO. Published by Elsevier Ltd. All rights reserved.

Practice advisory: The utility of EEG theta/beta power ratio in ADHD diagnosis

PubMed Central

Gloss, David; Varma, Jay K.; Pringsheim, Tamara; Nuwer, Marc R.

2016-01-01

Objective: To evaluate the evidence for EEG theta/beta power ratio for diagnosing, or helping to diagnose, attention-deficit/hyperactivity disorder (ADHD). Methods: We identified relevant studies and classified them using American Academy of Neurology criteria. Results: Two Class I studies assessing the ability of EEG theta/beta power ratio and EEG frontal beta power to identify patients with ADHD correctly identified 166 of 185 participants. Both studies evaluated theta/beta power ratio and frontal beta power in suspected ADHD or in syndromes typically included in an ADHD differential diagnosis. A bivariate model combining the diagnostic studies shows that the combination of EEG frontal beta power and theta/beta power ratio has relatively high sensitivity and specificity but is insufficiently accurate. Conclusions: It is unknown whether a combination of standard clinical examination and EEG theta/beta power ratio increases diagnostic certainty of ADHD compared with clinical examination alone. Recommendations: Level B: Clinicians should inform patients with suspected ADHD and their families that the combination of EEG theta/beta power ratio and frontal beta power should not replace a standard clinical evaluation. There is a risk for significant harm to patients from ADHD misdiagnosis because of the unacceptably high false-positive diagnostic rate of EEG theta/beta power ratio and frontal beta power. Level R: Clinicians should inform patients with suspected ADHD and their families that the EEG theta/beta power ratio should not be used to confirm an ADHD diagnosis or to support further testing after a clinical evaluation, unless such diagnostic assessments occur in a research setting. PMID:27760867

The Effects of Theta and Gamma tACS on Working Memory and Electrophysiology

PubMed Central

Pahor, Anja; Jaušovec, Norbert

2018-01-01

A single blind sham-controlled study was conducted to explore the effects of theta and gamma transcranial alternating current stimulation (tACS) on offline performance on working memory tasks. In order to systematically investigate how specific parameters of tACS affect working memory, we manipulated the frequency of stimulation (theta frequency vs. gamma frequency), the type of task (n-back vs. change detection task) and the content of the tasks (verbal vs. figural stimuli). A repeated measures design was used that consisted of three sessions: theta tACS, gamma tACS and sham tACS. In total, four experiments were conducted which differed only with respect to placement of tACS electrodes (bilateral frontal, bilateral parietal, left fronto-parietal and right-fronto parietal). Healthy female students (N = 72) were randomly assigned to one of these groups, hence we were able to assess the efficacy of theta and gamma tACS applied over different brain areas, contrasted against sham stimulation. The pre-post/sham resting electroencephalogram (EEG) analysis showed that theta tACS significantly affected theta amplitude, whereas gamma tACS had no significant effect on EEG amplitude in any of the frequency bands of interest. Gamma tACS did not significantly affect working memory performance compared to sham, and theta tACS led to inconsistent changes in performance on the n-back tasks. Active theta tACS significantly affected P3 amplitude and latency during performance on the n-back tasks in the bilateral parietal and right-fronto parietal protocols. PMID:29375347

Bursting synchronization dynamics of pancreatic β-cells with electrical and chemical coupling.

PubMed

Meng, Pan; Wang, Qingyun; Lu, Qishao

2013-06-01

Based on bifurcation analysis, the synchronization behaviors of two identical pancreatic β-cells connected by electrical and chemical coupling are investigated, respectively. Various firing patterns are produced in coupled cells when a single cell exhibits tonic spiking or square-wave bursting individually, irrespectively of what the cells are connected by electrical or chemical coupling. On the one hand, cells can burst synchronously for both weak electrical and chemical coupling when an isolated cell exhibits tonic spiking itself. In particular, for electrically coupled cells, under the variation of the coupling strength there exist complex transition processes of synchronous firing patterns such as "fold/limit cycle" type of bursting, then anti-phase continuous spiking, followed by the "fold/torus" type of bursting, and finally in-phase tonic spiking. On the other hand, it is shown that when the individual cell exhibits square-wave bursting, suitable coupling strength can make the electrically coupled system generate "fold/Hopf" bursting via "fold/fold" hysteresis loop; whereas, the chemically coupled cells generate "fold/subHopf" bursting. Especially, chemically coupled bursters can exhibit inverse period-adding bursting sequence. Fast-slow dynamics analysis is applied to explore the generation mechanism of these bursting oscillations. The above analysis of bursting types and the transition may provide us with better insight into understanding the role of coupling in the dynamic behaviors of pancreatic β-cells.

The post-pollination ethylene burst and the continuation of floral advertisement are harbingers of non-random mate selection in Nicotiana attenuata.

PubMed

Bhattacharya, Samik; Baldwin, Ian T

2012-08-01

The self-compatible plant Nicotiana attenuata grows in genetically diverse populations after fires, and produces flowers that remain open for 3 days and are visited by assorted pollinators. To determine whether and when post-pollination non-random mate selection occurs among self and non-self pollen, seed paternity and semi-in vivo pollen tube growth were determined in controlled single/mixed pollinations. Despite all pollen sources being equally proficient in siring seeds in single-genotype pollinations, self pollen was consistently selected in mixed pollinations, irrespective of maternal genotype. However, clear patterns of mate discrimination occurred amongst non-self pollen when mixed pollinations were performed soon after corollas open, including selection against hygromycin B resistance (transformation selectable marker) in wild-type styles and for it in transformed styles. However, mate choice among pollen genotypes was completely shut down in plants transformed to be unable to produce (irACO) or perceive (ETR1) ethylene. The post-pollination ethylene burst, which originates primarily from the stigma and upper style, was strongly correlated with mate selection in single and mixed hand-pollinations using eight pollen donors in two maternal ecotypes. The post-pollination ethylene burst was also negatively correlated with the continuation of emission of benzylacetone, the most abundant pollinator-attracting corolla-derived floral volatile. We conclude that ethylene signaling plays a pivotal role in mate choice, and the post-pollination ethylene burst and the termination of benzylacetone release are accurate predictors, both qualitatively and quantitatively, of pre-zygotic mate selection and seed paternity. © 2012 The Authors. The Plant Journal © 2012 Blackwell Publishing Ltd.

Posttranslationally caused bioluminescence burst of the Escherichia coli luciferase reporter strain.

PubMed

Ideguchi, Yamato; Oshikoshi, Yuta; Ryo, Masashi; Motoki, Shogo; Kuwano, Takashi; Tezuka, Takafumi; Aoki, Setsuyuki

2016-01-01

We continuously monitored bioluminescence from a wild-type reporter strain of Escherichia coli (lacp::luc+/WT), which carries the promoter of the lac operon (lacp) fused with the firefly luciferase gene (luc+). This strain showed a bioluminescence burst when shifted into the stationary growth phase. Bioluminescence profiles of other wild-type reporter strains (rpsPp::luc+ and argAp::luc+) and gene-deletion reporter strains (lacp::luc+/crp- and lacp::luc+/lacI-) indicate that transcriptional regulation is not responsible for generation of the burst. Consistently, changes in the luciferase protein levels did not recapitulate the profile of the burst. On the other hand, dissolved oxygen levels increased over the period across the burst, suggesting that the burst is, at least partially, caused by an increase in intracellular oxygen levels. We discuss limits of the firefly luciferase when used as a reporter for gene expression and its potential utility for monitoring metabolic changes in cells.

Transient reduction in theta power caused by interictal spikes in human temporal lobe epilepsy.

PubMed

Manling Ge; Jundan Guo; Yangyang Xing; Zhiguo Feng; Weide Lu; Xinxin Ma; Yuehua Geng; Xin Zhang

2017-07-01

The inhibitory impacts of spikes on LFP theta rhythms(4-8Hz) are investigated around sporadic spikes(SSs) based on intracerebral EEG of 4 REM sleep patients with temporal lobe epilepsy(TLE) under the pre-surgical monitoring. Sequential interictal spikes in both genesis area and extended propagation pathway are collected, that, SSs genesis only in anterior hippocampus(aH)(possible propagation pathway in Entorhinal cortex(EC)), only in EC(possible propagation pathway in aH), and in both aH and EC synchronously. Instantaneous theta power was estimated by using Gabor wavelet transform, and theta power level was estimated by averaged over time and frequency before SSs(350ms pre-spike) and after SSs(350ms post-spike). The inhibitory effect around spikes was evaluated by the ratio of theta power level difference between pre-spike and post-spike to pre-spike theta power level. The findings were that theta power level was reduced across SSs, and the effects were more sever in the case of SSs in both aH and EC synchronously than either SSs only in EC or SSs only in aH. It is concluded that interictal spikes impair LFP theta rhythms transiently and directly. The work suggests that the reduction of theta power after the interictal spike might be an evaluation indicator of damage of epilepsy to human cognitive rhythms.

Chemotherapy disrupts learning, neurogenesis and theta activity in the adult brain.

PubMed

Nokia, Miriam S; Anderson, Megan L; Shors, Tracey J

2012-12-01

Chemotherapy, especially if prolonged, disrupts attention, working memory and speed of processing in humans. Most cancer drugs that cross the blood-brain barrier also decrease adult neurogenesis. Because new neurons are generated in the hippocampus, this decrease may contribute to the deficits in working memory and related thought processes. The neurophysiological mechanisms that underlie these deficits are generally unknown. A possible mediator is hippocampal oscillatory activity within the theta range (3-12 Hz). Theta activity predicts and promotes efficient learning in healthy animals and humans. Here, we hypothesised that chemotherapy disrupts learning via decreases in hippocampal adult neurogenesis and theta activity. Temozolomide was administered to adult male Sprague-Dawley rats in a cyclic manner for several weeks. Treatment was followed by training with different types of eyeblink classical conditioning, a form of associative learning. Chemotherapy reduced both neurogenesis and endogenous theta activity, as well as disrupted learning and related theta-band responses to the conditioned stimulus. The detrimental effects of temozolomide only occurred after several weeks of treatment, and only on a task that requires the association of events across a temporal gap and not during training with temporally overlapping stimuli. Chemotherapy did not disrupt the memory for previously learned associations, a memory independent of (new neurons in) the hippocampus. In conclusion, prolonged systemic chemotherapy is associated with a decrease in hippocampal adult neurogenesis and theta activity that may explain the selective deficits in processes of learning that describe the 'chemobrain'. © 2012 Federation of European Neuroscience Societies and Blackwell Publishing Ltd.

QKD-Based Secured Burst Integrity Design for Optical Burst Switched Networks

NASA Astrophysics Data System (ADS)

Balamurugan, A. M.; Sivasubramanian, A.; Parvathavarthini, B.

2016-03-01

The field of optical transmission has undergone numerous advancements and is still being researched mainly due to the fact that optical data transmission can be done at enormous speeds. It is quite evident that people prefer optical communication when it comes to large amount of data involving its transmission. The concept of switching in networks has matured enormously with several researches, architecture to implement and methods starting with Optical circuit switching to Optical Burst Switching. Optical burst switching is regarded as viable solution for switching bursts over networks but has several security vulnerabilities. However, this work exploited the security issues associated with Optical Burst Switching with respect to integrity of burst. This proposed Quantum Key based Secure Hash Algorithm (QKBSHA-512) with enhanced compression function design provides better avalanche effect over the conventional integrity algorithms.

Local cortical dynamics of burst suppression in the anaesthetized brain.

PubMed

Lewis, Laura D; Ching, Shinung; Weiner, Veronica S; Peterfreund, Robert A; Eskandar, Emad N; Cash, Sydney S; Brown, Emery N; Purdon, Patrick L

2013-09-01

Burst suppression is an electroencephalogram pattern that consists of a quasi-periodic alternation between isoelectric 'suppressions' lasting seconds or minutes, and high-voltage 'bursts'. It is characteristic of a profoundly inactivated brain, occurring in conditions including hypothermia, deep general anaesthesia, infant encephalopathy and coma. It is also used in neurology as an electrophysiological endpoint in pharmacologically induced coma for brain protection after traumatic injury and during status epilepticus. Classically, burst suppression has been regarded as a 'global' state with synchronous activity throughout cortex. This assumption has influenced the clinical use of burst suppression as a way to broadly reduce neural activity. However, the extent of spatial homogeneity has not been fully explored due to the challenges in recording from multiple cortical sites simultaneously. The neurophysiological dynamics of large-scale cortical circuits during burst suppression are therefore not well understood. To address this question, we recorded intracranial electrocorticograms from patients who entered burst suppression while receiving propofol general anaesthesia. The electrodes were broadly distributed across cortex, enabling us to examine both the dynamics of burst suppression within local cortical regions and larger-scale network interactions. We found that in contrast to previous characterizations, bursts could be substantially asynchronous across the cortex. Furthermore, the state of burst suppression itself could occur in a limited cortical region while other areas exhibited ongoing continuous activity. In addition, we found a complex temporal structure within bursts, which recapitulated the spectral dynamics of the state preceding burst suppression, and evolved throughout the course of a single burst. Our observations imply that local cortical dynamics are not homogeneous, even during significant brain inactivation. Instead, cortical and, implicitly

The synchronous activity of lateral habenular neurons is essential for regulating hippocampal theta oscillation.

PubMed

Aizawa, Hidenori; Yanagihara, Shin; Kobayashi, Megumi; Niisato, Kazue; Takekawa, Takashi; Harukuni, Rie; McHugh, Thomas J; Fukai, Tomoki; Isomura, Yoshikazu; Okamoto, Hitoshi

2013-05-15

Lateral habenula (LHb) has attracted growing interest as a regulator of serotonergic and dopaminergic neurons in the CNS. However, it remains unclear how the LHb modulates brain states in animals. To identify the neural substrates that are under the influence of LHb regulation, we examined the effects of rat LHb lesions on the hippocampal oscillatory activity associated with the transition of brain states. Our results showed that the LHb lesion shortened the theta activity duration both in anesthetized and sleeping rats. Furthermore, this inhibitory effect of LHb lesion on theta maintenance depended upon an intact serotonergic median raphe, suggesting that LHb activity plays an essential role in maintaining hippocampal theta oscillation via the serotonergic raphe. Multiunit recording of sleeping rats further revealed that firing of LHb neurons showed significant phase-locking activity at each theta oscillation cycle in the hippocampus. LHb neurons showing activity that was coordinated with that of the hippocampal theta were localized in the medial LHb division, which receives afferents from the diagonal band of Broca (DBB), a pacemaker region for the hippocampal theta oscillation. Thus, our findings indicate that the DBB may pace not only the hippocampus, but also the LHb, during rapid eye movement sleep. Since serotonin is known to negatively regulate theta oscillation in the hippocampus, phase-locking activity of the LHb neurons may act, under the influence of the DBB, to maintain the hippocampal theta oscillation by modulating the activity of serotonergic neurons.

Theta dynamics reveal domain-specific control over stimulus and response conflict.

PubMed

Nigbur, Roland; Cohen, Michael X; Ridderinkhof, K Richard; Stürmer, Birgit

2012-05-01

Cognitive control allows us to adjust to environmental changes. The medial frontal cortex (MFC) is thought to detect conflicts and recruit additional resources from other brain areas including the lateral prefrontal cortices. Here we investigated how the MFC acts in concert with visual, motor, and lateral prefrontal cortices to support adaptations of goal-directed behavior. Physiologically, these interactions may occur through local and long-range synchronized oscillation dynamics, particularly in the theta range (4-8 Hz). A speeded flanker task allowed us to investigate conflict-type-specific control networks for perceptual and response conflicts. Theta power over MFC was sensitive to both perceptual and response conflict. Interareal theta phase synchrony, however, indicated a selective enhancement specific for response conflicts between MFC and left frontal cortex as well as between MFC and the presumed motor cortex contralateral to the response hand. These findings suggest that MFC theta-band activity is both generally involved in conflict processing and specifically involved in linking a neural network controlling response conflict.

Theta Oscillations Rapidly Convey Odor-Specific Content in Human Piriform Cortex.

PubMed

Jiang, Heidi; Schuele, Stephan; Rosenow, Joshua; Zelano, Christina; Parvizi, Josef; Tao, James X; Wu, Shasha; Gottfried, Jay A

2017-04-05

Olfactory oscillations are pervasive throughout vertebrate and invertebrate nervous systems. Such observations have long implied that rhythmic activity patterns play a fundamental role in odor coding. Using intracranial EEG recordings from rare patients with medically resistant epilepsy, we find that theta oscillations are a distinct electrophysiological signature of olfactory processing in the human brain. Across seven patients, odor stimulation enhanced theta power in human piriform cortex, with robust effects at the level of single trials. Importantly, classification analysis revealed that piriform oscillatory activity conveys olfactory-specific information that can be decoded within 110-518 ms of a sniff, and maximally within the theta frequency band. This temporal window was also associated with increased theta-specific phase coupling between piriform cortex and hippocampus. Together these findings suggest that human piriform cortex has access to olfactory content in the time-frequency domain and can utilize these signals to rapidly differentiate odor stimuli. Copyright © 2017 Elsevier Inc. All rights reserved.

Optogenetic activation of septal cholinergic neurons suppresses sharp wave ripples and enhances theta oscillations in the hippocampus.

PubMed

Vandecasteele, Marie; Varga, Viktor; Berényi, Antal; Papp, Edit; Barthó, Péter; Venance, Laurent; Freund, Tamás F; Buzsáki, György

2014-09-16

Theta oscillations in the limbic system depend on the integrity of the medial septum. The different populations of medial septal neurons (cholinergic and GABAergic) are assumed to affect different aspects of theta oscillations. Using optogenetic stimulation of cholinergic neurons in ChAT-Cre mice, we investigated their effects on hippocampal local field potentials in both anesthetized and behaving mice. Cholinergic stimulation completely blocked sharp wave ripples and strongly suppressed the power of both slow oscillations (0.5-2 Hz in anesthetized, 0.5-4 Hz in behaving animals) and supratheta (6-10 Hz in anesthetized, 10-25 Hz in behaving animals) bands. The same stimulation robustly increased both the power and coherence of theta oscillations (2-6 Hz) in urethane-anesthetized mice. In behaving mice, cholinergic stimulation was less effective in the theta (4-10 Hz) band yet it also increased the ratio of theta/slow oscillation and theta coherence. The effects on gamma oscillations largely mirrored those of theta. These findings show that medial septal cholinergic activation can both enhance theta rhythm and suppress peri-theta frequency bands, allowing theta oscillations to dominate.

Testing the effects of adolescent alcohol use on adult conflict-related theta dynamics.

PubMed

Harper, Jeremy; Malone, Stephen M; Iacono, William G

2017-11-01

Adolescent alcohol use (AAU) is associated with brain anomalies, but less is known about long-term neurocognitive effects. Despite theoretical models linking AAU to diminished cognitive control, empirical work testing this relationship with specific cognitive control neural correlates (e.g., prefrontal theta-band EEG dynamics) remains scarce. A longitudinal twin design was used to test the hypothesis that greater AAU is associated with reduced conflict-related EEG theta-band dynamics in adulthood, and to examine the genetic/environmental etiology of this association. In a large (N=718) population-based prospective twin sample, AAU was assessed at ages 11/14/17. Twins completed a flanker task at age 29 to elicit EEG theta-band medial frontal cortex (MFC) power and medial-dorsal prefrontal cortex (MFC-dPFC) connectivity. Two complementary analytic methods (cotwin control analysis; biometric modeling) were used to disentangle the genetic/shared environmental risk towards AAU from possible alcohol exposure effects on theta dynamics. AAU was negatively associated with adult cognitive control-related theta-band MFC power and MFC-dPFC functional connectivity. Genetic influences primarily underlie these associations. Findings provide strong evidence that genetic factors underlie the comorbidity between AAU and diminished cognitive control-related theta dynamics in adulthood. Conflict-related theta-band dynamics appear to be candidate brain-based endophenotypes/mechanisms for AAU. Copyright © 2017 International Federation of Clinical Neurophysiology. Published by Elsevier B.V. All rights reserved.

GRB 050717: A Long, Short-Lag Burst Observed by Swift and Konus

NASA Technical Reports Server (NTRS)

Krimm, H. A.; Hurkett, C.; Pal'shin, V.; Norris, J. P.; Zhang, B.; Barthelmy, S. D.; Burrows, D. N.; Gehrels, N.; Golenetskii, S.; Osborne, J. P.;

A repeating fast radio burst

NASA Astrophysics Data System (ADS)

Spitler, L. G.; Scholz, P.; Hessels, J. W. T.; Bogdanov, S.; Brazier, A.; Camilo, F.; Chatterjee, S.; Cordes, J. M.; Crawford, F.; Deneva, J.; Ferdman, R. D.; Freire, P. C. C.; Kaspi, V. M.; Lazarus, P.; Lynch, R.; Madsen, E. C.; McLaughlin, M. A.; Patel, C.; Ransom, S. M.; Seymour, A.; Stairs, I. H.; Stappers, B. W.; van Leeuwen, J.; Zhu, W. W.

2016-03-01

Fast radio bursts are millisecond-duration astronomical radio pulses of unknown physical origin that appear to come from extragalactic distances. Previous follow-up observations have failed to find additional bursts at the same dispersion measure (that is, the integrated column density of free electrons between source and telescope) and sky position as the original detections. The apparent non-repeating nature of these bursts has led to the suggestion that they originate in cataclysmic events. Here we report observations of ten additional bursts from the direction of the fast radio burst FRB 121102. These bursts have dispersion measures and sky positions consistent with the original burst. This unambiguously identifies FRB 121102 as repeating and demonstrates that its source survives the energetic events that cause the bursts. Additionally, the bursts from FRB 121102 show a wide range of spectral shapes that appear to be predominantly intrinsic to the source and which vary on timescales of minutes or less. Although there may be multiple physical origins for the population of fast radio bursts, these repeat bursts with high dispersion measure and variable spectra specifically seen from the direction of FRB 121102 support an origin in a young, highly magnetized, extragalactic neutron star.

A repeating fast radio burst.

PubMed

Spitler, L G; Scholz, P; Hessels, J W T; Bogdanov, S; Brazier, A; Camilo, F; Chatterjee, S; Cordes, J M; Crawford, F; Deneva, J; Ferdman, R D; Freire, P C C; Kaspi, V M; Lazarus, P; Lynch, R; Madsen, E C; McLaughlin, M A; Patel, C; Ransom, S M; Seymour, A; Stairs, I H; Stappers, B W; van Leeuwen, J; Zhu, W W

2016-03-10

Fast radio bursts are millisecond-duration astronomical radio pulses of unknown physical origin that appear to come from extragalactic distances. Previous follow-up observations have failed to find additional bursts at the same dispersion measure (that is, the integrated column density of free electrons between source and telescope) and sky position as the original detections. The apparent non-repeating nature of these bursts has led to the suggestion that they originate in cataclysmic events. Here we report observations of ten additional bursts from the direction of the fast radio burst FRB 121102. These bursts have dispersion measures and sky positions consistent with the original burst. This unambiguously identifies FRB 121102 as repeating and demonstrates that its source survives the energetic events that cause the bursts. Additionally, the bursts from FRB 121102 show a wide range of spectral shapes that appear to be predominantly intrinsic to the source and which vary on timescales of minutes or less. Although there may be multiple physical origins for the population of fast radio bursts, these repeat bursts with high dispersion measure and variable spectra specifically seen from the direction of FRB 121102 support an origin in a young, highly magnetized, extragalactic neutron star.

Topographical differences of frontal-midline theta activity reflect functional differences in cognitive control abilities.

PubMed

Eschmann, Kathrin C J; Bader, Regine; Mecklinger, Axel

2018-06-01

Electrophysiological oscillations are assumed to be the core mechanism for large-scale network communication. The specific role of frontal-midline theta oscillations as cognitive control mechanism is under debate. According to the dual mechanisms of control framework, cognitive control processes can be divided into proactive and reactive control. The present study aimed at investigating the role of frontal-midline theta activity by assessing oscillations in two tasks varying in the type of cognitive control needed. More specifically, a delayed match to sample (DMTS) task requiring proactive control and a color Stroop task recruiting reactive control processes were conducted within the same group of participants. Moreover, both tasks contained conditions with low and high need for cognitive control. As expected larger frontal-midline theta activity was found in conditions with high need for cognitive control. However, theta activity was focally activated at frontal sites in the DMTS task whereas it had a broader topographical distribution in the Stroop task, indicating that both proactive and reactive control are reflected in frontal-midline theta activity but reactive control is additionally characterized by a broader theta activation. These findings support the conclusion that frontal-midline theta acts functionally different depending on task requirements. Copyright © 2018 Elsevier Inc. All rights reserved.

Someone has to give in: theta oscillations correlate with adaptive behavior in social bargaining.

PubMed

Billeke, Pablo; Zamorano, Francisco; López, Tamara; Rodriguez, Carlos; Cosmelli, Diego; Aboitiz, Francisco

2014-12-01

During social bargain, one has to both figure out the others' intentions and behave strategically in such a way that the others' behaviors will be consistent with one's expectations. To understand the neurobiological mechanisms underlying these behaviors, we used electroencephalography while subjects played as proposers in a repeated ultimatum game. We found that subjects adapted their offers to obtain more acceptances in the last round and that this adaptation correlated negatively with prefrontal theta oscillations. People with higher prefrontal theta activity related to a rejection did not adapt their offers along the game to maximize their earning. Moreover, between-subject variation in posterior theta oscillations correlated positively with how individual theta activity influenced the change of offer after a rejection, reflecting a process of behavioral adaptation to the others' demands. Interestingly, people adapted better their offers when they knew that they where playing against a computer, although the behavioral adaptation did not correlate with prefrontal theta oscillation. Behavioral changes between human and computer games correlated with prefrontal theta activity, suggesting that low adaptation in human games could be a strategy. Taken together, these results provide evidence for specific roles of prefrontal and posterior theta oscillations in social bargaining. © The Author (2014). Published by Oxford University Press. For Permissions, please email: journals.permissions@oup.com.

Someone has to give in: theta oscillations correlate with adaptive behavior in social bargaining

PubMed Central

Zamorano, Francisco; López, Tamara; Rodriguez, Carlos; Cosmelli, Diego; Aboitiz, Francisco

2014-01-01

During social bargain, one has to both figure out the others’ intentions and behave strategically in such a way that the others’ behaviors will be consistent with one’s expectations. To understand the neurobiological mechanisms underlying these behaviors, we used electroencephalography while subjects played as proposers in a repeated ultimatum game. We found that subjects adapted their offers to obtain more acceptances in the last round and that this adaptation correlated negatively with prefrontal theta oscillations. People with higher prefrontal theta activity related to a rejection did not adapt their offers along the game to maximize their earning. Moreover, between-subject variation in posterior theta oscillations correlated positively with how individual theta activity influenced the change of offer after a rejection, reflecting a process of behavioral adaptation to the others’ demands. Interestingly, people adapted better their offers when they knew that they where playing against a computer, although the behavioral adaptation did not correlate with prefrontal theta oscillation. Behavioral changes between human and computer games correlated with prefrontal theta activity, suggesting that low adaptation in human games could be a strategy. Taken together, these results provide evidence for specific roles of prefrontal and posterior theta oscillations in social bargaining. PMID:24493841

SINGLE NEURON ACTIVITY AND THETA MODULATION IN POSTRHINAL CORTEX DURING VISUAL OBJECT DISCRIMINATION

PubMed Central

Furtak, Sharon C.; Ahmed, Omar J.; Burwell, Rebecca D.

2012-01-01

Postrhinal cortex, the rodent homolog of the primate parahippocampal cortex, processes spatial and contextual information. Our hypothesis of postrhinal function is that it serves to encode context, in part, by forming representations that link objects to places. We recorded postrhinal neuronal activity and local field potentials (LFPs) in rats trained on a two-choice, visual discrimination task. As predicted, a large proportion of postrhinal neurons signaled object-location conjunctions. In addition, postrhinal LFPs exhibited strong oscillatory rhythms in the theta band, and many postrhinal neurons were phase locked to theta. Although correlated with running speed, theta power was lower than predicted by speed alone immediately before and after choice. However, theta power was significantly increased following incorrect decisions, suggesting a role in signaling error. These findings provide evidence that postrhinal cortex encodes representations that link objects to places and suggest that postrhinal theta modulation extends to cognitive as well as spatial functions. PMID:23217745

Investigation of primordial black hole bursts using interplanetary network gamma-ray bursts

DOE PAGES

Ukwatta, Tilan Niranjan; Hurley, Kevin; MacGibbon, Jane H.; ...

2016-07-25

The detection of a gamma-ray burst (GRB) in the solar neighborhood would have very important implications for GRB phenomenology. The leading theories for cosmological GRBs would not be able to explain such events. The final bursts of evaporating primordial black holes (PBHs), however, would be a natural explanation for local GRBs. We present a novel technique that can constrain the distance to GRBs using detections from widely separated, non-imaging spacecraft. This method can determine the actual distance to the burst if it is local. We applied this method to constrain distances to a sample of 36 short-duration GRBs detected bymore » the Interplanetary Network (IPN) that show observational properties that are expected from PBH evaporations. These bursts have minimum possible distances in the 10 13–10 18 cm (7–10 5 au) range, which are consistent with the expected PBH energetics and with a possible origin in the solar neighborhood, although none of the bursts can be unambiguously demonstrated to be local. Furthermore, assuming that these bursts are real PBH events, we estimate lower limits on the PBH burst evaporation rate in the solar neighborhood.« less

DNA polymerase theta (POLQ) can extend from mismatches and from bases opposite a (6-4) photoproduct.

PubMed

Seki, Mineaki; Wood, Richard D

2008-01-01

DNA polymerase theta (pol theta) is a nuclear A-family DNA polymerase encoded by the POLQ gene in vertebrate cells. The biochemical properties of pol theta and of Polq-defective mice have suggested that pol theta participates in DNA damage tolerance. For example, pol theta was previously found to be proficient not only in incorporation of a nucleotide opposite a thymine glycol or an abasic site, but also extends a polynucleotide chain efficiently from the base opposite the lesion. We carried out experiments to determine whether this ability to extend from non-standard termini is a more general property of the enzyme. Pol theta extended relatively efficiently from matched termini as well as termini with A:G, A:T and A:C mismatches, with less descrimination than a well-studied A-family DNA polymerase, exonuclease-free pol I from E. coli. Although pol theta was unable to, by itself, bypass a cyclobutane pyrimidine dimer or a (6-4) photoproduct, it could perform some extension from primers with bases placed across from these lesions. When pol theta was combined with DNA polymerase iota, an enzyme that can insert a base opposite a UV-induced (6-4) photoproduct, complete bypass of a (6-4) photoproduct was possible. These data show that in addition to its ability to insert nucleotides opposite some DNA lesions, pol theta is proficient at extension of unpaired termini. These results show the potential of pol theta to act as an extender after incorporation of nucleotides by other DNA polymerases, and aid in understanding the role of pol theta in somatic mutagenesis and genome instability.

Event-induced theta responses as a window on the dynamics of memory.

PubMed

Bastiaansen, Marcel; Hagoort, Peter

2003-01-01

An important, but often ignored distinction in the analysis of EEG signals is that between evoked activity and induced activity. Whereas evoked activity reflects the summation of transient post-synaptic potentials triggered by an event, induced activity, which is mainly oscillatory in nature, is thought to reflect changes in parameters controlling dynamic interactions within and between brain structures. We hypothesize that induced activity may yield information about the dynamics of cell assembly formation, activation and subsequent uncoupling, which may play a prominent role in different types of memory operations. We then describe a number of analysis tools that can be used to study the reactivity of induced rhythmic activity, both in terms of amplitude changes and of phase variability. We briefly discuss how alpha, gamma and theta rhythms are thought to be generated, paying special attention to the hypothesis that the theta rhythm reflects dynamic interactions between the hippocampal system and the neocortex. This hypothesis would imply that studying the reactivity of scalp-recorded theta may provide a window on the contribution of the hippocampus to memory functions. We review studies investigating the reactivity of scalp-recorded theta in paradigms engaging episodic memory, spatial memory and working memory. In addition, we review studies that relate theta reactivity to processes at the interface of memory and language. Despite many unknowns, the experimental evidence largely supports the hypothesis that theta activity plays a functional role in cell assembly formation, a process which may constitute the neural basis of memory formation and retrieval. The available data provide only highly indirect support for the hypothesis that scalp-recorded theta yields information about hippocampal functioning. It is concluded that studying induced rhythmic activity holds promise as an additional important way to study brain function.

Theta Phase Synchronization Is the Glue that Binds Human Associative Memory.

PubMed

Clouter, Andrew; Shapiro, Kimron L; Hanslmayr, Simon

2017-10-23

Episodic memories are information-rich, often multisensory events that rely on binding different elements [1]. The elements that will constitute a memory episode are processed in specialized but distinct brain modules. The binding of these elements is most likely mediated by fast-acting long-term potentiation (LTP), which relies on the precise timing of neural activity [2]. Theta oscillations in the hippocampus orchestrate such timing as demonstrated by animal studies in vitro [3, 4] and in vivo [5, 6], suggesting a causal role of theta activity for the formation of complex memory episodes, but direct evidence from humans is missing. Here, we show that human episodic memory formation depends on phase synchrony between different sensory cortices at the theta frequency. By modulating the luminance of visual stimuli and the amplitude of auditory stimuli, we directly manipulated the degree of phase synchrony between visual and auditory cortices. Memory for sound-movie associations was significantly better when the stimuli were presented in phase compared to out of phase. This effect was specific to theta (4 Hz) and did not occur in slower (1.7 Hz) or faster (10.5 Hz) frequencies. These findings provide the first direct evidence that episodic memory formation in humans relies on a theta-specific synchronization mechanism. Copyright © 2017 Elsevier Ltd. All rights reserved.

Fast entrainment of human electroencephalogram to a theta-band photic flicker during successful memory encoding.

PubMed

Sato, Naoyuki

2013-01-01

Theta band power (4-8 Hz) in the scalp electroencephalogram (EEG) is thought to be stronger during memory encoding for subsequently remembered items than for forgotten items. According to simultaneous EEG-functional magnetic resonance imaging (fMRI) measurements, the memory-dependent EEG theta is associated with multiple regions of the brain. This suggests that the multiple regions cooperate with EEG theta synchronization during successful memory encoding. However, a question still remains: What kind of neural dynamic organizes such a memory-dependent global network? In this study, the modulation of the EEG theta entrainment property during successful encoding was hypothesized to lead to EEG theta synchronization among a distributed network. Then, a transient response of EEG theta to a theta-band photic flicker with a short duration was evaluated during memory encoding. In the results, flicker-induced EEG power increased and decreased with a time constant of several hundred milliseconds following the onset and the offset of the flicker, respectively. Importantly, the offset response of EEG power was found to be significantly decreased during successful encoding. Moreover, the offset response of the phase locking index was also found to associate with memory performance. According to computational simulations, the results are interpreted as a smaller time constant (i.e., faster response) of a driven harmonic oscillator rather than a change in the spontaneous oscillatory input. This suggests that the fast response of EEG theta forms a global EEG theta network among memory-related regions during successful encoding, and it contributes to a flexible formation of the network along the time course.

Gamma Ray Bursts - Observations

NASA Technical Reports Server (NTRS)

Gehrels, N.; Cannizzo, J. K.

2010-01-01

We are in an exciting period of discovery for gamma-ray bursts. The Swift observatory is detecting 100 bursts per year, providing arcsecond localizations and sensitive observations of the prompt and afterglow emission. The Fermi observatory is observing 250 bursts per year with its medium-energy GRB instrument and about 10 bursts per year with its high-energy LAT instrument. In addition, rapid-response telescopes on the ground are providing new capabilities to study optical emission during the prompt phase and spectral signatures of the host galaxies. The combined data set is enabling great advances in our understanding of GRBs including afterglow physics, short burst origin, and high energy emission.

Intermittent bursts induced by double tearing mode reconnection

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wei, Lai; Wang, Zheng-Xiong, E-mail: zxwang@dlut.edu.cn

Reversed magnetic shear (RMS) configuration is assumed to be the steady-state operation scenario for the future advanced tokamaks like International Thermonuclear Experimental Reactor. In this work, we numerically discover a phenomenon of violent intermittent bursts induced by self-organized double tearing mode (DTM) reconnection in the RMS configuration during the very long evolution, which may continuously lead to annular sawtooth crashes and thus badly impact the desired steady-state operation of the future advanced RMS tokamaks. The key process of the intermittent bursts in the off-axis region is similar to that of the typical sawtooth relaxation oscillation in the positive magnetic shearmore » configuration. It is interestingly found that in the decay phase of the DTM reconnection, the zonal field significantly counteracts equilibrium field to make the magnetic shear between the two rational surfaces so weak that the residual self-generated vortices of the previous DTM burst are able to trigger a reverse DTM reconnection by curling the field lines.« less

Intermittent bursts induced by double tearing mode reconnection

NASA Astrophysics Data System (ADS)

Wei, Lai; Wang, Zheng-Xiong

2014-06-01

Reversed magnetic shear (RMS) configuration is assumed to be the steady-state operation scenario for the future advanced tokamaks like International Thermonuclear Experimental Reactor. In this work, we numerically discover a phenomenon of violent intermittent bursts induced by self-organized double tearing mode (DTM) reconnection in the RMS configuration during the very long evolution, which may continuously lead to annular sawtooth crashes and thus badly impact the desired steady-state operation of the future advanced RMS tokamaks. The key process of the intermittent bursts in the off-axis region is similar to that of the typical sawtooth relaxation oscillation in the positive magnetic shear configuration. It is interestingly found that in the decay phase of the DTM reconnection, the zonal field significantly counteracts equilibrium field to make the magnetic shear between the two rational surfaces so weak that the residual self-generated vortices of the previous DTM burst are able to trigger a reverse DTM reconnection by curling the field lines.

[Quantitative evaluation of inhibitory effects of epileptic spikes on theta rhythms in the network of hippocampal CA3 and entorhinal cortex in patients with temporal lobe epilepsy].

PubMed

Ge, Man-Ling; Guo, Jun-Dan; Chen, Sheng-Hua; Zhang, Ji-Chang; Fu, Xiao-Xuan; Chen, Yu-Min

2017-02-25

Epileptic spike is an indicator of hyper-excitability and hyper-synchrony in the neural networks. The inhibitory effects of spikes on theta rhythms (4-8 Hz) might be helpful to understand the mechanism of epileptic damage on the cognitive functions. To quantitatively evaluate the inhibitory effects of spikes on theta rhythms, intracerebral electroencephalogram (EEG) recordings with both sporadic spikes (SSs) and spike-free transient period between adjacent spikes were selected in 4 patients in the status of rapid eyes movement (REM) sleep with temporal lobe epilepsy (TLE) under the pre-surgical monitoring. The electrodes of hippocampal CA3 and entorhinal cortex (EC) were employed, since CA3 and EC built up one of key loops to investigate cognition and epilepsy. These SSs occurred only in CA3, only in EC, or in both CA3 and EC synchronously. Theta power was respectively estimated around SSs and during the spike-free transient period by Gabor wavelet transform and Hilbert transform. The intermittent extent was then estimated to represent for the loss of theta rhythms during the spike-free transient period. The following findings were obtained: (1) The prominent rhythms were in theta frequency band; (2) The spikes could transiently reduce theta power, and the inhibitory effect was severer around SSs in both CA3 and EC synchronously than that around either SSs only in EC or SSs only in CA3; (3) During the spike-free transient period, theta rhythms were interrupted with the intermittent theta rhythms left and theta power level continued dropping, implying the inhibitory effect was sustained. Additionally, the intermittent extent of theta rhythms was converged to the inhibitory extent around SSs; (4) The average theta power level during the spike-free transient period might not be in line with the inhibitory extent of theta rhythms around SSs. It was concluded that the SSs had negative effects on theta rhythms transiently and directly, the inhibitory effects aroused by

Changes in hippocampal theta rhythm and their correlations with speed during different phases of voluntary wheel running in rats.

PubMed

Li, J-Y; Kuo, T B J; Hsieh, I-T; Yang, C C H

2012-06-28

Hippocampal theta rhythm (4-12 Hz) can be observed during locomotor behavior, but findings on the relationship between locomotion speed and theta frequency are inconsistent if not contradictory. The inconsistency may be because of the difficulties that previous analyses and protocols have had excluding the effects of behavior training. We recorded the first or second voluntary wheel running each day, and assumed that theta frequency and activity are correlated with speed in different running phases. By simultaneously recording electroencephalography, physical activity, and wheel running speed, this experiment explored the theta oscillations during spontaneous running of the 12-h dark period. The recording was completely wireless and allowed the animal to run freely while being recorded in the wheel. Theta frequency and theta power of middle frequency were elevated before running and theta frequency, theta power of middle frequency, physical activity, and running speed maintained persistently high levels during running. The slopes of the theta frequency and theta activity (4-9.5 Hz) during the initial running were different compared to the same values during subsequent running. During the initial running, the running speed was positively correlated with theta frequency and with theta power of middle frequency. Over the 12-h dark period, the running speed did not positively correlate with theta frequency but was significantly correlated with theta power of middle frequency. Thus, theta frequency was associated with running speed only at the initiation of running. Furthermore, theta power of middle frequency was associated with speed and with physical activity during running when chronological order was not taken into consideration. Copyright © 2012 IBRO. Published by Elsevier Ltd. All rights reserved.

Burst Mode ASIC-Based Modem

NASA Technical Reports Server (NTRS)

1997-01-01

The NASA Lewis Research Center is sponsoring the Advanced Communication Technology Insertion (ACTION) for Commercial Space Applications program. The goal of the program is to expedite the development of new technology with a clear path towards productization and enhancing the competitiveness of U.S. manufacturers. The industry has made significant investment in developing ASIC-based modem technology for continuous-mode applications and has made investigations into East, reliable acquisition of burst-mode digital communication signals. With rapid advances in analog and digital communications ICs, it is expected that more functions will be integrated onto these parts in the near future. In addition custom ASIC's can also be developed to address the areas not covered by the other IC's. Using the commercial chips and custom ASIC's, lower-cost, compact, reliable, and high-performance modems can be built for demanding satellite communication application. This report outlines a frequency-hop burst modem design based on commercially available chips.

Slow-theta power decreases during item-place encoding predict spatial accuracy of subsequent context recall.

PubMed

Crespo-García, Maité; Zeiller, Monika; Leupold, Claudia; Kreiselmeyer, Gernot; Rampp, Stefan; Hamer, Hajo M; Dalal, Sarang S

2016-11-15

Human hippocampal theta oscillations play a key role in accurate spatial coding. Associative encoding involves similar hippocampal networks but, paradoxically, is also characterized by theta power decreases. Here, we investigated how theta activity relates to associative encoding of place contexts resulting in accurate navigation. Using MEG, we found that slow-theta (2-5Hz) power negatively correlated with subsequent spatial accuracy for virtual contextual locations in posterior hippocampus and other cortical structures involved in spatial cognition. A rare opportunity to simultaneously record MEG and intracranial EEG in an epilepsy patient provided crucial insights: during power decreases, slow-theta in right anterior hippocampus and left inferior frontal gyrus phase-led the left temporal cortex and predicted spatial accuracy. Our findings indicate that decreased slow-theta activity reflects local and long-range neural mechanisms that encode accurate spatial contexts, and strengthens the view that local suppression of low-frequency activity is essential for more efficient processing of detailed information. Copyright © 2016 Elsevier Inc. All rights reserved.

Theta Coordinated Error-Driven Learning in the Hippocampus

PubMed Central

Ketz, Nicholas; Morkonda, Srinimisha G.; O'Reilly, Randall C.

2013-01-01

The learning mechanism in the hippocampus has almost universally been assumed to be Hebbian in nature, where individual neurons in an engram join together with synaptic weight increases to support facilitated recall of memories later. However, it is also widely known that Hebbian learning mechanisms impose significant capacity constraints, and are generally less computationally powerful than learning mechanisms that take advantage of error signals. We show that the differential phase relationships of hippocampal subfields within the overall theta rhythm enable a powerful form of error-driven learning, which results in significantly greater capacity, as shown in computer simulations. In one phase of the theta cycle, the bidirectional connectivity between CA1 and entorhinal cortex can be trained in an error-driven fashion to learn to effectively encode the cortical inputs in a compact and sparse form over CA1. In a subsequent portion of the theta cycle, the system attempts to recall an existing memory, via the pathway from entorhinal cortex to CA3 and CA1. Finally the full theta cycle completes when a strong target encoding representation of the current input is imposed onto the CA1 via direct projections from entorhinal cortex. The difference between this target encoding and the attempted recall of the same representation on CA1 constitutes an error signal that can drive the learning of CA3 to CA1 synapses. This CA3 to CA1 pathway is critical for enabling full reinstatement of recalled hippocampal memories out in cortex. Taken together, these new learning dynamics enable a much more robust, high-capacity model of hippocampal learning than was available previously under the classical Hebbian model. PMID:23762019

Dendritic brushes under theta and poor solvent conditions

NASA Astrophysics Data System (ADS)

Gergidis, Leonidas N.; Kalogirou, Andreas; Charalambopoulos, Antonios; Vlahos, Costas

2013-07-01

The effects of solvent quality on the internal stratification of polymer brushes formed by dendron polymers up to third generation were studied by means of molecular dynamics simulations with Langevin thermostat. The distributions of polymer units, of the free ends, the radii of gyration, and the back folding probabilities of the dendritic spacers were studied at the macroscopic states of theta and poor solvent. For high grafting densities we observed a small decrease in the height of the brush as the solvent quality decreases. The internal stratification in theta solvent was similar to the one we found in good solvent, with two and in some cases three kinds of populations containing short dendrons with weakly extended spacers, intermediate-height dendrons, and tall dendrons with highly stretched spacers. The differences increase as the grafting density decreases and single dendron populations were evident in theta and poor solvent. In poor solvent at low grafting densities, solvent micelles, polymeric pinned lamellae, spherical and single chain collapsed micelles were observed. The scaling dependence of the height of the dendritic brush at high density brushes for both solvents was found to be in agreement with existing analytical results.

Dynamical phases of the Hindmarsh-Rose neuronal model: studies of the transition from bursting to spiking chaos.

PubMed

Innocenti, Giacomo; Morelli, Alice; Genesio, Roberto; Torcini, Alessandro

2007-12-01

The dynamical phases of the Hindmarsh-Rose neuronal model are analyzed in detail by varying the external current I. For increasing current values, the model exhibits a peculiar cascade of nonchaotic and chaotic period-adding bifurcations leading the system from the silent regime to a chaotic state dominated by bursting events. At higher I-values, this phase is substituted by a regime of continuous chaotic spiking and finally via an inverse period doubling cascade the system returns to silence. The analysis is focused on the transition between the two chaotic phases displayed by the model: one dominated by spiking dynamics and the other by bursts. At the transition an abrupt shrinking of the attractor size associated with a sharp peak in the maximal Lyapunov exponent is observable. However, the transition appears to be continuous and smoothed out over a finite current interval, where bursts and spikes coexist. The beginning of the transition (from the bursting side) is signaled from a structural modification in the interspike interval return map. This change in the map shape is associated with the disappearance of the family of solutions responsible for the onset of the bursting chaos. The successive passage from bursting to spiking chaos is associated with a progressive pruning of unstable long-lasting bursts.

Abnormal-induced theta activity supports early directed-attention network deficits in progressive MCI.

PubMed

Deiber, Marie-Pierre; Ibañez, Vicente; Missonnier, Pascal; Herrmann, François; Fazio-Costa, Lara; Gold, Gabriel; Giannakopoulos, Panteleimon

2009-09-01

The electroencephalography (EEG) theta frequency band reacts to memory and selective attention paradigms. Global theta oscillatory activity includes a posterior phase-locked component related to stimulus processing and a frontal-induced component modulated by directed attention. To investigate the presence of early deficits in the directed attention-related network in elderly individuals with mild cognitive impairment (MCI), time-frequency analysis at baseline was used to assess global and induced theta oscillatory activity (4-6Hz) during n-back working memory tasks in 29 individuals with MCI and 24 elderly controls (EC). At 1-year follow-up, 13 MCI patients were still stable and 16 had progressed. Baseline task performance was similar in stable and progressive MCI cases. Induced theta activity at baseline was significantly reduced in progressive MCI as compared to EC and stable MCI in all n-back tasks, which were similar in terms of directed attention requirements. While performance is maintained, the decrease of induced theta activity suggests early deficits in the directed-attention network in progressive MCI, whereas this network is functionally preserved in stable MCI.

Effects of subjective preference of colors on attention-related occipital theta oscillations.

PubMed

Kawasaki, Masahiro; Yamaguchi, Yoko

2012-01-02

Human daily behaviors are often affected by subjective preferences. Studies have shown that physical responses are affected by unconscious preferences before conscious decision making. Accordingly, attention-related neural activities could be influenced by unconscious preferences. However, few neurological data exist on the relationship between visual attention and subjective preference. To address this issue, we focused on lateralization during visual attention and investigated the effects of subjective color preferences on visual attention-related brain activities. We recorded electroencephalograph (EEG) data during a preference judgment task that required 19 participants to choose their preferred color from 2 colors simultaneously presented to the right and left hemifields. In addition, to identify oscillatory activity during visual attention, we conducted a control experiment in which the participants focused on either the right or the left color without stating their preference. The EEG results showed enhanced theta (4-6 Hz) and decreased alpha (10-12 Hz) activities in the right and left occipital electrodes when the participants focused on the color in the opposite hemifield. Occipital theta synchronizations also increased contralaterally to the hemifield to which the preferred color was presented, whereas the alpha desynchronizations showed no lateralization. The contralateral occipital theta activity lasted longer than the ipsilateral occipital theta activity. Interestingly, theta lateralization was observed even when the preferred color was presented to the unattended side in the control experiment, revealing the strength of the preference-related theta-modulation effect irrespective of visual attention. These results indicate that subjective preferences modulate visual attention-related brain activities. Crown Copyright © 2011. Published by Elsevier Inc. All rights reserved.

Theta-band Oscillations in the Middle Temporal Gyrus Reflect Novel Word Consolidation.

PubMed

Bakker-Marshall, Iske; Takashima, Atsuko; Schoffelen, Jan-Mathijs; van Hell, Janet G; Janzen, Gabriele; McQueen, James M

2018-05-01

Like many other types of memory formation, novel word learning benefits from an offline consolidation period after the initial encoding phase. A previous EEG study has shown that retrieval of novel words elicited more word-like-induced electrophysiological brain activity in the theta band after consolidation [Bakker, I., Takashima, A., van Hell, J. G., Janzen, G., & McQueen, J. M. Changes in theta and beta oscillations as signatures of novel word consolidation. Journal of Cognitive Neuroscience, 27, 1286-1297, 2015]. This suggests that theta-band oscillations play a role in lexicalization, but it has not been demonstrated that this effect is directly caused by the formation of lexical representations. This study used magnetoencephalography to localize the theta consolidation effect to the left posterior middle temporal gyrus (pMTG), a region known to be involved in lexical storage. Both untrained novel words and words learned immediately before test elicited lower theta power during retrieval than existing words in this region. After a 24-hr consolidation period, the difference between novel and existing words decreased significantly, most strongly in the left pMTG. The magnitude of the decrease after consolidation correlated with an increase in behavioral competition effects between novel words and existing words with similar spelling, reflecting functional integration into the mental lexicon. These results thus provide new evidence that consolidation aids the development of lexical representations mediated by the left pMTG. Theta synchronization may enable lexical access by facilitating the simultaneous activation of distributed semantic, phonological, and orthographic representations that are bound together in the pMTG.

Frontal Theta Reflects Uncertainty and Unexpectedness during Exploration and Exploitation

PubMed Central

Figueroa, Christina M.; Cohen, Michael X; Frank, Michael J.

2012-01-01

In order to understand the exploitation/exploration trade-off in reinforcement learning, previous theoretical and empirical accounts have suggested that increased uncertainty may precede the decision to explore an alternative option. To date, the neural mechanisms that support the strategic application of uncertainty-driven exploration remain underspecified. In this study, electroencephalography (EEG) was used to assess trial-to-trial dynamics relevant to exploration and exploitation. Theta-band activities over middle and lateral frontal areas have previously been implicated in EEG studies of reinforcement learning and strategic control. It was hypothesized that these areas may interact during top-down strategic behavioral control involved in exploratory choices. Here, we used a dynamic reward–learning task and an associated mathematical model that predicted individual response times. This reinforcement-learning model generated value-based prediction errors and trial-by-trial estimates of exploration as a function of uncertainty. Mid-frontal theta power correlated with unsigned prediction error, although negative prediction errors had greater power overall. Trial-to-trial variations in response-locked frontal theta were linearly related to relative uncertainty and were larger in individuals who used uncertainty to guide exploration. This finding suggests that theta-band activities reflect prefrontal-directed strategic control during exploratory choices. PMID:22120491

Brain Responses to a 6-Hz Binaural Beat: Effects on General Theta Rhythm and Frontal Midline Theta Activity

PubMed Central

Jirakittayakorn, Nantawachara; Wongsawat, Yodchanan

2017-01-01

A binaural beat is a beat phenomenon that is generated by the dichotic presentation of two almost equivalent pure tones but with slightly different frequencies. The brain responses to binaural beats remain controversial; therefore, the aim of this study was to investigate theta activity responses to a binaural beat by controlling factors affecting localization, including beat frequency, carrier tone frequency, exposure duration, and recording procedure. Exposure to a 6-Hz binaural beat on a 250 Hz carrier tone for 30 min was utilized in this study. Quantitative electroencephalography (QEEG) was utilized as the recording modality. Twenty-eight participants were divided into experimental and control groups. Emotional states were evaluated by Brunel Mood Scale (BRMUS) before and after exposing to the stimulus. The results showed that theta activity was induced in the entire cortex within 10 min of exposure to the stimulus in the experimental group. Compared to the control group, theta activity was also induced at the frontal and parietal-central regions, which included the Fz position, and left hemisphere dominance was presented for other exposure durations. The pattern recorded for 10 min of exposure appeared to be brain functions of a meditative state. Moreover, tension factor of BRUMS was decreased in experimental group compared to control group which resembled the meditation effect. Thus, a 6-Hz binaural beat on a 250 Hz carrier tone was suggested as a stimulus for inducing a meditative state. PMID:28701912

Brain Responses to a 6-Hz Binaural Beat: Effects on General Theta Rhythm and Frontal Midline Theta Activity.

PubMed

Jirakittayakorn, Nantawachara; Wongsawat, Yodchanan

2017-01-01

A binaural beat is a beat phenomenon that is generated by the dichotic presentation of two almost equivalent pure tones but with slightly different frequencies. The brain responses to binaural beats remain controversial; therefore, the aim of this study was to investigate theta activity responses to a binaural beat by controlling factors affecting localization, including beat frequency, carrier tone frequency, exposure duration, and recording procedure. Exposure to a 6-Hz binaural beat on a 250 Hz carrier tone for 30 min was utilized in this study. Quantitative electroencephalography (QEEG) was utilized as the recording modality. Twenty-eight participants were divided into experimental and control groups. Emotional states were evaluated by Brunel Mood Scale (BRMUS) before and after exposing to the stimulus. The results showed that theta activity was induced in the entire cortex within 10 min of exposure to the stimulus in the experimental group. Compared to the control group, theta activity was also induced at the frontal and parietal-central regions, which included the Fz position, and left hemisphere dominance was presented for other exposure durations. The pattern recorded for 10 min of exposure appeared to be brain functions of a meditative state. Moreover, tension factor of BRUMS was decreased in experimental group compared to control group which resembled the meditation effect. Thus, a 6-Hz binaural beat on a 250 Hz carrier tone was suggested as a stimulus for inducing a meditative state.

The relationship between hippocampal EEG theta activity and locomotor behaviour in freely moving rats: effects of vigabatrin.

PubMed

Bouwman, B M; van Lier, H; Nitert, H E J; Drinkenburg, W H I M; Coenen, A M L; van Rijn, C M

2005-01-30

The relationship between hippocampal electroencephalogram (EEG) theta activity and locomotor speed in both spontaneous and forced walking conditions was studied in rats after vigabatrin injection (500 mg/kg i.p.). Vigabatrin increased the percentage of time that rats spent being immobile. During spontaneous walking in the open field, the speed of locomotion was increased by vigabatrin, while theta peak frequency was decreased. Vigabatrin also reduced the theta peak frequency during forced (speed controlled) walking. There was only a weak positive correlation (r=0.22) between theta peak frequency and locomotor speed for the saline condition. Furthermore, vigabatrin abolishes the weak relationship between speed of locomotion and theta peak frequency. Vigabatrin and saline did not differ in the slope of the regression line, but showed different offset points at the theta peak frequency axis. Thus, other factors than speed of locomotion seem to be involved in determination of the theta peak frequency.

Optical design of f-theta lens for dual wavelength selective laser melting

NASA Astrophysics Data System (ADS)

Feng, Lianhua; Cao, Hongzhong; Zhang, Ning; Xu, Xiping; Duan, Xuanming

2016-10-01

F-theta lens is an important unit for selective laser melting (SLM) manufacture. The dual wavelength f-theta lens has not been used in SLM manufacture. Here, we present the design of the f-theta lens which satisfies SLM manufacture with coaxial 532 nm and 1030 nm 1080 nm laser beams. It is composed of three pieces of spherical lenses. The focal spots for 532 nm laser and 1030 nm 1080 nm laser are smaller than 35 μm and 70 μm, respectively. The results meet the demands of high precision SLM. The chromatic aberration could cause separation between two laser focal spots in the scanning plane, so chromatic aberration correction is very important to our design. The lateral color of the designed f-theta lens is less than 11 μm within the scan area of 150 mm x 150 mm, which meet the application requirements of dual wavelength selective laser melting.

Bi-Directional Theta Modulation between the Septo-Hippocampal System and the Mammillary Area in Free-Moving Rats

PubMed Central

Ruan, Ming; Young, Calvin K.; McNaughton, Neil

2017-01-01

Hippocampal (HPC) theta oscillations have long been linked to various functions of the brain. Many cortical and subcortical areas that also exhibit theta oscillations have been linked to functional circuits with the hippocampus on the basis of coupled activities at theta frequencies. We examine, in freely moving rats, the characteristics of diencephalic theta local field potentials (LFPs) recorded in the supramammillary/mammillary (SuM/MM) areas that are bi-directionally connected to the HPC through the septal complex. Using partial directed coherence (PDC), we find support for previous suggestions that SuM modulates HPC theta at higher frequencies. We find weak separation of SuM and MM by dominant theta frequency recorded locally. Contrary to oscillatory cell activities under anesthesia where SuM is insensitive, but MM is sensitive to medial septal (MS) inactivation, theta LFPs persisted and became indistinguishable after MS-inactivation. However, MS-inactivation attenuated SuM/MM theta power, while increasing the frequency of SuM/MM theta. MS-inactivation also reduced root mean squared power in both HPC and SuM/MM equally, but reduced theta power differentially in the time domain. We provide converging evidence that SuM is preferentially involved in coding HPC theta at higher frequencies, and that the MS-HPC circuit normally imposes a frequency-limiting modulation over the SuM/MM area as suggested by cell-based recordings in anesthetized animals. In addition, we provide evidence that the postulated SuM-MS-HPC-MM circuit is under complex bi-directional control, rather than SuM and MM having roles as unidirectional relays in the network. PMID:28955209

A search for optical bursts from the repeating fast radio burst FRB 121102

NASA Astrophysics Data System (ADS)

Hardy, L. K.; Dhillon, V. S.; Spitler, L. G.; Littlefair, S. P.; Ashley, R. P.; De Cia, A.; Green, M. J.; Jaroenjittichai, P.; Keane, E. F.; Kerry, P.; Kramer, M.; Malesani, D.; Marsh, T. R.; Parsons, S. G.; Possenti, A.; Rattanasoon, S.; Sahman, D. I.

2017-12-01

We present a search for optical bursts from the repeating fast radio burst FRB 121102 using simultaneous observations with the high-speed optical camera ULTRASPEC on the 2.4-m Thai National Telescope and radio observations with the 100-m Effelsberg Radio Telescope. A total of 13 radio bursts were detected, but we found no evidence for corresponding optical bursts in our 70.7-ms frames. The 5σ upper limit to the optical flux density during our observations is 0.33 mJy at 767 nm. This gives an upper limit for the optical burst fluence of 0.046 Jy ms, which constrains the broad-band spectral index of the burst emission to α ≤ -0.2. Two of the radio pulses are separated by just 34 ms, which may represent an upper limit on a possible underlying periodicity (a rotation period typical of pulsars), or these pulses may have come from a single emission window that is a small fraction of a possible period.

Swift Burst Alert Telescope (BAT) Instrument Response

NASA Technical Reports Server (NTRS)

Parsons, A.; Hullinger, D.; Markwardt, C.; Barthelmy, S.; Cummings, J.; Gehrels, N.; Krimm, H.; Tueller, J.; Fenimore, E.; Palmer, D.

2004-01-01

The Burst Alert Telescope (BAT), a large coded aperture instrument with a wide field-of-view (FOV), provides the gamma-ray burst triggers and locations for the Swift Gamma-Ray Burst Explorer. In addition to providing this imaging information, BAT will perform a 15 keV - 150 keV all-sky hard x-ray survey based on the serendipitous pointings resulting from the study of gamma-ray bursts and will also monitor the sky for transient hard x-ray sources. For BAT to provide spectral and photometric information for the gamma-ray bursts, the transient sources and the all-sky survey, the BAT instrument response must be determined to an increasingly greater accuracy. In this talk, we describe the BAT instrument response as determined to an accuracy suitable for gamma-ray burst studies. We will also discuss the public data analysis tools developed to calculate the BAT response to sources at different energies and locations in the FOV. The level of accuracy required for the BAT instrument response used for the hard x-ray survey is significantly higher because this response must be used in the iterative clean algorithm for finding fainter sources. Because the bright sources add a lot of coding noise to the BAT sky image, fainter sources can be seen only after the counts due to the bright sources are removed. The better we know the BAT response, the lower the noise in the cleaned spectrum and thus the more sensitive the survey. Since the BAT detector plane consists of 32768 individual, 4 mm square CZT gamma-ray detectors, the most accurate BAT response would include 32768 individual detector response functions to separate mask modulation effects from differences in detector efficiencies! We describe OUT continuing work to improve the accuracy of the BAT instrument response and will present the current results of Monte Carlo simulations as well as BAT ground calibration data.

Symmetric Fold/Super-Hopf Bursting, Chaos and Mixed-Mode Oscillations in Pernarowski Model of Pancreatic Beta-Cells

NASA Astrophysics Data System (ADS)

Fallah, Haniyeh

Pancreatic beta-cells produce insulin to regularize the blood glucose level. Bursting is important in beta cells due to its relation to the release of insulin. Pernarowski model is a simple polynomial model of beta-cell activities indicating bursting oscillations in these cells. This paper presents bursting behaviors of symmetric type in this model. In addition, it is shown that the current system exhibits the phenomenon of period doubling cascades of canards which is a route to chaos. Canards are also observed symmetrically near folds of slow manifold which results in a chaotic transition between n and n + 1 spikes symmetric bursting. Furthermore, mixed-mode oscillations (MMOs) and combination of symmetric bursting together with MMOs are illustrated during the transition between symmetric bursting and continuous spiking.

swot: Super W Of Theta

NASA Astrophysics Data System (ADS)

Coupon, Jean; Leauthaud, Alexie; Kilbinger, Martin; Medezinski, Elinor

2017-07-01

SWOT (Super W Of Theta) computes two-point statistics for very large data sets, based on “divide and conquer” algorithms, mainly, but not limited to data storage in binary trees, approximation at large scale, parellelization (open MPI), and bootstrap and jackknife resampling methods “on the fly”. It currently supports projected and 3D galaxy auto and cross correlations, galaxy-galaxy lensing, and weighted histograms.

Palmitic acid mediates hypothalamic insulin resistance by altering PKC-theta subcellular localization in rodents.

PubMed

Benoit, Stephen C; Kemp, Christopher J; Elias, Carol F; Abplanalp, William; Herman, James P; Migrenne, Stephanie; Lefevre, Anne-Laure; Cruciani-Guglielmacci, Céline; Magnan, Christophe; Yu, Fang; Niswender, Kevin; Irani, Boman G; Holland, William L; Clegg, Deborah J

2009-09-01

Insulin signaling can be modulated by several isoforms of PKC in peripheral tissues. Here, we assessed whether one specific isoform, PKC-theta, was expressed in critical CNS regions that regulate energy balance and whether it mediated the deleterious effects of diets high in fat, specifically palmitic acid, on hypothalamic insulin activity in rats and mice. Using a combination of in situ hybridization and immunohistochemistry, we found that PKC-theta was expressed in discrete neuronal populations of the arcuate nucleus, specifically the neuropeptide Y/agouti-related protein neurons and the dorsal medial nucleus in the hypothalamus. CNS exposure to palmitic acid via direct infusion or by oral gavage increased the localization of PKC-theta to cell membranes in the hypothalamus, which was associated with impaired hypothalamic insulin and leptin signaling. This finding was specific for palmitic acid, as the monounsaturated fatty acid, oleic acid, neither increased membrane localization of PKC-theta nor induced insulin resistance. Finally, arcuate-specific knockdown of PKC-theta attenuated diet-induced obesity and improved insulin signaling. These results suggest that many of the deleterious effects of high-fat diets, specifically those enriched with palmitic acid, are CNS mediated via PKC-theta activation, resulting in reduced insulin activity.

On vortex bursting

NASA Technical Reports Server (NTRS)

Werle, H.

1984-01-01

Vortex bursting is studied by means of visualization. The physical behavior of the phenomenon is emphasized, and its similarity with boundary layer separation or wake bursting becomes apparent. The essential influence of an increasing pressure gradient on the initiation, the position and the type of bursting is clearly confirmed. The evolution of the phenomena as a function of several parameters is analyzed in the case of delta wings, alone or installed on aircraft models, and compared with the results of similar wind tunnel or flight tests.

The effects of mild hypothermia on thiopental-induced electroencephalogram burst suppression.

PubMed

Kim, J H; Kim, S H; Yoo, S K; Kim, J Y; Nam, Y T

1998-07-01

Thiopental intravenous injections before temporary clipping and mild hypothermia have protective effects in the setting of cerebral ischemia, and are used clinically in some centers. However, it is not known whether mild hypothermia affects thiopental-induced electroencephalogram (EEG) burst suppression. In this study, the authors compared the onset and duration of EEG suppression by thiopental in normothermic (n=10) and mildly hypothermic (n=10) patients undergoing cerebral aneurysm surgery. Spectral analysis was used to compare the prethiopentonal continuous EEG patterns in normothermic and mild hypothermic patients. The patients' body temperatures were controlled by a circulating water mattress and intravenous fluids (normothermia = 36.4+/-0.1 degrees C, mild hypothermia = 33.3+/-0.1 degrees C). Immediately before temporary clipping, thiopental sodium (5 mg/kg) was administered intravenously. Onset time (the amount of time from thiopental injection to the first complete EEG suppression), duration of suppression (the amount of time from the first complete EEG suppression to recovery on continuous EEG from burst suppression), and maximum duration of isoelectric EEG (the longest time interval between two bursts during burst suppression) were measured. Onset time was shortened (25.8+/-1.4 versus 43.5+/-5.6 seconds), and duration of suppression (531.0+/-56.6 versus 165.0+/-16.9 seconds) and the maximum duration of isoelectric EEG (47.7+/-5.8 versus 22.8+/-2.0 seconds) were prolonged in the patients with mild hypothermia. In two normothermic patients, the standard dose of thiopental did not produce burst suppression, but only a mild decrease in spectral edge frequency. The authors concluded that the effects of mild hypothermia on thiopental-induced EEG suppression are not simply additive, but synergistic.

Low-Frequency Radio Bursts and Space Weather

NASA Technical Reports Server (NTRS)

Gopalswamy, N.

2016-01-01

Low-frequency radio phenomena are due to the presence of nonthermal electrons in the interplanetary (IP) medium. Understanding these phenomena is important in characterizing the space environment near Earth and other destinations in the solar system. Substantial progress has been made in the past two decades, because of the continuous and uniform data sets available from space-based radio and white-light instrumentation. This paper highlights some recent results obtained on IP radio phenomena. In particular, the source of type IV radio bursts, the behavior of type III storms, shock propagation in the IP medium, and the solar-cycle variation of type II radio bursts are considered. All these phenomena are closely related to solar eruptions and active region evolution. The results presented were obtained by combining data from the Wind and SOHO missions.

Cardiac Arrhythmia and Injury Induced in Rats by Burst and Pulsed Mode Ultrasound with Gas Body Contrast Agent

PubMed Central

Miller, Douglas L.; Dou, Chunyan; Lucchesi, Benedict R.

2009-01-01

Objective Premature complexes (PCs) in the electrocardiogram (ECG) signal have been reported for myocardial contrast echocardiography and also for burst mode (physical therapy) ultrasound with gas body contrast agent at lower peak rarefactional pressure amplitudes (PRPAs). For contrast echocardiography, irreversibly injured cardiomyocytes have been associated with the arrhythmia. The objective was to determine if cardiomyocyte injury is associated with the PCs induced by the burst mode at lower PRPAs. Methods Anesthetized rats were exposed to focused 1.5 MHz ultrasound in a water bath. Evans blue dye was injected IP to stain injured cardiomyocytes and Definity ultrasound contrast agent was infused IV. Continuous burst mode simulated physical therapy ultrasound. Intermittent 2 ms bursts, or envelopes of pulses simulating diagnostic ultrasound, were triggered 1:4 at end systole. PCs were observed on ECG recordings and stained cardiomyocytes were counted in frozen sections. Results The continuous burst mode produced variable PCs and stained cells above 0.3 MPa PRPA. The triggered bursts above 0.3 MPa and pulse envelopes above 1.2 MPa produced statistically significant (P<0.01) PCs and stained cardiomyocytes. Conclusion Irreversible cardiomyocyte injury was associated with the development of PCs for burst mode and occurred at substantially lower PRPAs than for pulsed ultrasound. PMID:19854967

Gamma-ray burst models.

PubMed

King, Andrew

2007-05-15

I consider various possibilities for making gamma-ray bursts, particularly from close binaries. In addition to the much-studied neutron star+neutron star and black hole+neutron star cases usually considered good candidates for short-duration bursts, there are also other possibilities. In particular, neutron star+massive white dwarf has several desirable features. These systems are likely to produce long-duration gamma-ray bursts (GRBs), in some cases definitely without an accompanying supernova, as observed recently. This class of burst would have a strong correlation with star formation and occur close to the host galaxy. However, rare members of the class need not be near star-forming regions and could have any type of host galaxy. Thus, a long-duration burst far from any star-forming region would also be a signature of this class. Estimates based on the existence of a known progenitor suggest that this type of GRB may be quite common, in agreement with the fact that the absence of a supernova can only be established in nearby bursts.

Evidence for encoding versus retrieval scheduling in the hippocampus by theta phase and acetylcholine

PubMed Central

Douchamps, Vincent; Jeewajee, Ali; Blundell, Pam; Burgess, Neil; Lever, Colin

2013-01-01

The formation of new memories requires new information to be encoded in the face of proactive interference from the past. Two solutions have been proposed for hippocampal region CA1: 1) acetylcholine, released in novelty, selectively suppresses excitatory projections to CA1 from CA3 (mediating the products of retrieval), while sparing entorhinal inputs (mediating novel sensory information); 2) encoding preferentially occurs at the pyramidal-layer theta peak, coincident with input from entorhinal cortex, and retrieval occurs at the trough, coincident with input from CA3, consistent with theta-phase-dependent synaptic plasticity. We examined three predictions of these models: 1) In novel environments, the preferred theta phase of CA1 place cell firing should shift closer to the CA1 pyramidal-layer theta peak, shifting the encoding-retrieval balance towards encoding; 2) The encoding-related shift in novel environments should be disrupted by cholinergic antagonism; 3) In familiar environments, cholinergic antagonism should shift the preferred theta firing phase closer to the theta trough, shifting the encoding-retrieval balance even further towards retrieval. We tested these predictions by recording from CA1 pyramidal cells in freely moving rats as they foraged in open field environments under the influence of scopolamine (an amnestic cholinergic antagonist) or vehicle (saline). Results confirmed all three predictions, supporting both the theta phase and cholinergic models of encoding-vs-retrieval dynamics. Also consistent with cholinergic enhancement of encoding, scopolamine attenuated the formation of distinct spatial representations in a new environment, reducing the extent of place cell “remapping”. PMID:23678113

Decision time, slow inhibition, and theta rhythm.

PubMed

Smerieri, Anteo; Rolls, Edmund T; Feng, Jianfeng

2010-10-20

In this paper, we examine decision making in a spiking neuronal network and show that longer time constants for the inhibitory neurons can decrease the reaction times and produce theta rhythm. We analyze the mechanism and find that the spontaneous firing rate before the decision cues are applied can drift, and thereby influence the speed of the reaction time when the decision cues are applied. The drift of the firing rate in the population that will win the competition is larger if the time constant of the inhibitory interneurons is increased from 10 to 33 ms, and even larger if there are two populations of inhibitory neurons with time constants of 10 and 100 ms. Of considerable interest is that the decision that will be made can be influenced by the noise-influenced drift of the spontaneous firing rate over many seconds before the decision cues are applied. The theta rhythm associated with the longer time constant networks mirrors the greater integration in the firing rate drift produced by the recurrent connections over long time periods in the networks with slow inhibition. The mechanism for the effect of slow waves in the theta and delta range on decision times is suggested to be increased neuronal spiking produced by depolarization of the membrane potential on the positive part of the slow waves when the neuron's membrane potential is close to the firing threshold.

Midfrontal conflict-related theta-band power reflects neural oscillations that predict behavior.

PubMed

Cohen, Michael X; Donner, Tobias H

2013-12-01

Action monitoring and conflict resolution require the rapid and flexible coordination of activity in multiple brain regions. Oscillatory neural population activity may be a key physiological mechanism underlying such rapid and flexible network coordination. EEG power modulations of theta-band (4-8 Hz) activity over the human midfrontal cortex during response conflict have been proposed to reflect neural oscillations that support conflict detection and resolution processes. However, it has remained unclear whether this frequency-band-specific activity reflects neural oscillations or nonoscillatory responses (i.e., event-related potentials). Here, we show that removing the phase-locked component of the EEG did not reduce the strength of the conflict-related modulation of the residual (i.e., non-phase-locked) theta power over midfrontal cortex. Furthermore, within-subject regression analyses revealed that the non-phase-locked theta power was a significantly better predictor of the conflict condition than was the time-domain phase-locked EEG component. Finally, non-phase-locked theta power showed robust and condition-specific (high- vs. low-conflict) cross-trial correlations with reaction time, whereas the phase-locked component did not. Taken together, our results indicate that most of the conflict-related and behaviorally relevant midfrontal EEG signal reflects a modulation of ongoing theta-band oscillations that occurs during the decision process but is not phase-locked to the stimulus or to the response.

Power of theta waves in the EEG of human subjects increases during recall of haptic information.

PubMed

Grunwald, M; Weiss, T; Krause, W; Beyer, L; Rost, R; Gutberlet, I; Gertz, H J

1999-02-05

Several studies have reported a functional relationship between spectral power within the theta-band of the EEG (theta-power) and memory load while processing visual or semantic information. We investigated theta power during the processing of different complex haptic stimuli using a delayed recall design. The haptic explorations consisted of palpating the structure of twelve sunken reliefs with closed eyes. Subjects had to reproduce each relief by drawing it 10 s after the end of the exploration. The relationship between mean theta power and mean exploration time was analysed using a regression model. A linear relationship was found between the exploration time and theta power over fronto-central regions (Fp1, Fp2, F3, F7, F8, Fz, C3) directly before the recall of the relief. This result is interpreted in favour of the hypothesis that fronto-central theta power of the EEG correlates with the load of working memory independent of stimulus modality.

Solar microwave bursts - A review

NASA Technical Reports Server (NTRS)

Kundu, M. R.; Vlahos, L.

1982-01-01

Observational and theoretical results on the physics of microwave bursts that occur in the solar atmosphere are reviewed. Special attention is given to the advances made in burst physics over the last few years with the great improvement in spatial and time resolution, especially with instruments like the NRAO three-element interferometer, the Westerbork Synthesis Radio Telescope, and more recently the Very Large Array. Observations made on the preflare build-up of an active region at centimeter wavelengths are reviewed. Three distinct phases in the evolution of cm bursts, namely the impulsive phase, the post-burst phase, and the gradual rise and fall, are discussed. Attention is also given to the flux density spectra of centimeter bursts. Descriptions are given of observations of fine structures with temporal resolution of 10-100 ms in the intensity profiles of cm-wavelength bursts. High spatial resolution observations are analyzed, with special reference to the one- and two-dimensional maps of cm burst sources.

Why don't you like me? Midfrontal theta power in response to unexpected peer rejection feedback.

PubMed

van der Molen, M J W; Dekkers, L M S; Westenberg, P M; van der Veen, F M; van der Molen, M W

2017-02-01

Social connectedness theory posits that the brain processes social rejection as a threat to survival. Recent electrophysiological evidence suggests that midfrontal theta (4-8Hz) oscillations in the EEG provide a window on the processing of social rejection. Here we examined midfrontal theta dynamics (power and inter-trial phase synchrony) during the processing of social evaluative feedback. We employed the Social Judgment paradigm in which 56 undergraduate women (mean age=19.67 years) were asked to communicate their expectancies about being liked vs. disliked by unknown peers. Expectancies were followed by feedback indicating social acceptance vs. rejection. Results revealed a significant increase in EEG theta power to unexpected social rejection feedback. This EEG theta response could be source-localized to brain regions typically reported during activation of the saliency network (i.e., dorsal anterior cingulate cortex, insula, inferior frontal gyrus, frontal pole, and the supplementary motor area). Theta phase dynamics mimicked the behavior of the time-domain averaged feedback-related negativity (FRN) by showing stronger phase synchrony for feedback that was unexpected vs. expected. Theta phase, however, differed from the FRN by also displaying stronger phase synchrony in response to rejection vs. acceptance feedback. Together, this study highlights distinct roles for midfrontal theta power and phase synchrony in response to social evaluative feedback. Our findings contribute to the literature by showing that midfrontal theta oscillatory power is sensitive to social rejection but only when peer rejection is unexpected, and this theta response is governed by a widely distributed neural network implicated in saliency detection and conflict monitoring. Copyright © 2016 Elsevier Inc. All rights reserved.

A pulse-burst laser system for Thomson scattering on NSTX-U

NASA Astrophysics Data System (ADS)

Den Hartog, D. J.; Borchardt, M. T.; Holly, D. J.; Diallo, A.; LeBlanc, B.

2017-10-01

A pulse-burst laser system has been built for Thomson scattering on NSTX-U, and is currently being integrated into the NSTX-U Thomson scattering diagnostic system. The laser will be operated in three distinct modes. The base mode is continuous 30 Hz rep rate, and is the standard operating mode of the laser. The base mode will be interrupted to produce a "slow burst" (specified 1 kHz rep rate for 50 ms) or a "fast burst" (specified 10 kHz rep rate for 5 ms). The combination of base mode→ interruption→ burst mode is new and has not been implemented on any previous pulse-burst laser system. Laser pulsing is halted for a set period (~ 1 minute) following a burst to allow the YAG rods to cool; this type of operation is called a heat-capacity laser. The laser is Nd:YAG operated at 1064 nm, q-switched to produce >= 1.5 J pulses with ~ 20 ns FWHM. It is flashlamp pumped, with dual-rod oscillator (9 mm) and dual-rod amplifier (12 mm). Variable pulsewidth drive of the flashlamps is accomplished by IGBT (insulated gate bipolar transistor) switching of electrolytic capacitor banks. Direct control of the laser Pockels cell drive enables optimal pulse energy extraction. The laser system has demonstrated compliance with all specifications, and is capable of exceeding design specifications by significant margins, e.g., higher rep rates for longer burst periods. Burst operation of this laser system will be used to capture fast time evolution of the electron temperature and density profiles during events such as ELMs, the L-H transition, and various MHD modes.

Do gamma-ray burst sources repeat?

NASA Technical Reports Server (NTRS)

Meegan, C. A.; Hartmann, D. H.; Brainerd, J. J.; Briggs, M.; Paciesas, W. S.; Pendleton, G.; Kouveliotou, C.; Fishman, G.; Blumenthal, G.; Brock, M.

1994-01-01

The demonstration of repeated gamma-ray bursts from an individual source would severely constrain burst source models. Recent reports of evidence for repetition in the first BATSE burst catalog have generated renewed interest in this issue. Here, we analyze the angular distribution of 585 bursts of the second BATSE catalog (Meegan et al. 1994). We search for evidence of burst recurrence using the nearest and farthest neighbor statistic ad the two-point angular correlation function. We find the data to be consistent with the hypothesis that burst sources do not repeat; however, a repeater fraction of up to about 20% of the bursts cannot be excluded.

Transmitter release in the neuromuscular synapse of the protein kinase C theta-deficient adult mouse.

PubMed

Besalduch, Núria; Santafé, Manel M; Garcia, Neus; Gonzalez, Carmen; Tomás, Marta; Tomás, Josep; Lanuza, Maria A

2011-04-01

We studied structural and functional features of the neuromuscular junction in adult mice (P30) genetically deficient in the protein kinase C (PKC) theta isoform. Confocal and electron microscopy shows that there are no differences in the general morphology of the endplates between PKC theta-deficient and wild-type (WT) mice. Specifically, there is no difference in the density of the synaptic vesicles. However, the myelin sheath is not as thick in the intramuscular nerve fibers of the PKC theta-deficient mice. We found a significant reduction in the size of evoked endplate potentials and in the frequency of spontaneous, asynchronous, miniature endplate potentials in the PKC theta-deficient neuromuscular preparations in comparison with the WT, but the mean amplitude of the spontaneous potentials is not different. These changes indicate that PKC theta has a presynaptic role in the function of adult neuromuscular synapses. Copyright © 2010 Wiley-Liss, Inc.

Solar Radio Bursts and Space Weather

NASA Technical Reports Server (NTRS)

Gopalswamy, Natchimuthuk,

2012-01-01

Radio bursts from the Sun are produced by electron accelerated to relativistic energies by physical processes on the Sun such as solar flares and coronal mass ejections (CMEs). The radio bursts are thus good indicators of solar eruptions. Three types of nonthermal radio bursts are generally associated with CMEs. Type III bursts due to accelerated electrons propagating along open magnetic field lines. The electrons are thought to be accelerated at the reconnection region beneath the erupting CME, although there is another view that the electrons may be accelerated at the CME-driven shock. Type II bursts are due to electrons accelerated at the shock front. Type II bursts are also excellent indicators of solar energetic particle (SEP) events because the same shock is supposed accelerate electrons and ions. There is a hierarchical relationship between the wavelength range of type /I bursts and the CME kinetic energy. Finally, Type IV bursts are due to electrons trapped in moving or stationary structures. The low frequency stationary type IV bursts are observed occasionally in association with very fast CMEs. These bursts originate from flare loops behind the erupting CME and hence indicate tall loops. This paper presents a summary of radio bursts and their relation to CMEs and how they can be useful for space weather predictions.

Regulation of theta-antigen expression by agents altering cyclic AMP level and by thymic factor.

PubMed

Bach, M A; Fournier, C; Bach, J F

1975-02-28

Thymic factor, cyclic AMP, and products increasing its cellular level, such as Prostaglandin E1, induce the appearance of the theta-antigen on T-cell precursors whether assessed by a rossette-inhibition assay or a cytotoxic assay after cell fractionation on BSA discontinuous gradiet. Synergism has been demonstrated between cyclic AMPT and TF for that effect. Conversely, decrease of theta expression has been obtained by altering cyclic AMP level in theta-positive cells either increasing it by dibutyryl cAMP treatment or decreasing it by indomethacin treatment. Finally, these data suggest the involvement of cyclic AMP in the regulation of theta expression under thymic hormone control.

The first full-resolution measurements of Auroral Medium Frequency Burst Emissions

NASA Astrophysics Data System (ADS)

Bunch, N. L.; Labelle, J.; Weatherwax, A.; Hughes, J.

2008-12-01

Auroral MF burst is a naturally occurring auroral radio emission which appears unstructured on resolution of previous measurements, is observed in the frequency range of 0.8-4.5 MHz, and has typical amplitudes of around 10-14 V2/m2Hz, and durations of a few minutes. The emission occurs at substorm onset. Since Sept 2006, Dartmouth has operated a broadband (0-5 MHz) interferometer at Toolik Lake, Alaska (68° 38' N, 149° 36' W, 68.51 deg. magnetic latitude), designed for the study of auroral MF burst emissions. Normal operation involves taking snapshots of waveforms from four spaced antennas from which wave spectral and directional information is obtained. However, the experiment can also be run in "continuous mode" whereby the signal from a selected antenna is sampled continuously at 10 M samples/second. A "continuous mode" campaign was run 0800-1200 UT (~2200-0200 MLT) daily from March 21 to April 19, 2008. During this campaign more than twenty auroral MF burst emissions were observed, including three extraordinarily intense examples lasting approximately two minutes each. These observations represent the highest time and frequency resolution data ever collected of MF burst emissions. These data allow us to better characterize the null near twice the electron gyrofrequency identified in previous experiments, since examples of this feature observed during this campaign display a strong null ~50 kHz in bandwidth, with sharp boundaries and occasionally coincident with 2 fce auroral roar. These data also allow us to search for frequency-time structures embedded in MF-burst. One prominent feature appears to be a strong single frequency emission which broadens down to lower frequencies over time, spreading to approximately 500 kHz in bandwidth over ~10 ms. Among other features observed are a diffuse and unstructured emission, as well as what could potentially be several separate emission sources, with multiple emissions occurring simultaneously, appearing as weaker

Reward Expectancy Strengthens CA1 Theta and Beta Band Synchronization and Hippocampal-Ventral Striatal Coupling.

PubMed

Lansink, Carien S; Meijer, Guido T; Lankelma, Jan V; Vinck, Martin A; Jackson, Jadin C; Pennartz, Cyriel M A

2016-10-12

The use of information from the hippocampal memory system in motivated behavior depends on its communication with the ventral striatum. When an animal encounters cues that signal subsequent reward, its reward expectancy is raised. It is unknown, however, how this process affects hippocampal dynamics and their influence on target structures, such as ventral striatum. We show that, in rats, reward-predictive cues result in enhanced hippocampal theta and beta band rhythmic activity during subsequent action, compared with uncued goal-directed navigation. The beta band component, also labeled theta's harmonic, involves selective hippocampal CA1 cell groups showing frequency doubling of firing periodicity relative to theta rhythmicity and it partitions the theta cycle into segments showing clear versus poor spike timing organization. We found that theta phase precession occurred over a wider range than previously reported. This was apparent from spikes emitted near the peak of the theta cycle exhibiting large "phase precessing jumps" relative to spikes in foregoing cycles. Neither this phenomenon nor the regular manifestation of theta phase precession was affected by reward expectancy. Ventral striatal neuronal firing phase-locked not only to hippocampal theta, but also to beta band activity. Both hippocampus and ventral striatum showed increased synchronization between neuronal firing and local field potential activity during cued compared with uncued goal approaches. These results suggest that cue-triggered reward expectancy intensifies hippocampal output to target structures, such as the ventral striatum, by which the hippocampus may gain prioritized access to systems modulating motivated behaviors. Here we show that temporally discrete cues raising reward expectancy enhance both theta and beta band activity in the hippocampus once goal-directed navigation has been initiated. These rhythmic activities are associated with increased synchronization of neuronal firing

Modulation of Hippocampal Theta Oscillations and Spatial Memory by Relaxin-3 Neurons of the Nucleus Incertus

ERIC Educational Resources Information Center

Ma, Sherie; Olucha-Bordonau, Francisco E.; Hossain, M. Akhter; Lin, Feng; Kuei, Chester; Liu, Changlu; Wade, John D.; Sutton, Steven W.; Nunez, Angel; Gundlach, Andrew L.

2009-01-01

Hippocampal theta rhythm is thought to underlie learning and memory, and it is well established that "pacemaker" neurons in medial septum (MS) modulate theta activity. Recent studies in the rat demonstrated that brainstem-generated theta rhythm occurs through a multisynaptic pathway via the nucleus incertus (NI), which is the primary source of the…

Do gamma-ray burst sources repeat?

NASA Technical Reports Server (NTRS)

Meegan, Charles A.; Hartmann, Dieter H.; Brainerd, J. J.; Briggs, Michael S.; Paciesas, William S.; Pendleton, Geoffrey; Kouveliotou, Chryssa; Fishman, Gerald; Blumenthal, George; Brock, Martin

1995-01-01

The demonstration of repeated gamma-ray bursts from an individual source would severely constrain burst source models. Recent reports (Quashnock and Lamb, 1993; Wang and Lingenfelter, 1993) of evidence for repetition in the first BATSE burst catalog have generated renewed interest in this issue. Here, we analyze the angular distribution of 585 bursts of the second BATSE catalog (Meegan et al., 1994). We search for evidence of burst recurrence using the nearest and farthest neighbor statistic and the two-point angular correlation function. We find the data to be consistent with the hypothesis that burst sources do not repeat; however, a repeater fraction of up to about 20% of the observed bursts cannot be excluded.

EEG oscillations and recognition memory: theta correlates of memory retrieval and decision making.

PubMed

Jacobs, Joshua; Hwang, Grace; Curran, Tim; Kahana, Michael J

2006-08-15

Studies of memory retrieval have identified electroencephalographic (EEG) correlates of a test item's old-new status, reaction time, and memory load. In the current study, we used a multivariate analysis to disentangle the effects of these correlated variables. During retrieval, power of left-parietal theta (4-8 Hz) oscillations increased in proportion to how well a test item was remembered, and theta in central regions correlated with decision making. We also studied how these oscillatory dynamics complemented event-related potentials. These findings are the first to demonstrate that distinct patterns of theta oscillations can simultaneously relate to different aspects of behavior.

Optothermally actuated capillary burst valve

NASA Astrophysics Data System (ADS)

Eriksen, Johan; Bilenberg, Brian; Kristensen, Anders; Marie, Rodolphe

2017-04-01

We demonstrate the optothermal actuation of individual capillary burst valves in an all-polymer microfluidic device. The capillary burst valves are realised in a planar design by introducing a fluidic constriction in a microfluidic channel of constant depth. We show that a capillary burst valve can be burst by raising the temperature due to the temperature dependence of the fluid surface tension. We address individual valves by using a local heating platform based on a thin film of near infrared absorber dye embedded in the lid used to seal the microfluidic device [L. H. Thamdrup et al., Nano Lett. 10, 826-832 (2010)]. An individual valve is burst by focusing the laser in its vicinity. We demonstrate the capture of single polystyrene 7 μm beads in the constriction triggered by the bursting of the valve.

Cosmological gamma-ray bursts

NASA Technical Reports Server (NTRS)

Paczynski, Bohdan

1991-01-01

The distribution in angle and flux of gamma-ray bursts indicates that the majority of gamma-ray bursters are at cosmological distances, i.e., at z of about 1. The rate is then about 10 exp -8/yr in a galaxy like the Milky Way, i.e., orders of magnitude lower than the estimated rate for collisions between neutron stars in close binary systems. The energy per burst is about 10 exp 51 ergs, assuming isotropic emission. The events appear to be less energetic and more frequent if their emission is strongly beamed. Some tests for the distance scale are discussed: a correlation between the burst's strength and its spectrum; the absorption by the Galactic gas below about 2 keV; the X-ray tails caused by forward scattering by the Galactic dust; about 1 month recurrence of some bursts caused by gravitational lensing by foreground galaxies; and a search for gamma-ray bursts in M31. The bursts appear to be a manifestation of something exotic, but conventional compact objects can provide an explanation. The best possibility is offered by a decay of a bindary composed of a spinning-stellar-mass black-hole primary and a neutron or a strange-quark star secondary. In the final phase the secondary is tidally disrupted, forms an accretion disk, and up to 10 exp 54 ergs are released. A very small fraction of this energy powers the gamma-ray burst.

Donaldson-Witten theory and indefinite theta functions

NASA Astrophysics Data System (ADS)

Korpas, Georgios; Manschot, Jan

2017-11-01

We consider partition functions with insertions of surface operators of topologically twisted N=2 , SU(2) supersymmetric Yang-Mills theory, or Donaldson-Witten theory for short, on a four-manifold. If the metric of the compact four-manifold has positive scalar curvature, Moore and Witten have shown that the partition function is completely determined by the integral over the Coulomb branch parameter a, while more generally the Coulomb branch integral captures the wall-crossing behavior of both Donaldson polynomials and Seiberg-Witten invariants. We show that after addition of a \\overlineQ -exact surface operator to the Moore-Witten integrand, the integrand can be written as a total derivative to the anti-holomorphic coordinate ā using Zwegers' indefinite theta functions. In this way, we reproduce Göttsche's expressions for Donaldson invariants of rational surfaces in terms of indefinite theta functions for any choice of metric.

Intermittent θ burst stimulation over primary motor cortex enhances movement-related β synchronisation.

PubMed

Hsu, Ya-Fang; Liao, Kwong-Kum; Lee, Po-Lei; Tsai, Yun-An; Yeh, Chia-Lung; Lai, Kuan-Lin; Huang, Ying-Zu; Lin, Yung-Yang; Lee, I-Hui

2011-11-01

The objective of this study is to investigate how transcranial magnetic intermittent theta burst stimulation (iTBS) with a prolonged protocol affects human cortical excitability and movement-related oscillations. Using motor-evoked potentials (MEPs) and movement-related magnetoencephalography (MEG), we assessed the changes of corticospinal excitability and cortical oscillations after iTBS with double the conventional stimulation time (1200 pulses, iTBS1200) over the primary motor cortex (M1) in 10 healthy subjects. Continuous TBS (cTBS1200) and sham stimulation served as controls. iTBS1200 facilitated MEPs evoked from the conditioned M1, while inhibiting MEPs from the contralateral M1 for 30 min. By contrast, cTBS1200 inhibited MEPs from the conditioned M1. Importantly, empirical mode decomposition-based MEG analysis showed that the amplitude of post-movement beta synchronisation (16-26 Hz) was significantly increased by iTBS1200 at the conditioned M1, but was suppressed at the nonconditioned M1. Alpha (8-13 Hz) and low gamma-ranged (35-45 Hz) rhythms were not notably affected. Movement kinetics remained consistent throughout. TBS1200 modulated corticospinal excitability in parallel with the direction of conventional paradigms with modestly prolonged efficacy. Moreover, iTBS1200 increased post-movement beta synchronisation of the stimulated M1, and decreased that of the contralateral M1, probably through interhemispheric interaction. Our results provide insight into the underlying mechanism of TBS and reinforce the connection between movement-related beta synchronisation and corticospinal output. Copyright © 2011 International Federation of Clinical Neurophysiology. Published by Elsevier Ireland Ltd. All rights reserved.

Hippocampal-prefrontal theta-gamma coupling during performance of a spatial working memory task.

PubMed

Tamura, Makoto; Spellman, Timothy J; Rosen, Andrew M; Gogos, Joseph A; Gordon, Joshua A

2017-12-19

Cross-frequency coupling supports the organization of brain rhythms and is present during a range of cognitive functions. However, little is known about whether and how long-range cross-frequency coupling across distant brain regions subserves working memory. Here we report that theta-slow gamma coupling between the hippocampus and medial prefrontal cortex (mPFC) is augmented in a genetic mouse model of cognitive dysfunction. This increased cross-frequency coupling is observed specifically when the mice successfully perform a spatial working memory task. In wild-type mice, increasing task difficulty by introducing a long delay or by optogenetically interfering with encoding, also increases theta-gamma coupling during correct trials. Finally, epochs of high hippocampal theta-prefrontal slow gamma coupling are associated with increased synchronization of neurons within the mPFC. These findings suggest that enhancement of theta-slow gamma coupling reflects a compensatory mechanism to maintain spatial working memory performance in the setting of increased difficulty.

Complex transitions between spike, burst or chaos synchronization states in coupled neurons with coexisting bursting patterns

NASA Astrophysics Data System (ADS)

Gu, Hua-Guang; Chen, Sheng-Gen; Li, Yu-Ye

2015-05-01

We investigated the synchronization dynamics of a coupled neuronal system composed of two identical Chay model neurons. The Chay model showed coexisting period-1 and period-2 bursting patterns as a parameter and initial values are varied. We simulated multiple periodic and chaotic bursting patterns with non-(NS), burst phase (BS), spike phase (SS), complete (CS), and lag synchronization states. When the coexisting behavior is near period-2 bursting, the transitions of synchronization states of the coupled system follows very complex transitions that begins with transitions between BS and SS, moves to transitions between CS and SS, and to CS. Most initial values lead to the CS state of period-2 bursting while only a few lead to the CS state of period-1 bursting. When the coexisting behavior is near period-1 bursting, the transitions begin with NS, move to transitions between SS and BS, to transitions between SS and CS, and then to CS. Most initial values lead to the CS state of period-1 bursting but a few lead to the CS state of period-2 bursting. The BS was identified as chaos synchronization. The patterns for NS and transitions between BS and SS are insensitive to initial values. The patterns for transitions between CS and SS and the CS state are sensitive to them. The number of spikes per burst of non-CS bursting increases with increasing coupling strength. These results not only reveal the initial value- and parameter-dependent synchronization transitions of coupled systems with coexisting behaviors, but also facilitate interpretation of various bursting patterns and synchronization transitions generated in the nervous system with weak coupling strength. Project supported by the National Natural Science Foundation of China (Grant Nos. 11372224 and 11402039) and the Fundamental Research Funds for Central Universities designated to Tongji University (Grant No. 1330219127).

Solar Flares, Type III Radio Bursts, Coronal Mass Ejections, and Energetic Particles

NASA Technical Reports Server (NTRS)

Cane, Hilary V.; Erickson, W. C.; Prestage, N. P.; White, Nicholas E. (Technical Monitor)

2002-01-01

In this correlative study between greater than 20 MeV solar proton events, coronal mass ejections (CMEs), flares, and radio bursts it is found that essentially all of the proton events are preceded by groups of type III bursts and all are preceded by CMEs. These type III bursts (that are a flare phenomenon) usually are long-lasting, intense bursts seen in the low-frequency observations made from space. They are caused by streams of electrons traveling from close to the solar surface out to 1 AU. In most events the type III emissions extend into, or originate at, the time when type II and type IV bursts are reported (some 5 to 10 minutes after the start of the associated soft X-ray flare) and have starting frequencies in the 500 to approximately 100 MHz range that often get lower as a function of time. These later type III emissions are often not reported by ground-based observers, probably because of undue attention to type II bursts. It is suggested to call them type III-1. Type III-1 bursts have previously been called shock accelerated (SA) events, but an examination of radio dynamic spectra over an extended frequency range shows that the type III-1 bursts usually start at frequencies above any type II burst that may be present. The bursts sometimes continue beyond the time when type II emission is seen and, furthermore, sometimes occur in the absence of any type II emission. Thus the causative electrons are unlikely to be shock accelerated and probably originate in the reconnection regions below fast CMEs. A search did not find any type III-1 bursts that were not associated with CMEs. The existence of low-frequency type III bursts proves that open field lines extend from within 0.5 radius of the Sun into the interplanetary medium (the bursts start above 100 MHz, and such emission originates within 0.5 solar radius of the solar surface). Thus it is not valid to assume that only closed field lines exist in the flaring regions associated with CMEs and some

Learner Acquisition of Dialect Variation in a Study Abroad Context: The Case of the Spanish [Theta

ERIC Educational Resources Information Center

Ringer-Hilfinger, Kathryn

2012-01-01

The present study aims at analyzing the acquisition of dialect variation by native English-speaking university students who study Spanish for a semester in Spain. The selected variable is the phoneme /[theta]/ (theta). The goal is to assess learner awareness, opinion, and use of [theta]. Data were elicited through a set of oral and written tasks…

Observations of short gamma-ray bursts.

PubMed

Fox, Derek B; Roming, Peter W A

2007-05-15

We review recent observations of short-hard gamma-ray bursts and their afterglows. The launch and successful ongoing operations of the Swift satellite, along with several localizations from the High-Energy Transient Explorer mission, have provoked a revolution in short-burst studies: first, by quickly providing high-quality positions to observers; and second, via rapid and sustained observations from the Swift satellite itself. We make a complete accounting of Swift-era short-burst localizations and proposed host galaxies, and discuss the implications of these observations for the distances, energetics and environments of short bursts, and the nature of their progenitors. We then review the physical modelling of short-burst afterglows: while the simplest afterglow models are inadequate to explain the observations, there have been several notable successes. Finally, we address the case of an unusual burst that threatens to upset the simple picture in which long bursts are due to the deaths of massive stars, and short bursts to compact-object merger events.

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.

X-ray bursts: Observation versus theory

NASA Technical Reports Server (NTRS)

Lewin, W. H. G.

1981-01-01

Results of various observations of common type I X-ray bursts are discussed with respect to the theory of thermonuclear flashes in the surface layers of accreting neutron stars. Topics covered include burst profiles; irregular burst intervals; rise and decay times and the role of hydrogen; the accuracy of source distances; accuracy in radii determination; radius increase early in the burst; the super Eddington limit; temperatures at burst maximum; and the role of the magnetic field.

Study on creep behavior of Grade 91 heat-resistant steel using theta projection method

NASA Astrophysics Data System (ADS)

Ren, Facai; Tang, Xiaoying

2017-10-01

Creep behavior of Grade 91 heat-resistant steel used for steam cooler was characterized using the theta projection method. Creep tests were conducted at the temperature of 923K under the stress ranging from 100-150MPa. Based on the creep curve results, four theta parameters were established using a nonlinear least square fitting method. Four theta parameters showed a good linearity as a function of stress. The predicted curves coincided well with the experimental data and creep curves were also modeled to the low stress level of 60MPa.

Search for optical bursts from the gamma ray burst source GBS 0526-66

NASA Astrophysics Data System (ADS)

Seetha, S.; Sreenivasaiah, K. V.; Marar, T. M. K.; Kasturirangan, K.; Rao, U. R.; Bhattacharyya, J. C.

1985-08-01

Attempts were made to detect optical bursts from the gamma-ray burst source GBS 0526-66 during Dec. 31, 1984 to Jan. 2, 1985 and Feb. 23 to Feb. 24, 1985, using the one meter reflector of the Kavalur Observatory. Jan. 1, 1985 coincided with the zero phase of the predicted 164 day period of burst activity from the source (Rothschild and Lingenfelter, 1984). A new optical burst photon counting system with adjustable trigger threshold was used in parallel with a high speed photometer for the observations. The best time resolution was 1 ms and maximum count rate capability was 255,000 counts s(-1). Details of the instrumentation and observational results are presented.

Enhanced Burst-Suppression and Disruption of Local Field Potential Synchrony in a Mouse Model of Focal Cortical Dysplasia Exhibiting Spike-Wave Seizures.

PubMed

Williams, Anthony J; Zhou, Chen; Sun, Qian-Quan

2016-01-01

Focal cortical dysplasias (FCDs) are a common cause of brain seizures and are often associated with intractable epilepsy. Here we evaluated aberrant brain neurophysiology in an in vivo mouse model of FCD induced by neonatal freeze lesions (FLs) to the right cortical hemisphere (near S1). Linear multi-electrode arrays were used to record extracellular potentials from cortical and subcortical brain regions near the FL in anesthetized mice (5-13 months old) followed by 24 h cortical electroencephalogram (EEG) recordings. Results indicated that FL animals exhibit a high prevalence of spontaneous spike-wave discharges (SWDs), predominately during sleep (EEG), and an increase in the incidence of hyper-excitable burst/suppression activity under general anesthesia (extracellular recordings, 0.5%-3.0% isoflurane). Brief periods of burst activity in the local field potential (LFP) typically presented as an arrhythmic pattern of increased theta-alpha spectral peaks (4-12 Hz) on a background of low-amplitude delta activity (1-4 Hz), were associated with an increase in spontaneous spiking of cortical neurons, and were highly synchronized in control animals across recording sites in both cortical and subcortical layers (average cross-correlation values ranging from +0.73 to +1.0) with minimal phase shift between electrodes. However, in FL animals, cortical vs. subcortical burst activity was strongly out of phase with significantly lower cross-correlation values compared to controls (average values of -0.1 to +0.5, P < 0.05 between groups). In particular, a marked reduction in the level of synchronous burst activity was observed, the closer the recording electrodes were to the malformation (Pearson's Correlation = 0.525, P < 0.05). In a subset of FL animals (3/9), burst activity also included a spike or spike-wave pattern similar to the SWDs observed in unanesthetized animals. In summary, neonatal FLs increased the hyperexcitable pattern of burst activity induced by anesthesia

Interneuronal mechanisms of hippocampal theta oscillations in a full-scale model of the rodent CA1 circuit

PubMed Central

Bezaire, Marianne J; Raikov, Ivan; Burk, Kelly; Vyas, Dhrumil; Soltesz, Ivan

2016-01-01

The hippocampal theta rhythm plays important roles in information processing; however, the mechanisms of its generation are not well understood. We developed a data-driven, supercomputer-based, full-scale (1:1) model of the rodent CA1 area and studied its interneurons during theta oscillations. Theta rhythm with phase-locked gamma oscillations and phase-preferential discharges of distinct interneuronal types spontaneously emerged from the isolated CA1 circuit without rhythmic inputs. Perturbation experiments identified parvalbumin-expressing interneurons and neurogliaform cells, as well as interneuronal diversity itself, as important factors in theta generation. These simulations reveal new insights into the spatiotemporal organization of the CA1 circuit during theta oscillations. DOI: http://dx.doi.org/10.7554/eLife.18566.001 PMID:28009257

Episodic sequence memory is supported by a theta-gamma phase code.

PubMed

Heusser, Andrew C; Poeppel, David; Ezzyat, Youssef; Davachi, Lila

2016-10-01

The meaning we derive from our experiences is not a simple static extraction of the elements but is largely based on the order in which those elements occur. Models propose that sequence encoding is supported by interactions between high- and low-frequency oscillations, such that elements within an experience are represented by neural cell assemblies firing at higher frequencies (gamma) and sequential order is encoded by the specific timing of firing with respect to a lower frequency oscillation (theta). During episodic sequence memory formation in humans, we provide evidence that items in different sequence positions exhibit greater gamma power along distinct phases of a theta oscillation. Furthermore, this segregation is related to successful temporal order memory. Our results provide compelling evidence that memory for order, a core component of an episodic memory, capitalizes on the ubiquitous physiological mechanism of theta-gamma phase-amplitude coupling.

Finding Sub-threshold Short Gamma-ray Bursts in Fermi GBM Data

NASA Astrophysics Data System (ADS)

Burns, Eric; Fermi Gamma-ray Burst Monitor Team

2018-01-01

The all-sky monitoring capability of Fermi GBM makes it ideal for finding transients, and the most prolific detector of short gamma-ray bursts with about 40 on-board triggers per year. Because the observed brightness of short gamma-ray bursts has no correlation with redshift, weak short gamma-ray bursts are important during the gravitational wave era. With this in mind, we discuss two searches of GBM data to find short gamma-ray which were below the on-board trigger threshold. The untargeted search looks for significant background-subtracted signals in two or more detectors at various timescales in the continuous data, detecting ~80 additional short GRB candidates per year. The targeted search is the most sensitive search for weak gamma-ray signals in GBM data and is run over limited time intervals around sources of interest like gravitational waves.

Statistical properties of multi-theta polymer chains

NASA Astrophysics Data System (ADS)

Uehara, Erica; Deguchi, Tetsuo

2018-04-01

We study statistical properties of polymer chains with complex structures whose chemical connectivities are expressed by graphs. The multi-theta curve of m subchains with two branch points connected by them is one of the simplest graphs among those graphs having closed paths, i.e. loops. We denoted it by θm , and for m  =  2 it is given by a ring. We derive analytically the pair distribution function and the scattering function for the θm -shaped polymer chains consisting of m Gaussian random walks of n steps. Surprisingly, it is shown rigorously that the mean-square radius of gyration for the Gaussian θm -shaped polymer chain does not depend on the number m of subchains if each subchain has the same fixed number of steps. For m  =  3 we show the Kratky plot for the theta-shaped polymer chain consisting of hard cylindrical segments by the Monte-Carlo method including reflection at trivalent vertices.

Gamma-Ray Bursts: A Mystery Story

NASA Technical Reports Server (NTRS)

Parsons, Ann

2007-01-01

With the success of the Swift Gamma-Ray Burst Explorer currently in orbit, this is quite an exciting time in the history of Gamma Ray Bursts (GRBs). The study of GRBs is a modern astronomical mystery story that began over 30 years ago with the serendipitous discovery of these astronomical events by military satellites in the late 1960's. Until the launch of BATSE on the Compton Gamma-ray Observatory, astronomers had no clue whether GRBs originated at the edge of our solar system, in our own Milky Way Galaxy or incredibly far away near the edge of the observable Universe. Data from BATSE proved that GRBs are distributed isotropically on the sky and thus could not be the related to objects in the disk of our Galaxy. Given the intensity of the gamma-ray emission, an extragalactic origin would require an astounding amount of energy. Without sufficient data to decide the issue, a great debate continued about whether GRBs were located in the halo of our own galaxy or were at extragalactic - even cosmological distances. This debate continued until 1997 when the BeppoSAX mission discovered a fading X-ray afterglow signal in the same location as a GRB. This discovery enabled other telescopes, to observe afterglow emission at optical and radio wavelengths and prove that GRBs were at cosmological distances by measuring large redshifts in the optical spectra. Like BeppoSAX Swift, slews to new GRB locations to measure afterglow emission. In addition to improved GRB sensitivity, a significant advantage of Swift over BeppoSAX and other missions is its ability to slew very quickly, allowing x-ray and optical follow-up measurements to be made as early as a minute after the gamma-ray burst trigger rather than the previous 6-8 hour delay. Swift afterglow measurements along with follow-up ground-based observations, and theoretical work have allowed astronomers to identify two plausible scenarios for the creation of a GRB: either through core collapse of super massive stars or

Secured Hash Based Burst Header Authentication Design for Optical Burst Switched Networks

NASA Astrophysics Data System (ADS)

Balamurugan, A. M.; Sivasubramanian, A.; Parvathavarthini, B.

2017-12-01

The optical burst switching (OBS) is a promising technology that could meet the fast growing network demand. They are featured with the ability to meet the bandwidth requirement of applications that demand intensive bandwidth. OBS proves to be a satisfactory technology to tackle the huge bandwidth constraints, but suffers from security vulnerabilities. The objective of this proposed work is to design a faster and efficient burst header authentication algorithm for core nodes. There are two important key features in this work, viz., header encryption and authentication. Since the burst header is an important in optical burst switched network, it has to be encrypted; otherwise it is be prone to attack. The proposed MD5&RC4-4S based burst header authentication algorithm runs 20.75 ns faster than the conventional algorithms. The modification suggested in the proposed RC4-4S algorithm gives a better security and solves the correlation problems between the publicly known outputs during key generation phase. The modified MD5 recommended in this work provides 7.81 % better avalanche effect than the conventional algorithm. The device utilization result also shows the suitability of the proposed algorithm for header authentication in real time applications.

Solar Drift-Pair Bursts

NASA Astrophysics Data System (ADS)

Stanislavsky, A.; Volvach, Ya.; Konovalenko, A.; Koval, A.

2017-08-01

In this paper a new sight on the study of solar bursts historically called drift pairs (DPs) is presented. Having a simple morphology on dynamic spectra of radio records (two short components separated in time, and often they are very similar) and discovered at the dawn of radio astronomy, their features remain unexplained totally up to now. Generally, the DPs are observed during the solar storms of type III bursts, but not every storm of type III bursts is linked with DPs. Detected by ground-based instruments at decameter and meter wavelengths, the DP bursts are limited in frequency bandwidth. They can drift from high frequencies to low ones and vice versa. Their frequency drift rate may be both lower and higher than typical rates of type III bursts at the same frequency range. The development of low-frequency radio telescopes and data processing provide additional possibilities in the research. In this context the fresh analysis of DPs, made from recent observations in the summer campaign of 2015, are just considered. Their study was implemented by updated tools of the UTR-2 radio telescope at 9-33 MHz. During 10-12 July of 2015, DPs forming the longest patterns on dynamic spectra are about 7% of the total number of recorded DPs. Their marvelous resemblance in frequency drift rates with the solar S-bursts is discussed.

30 CFR 57.3461 - Rock bursts.

Code of Federal Regulations, 2011 CFR

2011-07-01

... 30 Mineral Resources 1 2011-07-01 2011-07-01 false Rock bursts. 57.3461 Section 57.3461 Mineral...-Underground Only § 57.3461 Rock bursts. (a) Operators of mines which have experienced a rock burst shall— (1) Within twenty four hours report to the nearest MSHA office each rock burst which: (i) Causes persons to...

30 CFR 57.3461 - Rock bursts.

Code of Federal Regulations, 2012 CFR

2012-07-01

... 30 Mineral Resources 1 2012-07-01 2012-07-01 false Rock bursts. 57.3461 Section 57.3461 Mineral...-Underground Only § 57.3461 Rock bursts. (a) Operators of mines which have experienced a rock burst shall— (1) Within twenty four hours report to the nearest MSHA office each rock burst which: (i) Causes persons to...

30 CFR 57.3461 - Rock bursts.

Code of Federal Regulations, 2014 CFR

2014-07-01

... 30 Mineral Resources 1 2014-07-01 2014-07-01 false Rock bursts. 57.3461 Section 57.3461 Mineral...-Underground Only § 57.3461 Rock bursts. (a) Operators of mines which have experienced a rock burst shall— (1) Within twenty four hours report to the nearest MSHA office each rock burst which: (i) Causes persons to...

30 CFR 57.3461 - Rock bursts.

Code of Federal Regulations, 2013 CFR

2013-07-01

... 30 Mineral Resources 1 2013-07-01 2013-07-01 false Rock bursts. 57.3461 Section 57.3461 Mineral...-Underground Only § 57.3461 Rock bursts. (a) Operators of mines which have experienced a rock burst shall— (1) Within twenty four hours report to the nearest MSHA office each rock burst which: (i) Causes persons to...

30 CFR 57.3461 - Rock bursts.

Code of Federal Regulations, 2010 CFR

2010-07-01

... 30 Mineral Resources 1 2010-07-01 2010-07-01 false Rock bursts. 57.3461 Section 57.3461 Mineral...-Underground Only § 57.3461 Rock bursts. (a) Operators of mines which have experienced a rock burst shall— (1) Within twenty four hours report to the nearest MSHA office each rock burst which: (i) Causes persons to...

Theta signal as the neural signature of social exclusion.

PubMed

Cristofori, Irene; Moretti, Laura; Harquel, Sylvain; Posada, Andres; Deiana, Gianluca; Isnard, Jean; Mauguière, François; Sirigu, Angela

2013-10-01

The feeling of being excluded from a social interaction triggers social pain, a sensation as intense as actual physical pain. Little is known about the neurophysiological underpinnings of social pain. We addressed this issue using intracranial electroencephalography in 15 patients performing a ball game where inclusion and exclusion blocks were alternated. Time-frequency analyses showed an increase in power of theta-band oscillations during exclusion in the anterior insula (AI) and posterior insula, the subgenual anterior cingulate cortex (sACC), and the fusiform "face area" (FFA). Interestingly, the AI showed an initial fast response to exclusion but the signal rapidly faded out. Activity in the sACC gradually increased and remained significant thereafter. This suggests that the AI may signal social pain by detecting emotional distress caused by the exclusion, whereas the sACC may be linked to the learning aspects of social pain. Theta activity in the FFA was time-locked to the observation of a player poised to exclude the participant, suggesting that the FFA encodes the social value of faces. Taken together, our findings suggest that theta activity represents the neural signature of social pain. The time course of this signal varies across regions important for processing emotional features linked to social information.

The Mystery of Gamma-Ray Bursts

NASA Technical Reports Server (NTRS)

Fishman, Gerald J.

2004-01-01

Gamma-ray bursts remain one of the greatest mysteries in astrophysics. Observations of gamma-ray bursts made by the BATSE experiment on the Compton Gamma-Ray Observatory will be described. Most workers in the field now believe that they originate from cosmological distances. This view has been reinforced by observations this year of several optical afterglow counterparts to gamma-ray bursts. A summary of these recent discoveries will be presented, along with their implications for models of the burst emission mechanism and the energy source of the bursts.

Stimulus induced bursts in severe postanoxic encephalopathy.

PubMed

Tjepkema-Cloostermans, Marleen C; Wijers, Elisabeth T; van Putten, Michel J A M

2016-11-01

To report on a distinct effect of auditory and sensory stimuli on the EEG in comatose patients with severe postanoxic encephalopathy. In two comatose patients admitted to the Intensive Care Unit (ICU) with severe postanoxic encephalopathy and burst-suppression EEG, we studied the effect of external stimuli (sound and touch) on the occurrence of bursts. In patient A bursts could be induced by either auditory or sensory stimuli. In patient B bursts could only be induced by touching different facial regions (forehead, nose and chin). When stimuli were presented with relatively long intervals, bursts persistently followed the stimuli, while stimuli with short intervals (<1s) did not induce bursts. In both patients bursts were not accompanied by myoclonia. Both patients deceased. Bursts in patients with a severe postanoxic encephalopathy can be induced by external stimuli, resulting in stimulus-dependent burst-suppression. Stimulus induced bursts should not be interpreted as prognostic favourable EEG reactivity. Copyright © 2016 International Federation of Clinical Neurophysiology. Published by Elsevier Ireland Ltd. All rights reserved.

Frontal Midline Theta Reflects Anxiety and Cognitive Control: Meta-Analytic Evidence

PubMed Central

Cavanagh, James F.; Shackman, Alexander J.

2014-01-01

Evidence from imaging and anatomical studies suggests that the midcingulate cortex (MCC) is a dynamic hub lying at the interface of affect and cognition. In particular, this neural system appears to integrate information about conflict and punishment in order to optimize behavior in the face of action-outcome uncertainty. In a series of meta-analyses, we show how recent human electrophysiological research provides compelling evidence that frontal-midline theta signals reflecting MCC activity are moderated by anxiety and predict adaptive behavioral adjustments. These findings underscore the importance of frontal theta activity to a broad spectrum of control operations. We argue that frontal-midline theta provides a neurophysiologically plausible mechanism for optimally adjusting behavior to uncertainty, a hallmark of situations that elicit anxiety and demand cognitive control. These observations compel a new perspective on the mechanisms guiding motivated learning and behavior and provide a framework for understanding the role of the MCC in temperament and psychopathology. PMID:24787485

Increase in short-term memory capacity induced by down-regulating individual theta frequency via transcranial alternating current stimulation.

PubMed

Vosskuhl, Johannes; Huster, René J; Herrmann, Christoph S

2015-01-01

Working memory (WM) and short-term memory (STM) supposedly rely on the phase-amplitude coupling (PAC) of neural oscillations in the theta and gamma frequency ranges. The ratio between the individually dominant gamma and theta frequencies is believed to determine an individual's memory capacity. The aim of this study was to establish a causal relationship between the gamma/theta ratio and WM/STM capacity by means of transcranial alternating current stimulation (tACS). To achieve this, tACS was delivered at a frequency below the individual theta frequency. Thereby the individual ratio of gamma to theta frequencies was changed, resulting in an increase of STM capacity. Healthy human participants (N = 33) were allocated to two groups, one receiving verum tACS, the other underwent a sham control protocol. The electroencephalogram (EEG) was measured before stimulation and analyzed with regard to the properties of PAC between theta and gamma frequencies to determine individual stimulation frequencies. After stimulation, EEG was recorded again in order to find after-effects of tACS in the oscillatory features of the EEG. Measures of STM and WM were obtained before, during and after stimulation. Frequency spectra and behavioral data were compared between groups and different measurement phases. The tACS- but not the sham stimulated group showed an increase in STM capacity during stimulation. WM was not affected in either groups. An increase in task-related theta amplitude after stimulation was observed only for the tACS group. These augmented theta amplitudes indicated that the manipulation of individual theta frequencies was successful and caused the increase in STM capacity.

From damselflies to pterosaurs: how burst and sustainable flight performance scale with size.

PubMed

Marden, J H

1994-04-01

Recent empirical data for short-burst lift and power production of flying animals indicate that mass-specific lift and power output scale independently (lift) or slightly positively (power) with increasing size. These results contradict previous theory, as well as simple observation, which argues for degradation of flight performance with increasing size. Here, empirical measures of lift and power during short-burst exertion are combined with empirically based estimates of maximum muscle power output in order to predict how burst and sustainable performance scale with body size. The resulting model is used to estimate performance of the largest extant flying birds and insects, along with the largest flying animals known from fossils. These estimates indicate that burst flight performance capacities of even the largest extinct fliers (estimated mass 250 kg) would allow takeoff from the ground; however, limitations on sustainable power output should constrain capacity for continuous flight at body sizes exceeding 0.003-1.0 kg, depending on relative wing length and flight muscle mass.

UWB dual burst transmit driver

DOEpatents

Dallum, Gregory E [Livermore, CA; Pratt, Garth C [Discovery Bay, CA; Haugen, Peter C [Livermore, CA; Zumstein, James M [Livermore, CA; Vigars, Mark L [Livermore, CA; Romero, Carlos E [Livermore, CA

2012-04-17

A dual burst transmitter for ultra-wideband (UWB) communication systems generates a pair of precisely spaced RF bursts from a single trigger event. An input trigger pulse produces two oscillator trigger pulses, an initial pulse and a delayed pulse, in a dual trigger generator. The two oscillator trigger pulses drive a gated RF burst (power output) oscillator. A bias driver circuit gates the RF output oscillator on and off and sets the RF burst packet width. The bias driver also level shifts the drive signal to the level that is required for the RF output device.

Selective Coupling between Theta Phase and Neocortical Fast Gamma Oscillations during REM-Sleep in Mice

PubMed Central

Scheffzük, Claudia; Kukushka, Valeriy I.; Vyssotski, Alexei L.; Draguhn, Andreas

2011-01-01

Background The mammalian brain expresses a wide range of state-dependent network oscillations which vary in frequency and spatial extension. Such rhythms can entrain multiple neurons into coherent patterns of activity, consistent with a role in behaviour, cognition and memory formation. Recent evidence suggests that locally generated fast network oscillations can be systematically aligned to long-range slow oscillations. It is likely that such cross-frequency coupling supports specific tasks including behavioural choice and working memory. Principal Findings We analyzed temporal coupling between high-frequency oscillations and EEG theta activity (4–12 Hz) in recordings from mouse parietal neocortex. Theta was exclusively present during active wakefulness and REM-sleep. Fast oscillations occurred in two separate frequency bands: gamma (40–100 Hz) and fast gamma (120–160 Hz). Theta, gamma and fast gamma were more prominent during active wakefulness as compared to REM-sleep. Coupling between theta and the two types of fast oscillations, however, was more pronounced during REM-sleep. This state-dependent cross-frequency coupling was particularly strong for theta-fast gamma interaction which increased 9-fold during REM as compared to active wakefulness. Theta-gamma coupling increased only by 1.5-fold. Significance State-dependent cross-frequency-coupling provides a new functional characteristic of REM-sleep and establishes a unique property of neocortical fast gamma oscillations. Interactions between defined patterns of slow and fast network oscillations may serve selective functions in sleep-dependent information processing. PMID:22163023

Rhythmic Activity and Individual Variability in Recognition Memory: Theta Oscillations Correlate with Performance whereas Alpha Oscillations Correlate with ERPs.

PubMed

Chen, Yvonne Y; Caplan, Jeremy B

2017-01-01

During study trials of a recognition memory task, alpha (∼10 Hz) oscillations decrease, and concurrently, theta (4-8 Hz) oscillations increase when later memory is successful versus unsuccessful (subsequent memory effect). Likewise, at test, reduced alpha and increased theta activity are associated with successful memory (retrieval success effect). Here we take an individual-differences approach to test three hypotheses about theta and alpha oscillations in verbal, old/new recognition, measuring the difference in oscillations between hit trials and miss trials. First, we test the hypothesis that theta and alpha oscillations have a moderately mutually exclusive relationship; but no support for this hypothesis was found. Second, we test the hypothesis that theta oscillations explain not only memory effects within participants, but also individual differences. Supporting this prediction, durations of theta (but not alpha) oscillations at study and at test correlated significantly with d' across participants. Third, we test the hypothesis that theta and alpha oscillations reflect familiarity and recollection processes by comparing oscillation measures to ERPs that are implicated in familiarity and recollection. The alpha-oscillation effects correlated with some ERP measures, but inversely, suggesting that the actions of alpha oscillations on memory processes are distinct from the roles of familiarity- and recollection-linked ERP signals. The theta-oscillation measures, despite differentiating hits from misses, did not correlate with any ERP measure; thus, theta oscillations may reflect elaborative processes not tapped by recollection-related ERPs. Our findings are consistent with alpha oscillations reflecting visual inattention, which can modulate memory, and with theta oscillations supporting recognition memory in ways that complement the most commonly studied ERPs.

Type 2 and type 3 burst theory

NASA Technical Reports Server (NTRS)

Smith, D. F.

1973-01-01

The present state of the theory of type 3 bursts is reviewed by dividing the problem into the exciting agency, radiation source, and propagation of radiation between the source and the observer. In-situ measurements indicate that the excitors are electron streams of energy about 40 keV which are continuously relaxing. An investigation of neutralization of an electron stream indicates that n sub s is much less than 100,000 n sub e, where n sub s is the stream density and n sub e the coronal electron density. In situ observations are consistent with this result. An analysis of propagation of electrons in the current sheets of coronal streamers shows that such propagation at heights greater than 1 solar radius is impossible. The mechanisms for radiation are reviewed; it is shown that fundamental radiation at high frequencies (approximately 100 MHz) is highly beamed in the radial direction and that near the earth second harmonic radiation must be dominant. Because of beaming of the fundamental at high frequencies, it can often be quite weak near the limb so that the second harmonic is dominant. In considering propagation to the observer, the results of scattering of radiation are discussed. The present state of the theory of type 2 bursts is reviewed in the same manner as type 3 bursts.

A Reconnection Switch to Trigger gamma-Ray Burst Jet Dissipation

DOE Office of Scientific and Technical Information (OSTI.GOV)

McKinney, Jonathan C.; Uzdensky, Dmitri A.

2012-03-14

Prompt gamma-ray burst (GRB) emission requires some mechanism to dissipate an ultrarelativistic jet. Internal shocks or some form of electromagnetic dissipation are candidate mechanisms. Any mechanism needs to answer basic questions, such as what is the origin of variability, what radius does dissipation occur at, and how does efficient prompt emission occur. These mechanisms also need to be consistent with how ultrarelativistic jets form and stay baryon pure despite turbulence and electromagnetic reconnection near the compact object and despite stellar entrainment within the collapsar model. We use the latest magnetohydrodynamical models of ultrarelativistic jets to explore some of these questionsmore » in the context of electromagnetic dissipation due to the slow collisional and fast collisionless reconnection mechanisms, as often associated with Sweet-Parker and Petschek reconnection, respectively. For a highly magnetized ultrarelativistic jet and typical collapsar parameters, we find that significant electromagnetic dissipation may be avoided until it proceeds catastrophically near the jet photosphere at large radii (r {approx} 10{sup 13}-10{sup 14}cm), by which the jet obtains a high Lorentz factor ({gamma} {approx} 100-1000), has a luminosity of L{sub j} {approx} 10{sup 50}-10{sup 51} erg s{sup -1}, has observer variability timescales of order 1s (ranging from 0.001-10s), achieves {gamma}{theta}{sub j} {approx} 10-20 (for opening half-angle {theta}{sub j}) and so is able to produce jet breaks, and has comparable energy available for both prompt and afterglow emission. A range of model parameters are investigated and simplified scaling laws are derived. This reconnection switch mechanism allows for highly efficient conversion of electromagnetic energy into prompt emission and associates the observed prompt GRB pulse temporal structure with dissipation timescales of some number of reconnecting current sheets embedded in the jet. We hope this work helps

Effects of Thermonuclear X-Ray Bursts on Non-burst Emissions in the Soft State of 4U 1728–34

NASA Astrophysics Data System (ADS)

Bhattacharyya, Sudip; Yadav, J. S.; Sridhar, Navin; Verdhan Chauhan, Jai; Agrawal, P. C.; Antia, H. M.; Pahari, Mayukh; Misra, Ranjeev; Katoch, Tilak; Manchanda, R. K.; Paul, Biswajit

2018-06-01

It has recently been shown that the persistent emission of a neutron star low-mass X-ray binary (LMXB) evolves during a thermonuclear (type-I) X-ray burst. The reason of this evolution, however, is not fully known. This uncertainty can introduce significant systematics in the neutron star radius measurement using burst spectra, particularly if an unknown but significant fraction of the burst emission, which is reprocessed, contributes to the changes in the persistent emission during the burst. Here, by analyzing individual burst data of AstroSat/LAXPC from the neutron star LMXB 4U 1728–34 in the soft state, we show that the burst emission is not significantly reprocessed by a corona covering the neutron star. Rather, our analysis suggests that the burst emission enhances the accretion disk emission, possibly by increasing the accretion rate via disk. This enhanced disk emission, which is Comptonized by a corona covering the disk, can explain an increased persistent emission observed during the burst. This finding provides an understanding of persistent emission components and their interaction with the thermonuclear burst emission. Furthermore, as burst photons are not significantly reprocessed, non-burst and burst emissions can be reliably separated, which is required to reduce systematic uncertainties in the stellar radius measurement.

The Mystery of Gamma-Ray Bursts

NASA Technical Reports Server (NTRS)

Fishman, Gerald J.

1998-01-01

Gamma-ray bursts remain on of the greatest mysteries in astrophysics in spite of recent observational advances and intense theoretical work. Although some of the basic properties of bursts were known 25 years ago, new and more detailed observations have been made by the BATSE (Burst and Transient Source Experiment) experiment on the Compton Gamma Ray Observatory in the past five years. Recent observations of bursts and some proposed models will be discussed.

Frontal beta-theta network during REM sleep

PubMed Central

Vijayan, Sujith; Lepage, Kyle Q; Kopell, Nancy J; Cash, Sydney S

2017-01-01

We lack detailed knowledge about the spatio-temporal physiological signatures of REM sleep, especially in humans. By analyzing intracranial electrode data from humans, we demonstrate for the first time that there are prominent beta (15–35 Hz) and theta (4–8 Hz) oscillations in both the anterior cingulate cortex (ACC) and the DLPFC during REM sleep. We further show that these theta and beta activities in the ACC and the DLPFC, two relatively distant but reciprocally connected regions, are coherent. These findings suggest that, counter to current prevailing thought, the DLPFC is active during REM sleep and likely interacting with other areas. Since the DLPFC and the ACC are implicated in memory and emotional regulation, and the ACC has motor areas and is thought to be important for error detection, the dialogue between these two areas could play a role in the regulation of emotions and in procedural motor and emotional memory consolidation. DOI: http://dx.doi.org/10.7554/eLife.18894.001 PMID:28121613

Role of Broca's Area in Implicit Motor Skill Learning: Evidence from Continuous Theta-Burst Magnetic Stimulation

ERIC Educational Resources Information Center

Clerget, Emeline; Poncin, William; Fadiga, Luciano; Olivier, Etienne

2012-01-01

Complex actions can be regarded as a concatenation of simple motor acts, arranged according to specific rules. Because the caudal part of the Broca's region (left Brodmann's area 44, BA 44) is involved in processing hierarchically organized behaviors, we aimed to test the hypothesis that this area may also play a role in learning structured motor…

BATSE Observations of Gamma-Ray Burst Tails

NASA Technical Reports Server (NTRS)

Connaughton, Valerie; Six, N. Frank (Technical Monitor)

2001-01-01

With the discovery of low-energy radiation appearing to come from the site of gamma-ray bursts in the hours to weeks after the initial burst of gamma rays, it would appear that astronomers have seen a cosmological imprint made by the burster on its surroundings. I discuss in this paper the phenomenon of post-burst emission in BATSE (Burst and Transient Source Experiment) gamma-ray bursts at energies traditionally associated with prompt emission. By summing the background-subtracted signals from hundreds of bursts, I find that tails out to hundreds of seconds after the trigger may be a common feature of long events (duration greater than 2s), and perhaps of the shorter bursts at a lower and shorter-lived level. The tail component appears independent of both the duration (within the long GRB sample) and brightness of the prompt burst emission, and may be softer. Some individual bursts have visible tails at gamma-ray energies and the spectrum in at least a few cases is different from that of the prompt emission. Afterglow at lower energies was detected for one of these bursts, GRB-991216, raising the possibility of afterglow observations over large energy ranges using the next generation of GRB detectors in conjunction with sensitive space or ground-based telescopes.

Fast Radio Bursts

NASA Astrophysics Data System (ADS)

Kaspi, Victoria M.

2017-01-01

Fast Radio Bursts (FRBs) are a recently discovered phenomenon consisting of short (few ms) bursts of radio waves that have dispersion measures that strongly suggest an extragalactic and possibly cosmological origin. Current best estimates for the rate of FRBs is several thousand per sky per day at radio frequencies near 1.4 GHz. Even with so high a rate, to date, fewer than 20 FRBs have been reported, with one source showing repeated bursts. In this talk I will describe known FRB properties including what is known about the lone repeating source, as well as models for the origin of these mysterious events. I will also describe the CHIME radio telescope, currently under construction in Canada. Thanks to its great sensitivity and unprecedented field-of-view, CHIME promises major progress on FRBs.

Theta-Pinch Thruster for Piloted Deep Space Exploration

NASA Technical Reports Server (NTRS)

LaPointe, Mike R.; Reddy, Dhanireddy (Technical Monitor)

2000-01-01

A new high-power propulsion concept that combines a rapidly pulsed theta-pinch discharge with upstream particle reflection by a magnetic mirror was evaluated under a Phase 1 grant awarded through the NASA Institute for Advanced Concepts. Analytic and numerical models were developed to predict the performance of a theta-pinch thruster operated over a wide range of initial gas pressures and discharge periods. The models indicate that a 1 m radius, 10 m long thruster operated with hydrogen propellant could provide impulse-bits ranging from 1 N-s to 330 N-s with specific impulse values of 7,500 s to 2,500 s, respectively. A pulsed magnetic field strength of 2 T is required to compress and heat the preionized hydrogen over a 10(exp -3) second discharge period, with about 60% of the heated plasma exiting the chamber each period to produce thrust. The unoptimized thruster efficiency is low, peaking at approximately 16% for an initial hydrogen chamber pressure of 100 Torr. The specific impulse and impulse-bit at this operating condition are 3,500 s and 90 N-s, respectively, and the required discharge energy is approximately 9x10(exp 6) J. For a pulse repetition rate of 10 Hz, the engine would produce an average thrust of 900 N at 3,500 s specific impulse. Combined with the electrodeless nature of the device, these performance parameters indicate that theta-pinch thrusters could provide unique, long-life propulsion systems for piloted deep space mission applications.

Excess close burst pairs in FRB 121102

NASA Astrophysics Data System (ADS)

Katz, J. I.

2018-05-01

The repeating FRB 121102 emitted a pair of apparently discrete bursts separated by 37 ms and another pair, 131 d later, separated by 34 ms, during observations that detected bursts at a mean rate of ˜2 × 10-4 s-1. While FRB 121102 is known to produce multipeaked bursts, here I assume that these `burst pairs' are truly separate bursts and not multicomponent single bursts, and consider the implications of that assumption. Their statistics are then non-Poissonian. Assuming that the emission comes from a narrow range of rotational phase, then the measured burst intervals constrain any possible periodic modulation underlying the highly episodic emission. If more such short intervals are measured a period may be determined or periodicity may be excluded. The excess of burst intervals much shorter than their mean recurrence time may be explained if FRB emit steady but narrow beams that execute a random walk in direction, perhaps indicating origin in a black hole's accretion disc.

Black Women Leaders: The Case of Delta Sigma Theta.

ERIC Educational Resources Information Center

Canady, Hortense

1985-01-01

Describes the leadership role taken by Delta Sigma Theta Sorority, Inc., in educational and economic development, international affairs, and physical and mental health since the organization's founding at Howard University in 1913. (GC)

The rotational phase dependence of magnetar bursts

NASA Astrophysics Data System (ADS)

Elenbaas, C.; Watts, A. L.; Huppenkothen, D.

2018-05-01

The trigger for the short bursts observed in γ-rays from many magnetar sources remains unknown. One particular open question in this context is the localization of burst emission to a singular active region or a larger area across the neutron star. While several observational studies have attempted to investigate this question by looking at the phase dependence of burst properties, results have been mixed. At the same time, it is not obvious a priori that bursts from a localized active region would actually give rise to a detectable phase dependence, taking into account issues such as geometry, relativistic effects, and intrinsic burst properties such brightness and duration. In this paper, we build a simple theoretical model to investigate the circumstances under which the latter effects could affect detectability of dependence of burst emission on rotational phase. We find that even for strongly phase-dependent emission, inferred burst properties may not show a rotational phase dependence, depending on the geometry of the system and the observer. Furthermore, the observed properties of bursts with durations short as 10-20 per cent of the spin period can vary strongly depending on the rotational phase at which the burst was emitted. We also show that detectability of a rotational phase dependence depends strongly on the minimum number of bursts observed, and find that existing burst samples may simply be too small to rule out a phase dependence.

Theta oscillations during holeboard training in rats: different learning strategies entail different context-dependent modulations in the hippocampus.

PubMed

Woldeit, M L; Korz, V

2010-02-03

A functional connection between theta rhythms, information processing, learning and memory formation is well documented by studies focusing on the impact of theta waves on motor activity, global context or phase coding in spatial learning. In the present study we analyzed theta oscillations during a spatial learning task and assessed which specific behavioral contexts were connected to changes in theta power and to the formation of memory. Therefore, we measured hippocampal dentate gyrus theta modulations in male rats that were allowed to establish a long-term spatial reference memory in a holeboard (fixed pattern of baited holes) in comparison to rats that underwent similar training conditions but could not form a reference memory (randomly baited holes). The first group established a pattern specific learning strategy, while the second developed an arbitrary search strategy, visiting increasingly more holes during training. Theta power was equally influenced during the training course in both groups, but was significantly higher when compared to untrained controls. A detailed behavioral analysis, however, revealed behavior- and context-specific differences within the experimental groups. In spatially trained animals theta power correlated with the amounts of reference memory errors in the context of the inspection of unbaited holes and exploration in which, as suggested by time frequency analyses, also slow wave (delta) power was increased. In contrast, in randomly trained animals positive correlations with working memory errors were found in the context of rearing behavior. These findings indicate a contribution of theta/delta to long-lasting memory formation in spatially trained animals, whereas in pseudo trained animals theta seems to be related to attention in order to establish trial specific short-term working memory. Implications for differences in neuronal plasticity found in earlier studies are discussed. Copyright 2010 IBRO. Published by Elsevier Ltd

Coupling between Theta Oscillations and Cognitive Control Network during Cross-Modal Visual and Auditory Attention: Supramodal vs Modality-Specific Mechanisms.

PubMed

Wang, Wuyi; Viswanathan, Shivakumar; Lee, Taraz; Grafton, Scott T

2016-01-01

Cortical theta band oscillations (4-8 Hz) in EEG signals have been shown to be important for a variety of different cognitive control operations in visual attention paradigms. However the synchronization source of these signals as defined by fMRI BOLD activity and the extent to which theta oscillations play a role in multimodal attention remains unknown. Here we investigated the extent to which cross-modal visual and auditory attention impacts theta oscillations. Using a simultaneous EEG-fMRI paradigm, healthy human participants performed an attentional vigilance task with six cross-modal conditions using naturalistic stimuli. To assess supramodal mechanisms, modulation of theta oscillation amplitude for attention to either visual or auditory stimuli was correlated with BOLD activity by conjunction analysis. Negative correlation was localized to cortical regions associated with the default mode network and positively with ventral premotor areas. Modality-associated attention to visual stimuli was marked by a positive correlation of theta and BOLD activity in fronto-parietal area that was not observed in the auditory condition. A positive correlation of theta and BOLD activity was observed in auditory cortex, while a negative correlation of theta and BOLD activity was observed in visual cortex during auditory attention. The data support a supramodal interaction of theta activity with of DMN function, and modality-associated processes within fronto-parietal networks related to top-down theta related cognitive control in cross-modal visual attention. On the other hand, in sensory cortices there are opposing effects of theta activity during cross-modal auditory attention.

FRB121102 Bursts Show Detailed Spectrotemporal Structure

NASA Astrophysics Data System (ADS)

Hessels, Jason; Seymour, Andrew; Spitler, Laura; Michilli, Daniele; Lynch, Ryan S.; Gajjar, Vishal; Gourdji, Kelly

2018-01-01

FRB121102 is a sporadic emitter of millisecond-duration radio bursts, and is associated with a compact, persistent radio source in the primary star-forming region of a dwarf galaxy at ~ 1 Gpc. Key to understanding FRB121102's physical nature is using the observed burst properties to elucidate the underlying emission mechanism and its local environment. Here we present a sample of high signal-to-noise bursts that reveal hitherto unseen spectrotemporal features. We find that the bursts are often composed of sub-bursts with finite bandwidths, and characteristic frequencies that drift downwards during the burst. While this behavior could be an intrinsic feature of the burst emission mechanism, we also discuss an interpretation in terms of plasma lensing in the source environment, similar to the pulse echoes sometimes seen from the Crab pulsar.

Gamma-Ray Bursts: An Overview

NASA Technical Reports Server (NTRS)

Fishman, Gerald J.

1995-01-01

A history and overview of the observed properties of gamma-ray bursts are presented. The phenomenon of gamma-ray bursts is without precedent in astronomy, having no observed property that would be a direct indicator of their distance and no counterpart object in another wavelength region. Their brief, random appearance only in the gamma-ray region has made their study difficult. The observed time profiles, spectral properties, and durations of gamma-ray bursts cover a wide range. All proposed models for their origin must be considered speculative. It is humbling to think that even after 25 years since their discovery, the distance scale of gamma-ray bursts is still very much debatable.

Stimulus sequence context differentially modulates inhibition-related theta and delta band activity in a go/nogo task

PubMed Central

Harper, Jeremy; Malone, Stephen M.; Bachman, Matthew D.; Bernat, Edward M.

2015-01-01

Recent work suggests that dissociable activity in theta and delta frequency bands underlies several common event-related potential (ERP) components, including the nogo N2/P3 complex, which can better index separable functional processes than traditional time-domain measures. Reports have also demonstrated that neural activity can be affected by stimulus sequence context information (i.e., the number and type of preceding stimuli). Stemming from prior work demonstrating that theta and delta index separable processes during response inhibition, the current study assessed sequence context in a Go/Nogo paradigm in which the number of go stimuli preceding each nogo was selectively manipulated. Principal component analysis (PCA) of time-frequency representations revealed differential modulation of evoked theta and delta related to sequence context, where delta increased robustly with additional preceding go stimuli, while theta did not. Findings are consistent with the view that theta indexes simpler initial salience-related processes, while delta indexes more varied and complex processes related to a variety of task parameters. PMID:26751830

Genetic variability in the human cannabinoid receptor 1 is associated with resting state EEG theta power in humans.

PubMed

Heitland, I; Kenemans, J L; Böcker, K B E; Baas, J M P

2014-11-01

It has long been postulated that exogenous cannabinoids have a profound effect on human cognitive functioning. These cannabinoid effects are thought to depend, at least in parts, on alterations of phase-locking of local field potential neuronal firing. The latter can be measured as activity in the theta frequency band (4-7Hz) by electroencephalogram. Theta oscillations are supposed to serve as a mechanism in neural representations of behaviorally relevant information. However, it remains unknown whether variability in endogenous cannabinoid activity is involved in theta rhythms and therefore, may serve as an individual differences index of human cognitive functioning. To clarify this issue, we recorded resting state EEG activity in 164 healthy human subjects and extracted EEG power across frequency bands (δ, θ, α, and β). To assess variability in the endocannabinoid system, two genetic polymorphisms (rs1049353, rs2180619) within the cannabinoid receptor 1 (CB1) were determined in all participants. As expected, we observed significant effects of rs1049353 on EEG power in the theta band at frontal, central and parietal electrode regions. Crucially, these effects were specific for the theta band, with no effects on activity in the other frequency bands. Rs2180619 showed no significant associations with theta power after Bonferroni correction. Taken together, we provide novel evidence in humans showing that genetic variability in the cannabinoid receptor 1 is associated with resting state EEG power in the theta frequency band. This extends prior findings of exogenous cannabinoid effects on theta power to the endogenous cannabinoid system. Copyright © 2014 Elsevier B.V. All rights reserved.

The GLAST Burst Monitor

NASA Technical Reports Server (NTRS)

Meegan, Charles A.

2004-01-01

The Gamma Ray Large Area Space Telescope (GLAST) observatory, scheduled for launch in 2007, comprises the Large Area Telescope (LAT) and the GLAST Burst Monitor (GBM). spectral changes that are known to occur within GRBs. between the NASA Marshall Space Flight Center, the University of Alabama in Huntsville, and the Max Planck Institute for Extraterrestrial Physics. It consists of an array of NaI and BGO scintillation detectors operating in the 10 kev to 25 MeV range. The field of view includes the entire unocculted sky when the observatory is pointing close to the zenith. The GBM will enhance LAT observations of GRBs by extending the spectral coverage into the range of current GRB databases, and will provide a trigger for reorienting the spacecraft to observe delayed emission from bursts outside the LAT field of view. GBM is expected to trigger on about 200 bursts per year, and will provide on-board locations of strong bursts accurate to better than 10 degrees.

Critical Bursts in Filtration

NASA Astrophysics Data System (ADS)

Bianchi, Filippo; Thielmann, Marcel; de Arcangelis, Lucilla; Herrmann, Hans Jürgen

2018-01-01

Particle detachment bursts during the flow of suspensions through porous media are a phenomenon that can severely affect the efficiency of deep bed filters. Despite the relevance in several industrial fields, little is known about the statistical properties and the temporal organization of these events. We present experiments of suspensions of deionized water carrying quartz particles pushed with a peristaltic pump through a filter of glass beads measuring simultaneously the pressure drop, flux, and suspension solid fraction. We find that the burst size distribution scales consistently with a power law, suggesting that we are in the presence of a novel experimental realization of a self-organized critical system. Temporal correlations are present in the time series, like in other phenomena such as earthquakes or neuronal activity bursts, and also an analog to Omori's law can be shown. The understanding of burst statistics could provide novel insights in different fields, e.g., in the filter and petroleum industries.

Resolution improvement by nonconfocal theta microscopy.

PubMed

Lindek, S; Stelzer, E H

1999-11-01

We present a novel scanning fluorescence microscopy technique, nonconfocal theta microscopy (NCTM), that provides almost isotropic resolution. In NCTM, multiphoton absorption from two orthogonal illumination directions is used to induce fluorescence emission. Therefore the point-spread function of the microscope is described by the product of illumination point-spread functions with reduced spatial overlap, which provides the resolution improvement and the more isotropic observation volume. We discuss the technical details of this new method.

Different types of theta rhythmicity are induced by social and fearful stimuli in a network associated with social memory.

PubMed

Tendler, Alex; Wagner, Shlomo

2015-02-16

Rhythmic activity in the theta range is thought to promote neuronal communication between brain regions. In this study, we performed chronic telemetric recordings in socially behaving rats to monitor electrophysiological activity in limbic brain regions linked to social behavior. Social encounters were associated with increased rhythmicity in the high theta range (7-10 Hz) that was proportional to the stimulus degree of novelty. This modulation of theta rhythmicity, which was specific for social stimuli, appeared to reflect a brain-state of social arousal. In contrast, the same network responded to a fearful stimulus by enhancement of rhythmicity in the low theta range (3-7 Hz). Moreover, theta rhythmicity showed different pattern of coherence between the distinct brain regions in response to social and fearful stimuli. We suggest that the two types of stimuli induce distinct arousal states that elicit different patterns of theta rhythmicity, which cause the same brain areas to communicate in different modes.

Semantic congruence enhances memory of episodic associations: role of theta oscillations.

PubMed

Atienza, Mercedes; Crespo-Garcia, Maite; Cantero, Jose L

2011-01-01

Growing evidence suggests that theta oscillations play a crucial role in episodic encoding. The present study evaluates whether changes in electroencephalographic theta source dynamics mediate the positive influence of semantic congruence on incidental associative learning. Here we show that memory for episodic associations (face-location) is more accurate when studied under semantically congruent contexts. However, only participants showing RT priming effect in a conceptual priming test (priming group) also gave faster responses when recollecting source information of semantically congruent faces as compared with semantically incongruent faces. This improved episodic retrieval was positively correlated with increases in theta power during the study phase mainly in the bilateral parahippocampal gyrus, left superior temporal gyrus, and left lateral posterior parietal lobe. Reconstructed signals from the estimated sources showed higher theta power for congruent than incongruent faces and also for the priming than the nonpriming group. These results are in agreement with the attention to memory model. Besides directing top-down attention to goal-relevant semantic information during encoding, the dorsal parietal lobe may also be involved in redirecting attention to bottom-up-driven memories thanks to connections between the medial-temporal and the left ventral parietal lobe. The latter function can either facilitate or interfere with encoding of face-location associations depending on whether they are preceded by semantically congruent or incongruent contexts, respectively, because only in the former condition retrieved representations related to the cue and the face are both coherent with the person identity and are both associated with the same location.

Alcohol Hits You When It Is Hard: Intoxication, Task Difficulty, and Theta Brain Oscillations.

PubMed

Rosen, Burke Q; Padovan, Nevena; Marinkovic, Ksenija

2016-04-01

Alcohol intoxication is known to impair decision making in a variety of situations. Previous neuroimaging evidence suggests that the neurofunctional system subserving controlled processing is especially vulnerable to alcohol in conflict-evoking tasks. The present study investigated the effects of moderate alcohol intoxication on the spatiotemporal neural dynamics of event-related total theta (4 to 7 Hz) power as a function of task difficulty. Two variants of the Simon task manipulated incongruity via simple spatial stimulus-response mismatch and, in a more difficult version, by combining spatial and semantic interference. Healthy social drinkers participated in both alcohol (0.6 g/kg ethanol for men, 0.55 g/kg for women) and placebo conditions in a counterbalanced design. Whole-head magnetoencephalography (MEG) signals were acquired and event-related total theta power was calculated on each trial with Morlet wavelets. MEG sources were estimated using anatomically constrained, noise-normalized, spectral dynamic statistical parametric mapping. Longer reaction times and lower accuracy confirmed the difficulty manipulation. Response conflict (incongruity) increased and alcohol intoxication decreased event-related theta power overall during both tasks bilaterally in the medial and ventrolateral prefrontal cortices. However, alcohol-induced theta suppression was selective for conflict only in the more difficult task which engaged the dorsal anterior cingulate (dAC) and anterior inferolateral prefrontal cortices. Theta power correlated negatively with drinking levels and disinhibition, suggesting that cognitive control is susceptible in more impulsive individuals with higher alcohol intake. The spatiotemporal theta profile across the 2 tasks supports the concept of a rostrocaudal activity gradient in the medial prefrontal cortex that is modulated by task difficulty, with the dAC as the key node in the network subserving cognitive control. Conflict-related theta power was

X-Ray Bursts from NGC 6652

NASA Astrophysics Data System (ADS)

Morgan, Edward

The possibly transient X-ray Source in the globular cluster NGC 6652 has been seen by BeppoSax and the ASM on RXTE to undergo X-ray bursts, possibly Type I. Very little is known about this X-ray source, and confirmation of its bursts type-I nature would identify it as a neutron star binary. Type I bursts in 6 other sources have been shown to exhibit intervals of millisecond ocsillation that most likely indicate the neutron star spin period. Radius-expansion bursts can reveal information about the mass and size of the neutron star. We propose to use the ASM to trigger an observation of this source to maximize the probability of catching a burst in the PCA.

Transitions to Synchrony in Coupled Bursting Neurons

NASA Astrophysics Data System (ADS)

Dhamala, Mukeshwar; Jirsa, Viktor K.; Ding, Mingzhou

2004-01-01

Certain cells in the brain, for example, thalamic neurons during sleep, show spike-burst activity. We study such spike-burst neural activity and the transitions to a synchronized state using a model of coupled bursting neurons. In an electrically coupled network, we show that the increase of coupling strength increases incoherence first and then induces two different transitions to synchronized states, one associated with bursts and the other with spikes. These sequential transitions to synchronized states are determined by the zero crossings of the maximum transverse Lyapunov exponents. These results suggest that synchronization of spike-burst activity is a multi-time-scale phenomenon and burst synchrony is a precursor to spike synchrony.

Real-time segmentation of burst suppression patterns in critical care EEG monitoring

PubMed Central

Westover, M. Brandon; Shafi, Mouhsin M.; Ching, ShiNung; Chemali, Jessica J.; Purdon, Patrick L.; Cash, Sydney S.; Brown, Emery N.

2014-01-01

Objective Develop a real-time algorithm to automatically discriminate suppressions from non-suppressions (bursts) in electroencephalograms of critically ill adult patients. Methods A real-time method for segmenting adult ICU EEG data into bursts and suppressions is presented based on thresholding local voltage variance. Results are validated against manual segmentations by two experienced human electroencephalographers. We compare inter-rater agreement between manual EEG segmentations by experts with inter-rater agreement between human vs automatic segmentations, and investigate the robustness of segmentation quality to variations in algorithm parameter settings. We further compare the results of using these segmentations as input for calculating the burst suppression probability (BSP), a continuous measure of depth-of-suppression. Results Automated segmentation was comparable to manual segmentation, i.e. algorithm-vs-human agreement was comparable to human-vs-human agreement, as judged by comparing raw EEG segmentations or the derived BSP signals. Results were robust to modest variations in algorithm parameter settings. Conclusions Our automated method satisfactorily segments burst suppression data across a wide range adult ICU EEG patterns. Performance is comparable to or exceeds that of manual segmentation by human electroencephalographers. Significance Automated segmentation of burst suppression EEG patterns is an essential component of quantitative brain activity monitoring in critically ill and anesthetized adults. The segmentations produced by our algorithm provide a basis for accurate tracking of suppression depth. PMID:23891828

Real-time segmentation of burst suppression patterns in critical care EEG monitoring.

PubMed

Brandon Westover, M; Shafi, Mouhsin M; Ching, Shinung; Chemali, Jessica J; Purdon, Patrick L; Cash, Sydney S; Brown, Emery N

2013-09-30

Develop a real-time algorithm to automatically discriminate suppressions from non-suppressions (bursts) in electroencephalograms of critically ill adult patients. A real-time method for segmenting adult ICU EEG data into bursts and suppressions is presented based on thresholding local voltage variance. Results are validated against manual segmentations by two experienced human electroencephalographers. We compare inter-rater agreement between manual EEG segmentations by experts with inter-rater agreement between human vs automatic segmentations, and investigate the robustness of segmentation quality to variations in algorithm parameter settings. We further compare the results of using these segmentations as input for calculating the burst suppression probability (BSP), a continuous measure of depth-of-suppression. Automated segmentation was comparable to manual segmentation, i.e. algorithm-vs-human agreement was comparable to human-vs-human agreement, as judged by comparing raw EEG segmentations or the derived BSP signals. Results were robust to modest variations in algorithm parameter settings. Our automated method satisfactorily segments burst suppression data across a wide range adult ICU EEG patterns. Performance is comparable to or exceeds that of manual segmentation by human electroencephalographers. Automated segmentation of burst suppression EEG patterns is an essential component of quantitative brain activity monitoring in critically ill and anesthetized adults. The segmentations produced by our algorithm provide a basis for accurate tracking of suppression depth. Copyright © 2013 Elsevier B.V. All rights reserved.

Observation of a Unipolar Field-aligned Current System Associated With IMF By-triggered Theta Auroras

NASA Astrophysics Data System (ADS)

Hairston, M. R.; Watanabe, M.

2016-12-01

We investigate the existence of a specific field-aligned current (FAC) system predicted by numerical magnetohydrodynamic simulations in a past study. The FAC system is expected to occur when a drifting theta aurora is formed in response to a stepwise transition of interplanetary magnetic field (IMF) By during strongly northward IMF periods. When the IMF By changes from positive to negative, a crossbar forms in the Northern Hemisphere that moves dawnward, while in the Southern Hemisphere the crossbar moves in the opposite direction. The crossbar motion reverses when the IMF By changes from negative to positive. The FAC system appears on the trailing side of the drifting crossbar of the theta aurora as it moves either dawnward or duskward. When the theta aurora is drifting dawnward, the FACs flow into the ionosphere. The FAC polarity reverses when the theta aurora is drifting duskward. Using low-altitude satellite data, we confirmed the real existence of the above model-predicted FAC system.

Selective Entrainment of Theta Oscillations in the Dorsal Stream Causally Enhances Auditory Working Memory Performance.

PubMed

Albouy, Philippe; Weiss, Aurélien; Baillet, Sylvain; Zatorre, Robert J

2017-04-05

The implication of the dorsal stream in manipulating auditory information in working memory has been recently established. However, the oscillatory dynamics within this network and its causal relationship with behavior remain undefined. Using simultaneous MEG/EEG, we show that theta oscillations in the dorsal stream predict participants' manipulation abilities during memory retention in a task requiring the comparison of two patterns differing in temporal order. We investigated the causal relationship between brain oscillations and behavior by applying theta-rhythmic TMS combined with EEG over the MEG-identified target (left intraparietal sulcus) during the silent interval between the two stimuli. Rhythmic TMS entrained theta oscillation and boosted participants' accuracy. TMS-induced oscillatory entrainment scaled with behavioral enhancement, and both gains varied with participants' baseline abilities. These effects were not seen for a melody-comparison control task and were not observed for arrhythmic TMS. These data establish theta activity in the dorsal stream as causally related to memory manipulation. VIDEO ABSTRACT. Copyright © 2017 Elsevier Inc. All rights reserved.

Correlation of hippocampal theta rhythm with changes in cutaneous temperature. [evoked neuron response in thermoregulation

NASA Technical Reports Server (NTRS)

Horowitz, J. M.; Saleh, M. A.; Karem, R. D.

1974-01-01

A possible role for the hippocampus in alerting an animal to changes in cutaneous temperature was examined. Following local warming or cooling of the ears of unanesthetized, loosely restrained rabbits, theta waves (4-7 Hz EEG waves) were recorded from electrodes straddling the hippocampus. The onset of the hippocampal theta rhythm was correlated with changes in cutaneous temperature, an observation consistent with studies indicating that the theta rhythm is a nonspecific response evoked by stimulation of several sensory modalities. Additional data from cats and rabbits were correlated with specific neurons within the hippocampus, namely pyramidal cells. Post stimulus time histograms obtained by excitation of the dorsal fornix were interpreted in terms of excitatory and inhibitory inputs to pyramidal cells. Thus, the theta rhythm, which appears to be evoked by changes in cutaneous temperature, can be related to a specific type of hippocampal neuron which is in turn connected with other areas of the brain involved in temperature regulation.

Dissociation of frontal-midline delta-theta and posterior alpha oscillations: A mobile EEG study.

PubMed

Liang, Mingli; Starrett, Michael J; Ekstrom, Arne D

2018-04-22

Numerous reports have demonstrated low-frequency oscillations during navigation using invasive recordings in the hippocampus of both rats and human patients. Given evidence, in some cases, of low-frequency synchronization between midline cortex and hippocampus, it is also possible that low-frequency movement-related oscillations manifest in healthy human neocortex. However, this possibility remains largely unexplored, in part due to the difficulties of coupling free ambulation and effective scalp EEG recordings. In the current study, participants freely ambulated on an omnidirectional treadmill and explored an immersive virtual reality city rendered on a head-mounted display while undergoing simultaneous wireless scalp EEG recordings. We found that frontal-midline (FM) delta-theta (2-7.21 Hz) oscillations increased during movement compared to standing still periods, consistent with a role in navigation. In contrast, posterior alpha (8.32-12.76 Hz) oscillations were suppressed in the presence of visual input, independent of movement. Our findings suggest that FM delta-theta and posterior alpha oscillations arise at independent frequencies, under complementary behavioral conditions, and, at least for FM delta-theta oscillations, at independent recordings sites. Together, our findings support a double dissociation between movement-related FM delta-theta and resting-related posterior alpha oscillations. Our study thus provides novel evidence that FM delta-theta oscillations arise, in part, from real-world ambulation, and are functionally independent from posterior alpha oscillations. © 2018 Society for Psychophysiological Research.

BATSE Observations of Gamma-Ray Burst Tails

NASA Technical Reports Server (NTRS)

Connaughton, Valerie

2002-01-01

With the observation of low-energy radiation coming from the site of gamma-ray bursts in the hours to weeks after the initial gamma ray burst, it appears that astronomers have discovered a cosmological imprint made by the burster on its surroundings. This paper discusses the phenomenon of postburst emission in Burst and Transient Source Experiment (BATSE) gamma-ray bursts at energies usually associated with prompt emission. After summing up the background-subtracted signals from hundreds of bursts, it is found that tails out to hundreds of seconds after the trigger could be a common feature of events of a duration greater than 2 seconds, and perhaps of the shorter bursts at a lower and shorter-lived level. The tail component may be softer and seems independent of the duration (within the long-GRB sample) and brightness of the prompt burst emission. Some individual bursts have visible tails at gamma-ray energies, and the spectrum in a few cases differs from that of the prompt emission. For one of these bursts, GRB 991216, afterglow at lower energies was detected, which raised the possibility of seeing afterglow observations over large energy ranges using the next generation of GRB detectors in addition to sensitive space- or ground-based telescopes.

The Second SWIFT Burst Alert Telescope (BAT) Gamma-Ray Burst Catalog

NASA Technical Reports Server (NTRS)

Sakamoto, T.; Barthelmy, S. D.; Baumgartner, W. H.; Cummings, J. R.; Fenimore, E. E.; Gehrels, N.; Krimm, H. A.; Markwardt, C. B.; Palmer, D. M.; Parsons, A. M.;

ADP study of gamma-ray bursts

NASA Technical Reports Server (NTRS)

Lamb, Don Q.; Wang, John C. L.; Heuter, Geoffry J.; Graziani, Carlo; Loredo, Tom; Freeman, Peter

1991-01-01

This grant supported study of cyclotron scattering lines in the spectra of gamma-ray bursts through analysis of Ginga and HEAO-1 archival data, and modeling of the results in terms of radiation transfer calculations of cyclotron scattering in a strong magnetic field. A Monte Carlo radiation transfer code with which we are able to calculate the expected properties of cyclotron scattering lines in the spectra of gamma-ray bursts was developed. The extensive software necessary in order to carry out fits of these model spectra to gamma-ray burst spectral data, including folding of the model spectra through the detector response functions was also developed. Fits to Ginga satellite data on burst GB880205 were completed and fits to Ginga satellite data on burst GB870303 are being carried out. These fits have allowed us to test our software, as well as to garner new scientific results. This work has demonstrated that cyclotron resonant scattering successfully accounts for the locations, strengths, and widths of the observed line features in GB870303 and GB880205. The success of the model provides compelling evidence that these gamma-ray bursts come from strongly magnetic neutron stars and are galactic in origin, resolving longstanding controversies about the nature and distance of the burst sources. These results were reported in two papers which are in press in the proceedings of the Taos Workshop on Gamma-Ray Bursts, and in a paper submitted for publication.

Theta band oscillations reflect more than entrainment: behavioral and neural evidence demonstrates an active chunking process.

PubMed

Teng, Xiangbin; Tian, Xing; Doelling, Keith; Poeppel, David

2017-10-17

Parsing continuous acoustic streams into perceptual units is fundamental to auditory perception. Previous studies have uncovered a cortical entrainment mechanism in the delta and theta bands (~1-8 Hz) that correlates with formation of perceptual units in speech, music, and other quasi-rhythmic stimuli. Whether cortical oscillations in the delta-theta bands are passively entrained by regular acoustic patterns or play an active role in parsing the acoustic stream is debated. Here, we investigate cortical oscillations using novel stimuli with 1/f modulation spectra. These 1/f signals have no rhythmic structure but contain information over many timescales because of their broadband modulation characteristics. We chose 1/f modulation spectra with varying exponents of f, which simulate the dynamics of environmental noise, speech, vocalizations, and music. While undergoing magnetoencephalography (MEG) recording, participants listened to 1/f stimuli and detected embedded target tones. Tone detection performance varied across stimuli of different exponents and can be explained by local signal-to-noise ratio computed using a temporal window around 200 ms. Furthermore, theta band oscillations, surprisingly, were observed for all stimuli, but robust phase coherence was preferentially displayed by stimuli with exponents 1 and 1.5. We constructed an auditory processing model to quantify acoustic information on various timescales and correlated the model outputs with the neural results. We show that cortical oscillations reflect a chunking of segments, > 200 ms. These results suggest an active auditory segmentation mechanism, complementary to entrainment, operating on a timescale of ~200 ms to organize acoustic information. © 2017 Federation of European Neuroscience Societies and John Wiley & Sons Ltd.

Type III Radio Burst Duration and SEP Events

NASA Technical Reports Server (NTRS)

Gopalswamy, N.; Makela, P.; Xie, H.

2010-01-01

Long-duration (>15 min), low-frequency (<14 MHz) type III radio bursts have been reported to be indicative of solar energetic particle events. We measured the durations of type III bursts associated with large SEP events of solar cycle 23. The Type III durations are distributed symmetrically at 1 MHz yielding a mean value of approximately 33 min (median = 32 min) for the large SEP events. When the SEP events with ground level enhancement (GLE,) are considered, the distribution is essentially unchanged (mean = 32 min, median = 30 min). To test the importance of type III bursts in indicating SEP events, we considered a set of six type III bursts from the same active region (AR 10588) whose durations fit the "long duration" criterion. We analyzed the coronal mass ejections (CMEs), flares, and type II radio bursts associated with the type III bursts. The CMEs were of similar speeds and the flares are also of similar size and duration. All but one of the type III bursts was not associated with a type II burst in the metric or longer wavelength domains. The burst without type II burst also lacked a solar energetic particle (SEP) event at energies >25 MeV. The 1-MHz duration of the type III burst (28 rein) is near the median value of type III durations found for gradual SEP events and ground level enhancement (GLE) events. Yet, there was no sign of SEP events. On the other hand, two other type III bursts from the same active region had similar duration but accompanied by WAVES type 11 bursts; these bursts were also accompanied by SEP events detected by SOHO/ERNE. This study suggests that the type III burst duration may not be a good indicator of an SEP event, consistent with the statistical study of Cliver and Ling (2009, ApJ ).

Current source density analysis of the hippocampal theta rhythm: associated sustained potentials and candidate synaptic generators.

PubMed

Brankack, J; Stewart, M; Fox, S E

1993-07-02

Single-electrode depth profiles of the hippocampal EEG were made in urethane-anesthetized rats and rats trained in an alternating running/drinking task. Current source density (CSD) was computed from the voltage as a function of depth. A problem inherent to AC-coupled profiles was eliminated by incorporating sustained potential components of the EEG. 'AC' profiles force phasic current sinks to alternate with current sources at each lamina, changing the magnitude and even the sign of the computed membrane current. It was possible to include DC potentials in the profiles from anesthetized rats by using glass micropipettes for recording. A method of 'subtracting' profiles of the non-theta EEG from theta profiles was developed as an approach to including sustained potentials in recordings from freely-moving animals implanted with platinum electrodes. 'DC' profiles are superior to 'AC' profiles for analysis of EEG activity because 'DC'-CSD values can be considered correct in sign and more closely represent the actual membrane current magnitudes. Since hippocampal inputs are laminated, CSD analysis leads to straightforward predictions of the afferents involved. Theta-related activity in afferents from entorhinal neurons, hippocampal interneurons and ipsi- and contralateral hippocampal pyramids all appear to contribute to sources and sinks in CA1 and the dentate area. The largest theta-related generator was a sink at the fissure, having both phasic and tonic components. This sink may reflect activity in afferents from the lateral entorhinal cortex. The phase of the dentate mid-molecular sink suggests that medial entorhinal afferents drive the theta-related granule and pyramidal cell firing. The sustained components may be simply due to different average rates of firing during theta rhythm than during non-theta EEG in afferents whose firing rates are also phasically modulated.

UWB multi-burst transmit driver for averaging receivers

DOEpatents

Dallum, Gregory E

2012-11-20

A multi-burst transmitter for ultra-wideband (UWB) communication systems generates a sequence of precisely spaced RF bursts from a single trigger event. There are two oscillators in the transmitter circuit, a gated burst rate oscillator and a gated RF burst or RF power output oscillator. The burst rate oscillator produces a relatively low frequency, i.e., MHz, square wave output for a selected transmit cycle, and drives the RF burst oscillator, which produces RF bursts of much higher frequency, i.e., GHz, during the transmit cycle. The frequency of the burst rate oscillator sets the spacing of the RF burst packets. The first oscillator output passes through a bias driver to the second oscillator. The bias driver conditions, e.g., level shifts, the signal from the first oscillator for input into the second oscillator, and also controls the length of each RF burst. A trigger pulse actuates a timing circuit, formed of a flip-flop and associated reset time delay circuit, that controls the operation of the first oscillator, i.e., how long it oscillates (which defines the transmit cycle).

Effect of dopaminergic drugs on the reserpine-induced lowering of hippocampal theta wave frequency in rats.

PubMed

Nakagawa, T; Ukai, K; Ohyama, T; Gomita, Y; Okamura, H

2000-05-01

The effects of dopaminergic drugs on the lowering of hippocampal theta wave frequency induced by reserpine 1 mg/kg s.c. were examined. Sibutramine (monoamine reuptake inhibitor) 10 mg/kg p.o., methamphetamine (monoamine releaser) 1 mg/kg, quinpirole (dopamine D2 receptor agonist) 10 mg/kg i.p., and SKF 38393 (dopamine D1 receptor agonist) 10 mg/kg i.p. each antagonized the reserpine-induced lowering of hippocampal theta wave frequency in rats. Moreover, the combined administration of SKF 38393 1 mg/kg i.p. and quinpirole 1 mg/kg i.p. synergistically antagonized a reserpine-induced lowering of this frequency. Dosulepin, amitriptyline, and desipramine, which are weak inhibitors of dopamine reuptake, each had little effect on the reserpine-induced lowering of theta wave frequency at a dose of 40 mg/kg p.o. Furthermore, atropine (muscarinic anticholinergic drug) 20 mg/kg p.o. decreased theta wave power in the low-frequency range following a shift to the lower range by reserpine. A positive correlation was observed for each of the above drugs between a reversal of reserpine-induced lowering of theta wave frequency and a reversal of impairment of reserpine-induced conditioned avoidance responses (ACAR) in rats. These results suggest that the reserpine-induced lowering of hippocampal theta wave frequency plays a role in the impairment of reserpine-induced ACAR, and that dopamine D1 and D2 receptors play important roles in antagonizing this lowering of frequency.

Holomorphic projections and Ramanujan’s mock theta functions

PubMed Central

Imamoğlu, Özlem; Raum, Martin; Richter, Olav K.

2014-01-01

We use spectral methods of automorphic forms to establish a holomorphic projection operator for tensor products of vector-valued harmonic weak Maass forms and vector-valued modular forms. We apply this operator to discover simple recursions for Fourier series coefficients of Ramanujan’s mock theta functions. PMID:24591582

Long-Lag, Wide-pulse Gamma-Ray Bursts

NASA Technical Reports Server (NTRS)

Norris, J. P.; Bonnell, J. T.; Kazanas, D.; Scargle, . D.; Hakkila, J.; Giblin, T. W.

2004-01-01

Currently, the best available probe of the early phase of gamma-ray burst (GRB) jet attributes is the prompt gamma-ray emission, in which several intrinsic and extrinsic variables determine GRB pulse evolution. Bright, usually complex bursts have many narrow pulses that are difficult to model due to overlap. However, the relatively simple, long spectral lag, wide-pulse bursts may have simpler physics and are easier to model. In this work we analyze the temporal and spectral behavior of wide pulses in 24 long-lag bursts, using a pulse model with two shape parameters - width and asymmetry - and the Band spectral model with three shape parameters. We find that pulses in long-lag bursts are distinguished both temporally and spectrally from those in bright bursts: the pulses in long spectral lag bursts are few in number, and approximately 100 times wider (10s of seconds), have systematically lower peaks in vF(v), harder low-energy spectra and softer high-energy spectra. We find that these five pulse descriptors are essentially uncorrelated for our long-lag sample, suggesting that at least approximately 5 parameters are needed to model burst temporal and spectral behavior. However, pulse width is strongly correlated with spectral lag; hence these two parameters may be viewed as mutual surrogates. We infer that accurate formulations for estimating GRB luminosity and total energy will depend on several gamma-ray attributes, at least for long-lag bursts. The prevalence of long-lag bursts near the BATSE trigger threshold, their predominantly low vF(v) spectral peaks, and relatively steep upper power-law spectral indices indicate that Swift will detect many such bursts.

Frontal theta and beta synchronizations for monetary reward increase visual working memory capacity.

PubMed

Kawasaki, Masahiro; Yamaguchi, Yoko

2013-06-01

Visual working memory (VWM) capacity is affected by motivational influences; however, little is known about how reward-related brain activities facilitate the VWM systems. To investigate the dynamic relationship between VWM- and reward-related brain activities, we conducted time-frequency analyses using electroencephalograph (EEG) data obtained during a monetary-incentive delayed-response task that required participants to memorize the position of colored disks. In case of a correct answer, participants received a monetary reward (0, 10 or 50 Japanese yen) announced at the beginning of each trial. Behavioral results showed that VWM capacity under high-reward condition significantly increased compared with that under low- or no-reward condition. EEG results showed that frontal theta (6 Hz) amplitudes enhanced during delay periods and positively correlated with VWM capacity, indicating involvement of theta local synchronizations in VWM. Moreover, frontal beta activities (24 Hz) were identified as reward-related activities, because delay-period amplitudes correlated with increases in VWM capacity between high-reward and no-reward conditions. Interestingly, cross-frequency couplings between frontal theta and beta phases were observed only under high-reward conditions. These findings suggest that the functional dynamic linking between VWM-related theta and reward-related beta activities on the frontal regions plays an integral role in facilitating increases in VWM capacity.

SGR J1550-5418 Bursts Detected with the Fermi Gamma-Ray Burst Monitor during Its Most Prolific Activity

NASA Technical Reports Server (NTRS)

vanderHorst, A. J.; Kouveliotou, C.; Gorgone, N. M.; Kaneko, Y.; Baring, M. G.; Guiriec, S.; Gogus, E,; Granot, J.; Watts, A. L.; Lin, L.;

Acoustic waveform of continuous bubbling in a non-Newtonian fluid.

PubMed

Vidal, Valérie; Ichihara, Mie; Ripepe, Maurizio; Kurita, Kei

2009-12-01

We study experimentally the acoustic signal associated with a continuous bubble bursting at the free surface of a non-Newtonian fluid. Due to the fluid rheological properties, the bubble shape is elongated, and, when bursting at the free surface, acts as a resonator. For a given fluid concentration, at constant flow rate, repetitive bubble bursting occurs at the surface. We report a modulation pattern of the acoustic waveform through time. Moreover, we point out the existence of a precursor acoustic signal, recorded on the microphone array, previous to each bursting. The time delay between this precursor and the bursting signal is well correlated with the bursting signal frequency content. Their joint modulation through time is driven by the fluid rheology, which strongly depends on the presence of small satellite bubbles trapped in the fluid due to the yield stress.

Alpha-theta border EEG abnormalities in preclinical Huntington's disease.

PubMed

Ponomareva, Natalya; Klyushnikov, Sergey; Abramycheva, Natalya; Malina, Daria; Scheglova, Nadejda; Fokin, Vitaly; Ivanova-Smolenskaia, Irina; Illarioshkin, Sergey

2014-09-15

Brain dysfunction precedes clinical manifestation of Huntington's disease (HD) by decades. This study was aimed to determine whether resting EEG is altered in preclinical HD mutations carriers (pre-HD). We examined relative power of broad traditional EEG bands as well as 1-Hz sub-bands of theta and alpha from the resting-state EEG of 29 pre-HD individuals and of 29 age-matched normal controls. The relative power of the narrow sub-band in the border of theta-alpha (7-8 Hz) was significantly reduced in pre-HD subjects as compared to normal controls, while the alterations in relative power of the broad frequency bands were not significant. In pre-HD subjects, the number of CAG repeats in the huntingtin (HTT) gene as well as the disease burden score (DBS) showed a positive correlation with relative power of the delta and theta frequency bands and their sub-bands and a negative correlation with alpha band relative power and the differences of relative power of the 7-8 Hz and 4-5 Hz frequency sub-bands. The obtained results suggest that EEG alterations in pre-HD individuals may be related to the course of the pathological process and to HD endophenotype. Analysis of the narrow EEG bands was found to be more useful for assessing EEG alterations in pre-HD individuals than a more traditional approach using broad bandwidths. Copyright © 2014 Elsevier B.V. All rights reserved.

COMPTEL Studies of Gamma-Ray Bursts at MeV Energies

NASA Technical Reports Server (NTRS)

McConnell, Mark L.

1999-01-01

The purpose of this program was to analyse and interpret gamma-ray burst (GRB) data using both telescope mode data and single detector burst mode data from COMPTEL. Collectively, these data span the energy range from 300 keV up to 30 MeV. The initial goal of our proposal was to perform a standard analysis for each significant GRB event seen by COMPTEL. This includes GRBs that are registered by the telescope mode data as well as GRBs that are registered only in the burst mode data. (The latter category includes both GRBs that he outside of the FoV as well as GRBs within the FoV that are too weak to be seen in the telescope mode.) A second goal of our proposal was to define a set of data products (including deconvolved photon spectra) that, for each detected GRB event, would be made available via the COMPTEL GRB Web Page. The third goal of our program was to perform more detailed studies of selected GRB events. This represented a continuation of past GRB studies by the COMPTEL team. In general, we have met with only limited success in achieving these goals, in part due to the limited resources provided and our philosophy of utilizing local high school students to participate in this effort. Using local high school student support, however, we expect that considerable progress will be made in our efforts to catalog the COMPTEL gamma-ray burst data between now and the end of the current academic year. In addition, observations with COMPTEL contributed to an analysis of GRB 990123, the first gamma-ray burst with simultaneous optical observations.

Therapeutic burst-suppression coma in pediatric febrile refractory status epilepticus.

PubMed

Lin, Jainn-Jim; Chou, Cheng-Che; Lan, Shih-Yun; Hsiao, Hsiang-Ju; Wang, Yu; Chan, Oi-Wa; Hsia, Shao-Hsuan; Wang, Huei-Shyong; Lin, Kuang-Lin

2017-09-01

Evidence for the beneficial effect of therapeutic burst-suppression coma in pediatric patients with febrile refractory status epilepticus is limited, and the clinical outcomes of this treatment strategy are largely unknown. Therefore, the aim of this study was to explore the outcomes of therapeutic burst-suppression coma in a series of children with febrile refractory status epilepticus. We retrospectively reviewed consecutive pediatric patients with febrile refractory status epilepticus admitted to our pediatric intensive care unit between January 2000 and December 2013. The clinical characteristics were analyzed. Thirty-five patients (23 boys; age range: 1-18years) were enrolled, of whom 28 (80%) developed super-refractory status epilepticus. All of the patients received the continuous administration of intravenous antiepileptic drugs for febrile refractory status epilepticus, and 26 (74.3%) achieved therapeutic burst-suppression coma. All of the patients received mechanical ventilatory support, and 26 (74.3%) received inotropic agents. Eight (22.9%) patients died within 1month. The neurologically functional outcomes at 6months were good in six (27.3%) of the 22 survivors, of whom two returned to clinical baseline. The patients with therapeutic burst-suppression coma were significantly associated with hemodynamic support than the patients with electrographic seizures control (p=0.03), and had a trend of higher 1-month mortality rate, worse 6months outcomes, and a longer duration of hospitalization. Our results suggest that therapeutic burst-suppression coma to treat febrile refractory status epilepticus may lead to an increased risk of hemodynamic instability and a trend of worse outcomes. Copyright © 2017 The Japanese Society of Child Neurology. Published by Elsevier B.V. All rights reserved.

Gamma Ray Bursts-Afterglows and Counterparts

NASA Technical Reports Server (NTRS)

Fishman, Gerald J

1998-01-01

Several breakthrough discoveries were made last year of x-ray, optical and radio afterglows and counterparts to gamma-ray bursts, and a redshift has been associated with at least one of these. These discoveries were made possible by the fast, accurate gamma-ray burst locations of the BeppoSAX satellite. It is now generally believed that the burst sources are at cosmological distances and that they represent the most powerful explosions in the Universe. These observations also open new possibilities for the study of early star formation, the physics of extreme conditions and perhaps even cosmology. This session will concentrate on recent x-ray, optical and radio afterglow observations of gamma-ray bursts, associated redshift measurements, and counterpart observations. Several review and theory talks will also be presented, along with a summary of the astrophysical implications of the observations. There will be additional poster contributions on observations of gamma-ray burst source locations at wavelengths other than gamma rays. Posters are also solicited that describe new observational capabilities for rapid follow-up observations of gamma-ray bursts.

Human θ burst stimulation enhances subsequent motor learning and increases performance variability.

PubMed

Teo, James T H; Swayne, Orlando B C; Cheeran, Binith; Greenwood, Richard J; Rothwell, John C

2011-07-01

Intermittent theta burst stimulation (iTBS) transiently increases motor cortex excitability in healthy humans by a process thought to involve synaptic long-term potentiation (LTP), and this is enhanced by nicotine. Acquisition of a ballistic motor task is likewise accompanied by increased excitability and presumed intracortical LTP. Here, we test how iTBS and nicotine influences subsequent motor learning. Ten healthy subjects participated in a double-blinded placebo-controlled trial testing the effects of iTBS and nicotine. iTBS alone increased the rate of learning but this increase was blocked by nicotine. We then investigated factors other than synaptic strengthening that may play a role. Behavioral analysis and modeling suggested that iTBS increased performance variability, which correlated with learning outcome. A control experiment confirmed the increase in motor output variability by showing that iTBS increased the dispersion of involuntary transcranial magnetic stimulation-evoked thumb movements. We suggest that in addition to the effect on synaptic plasticity, iTBS may have facilitated performance by increasing motor output variability; nicotine negated this effect on variability perhaps via increasing the signal-to-noise ratio in cerebral cortex.

Homologous and Homologous like Microwave Solar Radio Bursts

NASA Astrophysics Data System (ADS)

Trevisan, R. H.; Sawant, H. S.; Kalman, B.; Gesztelyi, L.

1990-11-01

ABSTRACT. Solar radio observations at 1.6 GHz were carried out in the month of July, 1985 by using 13.7 m diameter Itapetinga antenna with time resolution of 3 ms. Homologous Bursts, with total duration of about couple of seconds and repeated by some seconds were observed associated with Homologous H- flares. These H- flares were having periodicities of about 40 min. Observed long periodicities were attributed to oscillation of prominences, and small periods were attributed to removal of plasma from the field interaction zone. Also observed are "Homologous-Like" bursts. These bursts are double peak bursts with same time profile repeating in time. In addition to this, the ratio of the total duration of the bursts to time difference in the peaks of bursts remain constant. Morphological studies of these bursts have been presented. Keq tuoit : SUN-BURSTS - SUN-FLARE

Theta frequency background tunes transmission but not summation of spiking responses.

PubMed

Parameshwaran, Dhanya; Bhalla, Upinder S

2013-01-01

Hippocampal neurons are known to fire as a function of frequency and phase of spontaneous network rhythms, associated with the animal's behaviour. This dependence is believed to give rise to precise rate and temporal codes. However, it is not well understood how these periodic membrane potential fluctuations affect the integration of synaptic inputs. Here we used sinusoidal current injection to the soma of CA1 pyramidal neurons in the rat brain slice to simulate background oscillations in the physiologically relevant theta and gamma frequency range. We used a detailed compartmental model to show that somatic current injection gave comparable results to more physiological synaptically driven theta rhythms incorporating excitatory input in the dendrites, and inhibitory input near the soma. We systematically varied the phase of synaptic inputs with respect to this background, and recorded changes in response and summation properties of CA1 neurons using whole-cell patch recordings. The response of the cell was dependent on both the phase of synaptic inputs and frequency of the background input. The probability of the cell spiking for a given synaptic input was up to 40% greater during the depolarized phases between 30-135 degrees of theta frequency current injection. Summation gain on the other hand, was not affected either by the background frequency or the phasic afferent inputs. This flat summation gain, coupled with the enhanced spiking probability during depolarized phases of the theta cycle, resulted in enhanced transmission of summed inputs during the same phase window of 30-135 degrees. Overall, our study suggests that although oscillations provide windows of opportunity to selectively boost transmission and EPSP size, summation of synaptic inputs remains unaffected during membrane oscillations.

Mosquito drinking with a burst in reserve: explaining behavior with a fluid mechanics model

NASA Astrophysics Data System (ADS)

Chatterjee, Souvick; Socha, Jake; Stremler, Mark

2014-03-01

Mosquitoes drink using a pair of in-line pumps in the head that draw liquid food through a long drinking channel, or proboscis. Experimental observations indicate two modes of drinking: a predominantly occurring continuous mode, in which the cibarial and pharyngeal pumps expand cyclically at a constant phase difference, and an isolated burst mode, in which the pharyngeal pump expansion is several orders of magnitude larger than in the continuous mode. We use a reduced order model of the fluid mechanics to hypothesize an explanation of this naturally occurring drinking behavior. Our model results show that the continuous mode is the more efficient mode in terms of energy expenditure, and the burst mode creates a large pressure difference across the proboscis. We speculate that the mosquito uses this pressure drop to clear blockages in the proboscis. We compared the two-pump system with one-pump configurations, as found in some other insects like butterflies, and show that the two pumps have unique roles in mosquito feeding.

The association of a J-burst with a solar jet

NASA Astrophysics Data System (ADS)

Morosan, D. E.; Gallagher, P. T.; Fallows, R. A.; Reid, H.; Mann, G.; Bisi, M. M.; Magdalenić, J.; Rucker, H. O.; Thidé, B.; Vocks, C.; Anderson, J.; Asgekar, A.; Avruch, I. M.; Bell, M. E.; Bentum, M. J.; Best, P.; Blaauw, R.; Bonafede, A.; Breitling, F.; Broderick, J. W.; Brüggen, M.; Cerrigone, L.; Ciardi, B.; de Geus, E.; Duscha, S.; Eislöffel, J.; Falcke, H.; Garrett, M. A.; Grießmeier, J. M.; Gunst, A. W.; Hoeft, M.; Iacobelli, M.; Juette, E.; Kuper, G.; McFadden, R.; McKay-Bukowski, D.; McKean, J. P.; Mulcahy, D. D.; Munk, H.; Nelles, A.; Orru, E.; Paas, H.; Pandey-Pommier, M.; Pandey, V. N.; Pizzo, R.; Polatidis, A. G.; Reich, W.; Schwarz, D. J.; Sluman, J.; Smirnov, O.; Steinmetz, M.; Tagger, M.; ter Veen, S.; Thoudam, S.; Toribio, M. C.; Vermeulen, R.; van Weeren, R. J.; Wucknitz, O.; Zarka, P.

2017-10-01

Context. The Sun is an active star that produces large-scale energetic events such as solar flares and coronal mass ejections, and numerous smaller scale events such as solar jets. These events are often associated with accelerated particles that can cause emission at radio wavelengths. The reconfiguration of the solar magnetic field in the corona is believed to be the cause of the majority of solar energetic events and accelerated particles. Aims: Here, we investigate a bright J-burst that was associated with a solar jet and the possible emission mechanism causing these two phenomena. Methods: We used data from the Solar Dynamics Observatory (SDO) to observe a solar jet and radio data from the Low Frequency Array (LOFAR) and the Nançay Radioheliograph (NRH) to observe a J-burst over a broad frequency range (33-173 MHz) on 9 July 2013 at 11:06 UT. Results: The J-burst showed fundamental and harmonic components and was associated with a solar jet observed at extreme ultraviolet wavelengths with SDO. The solar jet occurred in the northern hemisphere at a time and location coincident with the radio burst and not inside a group of complex active regions in the southern hemisphere. The jet occurred in the negative polarity region of an area of bipolar plage. Newly emerged positive flux in this region appeared to be the trigger of the jet. Conclusions: Magnetic reconnection between the overlying coronal field lines and the newly emerged positive field lines is most likely the cause of the solar jet. Radio imaging provides a clear association between the jet and the J-burst, which shows the path of the accelerated electrons. These electrons travelled from a region in the vicinity of the solar jet along closed magnetic field lines up to the top of a closed magnetic loop at a height of 360 Mm. Such small-scale complex eruptive events arising from magnetic reconnection could facilitate accelerated electrons to produce continuously the large numbers of Type III bursts

A Temporal Correlation in Quiescent Gamma-Ray Burst Prompt Emission: Evidence for Prognitor Memory

NASA Astrophysics Data System (ADS)

Patton, Thomas L.; Giblin, Timothy; Hakkila, Jon E.

2018-06-01

In spite of the insight gained into the nature of the Gamma-Ray Bursts (GRB) from early and late-time X-Ray observations in the Swift era, GRB prompt emission continues to provide clues and new insight into the activity of the central engine. A comprehensive understanding of all emission components observed in GRBs, from the traditional prompt GRB emission to the long lived X-Ray and optical decay super- imposed with late-time flaring activity, currently remains allusive. Using data from the Swift Burst Alert Telescope (BAT), we've identified and measured durations observed in GRBs that exhibit multi-episodic prompt emission behavior. Duration analysis of the burst attributes revealed no significant correlations between emissions and quiet time durations. This variability allows us to extrapolate that the central engine is constantly active.

FRBCAT: The Fast Radio Burst Catalogue

NASA Astrophysics Data System (ADS)

Petroff, E.; Barr, E. D.; Jameson, A.; Keane, E. F.; Bailes, M.; Kramer, M.; Morello, V.; Tabbara, D.; van Straten, W.

2016-09-01

Here, we present a catalogue of known Fast Radio Burst sources in the form of an online catalogue, FRBCAT. The catalogue includes information about the instrumentation used for the observations for each detected burst, the measured quantities from each observation, and model-dependent quantities derived from observed quantities. To aid in consistent comparisons of burst properties such as width and signal-to-noise ratios, we have re-processed all the bursts for which we have access to the raw data, with software which we make available. The originally derived properties are also listed for comparison. The catalogue is hosted online as a Mysql database which can also be downloaded in tabular or plain text format for off-line use. This database will be maintained for use by the community for studies of the Fast Radio Burst population as it grows.

The Five Year Fermi/GBM Magnetar Burst Catalog

NASA Astrophysics Data System (ADS)

Collazzi, A. C.; Kouveliotou, C.; van der Horst, A. J.; Younes, G. A.; Kaneko, Y.; Göğüş, E.; Lin, L.; Granot, J.; Finger, M. H.; Chaplin, V. L.; Huppenkothen, D.; Watts, A. L.; von Kienlin, A.; Baring, M. G.; Gruber, D.; Bhat, P. N.; Gibby, M. H.; Gehrels, N.; McEnery, J.; van der Klis, M.; Wijers, R. A. M. J.

2015-05-01

Since launch in 2008, the Fermi Gamma-ray Burst Monitor (GBM) has detected many hundreds of bursts from magnetar sources. While the vast majority of these bursts have been attributed to several known magnetars, there is also a small sample of magnetar-like bursts of unknown origin. Here, we present the Fermi/GBM magnetar catalog, providing the results of the temporal and spectral analyses of 440 magnetar bursts with high temporal and spectral resolution. This catalog covers the first five years of GBM magnetar observations, from 2008 July to 2013 June. We provide durations, spectral parameters for various models, fluences, and peak fluxes for all the bursts, as well as a detailed temporal analysis for SGR J1550-5418 bursts. Finally, we suggest that some of the bursts of unknown origin are associated with the newly discovered magnetar 3XMM J185246.6+0033.7.

Anxiety and feedback processing in a gambling task: Contributions of time-frequency theta and delta.

PubMed

Ellis, Jessica S; Watts, Adreanna T M; Schmidt, Norman; Bernat, Edward M

2018-05-02

The feedback negativity (FN) event-related potential (ERP) is widely studied during gambling feedback tasks. However, research on FN and anxiety is minimal and the findings are mixed. To clarify these discrepancies, the current study (N = 238) used time-frequency analysis to disentangle overlapping contributions of delta (0-3 Hz) and theta (3-7 Hz) to feedback processing in a clinically anxious sample, with severity assessed through general worry and physiological arousal scales. Greater general worry showed enhanced delta- and theta-FN broadly across both gain and loss conditions, with theta-FN stronger for losses. Regressions indicated delta-FN maintained unique effects, accounted for theta, and explained the blunted time domain FN for general worry. Increased delta was also associated with physiological arousal, but the effects were accounted for by general worry. Broadly, anxiety-related alterations in feedback processing can be explained by an overall heightened sensitivity to feedback as represented by enhanced delta-FN in relation to the general worry facet of anxiety. Copyright © 2018 Elsevier B.V. All rights reserved.

Complementary theta resonance filtering by two spatially segregated mechanisms in CA1 hippocampal pyramidal neurons.

PubMed

Hu, Hua; Vervaeke, Koen; Graham, Lyle J; Storm, Johan F

2009-11-18

Synaptic input to a neuron may undergo various filtering steps, both locally and during transmission to the soma. Using simultaneous whole-cell recordings from soma and apical dendrites from rat CA1 hippocampal pyramidal cells, and biophysically detailed modeling, we found two complementary resonance (bandpass) filters of subthreshold voltage signals. Both filters favor signals in the theta (3-12 Hz) frequency range, but have opposite location, direction, and voltage dependencies: (1) dendritic H-resonance, caused by h/HCN-channels, filters signals propagating from soma to dendrite when the membrane potential is close to rest; and (2) somatic M-resonance, caused by M/Kv7/KCNQ and persistent Na(+) (NaP) channels, filters signals propagating from dendrite to soma when the membrane potential approaches spike threshold. Hippocampal pyramidal cells participate in theta network oscillations during behavior, and we suggest that that these dual, polarized theta resonance mechanisms may convey voltage-dependent tuning of theta-mediated neural coding in the entorhinal/hippocampal system during locomotion, spatial navigation, memory, and sleep.

Rostral Anterior Cingulate Cortex Theta Current Density and Response to Antidepressants and Placebo in Major Depression

PubMed Central

Korb, Alexander S.; Hunter, Aimee M.; Cook, Ian A.; Leuchter, Andrew F.

2009-01-01

Objective To assess whether pretreatment theta current density in the rostral anterior cingulate (rACC) and medial orbitofrontal cortex (mOFC) differentiates responders from non-responders to antidepressant medication or placebo in a double-blinded study. Methods Pretreatment EEGs were collected from 72 subjects with Major Depressive Disorder (MDD) who participated in one of three placebo-controlled trials. Subjects were randomized to receive treatment with fluoxetine, venlafaxine, or placebo. Low-resolution brain electromagnetic tomography (LORETA) was used to assess theta current density in the rACC and mOFC. Results Medication responders showed elevated rACC and mOFC theta current density compared to medication non-responders (rACC: p=0.042; mOFC: p=0.039). There was no significant difference in either brain region between placebo responders and placebo non-responders. Conclusions Theta current density in the rACC and mOFC may be useful as a biomarker for prediction of response to antidepressant medication. Significance This is the first double-blinded treatment study to examine pretreatment rACC and mOFC theta current density in relation to antidepressant response and placebo response. Results support the potential clinical utility of this approach for predicting clinical outcome to antidepressant treatments in MDD. PMID:19539524

X-ray observations of the burst source MXB 1728 - 34

NASA Technical Reports Server (NTRS)

Basinska, E. M.; Lewin, W. H. G.; Sztajno, M.; Cominsky, L. R.; Marshall, F. J.

1984-01-01

Where sufficient information has been obtained, attention is given to the maximum burst flux, integrated burst flux, spectral hardness, rise time, etc., of 96 X-ray bursts observed from March 1976 to March 1979. The integrated burst flux and the burst frequency appear to be correlated; the longer the burst interval, the larger the integrated burst flux, as expected on the basis of simple thermonuclear flash models. The maximum burst flux and the integrated burst flux are strongly correlated; for low flux levels their dependence is approximately linear, while for increasing values of the integrated burst flux, the flux at burst maximum saturates and reaches a plateau.

Changes in absolute theta power in bipolar patients during a saccadic attention task.

PubMed

Cartier, Consuelo; Diniz, Claudia; Di Girogio, Luiza; Bittencourt, Juliana; Gongora, Mariana; Ken Tanaka, Guaraci; Teixeira, Silmar; Basile, Luis F; Novis, Fernanda; Angélica Silveira, Luciana; da Silva, Rafael de Assis; Cagy, Mauricio; Cheniaux, Elie; Ribeiro, Pedro; Velasques, Bruna

2015-08-30

The present study analyzed absolute theta power (ATP) in brain areas involved with attention in the three phase of BD while the patients performing a saccadic attention task. We hypothesized that patients in depression and mania states show a higher ATP compared to euthymic patients, since a higher ATP is indicative of attention deficit. We analyzed the frontal (F7, F3, Fz, F4 and F8) and central (C3, Cz and C4) areas. Thirty bipolar patients were enrolled in this study. The subjects performed a saccadic attention task while their brain activity pattern was recorded using quantitative electroencephalography (20 channels). Our results showed a main effect for group over C3, C4, Cz, F7, F4, F8 electrodes, and a main effect for moment over Cz, F7, F8 electrodes. These results indicate that both task and groups produce changes in theta activity in distinct cortical areas that participate in the organization of attention. Our results therefore demonstrate that, although it is well established in the literature that theta has a relevant role in the attention process, it is necessary to deepen the investigations to better understand the specifics of theta during visual processing tasks that have a demand for attention. Copyright © 2015 Elsevier Ireland Ltd. All rights reserved.

Frontal theta and beta synchronizations for monetary reward increase visual working memory capacity

PubMed Central

Yamaguchi, Yoko

2013-01-01

Visual working memory (VWM) capacity is affected by motivational influences; however, little is known about how reward-related brain activities facilitate the VWM systems. To investigate the dynamic relationship between VWM- and reward-related brain activities, we conducted time–frequency analyses using electroencephalograph (EEG) data obtained during a monetary-incentive delayed-response task that required participants to memorize the position of colored disks. In case of a correct answer, participants received a monetary reward (0, 10 or 50 Japanese yen) announced at the beginning of each trial. Behavioral results showed that VWM capacity under high-reward condition significantly increased compared with that under low- or no-reward condition. EEG results showed that frontal theta (6 Hz) amplitudes enhanced during delay periods and positively correlated with VWM capacity, indicating involvement of theta local synchronizations in VWM. Moreover, frontal beta activities (24 Hz) were identified as reward-related activities, because delay-period amplitudes correlated with increases in VWM capacity between high-reward and no-reward conditions. Interestingly, cross-frequency couplings between frontal theta and beta phases were observed only under high-reward conditions. These findings suggest that the functional dynamic linking between VWM-related theta and reward-related beta activities on the frontal regions plays an integral role in facilitating increases in VWM capacity. PMID:22349800

The theta/gamma discrete phase code occuring during the hippocampal phase precession may be a more general brain coding scheme.

PubMed

Lisman, John

2005-01-01

In the hippocampus, oscillations in the theta and gamma frequency range occur together and interact in several ways, indicating that they are part of a common functional system. It is argued that these oscillations form a coding scheme that is used in the hippocampus to organize the readout from long-term memory of the discrete sequence of upcoming places, as cued by current position. This readout of place cells has been analyzed in several ways. First, plots of the theta phase of spikes vs. position on a track show a systematic progression of phase as rats run through a place field. This is termed the phase precession. Second, two cells with nearby place fields have a systematic difference in phase, as indicated by a cross-correlation having a peak with a temporal offset that is a significant fraction of a theta cycle. Third, several different decoding algorithms demonstrate the information content of theta phase in predicting the animal's position. It appears that small phase differences corresponding to jitter within a gamma cycle do not carry information. This evidence, together with the finding that principle cells fire preferentially at a given gamma phase, supports the concept of theta/gamma coding: a given place is encoded by the spatial pattern of neurons that fire in a given gamma cycle (the exact timing within a gamma cycle being unimportant); sequential places are encoded in sequential gamma subcycles of the theta cycle (i.e., with different discrete theta phase). It appears that this general form of coding is not restricted to readout of information from long-term memory in the hippocampus because similar patterns of theta/gamma oscillations have been observed in multiple brain regions, including regions involved in working memory and sensory integration. It is suggested that dual oscillations serve a general function: the encoding of multiple units of information (items) in a way that preserves their serial order. The relationship of such coding to

SOME COMMENTS ON TYPE IV BURSTS

DOE Office of Scientific and Technical Information (OSTI.GOV)

Tanaka, H.; Kakinuma, T.

1962-01-01

It has become clear that a large continuum burst is composed of 4 distinctive types, CM/sub 1/, CM/sub 2/, DM, and IV, which originate from different altitudes over the photosphere. The observational characters of each type are given. CM/sub 1/ is the main phase of a centimeter-wave burst originating from about 0.02-0.05 R/sub S/ in height. DM burst is polarized in the ordinary sense, which is the cause of reversal of polarization with frequency. Its center frequency lies between about 1000 and 200 Mc/s, and is often misunderstood as the original Type IV burst. The movement of magnetic field duringmore » a burst is suggested. CM/sub 2/ may be considered as an enhancement of the upper part of the source of S-component caused by this movement of the field. (auth)« less

Herringbone bursts associated with type II solar radio emission

NASA Technical Reports Server (NTRS)

Cairns, I. H.; Robinson, R. D.

1987-01-01

Detailed observations of the herringbone (HB) fine structure on type II solar radio bursts are presented. Data from the Culgoora radiospectrograph, radiometer and radioheliograph are analyzed. The characteristic spectral profiles, frequency drift rates and exciter velocities, fluxes, source sizes, brightness temperatures, and polarizations of individual HB bursts are determined. Correlations between individual bursts within the characteristic groups of bursts and the properties of the associated type II bursts are examined. These data are compatible with HB bursts being radiation at multiples of the plasma frequency generated by electron streams accelerated by the type II shock. HB bursts are physically distinct phenomena from type II and type III bursts, differing significantly in emission processes and/or source conditions; this conclusion indicates that many of the presently available theoretical ideas for HB bursts are incorrect.

Entorhinal-CA3 Dual-Input Control of Spike Timing in the Hippocampus by Theta-Gamma Coupling.

PubMed

Fernández-Ruiz, Antonio; Oliva, Azahara; Nagy, Gergő A; Maurer, Andrew P; Berényi, Antal; Buzsáki, György

2017-03-08

Theta-gamma phase coupling and spike timing within theta oscillations are prominent features of the hippocampus and are often related to navigation and memory. However, the mechanisms that give rise to these relationships are not well understood. Using high spatial resolution electrophysiology, we investigated the influence of CA3 and entorhinal inputs on the timing of CA1 neurons. The theta-phase preference and excitatory strength of the afferent CA3 and entorhinal inputs effectively timed the principal neuron activity, as well as regulated distinct CA1 interneuron populations in multiple tasks and behavioral states. Feedback potentiation of distal dendritic inhibition by CA1 place cells attenuated the excitatory entorhinal input at place field entry, coupled with feedback depression of proximal dendritic and perisomatic inhibition, allowing the CA3 input to gain control toward the exit. Thus, upstream inputs interact with local mechanisms to determine theta-phase timing of hippocampal neurons to support memory and spatial navigation. Copyright © 2017 Elsevier Inc. All rights reserved.

Associative-memory representations emerge as shared spatial patterns of theta activity spanning the primate temporal cortex

PubMed Central

Nakahara, Kiyoshi; Adachi, Ken; Kawasaki, Keisuke; Matsuo, Takeshi; Sawahata, Hirohito; Majima, Kei; Takeda, Masaki; Sugiyama, Sayaka; Nakata, Ryota; Iijima, Atsuhiko; Tanigawa, Hisashi; Suzuki, Takafumi; Kamitani, Yukiyasu; Hasegawa, Isao

2016-01-01

Highly localized neuronal spikes in primate temporal cortex can encode associative memory; however, whether memory formation involves area-wide reorganization of ensemble activity, which often accompanies rhythmicity, or just local microcircuit-level plasticity, remains elusive. Using high-density electrocorticography, we capture local-field potentials spanning the monkey temporal lobes, and show that the visual pair-association (PA) memory is encoded in spatial patterns of theta activity in areas TE, 36, and, partially, in the parahippocampal cortex, but not in the entorhinal cortex. The theta patterns elicited by learned paired associates are distinct between pairs, but similar within pairs. This pattern similarity, emerging through novel PA learning, allows a machine-learning decoder trained on theta patterns elicited by a particular visual item to correctly predict the identity of those elicited by its paired associate. Our results suggest that the formation and sharing of widespread cortical theta patterns via learning-induced reorganization are involved in the mechanisms of associative memory representation. PMID:27282247

The modulatory effect of adaptive deep brain stimulation on beta bursts in Parkinson’s disease

PubMed Central

Tinkhauser, Gerd; Pogosyan, Alek; Little, Simon; Beudel, Martijn; Herz, Damian M.; Tan, Huiling

2017-01-01

Abstract Adaptive deep brain stimulation uses feedback about the state of neural circuits to control stimulation rather than delivering fixed stimulation all the time, as currently performed. In patients with Parkinson’s disease, elevations in beta activity (13–35 Hz) in the subthalamic nucleus have been demonstrated to correlate with clinical impairment and have provided the basis for feedback control in trials of adaptive deep brain stimulation. These pilot studies have suggested that adaptive deep brain stimulation may potentially be more effective, efficient and selective than conventional deep brain stimulation, implying mechanistic differences between the two approaches. Here we test the hypothesis that such differences arise through differential effects on the temporal dynamics of beta activity. The latter is not constantly increased in Parkinson’s disease, but comes in bursts of different durations and amplitudes. We demonstrate that the amplitude of beta activity in the subthalamic nucleus increases in proportion to burst duration, consistent with progressively increasing synchronization. Effective adaptive deep brain stimulation truncated long beta bursts shifting the distribution of burst duration away from long duration with large amplitude towards short duration, lower amplitude bursts. Critically, bursts with shorter duration are negatively and bursts with longer duration positively correlated with the motor impairment off stimulation. Conventional deep brain stimulation did not change the distribution of burst durations. Although both adaptive and conventional deep brain stimulation suppressed mean beta activity amplitude compared to the unstimulated state, this was achieved by a selective effect on burst duration during adaptive deep brain stimulation, whereas conventional deep brain stimulation globally suppressed beta activity. We posit that the relatively selective effect of adaptive deep brain stimulation provides a rationale for why this

An Ephemeral Burst-Buffer File System for Scientific Applications

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wang, Teng; Moody, Adam; Yu, Weikuan

BurstFS is a distributed file system for node-local burst buffers on high performance computing systems. BurstFS presents a shared file system space across the burst buffers so that applications that use shared files can access the highly-scalable burst buffers without changing their applications.

Learning curves of theta/beta neurofeedback in children with ADHD.

PubMed

Janssen, Tieme W P; Bink, Marleen; Weeda, Wouter D; Geladé, Katleen; van Mourik, Rosa; Maras, Athanasios; Oosterlaan, Jaap

2017-05-01

Neurofeedback is widely applied as non-pharmacological intervention aimed at reducing symptoms of ADHD, even though efficacy has not been unequivocally established. Neuronal changes during the neurofeedback intervention that resemble learning can provide crucial evidence for the feasibility and specificity of this intervention. A total of 38 children (aged between 7 and 13 years) with a DSM-IV-TR diagnosis of ADHD, completed on average 29 sessions of theta (4-8 Hz)/beta (13-20 Hz) neurofeedback training. Dependent variables included training-related measures as well as theta and beta power during baseline and training runs for each session. Learning effects were analyzed both within and between sessions. To further specify findings, individual learning curves were explored and correlated with behavioral changes in ADHD symptoms. Over the course of the training, there was a linear increase in participants' mean training level, highest obtained training level and the number of earned credits (range b = 0.059, -0.750, p < 0.001). Theta remained unchanged over the course of the training, while beta activity increased linearly within training sessions (b = 0.004, 95% CI = [0.0013-0.0067], p = 0.005) and over the course of the intervention (b = 0.0052, 95% CI = [0.0039-0.0065], p < 0.001). In contrast to the group analyses, significant individual learning curves were found for both theta and beta over the course of the intervention in 39 and 53%, respectively. Individual learning curves were not significantly correlated with behavioral changes. This study shows that children with ADHD can gain control over EEG states during neurofeedback, although a lack of behavioral correlates may indicate insufficient transfer to daily functioning, or to confounding reinforcement of electromyographic activity. This trial is registered at the US National Institutes of Health (ClinicalTrials.gov, ref. no: NCT01363544); https://clinicaltrials.gov/show/NCT01363544 .

Dark gamma-ray bursts

NASA Astrophysics Data System (ADS)

Brdar, Vedran; Kopp, Joachim; Liu, Jia

2017-03-01

Many theories of dark matter (DM) predict that DM particles can be captured by stars via scattering on ordinary matter. They subsequently condense into a DM core close to the center of the star and eventually annihilate. In this work, we trace DM capture and annihilation rates throughout the life of a massive star and show that this evolution culminates in an intense annihilation burst coincident with the death of the star in a core collapse supernova. The reason is that, along with the stellar interior, also its DM core heats up and contracts, so that the DM density increases rapidly during the final stages of stellar evolution. We argue that, counterintuitively, the annihilation burst is more intense if DM annihilation is a p -wave process than for s -wave annihilation because in the former case, more DM particles survive until the supernova. If among the DM annihilation products are particles like dark photons that can escape the exploding star and decay to standard model particles later, the annihilation burst results in a flash of gamma rays accompanying the supernova. For a galactic supernova, this "dark gamma-ray burst" may be observable in the Čerenkov Telescope Array.

Dual Roles for DNA Polymerase Theta in Alternative End-Joining Repair of Double-Strand Breaks in Drosophila

PubMed Central

McVey, Mitch

2010-01-01

DNA double-strand breaks are repaired by multiple mechanisms that are roughly grouped into the categories of homology-directed repair and non-homologous end joining. End-joining repair can be further classified as either classical non-homologous end joining, which requires DNA ligase 4, or “alternative” end joining, which does not. Alternative end joining has been associated with genomic deletions and translocations, but its molecular mechanism(s) are largely uncharacterized. Here, we report that Drosophila melanogaster DNA polymerase theta (pol theta), encoded by the mus308 gene and previously implicated in DNA interstrand crosslink repair, plays a crucial role in DNA ligase 4-independent alternative end joining. In the absence of pol theta, end joining is impaired and residual repair often creates large deletions flanking the break site. Analysis of break repair junctions from flies with mus308 separation-of-function alleles suggests that pol theta promotes the use of long microhomologies during alternative end joining and increases the likelihood of complex insertion events. Our results establish pol theta as a key protein in alternative end joining in Drosophila and suggest a potential mechanistic link between alternative end joining and interstrand crosslink repair. PMID:20617203

Long-Lag, Wide-pulse Gamma-Ray Bursts

NASA Technical Reports Server (NTRS)

Norris, J. P.; Bonnell, J. T.; Kazanas, D.; Scargie, J. D.; Hakkila, J.; Giblin, T. W.

2005-01-01

The best available probe of the early phase of gamma-ray burst (GRB) jet attributes is the prompt gamma-ray emission, in which several intrinsic and extrinsic variables determine observed GRB pulse evolution, including at least: jet opening angle, profiles of Lorentz factor and matter/field density, distance of emission region from central source, and viewing angle. Bright, usually complex bursts have many narrow pulses that are difficult to model due to overlap. However, the relatively simple, long spectral lag, wide-pulse bursts may have simpler physics and are easier to model. We have analyzed the temporal and spectral behavior of wide pulses in 24 long-lag bursts from the BATSE sample, using a pulse model with two shape parameters - width and asymmetry - and the Band spectral model with three shape parameters. We find that pulses in long-lag bursts are distinguished both temporally and spectrally from those in bright bursts: the pulses in long spectral lag bursts are few in number, and approximately 100 times wider (10s of seconds), have systemtically lower peaks in nu*F(nu), harder low-energy spectra and softer high-energy spectra. These five pulse descriptors are essentially uncorrelated for our long-lag sample, suggesting that at least approximately 5 parameters are needed to model burst temporal and spectral behavior, roughly commensurate with the theoretical phase space. However, we do find that pulse width is strongly correlated with spectral lag; hence these two parameters may be viewed as mutual surrogates. The prevalence of long-lag bursts near the BATSE trigger threshold, their predominantly low nu*F(nu) spectral peaks, and relatively steep upper power-law spectral indices indicate that Swiift will detect many such bursts.

BURST AND OUTBURST CHARACTERISTICS OF MAGNETAR 4U 0142+61

DOE Office of Scientific and Technical Information (OSTI.GOV)

Göğüş, Ersin; Chakraborty, Manoneeta; Kaneko, Yuki

2017-01-20

We have compiled the most comprehensive burst sample from magnetar 4U 0142+61, comprising 27 bursts from its three burst-active episodes in 2011, 2012 and the latest one in 2015 observed with Swift /Burst Alert Telescope and Fermi /Gamma-ray Burst Monitor. Bursts from 4U 0142+61 morphologically resemble typical short bursts from other magnetars. However, 4U 0142+61 bursts are less energetic compared to the bulk of magnetar bursts. We uncovered an extended tail emission following a burst on 2015 February 28, with a thermal nature, cooling over a timescale of several minutes. During this tail emission, we also uncovered pulse peak phasemore » aligned X-ray bursts, which could originate from the same underlying mechanism as that of the extended burst tail, or an associated and spatially coincident but different mechanism.« less

Burst-type noise mechanisms in bipolar transistors

NASA Astrophysics Data System (ADS)

Wu, X. L.; van der Ziel, A.; Birbas, A. N.; van Rheenen, A. D.

1989-11-01

Two types of burst noise have been observed in silicon bipolar transistors. They can be characterized by the typical frequency dependence of their current fluctuation spectra. Interestingly, observation of the noise signal in the time domain gives two distinctively different pictures of the bistable waveform. Also, amplification of the noise signal yields different sounds when fed to a speaker. One of the noise spectra is the superposition of 1/ƒ noise and a Lorentzian component (burst noise) and the other can be described mathematically as 1/ƒ noise modulated by the burst noise. The classification of those two types of burst noise and the mathematical explanation will lead to a better understanding of the bipolar transistor burst noise itself.

Confining Domains Lead to Reaction Bursts: Reaction Kinetics in the Plasma Membrane

PubMed Central

Kalay, Ziya; Fujiwara, Takahiro K.; Kusumi, Akihiro

2012-01-01

Confinement of molecules in specific small volumes and areas within a cell is likely to be a general strategy that is developed during evolution for regulating the interactions and functions of biomolecules. The cellular plasma membrane, which is the outermost membrane that surrounds the entire cell, was considered to be a continuous two-dimensional liquid, but it is becoming clear that it consists of numerous nano-meso-scale domains with various lifetimes, such as raft domains and cytoskeleton-induced compartments, and membrane molecules are dynamically trapped in these domains. In this article, we give a theoretical account on the effects of molecular confinement on reversible bimolecular reactions in a partitioned surface such as the plasma membrane. By performing simulations based on a lattice-based model of diffusion and reaction, we found that in the presence of membrane partitioning, bimolecular reactions that occur in each compartment proceed in bursts during which the reaction rate is sharply and briefly increased even though the asymptotic reaction rate remains the same. We characterized the time between reaction bursts and the burst amplitude as a function of the model parameters, and discussed the biological significance of the reaction bursts in the presence of strong inhibitor activity. PMID:22479350

Theta/beta neurofeedback in children with ADHD: Feasibility of a short-term setting and plasticity effects.

PubMed

Van Doren, Jessica; Heinrich, Hartmut; Bezold, Mareile; Reuter, Nina; Kratz, Oliver; Horndasch, Stefanie; Berking, Matthias; Ros, Tomas; Gevensleben, Holger; Moll, Gunther H; Studer, Petra

2017-02-01

Neurofeedback (NF) is increasingly used as a therapy for attention-deficit/hyperactivity disorder (ADHD), however behavioral improvements require 20 plus training sessions. More economic evaluation strategies are needed to test methodological optimizations and mechanisms of action. In healthy adults, neuroplastic effects have been demonstrated directly after a single session of NF training. The aim of our study was to test the feasibility of short-term theta/beta NF in children with ADHD and to learn more about the mechanisms underlying this protocol. Children with ADHD conducted two theta/beta NF sessions. In the first half of the sessions, three NF trials (puzzles as feedback animations) were run with pre- and post-reading and picture search tasks. A significant decrease of the theta/beta ratio (TBR), driven by a decrease of theta activity, was found in the NF trials of the second session demonstrating rapid and successful neuroregulation by children with ADHD. For pre-post comparisons, children were split into good vs. poor regulator groups based on the slope of their TBR over the NF trials. For the reading task, significant EEG changes were seen for the theta band from pre- to post-NF depending on individual neuroregulation ability. This neuroplastic effect was not restricted to the feedback electrode Cz, but appeared as a generalized pattern, maximal over midline and right-hemisphere electrodes. Our findings indicate that short-term NF may be a valuable and economical tool to study the neuroplastic mechanisms of targeted NF protocols in clinical disorders, such as theta/beta training in children with ADHD. Copyright © 2016 Elsevier B.V. All rights reserved.

What is the function of hippocampal theta rhythm?--Linking behavioral data to phasic properties of field potential and unit recording data.

PubMed

Hasselmo, Michael E

2005-01-01

The extensive physiological data on hippocampal theta rhythm provide an opportunity to evaluate hypotheses about the role of theta rhythm for hippocampal network function. Computational models based on these hypotheses help to link behavioral data with physiological measurements of different variables during theta rhythm. This paper reviews work on network models in which theta rhythm contributes to the following functions: (1) separating the dynamics of encoding and retrieval, (2) enhancing the context-dependent retrieval of sequences, (3) buffering of novel information in entorhinal cortex (EC) for episodic encoding, and (4) timing interactions between prefrontal cortex and hippocampus for memory-guided action selection. Modeling shows how these functional mechanisms are related to physiological data from the hippocampal formation, including (1) the phase relationships of synaptic currents during theta rhythm measured by current source density analysis of electroencephalographic data from region CA1 and dentate gyrus, (2) the timing of action potentials, including the theta phase precession of single place cells during running on a linear track, the context-dependent changes in theta phase precession across trials on each day, and the context-dependent firing properties of hippocampal neurons in spatial alternation (e.g., "splitter cells"), (3) the cholinergic regulation of sustained activity in entorhinal cortical neurons, and (4) the phasic timing of prefrontal cortical neurons relative to hippocampal theta rhythm. Copyright 2005 Wiley-Liss, Inc.

Frontal theta accounts for individual differences in the cost of conflict on decision making.

PubMed

Pinner, John F L; Cavanagh, James F

2017-10-01

Cognitive conflict is often experienced as a difficult, frustrating, and aversive state. Recent studies have indicated that conflict acts as an implicit cost during learning, valuation, and the instantiation of cognitive control. Here we investigated if an implicit manipulation of conflict also influences explicit decision making to risk. Participants were required to perform a Balloon Analogue Risk Task wherein the virtual balloon was inflated by performing a flankers task. By varying the percent of incongruent flanker trials between balloons, we hypothesized that participants would pump the balloon fewer times in conditions of higher conflict and that frontal midline theta would account for significant variance in this relationship. Across two studies, we demonstrate that conflict did not elicit reliable behavioral changes in this task across participants. However, individual differences in frontal theta power accounted for significant variance by predicting diminished balloon pumps. Thus, while conflict costs may act as investments to some individuals (invigorating behavior), it is aversive to others (diminishing behavior), and frontal midline theta power accounts for these varying behavioral tendencies between individuals. These findings demonstrate how frontal midline theta is not only a candidate mechanism for implementing cognitive control, but it is sensitive to the inherent costs therein. Copyright © 2017 Elsevier B.V. All rights reserved.

Microinjection of procaine and electrolytic lesion in the ventral tegmental area suppresses hippocampal theta rhythm in urethane-anesthetized rats.

PubMed

Orzeł-Gryglewska, Jolanta; Jurkowlaniec, Edyta; Trojniar, Weronika

2006-01-30

The midbrain ventral tegmental area (VTA), a key structure of the mesocorticolimbic system is anatomically connected with the hippocampal formation. In addition mesocortical dopamine was found to influence hippocampus-related memory and hippocampal synaptic plasticity, both being linked to the theta rhythm. Therefore, the aim of the present study was to evaluate the possible role of the VTA in the regulation of the hippocampal theta activity. The study was performed on urethane-anesthetized male Wistar rats in which theta rhythm was evoked by tail pinch. It was found that unilateral, temporal inactivation of the VTA by means of direct procaine injection resulted in bilateral suppression of the hippocampal theta which manifested as a loss of synchronization of hippocampal EEG and respective reduction of the power and also the frequency of the 3-6 Hz theta band. Depression of the power of the 3-6 Hz component of the EEG signal was also seen in spontaneous hippocampal EEG after procaine. The permanent destruction of the VTA by means of unilateral electrocoagulation evoked a long-lasting, mainly ipsilateral depression of the power of the theta with some influence on its frequency. Simultaneously, there was a substantial increase of the power in higher frequency bands indicating decrease of a synchrony of the hippocampal EEG activity. On the basis of these results indicating impairment of synchronization of the hippocampal activity the VTA may be considered as another part of the brainstem theta synchroning system.

The modulatory effect of adaptive deep brain stimulation on beta bursts in Parkinson's disease.

PubMed

Tinkhauser, Gerd; Pogosyan, Alek; Little, Simon; Beudel, Martijn; Herz, Damian M; Tan, Huiling; Brown, Peter

2017-04-01

Adaptive deep brain stimulation uses feedback about the state of neural circuits to control stimulation rather than delivering fixed stimulation all the time, as currently performed. In patients with Parkinson's disease, elevations in beta activity (13-35 Hz) in the subthalamic nucleus have been demonstrated to correlate with clinical impairment and have provided the basis for feedback control in trials of adaptive deep brain stimulation. These pilot studies have suggested that adaptive deep brain stimulation may potentially be more effective, efficient and selective than conventional deep brain stimulation, implying mechanistic differences between the two approaches. Here we test the hypothesis that such differences arise through differential effects on the temporal dynamics of beta activity. The latter is not constantly increased in Parkinson's disease, but comes in bursts of different durations and amplitudes. We demonstrate that the amplitude of beta activity in the subthalamic nucleus increases in proportion to burst duration, consistent with progressively increasing synchronization. Effective adaptive deep brain stimulation truncated long beta bursts shifting the distribution of burst duration away from long duration with large amplitude towards short duration, lower amplitude bursts. Critically, bursts with shorter duration are negatively and bursts with longer duration positively correlated with the motor impairment off stimulation. Conventional deep brain stimulation did not change the distribution of burst durations. Although both adaptive and conventional deep brain stimulation suppressed mean beta activity amplitude compared to the unstimulated state, this was achieved by a selective effect on burst duration during adaptive deep brain stimulation, whereas conventional deep brain stimulation globally suppressed beta activity. We posit that the relatively selective effect of adaptive deep brain stimulation provides a rationale for why this approach could

The Double Firing Burst

NASA Astrophysics Data System (ADS)

2008-09-01

Astronomers from around the world combined data from ground- and space-based telescopes to paint a detailed portrait of the brightest explosion ever seen. The observations reveal that the jets of the gamma-ray burst called GRB 080319B were aimed almost directly at the Earth. Uncovering the disc ESO PR Photo 28/08 A Gamma-Ray Burst with Two Jets Read more on this illuminating blast in the additional story. GRB 080319B was so intense that, despite happening halfway across the Universe, it could have been seen briefly with the unaided eye (ESO 08/08). In a paper to appear in the 11 September issue of Nature, Judith Racusin of Penn State University, Pennsylvania (USA), and a team of 92 co-authors report observations across the electromagnetic spectrum that began 30 minutes before the explosion and followed it for months afterwards. "We conclude that the burst's extraordinary brightness arose from a jet that shot material almost directly towards Earth at almost the speed of light - the difference is only 1 part in 20 000," says Guido Chincarini, a member of the team. Gamma-ray bursts are the Universe's most luminous explosions. Most occur when massive stars run out of fuel. As a star collapses, it creates a black hole or neutron star that, through processes not fully understood, drives powerful gas jets outward. As the jets shoot into space, they strike gas previously shed by the star and heat it, thereby generating bright afterglows. The team believes the jet directed toward Earth contained an ultra-fast component just 0.4 degrees across (this is slightly smaller than the apparent size of the Full Moon). This jet is contained within another slightly less energetic jet about 20 times wider. The broad component is more typical of other bursts. "Perhaps every gamma-ray burst has a narrow jet, but astronomers miss it most of the time," says team member Stefano Covino. "We happened to view this monster down the barrel of the very narrow and energetic jet, and the chance for

Intrahemispheric theta rhythm desynchronization impairs working memory.

PubMed

Alekseichuk, Ivan; Pabel, Stefanie Corinna; Antal, Andrea; Paulus, Walter

2017-01-01

There is a growing interest in large-scale connectivity as one of the crucial factors in working memory. Correlative evidence has revealed the anatomical and electrophysiological players in the working memory network, but understanding of the effective role of their connectivity remains elusive. In this double-blind, placebo-controlled study we aimed to identify the causal role of theta phase connectivity in visual-spatial working memory. The frontoparietal network was over- or de-synchronized in the anterior-posterior direction by multi-electrode, 6 Hz transcranial alternating current stimulation (tACS). A decrease in memory performance and increase in reaction time was caused by frontoparietal intrahemispheric desynchronization. According to the diffusion drift model, this originated in a lower signal-to-noise ratio, known as the drift rate index, in the memory system. The EEG analysis revealed a corresponding decrease in phase connectivity between prefrontal and parietal areas after tACS-driven desynchronization. The over-synchronization did not result in any changes in either the behavioral or electrophysiological levels in healthy participants. Taken together, we demonstrate the feasibility of manipulating multi-site large-scale networks in humans, and the disruptive effect of frontoparietal desynchronization on theta phase connectivity and visual-spatial working memory.

Physics of Gamma Ray Burst Sources

NASA Technical Reports Server (NTRS)

Meszaros, Peter

2004-01-01

During this grant period, the physics of gamma-ray bursts was investigated. A number of new results have emerged. The importance of pair formation in high compactness burst spectra may help explain x-ray flashes; a universal jet shape is a likely explanation for the distribution of jet break times; gravitational waves may be copiously produced both in short bursts from compact mergers and in long bursts arising from collapsars; x-ray iron lines are likely to be due to interaction with the stellar atmosphere of the progenitor; prompt optical flashes from reverse shocks will give diagnostics on the Lorentz factor and the environment; GeV and TeV emission from bursts may be expected in the external shock; etc. The group working with the PI included postdocs Dr. Bing Zhang (now assistant professor at University of Nevada); Dr. Shiho Kobayashi; graduate student Lijun Gou; collaborators Drs. Tim Kallman and Martin Rees. Meszaros shared with Rees and Dr. Bohan Paczynsky the AAS Rossi Prize in 2000 for their work on the theory of gamma ray bursts. The refereed publications and conference proceedings resulting from this research are summarized below. The PI gave a number of invited talks at major conferences, also listed.

Mosquitoes drink with a burst in reserve: explaining pumping behavior with a fluid mechanics model

NASA Astrophysics Data System (ADS)

Chatterjee, Souvick; Socha, Jake; Stremler, Mark

2014-11-01

Mosquitoes drink using a pair of in-line pumps in the head that draw liquid food through the proboscis. Experimental observations with synchrotron x-ray imaging indicate two modes of drinking: a predominantly occurring continuous mode, in which the cibarial and pharyngeal pumps expand cyclically at a constant phase difference, and an occasional, isolated burst mode, in which the pharyngeal pump expansion is 10 to 30 times larger than in the continuous mode. We have used a reduced order model of the fluid mechanics to hypothesize an explanation of this variation in drinking behavior. Our model results show that the continuous mode is more energetically efficient, whereas the burst mode creates a large pressure drop across the proboscis, which could potentially be used to clear blockages. Comparisons with pump knock-out configurations demonstrate different functional roles of the pumps in mosquito feeding. This material is based upon work supported by the NSF under Grant No. #0938047.

Intrahippocampal infusion of the Ih blocker ZD7288 slows evoked theta rhythm and produces anxiolytic-like effects in the elevated plus maze.

PubMed

Yeung, Michelle; Dickson, Clayton T; Treit, Dallas

2013-04-01

Hippocampal theta rhythm has been associated with a number of behavioral processes, including learning and memory, spatial behavior, sensorimotor integration and affective responses. Suppression of hippocampal theta frequency has been shown to be a reliable neurophysiological signature of anxiolytic drug action in tests using known anxiolytic drugs (i.e., correlational evidence), but only one study to date (Yeung et al. (2012) Neuropharmacology 62:155-160) has shown that a drug with no known effect on either hippocampal theta or anxiety can in fact separately suppress hippocampal theta and anxiety in behavioral tests (i.e., prima facie evidence). Here, we attempt a further critical test of the hippocampal theta model by performing intrahippocampal administrations of the Ih blocker ZD7288, which is known to disrupt theta frequency subthreshold oscillations and resonance at the membrane level but is not known to have anxiolytic action. Intrahippocampal microinfusions of ZD7288 at high (15 µg), but not low (1 µg) doses slowed brainstem-evoked hippocampal theta responses in the urethane anesthetized rat, and more importantly, promoted anxiolytic action in freely behaving rats in the elevated plus maze. Taken together with our previous demonstration, these data provide converging, prima facie evidence of the validity of the theta suppression model. Copyright © 2012 Wiley Periodicals, Inc.

"Short, Hard Gamma-Ray Bursts - Mystery Solved?????"

NASA Technical Reports Server (NTRS)

Parsons, A.

2006-01-01

After over a decade of speculation about the nature of short-duration hard-spectrum gamma-ray bursts (GRBs), the recent detection of afterglow emission from a small number of short bursts has provided the first physical constraints on possible progenitor models. While the discovery of afterglow emission from long GRBs was a real breakthrough linking their origin to star forming galaxies, and hence the death of massive stars, the progenitors, energetics, and environments for short gamma-ray burst events remain elusive despite a few recent localizations. Thus far, the nature of the host galaxies measured indicates that short GRBs arise from an old (> 1 Gyr) stellar population, strengthening earlier suggestions and providing support for coalescing compact object binaries as the progenitors. On the other hand, some of the short burst afterglow observations cannot be easily explained in the coalescence scenario. These observations raise the possibility that short GRBs may have different or multiple progenitors systems. The study of the short-hard GRB afterglows has been made possible by the Swift Gamma-ray Burst Explorer, launched in November of 2004. Swift is equipped with a coded aperture gamma-ray telescope that can observe up to 2 steradians of the sky and can compute the position of a gamma-ray burst to within 2-3 arcmin in less than 10 seconds. The Swift spacecraft can slew on to this burst position without human intervention, allowing its on-board x ray and optical telescopes to study the afterglow within 2 minutes of the original GRB trigger. More Swift short burst detections and afterglow measurements are needed before we can declare that the mystery of short gamma-ray burst is solved.

GLAST's GBM Burst Trigger

NASA Technical Reports Server (NTRS)

Band, D.; Briggs, M.; Connaughton, V.; Kippen, M.; Preece, R.

2003-01-01

The GLAST Burst Monitor (GBM) will detect and localize bursts for the GLAST mission, and provide the spectral and temporal context in the traditional 10 keV to 25 MeV band for the high energy observations by the Large Area Telescope (LAT). The GBM will use traditional rate triggers in up to three energy bands, and on a variety of timescales between 16 ms and 16 s.

Decreased theta power at encoding and cognitive mapping deficits in elderly individuals during a spatial memory task.

PubMed

Lithfous, Ségolène; Tromp, Delphine; Dufour, André; Pebayle, Thierry; Goutagny, Romain; Després, Olivier

2015-10-01

The purpose of this study was to investigate the role of theta activity in cognitive mapping, and to determine whether age-associated decreased theta power may account for navigational difficulties in elderly individuals. Cerebral activity was recorded using electroencephalograph in young and older individuals performing a spatial memory task that required the creation of cognitive maps. Power spectra were computed in the frontal and parietal regions and correlated with recognition performance. We found that accuracy of cognitive mapping was positively correlated with left frontal theta activity during encoding in young adults but not in older individuals. Compared with young adults, older participants were impaired in the creation of cognitive maps and showed reduced theta and alpha activity at encoding. These results suggest that encoding processes are impaired in older individual, which may explain age-related cognitive mapping deficits. Copyright © 2015 Elsevier Inc. All rights reserved.

Changes in interoceptive processes following brain stimulation

PubMed Central

Mai, Sandra

2016-01-01

The processing and perception of individual internal bodily signals (interoception) has been differentiated to comprise different levels and processes involved. The so-called heartbeat-evoked potential (HEP) offers an additional possibility to examine automatic processing of cardiac signals. Knowledge on neural structures potentially supporting different facets of interoception is still sparse. One way to get insights into neuroanatomical function is to manipulate the activity of different brain structures. In this study, we used repetitive transcranial magnetic stimulation (rTMS) and a continuous theta-burst protocol to inhibit specific central locations of the interoceptive network including the right anterior insula and the right somatosensory cortices and assessed effects on interoceptive facets and the HEP in 18 male participants. Main results were that inhibiting anterior insula resulted in a significant decline in cardiac and respiratory interoceptive accuracy (IAc) and in a consistent decrease in perception confidence. Continuous theta-burst stimulation (cTBS) over somatosensory cortices reduced only cardiac IAc and affected perception confidence. Inhibiting right anterior insula and right somatosensory cortices increased interoceptive sensibility and reduced the HEP amplitude over frontocentral locations. Our findings strongly suggest that cTBS is an effective tool to investigate the neural network supporting interoceptive processes. This article is part of the themed issue ‘Interoception beyond homeostasis: affect, cognition and mental health’. PMID:28080973

Optimal Codes for the Burst Erasure Channel

NASA Technical Reports Server (NTRS)

Hamkins, Jon

2010-01-01

Deep space communications over noisy channels lead to certain packets that are not decodable. These packets leave gaps, or bursts of erasures, in the data stream. Burst erasure correcting codes overcome this problem. These are forward erasure correcting codes that allow one to recover the missing gaps of data. Much of the recent work on this topic concentrated on Low-Density Parity-Check (LDPC) codes. These are more complicated to encode and decode than Single Parity Check (SPC) codes or Reed-Solomon (RS) codes, and so far have not been able to achieve the theoretical limit for burst erasure protection. A block interleaved maximum distance separable (MDS) code (e.g., an SPC or RS code) offers near-optimal burst erasure protection, in the sense that no other scheme of equal total transmission length and code rate could improve the guaranteed correctible burst erasure length by more than one symbol. The optimality does not depend on the length of the code, i.e., a short MDS code block interleaved to a given length would perform as well as a longer MDS code interleaved to the same overall length. As a result, this approach offers lower decoding complexity with better burst erasure protection compared to other recent designs for the burst erasure channel (e.g., LDPC codes). A limitation of the design is its lack of robustness to channels that have impairments other than burst erasures (e.g., additive white Gaussian noise), making its application best suited for correcting data erasures in layers above the physical layer. The efficiency of a burst erasure code is the length of its burst erasure correction capability divided by the theoretical upper limit on this length. The inefficiency is one minus the efficiency. The illustration compares the inefficiency of interleaved RS codes to Quasi-Cyclic (QC) LDPC codes, Euclidean Geometry (EG) LDPC codes, extended Irregular Repeat Accumulate (eIRA) codes, array codes, and random LDPC codes previously proposed for burst erasure

What the cerveau isolé preparation tells us nowadays about sleep-wake mechanisms?

PubMed

Gottesmann, C

1988-01-01

The intercollicular transected preparation opened a rich field for investigations of sleep-wake mechanisms. Initial results showed that brain stem ascending influences are essential for maintaining an activated cortex. It was subsequently shown that the forebrain also develops activating influences, since EEG desynchronization of the cortex reappears in the chronic cerveau isolé preparation, and continuous or almost continuous theta rhythm is able to occur in the acute cerveau isolé preparation. A brief "intermediate stage" of sleep occurs during natural sleep just prior to and after paradoxical sleep. It is characterized by cortical spindle bursts, hippocampal low frequency theta activity (two patterns of the acute cerveau isolé preparation) and is accompanied by a very low thalamic transmission level, suggesting a cerveau isolé-like state. The chronic cerveau isolé preparation also demonstrates that the executive processes of paradoxical sleep are located in the lower brain stem, while the occurrence of this sleep stage seems to be modulated by forebrain structures.

Theta and Alpha Oscillations in Attentional Interaction during Distracted Driving

PubMed Central

Wang, Yu-Kai; Jung, Tzyy-Ping; Lin, Chin-Teng

2018-01-01

Performing multiple tasks simultaneously usually affects the behavioral performance as compared with executing the single task. Moreover, processing multiple tasks simultaneously often involve more cognitive demands. Two visual tasks, lane-keeping task and mental calculation, were utilized to assess the brain dynamics through 32-channel electroencephalogram (EEG) recorded from 14 participants. A 400-ms stimulus onset asynchrony (SOA) factor was used to induce distinct levels of attentional requirements. In the dual-task conditions, the deteriorated behavior reflected the divided attention and the overlapping brain resources used. The frontal, parietal and occipital components were decomposed by independent component analysis (ICA) algorithm. The event- and response-related theta and alpha oscillations in selected brain regions were investigated first. The increased theta oscillation in frontal component and decreased alpha oscillations in parietal and occipital components reflect the cognitive demands and attentional requirements as executing the designed tasks. Furthermore, time-varying interactive over-additive (O-Add), additive (Add) and under-additive (U-Add) activations were explored and summarized through the comparison between the summation of the elicited spectral perturbations in two single-task conditions and the spectral perturbations in the dual task. Add and U-Add activations were observed while executing the dual tasks. U-Add theta and alpha activations dominated the posterior region in dual-task situations. Our results show that both deteriorated behaviors and interactive brain activations should be comprehensively considered for evaluating workload or attentional interaction precisely. PMID:29479310

Subthalamic nucleus local field potential activity during the Eriksen flanker task reveals a novel role for theta phase during conflict monitoring.

PubMed

Zavala, Baltazar; Brittain, John-Stuart; Jenkinson, Ned; Ashkan, Keyoumars; Foltynie, Thomas; Limousin, Patricia; Zrinzo, Ludvic; Green, Alexander L; Aziz, Tipu; Zaghloul, Kareem; Brown, Peter

2013-09-11

The subthalamic nucleus (STN) is thought to play a central role in modulating responses during conflict. Computational models have suggested that the location of the STN in the basal ganglia, as well as its numerous connections to conflict-related cortical structures, allows it to be ideally situated to act as a global inhibitor during conflict. Additionally, recent behavioral experiments have shown that deep brain stimulation to the STN results in impulsivity during high-conflict situations. However, the precise mechanisms that mediate the "hold-your-horses" function of the STN remain unclear. We recorded from deep brain stimulation electrodes implanted bilaterally in the STN of 13 human subjects with Parkinson's disease while they performed a flanker task. The incongruent trials with the shortest reaction times showed no behavioral or electrophysiological differences from congruent trials, suggesting that the distracter stimuli were successfully ignored. In these trials, cue-locked STN theta band activity demonstrated phase alignment across trials and was followed by a periresponse increase in theta power. In contrast, incongruent trials with longer reaction times demonstrated a relative reduction in theta phase alignment followed by higher theta power. Theta phase alignment negatively correlated with subject reaction time, and theta power positively correlated with trial reaction time. Thus, when conflicting stimuli are not properly ignored, disruption of STN theta phase alignment may help operationalize the hold-your-horses role of the nucleus, whereas later increases in the amplitude of theta oscillations may help overcome this function.

Oscillatory theta activity during memory formation and its impact on overnight consolidation: a missing link?

PubMed

Heib, Dominik P J; Hoedlmoser, Kerstin; Anderer, Peter; Gruber, Georg; Zeitlhofer, Josef; Schabus, Manuel

2015-08-01

Sleep has been shown to promote memory consolidation driven by certain oscillatory patterns, such as sleep spindles. However, sleep does not consolidate all newly encoded information uniformly but rather "selects" certain memories for consolidation. It is assumed that such selection depends on salience tags attached to the new memories before sleep. However, little is known about the underlying neuronal processes reflecting presleep memory tagging. The current study sought to address the question of whether event-related changes in spectral theta power (theta ERSP) during presleep memory formation could reflect memory tagging that influences subsequent consolidation during sleep. Twenty-four participants memorized 160 word pairs before sleep; in a separate laboratory visit, they performed a nonlearning control task. Memory performance was tested twice, directly before and after 8 hr of sleep. Results indicate that participants who improved their memory performance overnight displayed stronger theta ERSP during the memory task in comparison with the control task. They also displayed stronger memory task-related increases in fast sleep spindle activity. Furthermore, presleep theta activity was directly linked to fast sleep spindle activity, indicating that processes during memory formation might indeed reflect memory tagging that influences subsequent consolidation during sleep. Interestingly, our results further indicate that the suggested relation between sleep spindles and overnight performance change is not as direct as once believed. Rather, it appears to be mediated by processes beginning during presleep memory formation. We conclude that theta ERSP during presleep memory formation reflects cortico-hippocampal interactions that lead to a better long-term accessibility by tagging memories for sleep spindle-related reprocessing.

Chondrocyte burst promotes space for mineral expansion.

PubMed

Hara, Emilio Satoshi; Okada, Masahiro; Nagaoka, Noriyuki; Hattori, Takako; Iida, Letycia Mary; Kuboki, Takuo; Nakano, Takayoshi; Matsumoto, Takuya

2018-01-22

Analysis of tissue development from multidisciplinary approaches can result in more integrative biological findings, and can eventually allow the development of more effective bioengineering methods. In this study, we analyzed the initial steps of mineral formation during secondary ossification of mouse femur based on biological and bioengineering approaches. We first found that some chondrocytes burst near the mineralized area. External factors that could trigger chondrocyte burst were then investigated. Chondrocyte burst was shown to be modulated by mechanical and osmotic pressure. A hypotonic solution, as well as mechanical stress, significantly induced chondrocyte burst. We further hypothesized that chondrocyte burst could be associated with space-making for mineral expansion. In fact, ex vivo culture of femur epiphysis in hypotonic conditions, or under mechanical pressure, enhanced mineral formation, compared to normal culture conditions. Additionally, the effect of mechanical pressure on bone formation in vivo was investigated by immobilization of mouse lower limbs to decrease the body pressure onto the joints. The results showed that limb immobilization suppressed bone formation. Together, these results suggest chondrocyte burst as a novel fate of chondrocytes, and that manipulation of chondrocyte burst with external mechano-chemical stimuli could be an additional approach for cartilage and bone tissue engineering.

Observations of energitic radiation bursts from thunder activities

NASA Astrophysics Data System (ADS)

Tsuchiya, H.; Enoto, T.; Torii, T.; Yuasa, T.; Yamada, S.; Kitacuhi, T.; Nakazawa, K.; Kato, H.; Okano, M.; Makishima, K.

2009-04-01

Energetic radiation bursts have been observed during strong thunderstorms by ground-based detectors as well as high-mountain ones. Those radiation bursts are thought to result from runaway electrons originating from electrons accelerated by strong electric field in lightning discharges and thunderclouds, and hence provide a valuable key to understand particle acceleration in thunder activity. Interestingly, they can be categorized into two bursts by their duration. One consists of short bursts lasting for milli-seconds or less. The other comprises long bursts having duration of a few seconds. In order to better understand both short and long bursts, we have conducted experiments at coastal area of the Japan Sea and a 2770-m altitude observatory. In this talk, we will report on those experiments, showing the two experiments has successfully observed both short and long bursts. Especially, we will focus on high-energy radiations extending over MeV energies, and then discuss a plausible model to explain how those high-energy radiations are produced in thunder activity.

Theta synchronization between medial prefrontal cortex and cerebellum is associated with adaptive performance of associative learning behavior

PubMed Central

Chen, Hao; Wang, Yi-jie; Yang, Li; Sui, Jian-feng; Hu, Zhi-an; Hu, Bo

2016-01-01

Associative learning is thought to require coordinated activities among distributed brain regions. For example, to direct behavior appropriately, the medial prefrontal cortex (mPFC) must encode and maintain sensory information and then interact with the cerebellum during trace eyeblink conditioning (TEBC), a commonly-used associative learning model. However, the mechanisms by which these two distant areas interact remain elusive. By simultaneously recording local field potential (LFP) signals from the mPFC and the cerebellum in guinea pigs undergoing TEBC, we found that theta-frequency (5.0–12.0 Hz) oscillations in the mPFC and the cerebellum became strongly synchronized following presentation of auditory conditioned stimulus. Intriguingly, the conditioned eyeblink response (CR) with adaptive timing occurred preferentially in the trials where mPFC-cerebellum theta coherence was stronger. Moreover, both the mPFC-cerebellum theta coherence and the adaptive CR performance were impaired after the disruption of endogenous orexins in the cerebellum. Finally, association of the mPFC -cerebellum theta coherence with adaptive CR performance was time-limited occurring in the early stage of associative learning. These findings suggest that the mPFC and the cerebellum may act together to contribute to the adaptive performance of associative learning behavior by means of theta synchronization. PMID:26879632

Theta oscillations are sensitive to both early and late conflict processing stages: effects of alcohol intoxication.

PubMed

Kovacevic, Sanja; Azma, Sheeva; Irimia, Andrei; Sherfey, Jason; Halgren, Eric; Marinkovic, Ksenija

2012-01-01

Prior neuroimaging evidence indicates that decision conflict activates medial and lateral prefrontal and parietal cortices. Theoretical accounts of cognitive control highlight anterior cingulate cortex (ACC) as a central node in this network. However, a better understanding of the relative primacy and functional contributions of these areas to decision conflict requires insight into the neural dynamics of successive processing stages including conflict detection, response selection and execution. Moderate alcohol intoxication impairs cognitive control as it interferes with the ability to inhibit dominant, prepotent responses when they are no longer correct. To examine the effects of moderate intoxication on successive processing stages during cognitive control, spatio-temporal changes in total event-related theta power were measured during Stroop-induced conflict. Healthy social drinkers served as their own controls by participating in both alcohol (0.6 g/kg ethanol for men, 0.55 g/kg women) and placebo conditions in a counterbalanced design. Anatomically-constrained magnetoencephalography (aMEG) approach was applied to complex power spectra for theta (4-7 Hz) frequencies. The principal generator of event-related theta power to conflict was estimated to ACC, with contributions from fronto-parietal areas. The ACC was uniquely sensitive to conflict during both early conflict detection, and later response selection and execution stages. Alcohol attenuated theta power to conflict across successive processing stages, suggesting that alcohol-induced deficits in cognitive control may result from theta suppression in the executive network. Slower RTs were associated with attenuated theta power estimated to ACC, indicating that alcohol impairs motor preparation and execution subserved by the ACC. In addition to their relevance for the currently prevailing accounts of cognitive control, our results suggest that alcohol-induced impairment of top-down strategic processing

EGRET observations of bursts at MeV energies

NASA Astrophysics Data System (ADS)

Catelli, J. R.; Dingus, B. L.; Schneid, E. J.

1998-05-01

We present preliminary results from the analysis of 16 bright bursts that have been observed by the EGRET NaI calorimeter, or TASC. Seven bursts have been imaged in the EGRET spark chamber above 30 MeV, but in most cases the TASC data gives the highest energy spectra available for these bursts. The TASC can obtain spectral and rate information for bursts well outside the field of view of the EGRET spark chambers, and is sensitive in the energy range from 1 to 200 MeV. The spectra for these bursts are mostly consistent with a simple power law with spectral index in the range from 1.7 to 3.7, with several of the brighter bursts showing emission past 100 MeV. No high energy cutoff has been observed. These high energy photons offer important clues to the physical processes involved at the origin of burst emission. For bursts at cosmological distances extremely high bulk Lorentz factors are implied by the presence of MeV and GeV photons which have not been attenuated by pair production with the lower energy photons from the source.

The Fermi-GBM Three-year X-Ray Burst Catalog

NASA Astrophysics Data System (ADS)

Jenke, P. A.; Linares, M.; Connaughton, V.; Beklen, E.; Camero-Arranz, A.; Finger, M. H.; Wilson-Hodge, C. A.

2016-08-01

The Fermi Gamma-ray Burst Monitor (GBM) is an all-sky gamma-ray monitor well known in the gamma-ray burst (GRB) community. Although GBM excels in detecting the hard, bright extragalactic GRBs, its sensitivity above 8 keV and its all-sky view make it an excellent instrument for the detection of rare, short-lived Galactic transients. In 2010 March, we initiated a systematic search for transients using GBM data. We conclude this phase of the search by presenting a three-year catalog of 1084 X-ray bursts. Using spectral analysis, location, and spatial distributions we classified the 1084 events into 752 thermonuclear X-ray bursts, 267 transient events from accretion flares and X-ray pulses, and 65 untriggered gamma-ray bursts. All thermonuclear bursts have peak blackbody temperatures broadly consistent with photospheric radius expansion (PRE) bursts. We find an average rate of 1.4 PRE bursts per day, integrated over all Galactic bursters within about 10 kpc. These include 33 and 10 bursts from the ultra-compact X-ray binaries 4U 0614+09 and 2S 0918-549, respectively. We discuss these recurrence times and estimate the total mass ejected by PRE bursts in our Galaxy.

Classification of Radiological Changes in Burst Fractures

PubMed Central

Şentürk, Salim; Öğrenci, Ahmet; Gürçay, Ahmet Gürhan; Abdioğlu, Ahmet Atilla; Yaman, Onur; Özer, Ali Fahir

2018-01-01

AIM: Burst fractures can occur with different radiological images after high energy. We aimed to simplify radiological staging of burst fractures. METHODS: Eighty patients whom exposed spinal trauma and had burst fracture were evaluated concerning age, sex, fracture segment, neurological deficit, secondary organ injury and radiological changes that occurred. RESULTS: We performed a new classification in burst fractures at radiological images. CONCLUSIONS: According to this classification system, secondary organ injury and neurological deficit can be an indicator of energy exposure. If energy is high, the clinical status will be worse. Thus, we can get an idea about the likelihood of neurological deficit and secondary organ injuries. This classification has simplified the radiological staging of burst fractures and is a classification that gives a very accurate idea about the neurological condition. PMID:29531604

Joule Heating and Thermal Denaturation of Proteins in Nano-ESI Theta Tips

NASA Astrophysics Data System (ADS)

Zhao, Feifei; Matt, Sarah M.; Bu, Jiexun; Rehrauer, Owen G.; Ben-Amotz, Dor; McLuckey, Scott A.

2017-10-01

Electro-osmotically induced Joule heating in theta tips and its effect on protein denaturation were investigated. Myoglobin, equine cytochrome c, bovine cytochrome c, and carbonic anhydrase II solutions were subjected to electro-osmosis in a theta tip and all of the proteins were denatured during the process. The extent of protein denaturation was found to increase with the applied square wave voltage and electrolyte concentration. The solution temperature at the end of a theta tip was measured directly by Raman spectroscopy and shown to increase with the square wave voltage, thereby demonstrating the effect of Joule heating through an independent method. The electro-osmosis of a solution comprised of myoglobin, bovine cytochrome c, and ubiquitin demonstrated that the magnitude of Joule heating that causes protein denaturation is positively correlated with protein melting temperature. This allows for a quick determination of a protein's relative thermal stability. This work establishes a fast, novel method for protein conformation manipulation prior to MS analysis and provides a temperature-controllable platform for the study of processes that take place in solution with direct coupling to mass spectrometry. [Figure not available: see fulltext.

DE 1 observations of theta aurora plasma source regions and Birkeland current charge carriers

NASA Technical Reports Server (NTRS)

Menietti, J. D.; Burch, J. L.

1987-01-01

Detailed analyses of the DE 1 high-altitude plasma instrument electron and ion data have been performed for four passes during which theta auroras were observed. The data indicate that the theta auroras occur on what appear to be closed field lines with particle signatures and plasma parameters that are quite similar to those of the magnetospheric boundary plasma sheet. The field-aligned currents computed from particle fluxes in the energy range 18-13 keV above the theta auroras are observed to be generally downward on the dawnside of the arcs with a narrower region of larger (higher density) upward currents on the duskside of the arcs. These currents are carried predominantly by field-aligned beams of accelerated cold electrons. Of particualr interest in regions of upward field-aligned current are downward electron beams at energies less than the inferred potential drop above the spacecraft.

Prestimulus delta and theta contributions to equiprobable Go/NoGo processing in healthy ageing.

PubMed

De Blasio, Frances M; Barry, Robert J

2018-05-15

Ongoing EEG activity contributes to ERP outcomes of stimulus processing, and each of these measures is known to undergo (sometimes significant) age-related change. Variation in their relationship across the life-span may thus elucidate mechanisms of normal and pathological ageing. This study assessed the relationships between low-frequency EEG prestimulus brain states, the ERP, and behavioural outcomes in a simple equiprobable auditory Go/NoGo paradigm, comparing these for 20 young (M age  = 20.4 years) and 20 healthy older (M age  = 68.2 years) adults. Prestimulus delta and theta amplitudes were separately assessed; these were each dominant across the midline region, and reduced in the older adults. For each band, (within-subjects) trials were sorted into ten increasing prestimulus EEG levels for which separate ERPs were derived. The set of ten ERPs for each band-sort was then quantified by PCA, independently for each group (young, older adults). Four components were primarily assessed (P1, N1-1, P2/N2b complex, and P3), with each showing age-related change. Mean RT was comparable, but intra-individual RT variability increased in older adults. Prestimulus delta and theta each generally modulated component positivity, indicating broad influence on task processing. Prestimulus delta was primarily associated with the early sensory processes, and theta more with the later stimulus-specific processes; prestimulus theta also inversely modulated intra-individual RT variability across the groups. These prestimulus EEG-ERP dynamics were consistent between the young and older adults in each band for all components except the P2/N2b, suggesting that across the lifespan, Go/NoGo categorisation is differentially affected by prestimulus delta and theta. Copyright © 2017. Published by Elsevier B.V.

NICER Eyes on Bursting Stars

NASA Astrophysics Data System (ADS)

Kohler, Susanna

2018-03-01

What happens to a neutron stars accretion disk when its surface briefly explodes? A new instrument recently deployed at the International Space Station (ISS) is now watching bursts from neutron stars and reporting back.Deploying a New X-Ray MissionLaunch of NICER aboard a Falcon 9 rocket in June 2017. [NASA/Tony Gray]In early June of 2017, a SpaceX Dragon capsule on a Falcon 9 rocket launched on a resupply mission to the ISS. The pressurized interior of the Dragon contained the usual manifest of crew supplies, spacewalk equipment, and vehicle hardware. But the unpressurized trunk of the capsule held something a little different: the Neutron star Interior Composition Explorer (NICER).In the two weeks following launch, NICER was extracted from the SpaceX Dragon capsule and installed on the ISS. And by the end of the month, the instrument was already collecting its first data set: observations of a bright X-ray burst from Aql X-1, a neutron star accreting matter from a low-mass binary companion.Impact of BurstsNICERs goal is to provide a new view of neutron-star physics at X-ray energies of 0.212 keV a window that allows us to explore bursts of energy that neutron stars sometimes emit from their surfaces.Artists impression of an X-ray binary, in which a compact object accretes material from a companion star. [ESA/NASA/Felix Mirabel]In X-ray burster systems, hydrogen- and helium-rich material from a low-mass companion star piles up in an accretion disk around the neutron star. This material slowly funnels onto the neutron stars surface, forming a layer that gravitationally compresses and eventually becomes so dense and hot that runaway nuclear fusion ignites.Within seconds, the layer of material is burned up, producing a burst of emission from the neutron star that outshines even the inner regions of the hot accretion disk. Then more material funnels onto the neutron star and the process begins again.Though we have a good picture of the physics that causes these bursts

Event-related theta oscillatory substrates for facilitation and interference effects of negative emotion on children's cognition.

PubMed

Jiang, Zhongqing; Waters, Allison C; Liu, Ying; Li, Wenhui; Yang, Lizhu

2017-06-01

We investigated the brain oscillatory contribution to emotion-cognition interaction in young children. Five-year-old participants (n=27) underwent EEG recording while engaged in a color identification task. Each trial began with an emotional prime. Response times indicated whether emotional primes facilitated or interfered with performance. Related effects were detected in theta-band power over parietal-occipital cortex, early in the response epoch (<500ms). Children in the emotion facilitation group showed greater theta synchronization for negative stimuli. The opposite trend was observed in the interference group. Results suggest a role for theta oscillations in children's adaptive response to emotional content in cognitive performance. Copyright © 2017 Elsevier B.V. All rights reserved.

A burst compression and expansion technique for variable-rate users in satellite-switched TDMA networks

NASA Technical Reports Server (NTRS)

Budinger, James M.

1990-01-01

A burst compression and expansion technique is described for asynchronously interconnecting variable-data-rate users with cost-efficient ground terminals in a satellite-switched, time-division-multiple-access (SS/TDMA) network. Compression and expansion buffers in each ground terminal convert between lower rate, asynchronous, continuous-user data streams and higher-rate TDMA bursts synchronized with the satellite-switched timing. The technique described uses a first-in, first-out (FIFO) memory approach which enables the use of inexpensive clock sources by both the users and the ground terminals and obviates the need for elaborate user clock synchronization processes. A continous range of data rates from kilobits per second to that approaching the modulator burst rate (hundreds of megabits per second) can be accommodated. The technique was developed for use in the NASA Lewis Research Center System Integration, Test, and Evaluation (SITE) facility. Some key features of the technique have also been implemented in the gound terminals developed at NASA Lewis for use in on-orbit evaluation of the Advanced Communications Technology Satellite (ACTS) high burst rate (HBR) system.

The Third BATSE Gamma-Ray Burst Catalog

NASA Technical Reports Server (NTRS)

Meegan, Charles A.; Pendleton, Geoffrey N.; Briggs, Michael S.; Kouveliotou, Chryssa; Koshut, Thomas M.; Lestrade, John Patrick; Paciesas, William S.; McCollough, Michael L.; Brainerd, Jerome J.; Horack, John M.;

Prompt optical emission from gamma-ray bursts

NASA Astrophysics Data System (ADS)

Kehoe, Robert; Akerlof, Karl; Balsano, Richard; Barthelmy, Scott; Bloch, Jeff; Butterworth, Paul; Casperson, Don; Cline, Tom; Fletcher, Sandra; Frontera, Fillippo; Gisler, Galen; Heise, John; Hills, Jack; Hurley, Kevin; Lee, Brian; Marshall, Stuart; McKay, Tim; Pawl, Andrew; Piro, Luigi; Priedhorsky, Bill; Szymanski, John; Wren, Jim

The Robotic Optical Transient Search Experiment (ROTSE) seeks to measure contemporaneous and early afterglow optical emission from gamma-ray bursts (GRBs). The ROTSE-I telescope array has been fully automated and responding to burst alerts from the GRB Coordinates Network since March 1998, taking prompt optical data for 30 bursts in its first year. We will briefly review observations of GRB990123 which revealed the first detection of an optical burst occurring during the gamma-ray emission, reaching 9th magnitude at its peak. In addition, we present here preliminary optical results for seven other gamma-ray bursts. No other optical counterparts were seen in this analysis, and the best limiting senisitivities are mV > 13.0 at 14.7 seconds after the gamma-ray rise, and mmV > 16.4 at 62 minutes. These are the most stringent limits obtained for GRB optical counterpart brightness in the first hour after the burst. This analysis suggests that there is not a strong correlation between optical flux and gamma-ray emission.

Pressure vessel burst test program - Initial program paper

NASA Technical Reports Server (NTRS)

Cain, Maurice R.; Sharp, Douglas E.; Coleman, Michael D.; Webb, Bobby L.

1990-01-01

The current status of a pressure vessel burst test program, aimed at the study of the blast waves and fragmentation characteristics of ruptured gas-filled pressure vessels, is reported. The program includes a series of test plans, each involving multiple bursts with burst pressures ranging to 7500 psig. The discussion covers the identification of concerns and hazards, application of the data generated, and a brief review of the current methods for assessing vessel safety and burst parameters. Attention is also given to pretest activities, including completed vessel and facility/instrumentation preparation and results of completed preliminary burst tests.

Swift Gamma-Ray Burst Explorer: Mission Design for Rapid, Accurate Location of Gamma-ray Bursts

NASA Technical Reports Server (NTRS)

Bundas, David J.

2004-01-01

The Swift Gamma-ray Burst Explorer is a NASA Mid-sized Explorer (MIDEX) with the primary mission of determining the origins of Gamma-Ray Bursts (GRBs). It will be the first mission to autonomously respond to newly-discovered GRBs and provide immediate follow-up with narrow field instruments capable of multi-wavelength (UV, Optical, X-ray) observations. The characteristics of GRBs that are the key mission design drivers, are their non-repeating and brief duration bursts of multi-wavelength photons. In addition, rapid notification of the location and characteristics of the GRBs to ground-and-space-based observatories drive the end-to-end data analysis and distribution requirements.

Swift Gamma-ray Burst Explorer: Mission Design for Rapid, Accurate Location of Gamma-ray Bursts

NASA Technical Reports Server (NTRS)

Bundas, David J.

2005-01-01

The Swift Gamma-ray Burst Explorer is a NASA Mid-sized Explorer (MIDEX) with the primary mission of determining the origins of Gamma-Ray Bursts (GRBs). It will be the first mission to autonomously respond to newly-discovered GRBs and provide immediate follow-up with narrow field instruments capable of multi-wavelength (UT, Optical, X-ray) observations. The characteristics of GRBs that are the key mission design drivers, are their non-repeating and brief duration bursts of multi-wavelength photons. In addition, rapid notification of the location and characteristics of the GRBs to ground-and-space-based observatories drive the end-to-end data analysis and distribution requirements.

Hippocampal theta activity is selectively associated with contingency detection but not discrimination in rabbit discrimination-reversal eyeblink conditioning.

PubMed

Nokia, Miriam S; Wikgren, Jan

2010-04-01

The relative power of the hippocampal theta-band ( approximately 6 Hz) activity (theta ratio) is thought to reflect a distinct neural state and has been shown to affect learning rate in classical eyeblink conditioning in rabbits. We sought to determine if the theta ratio is mostly related to the detection of the contingency between the stimuli used in conditioning or also to the learning of more complex inhibitory associations when a highly demanding delay discrimination-reversal eyeblink conditioning paradigm is used. A high hippocampal theta ratio was not only associated with a fast increase in conditioned responding in general but also correlated with slow emergence of discriminative responding due to sustained responding to the conditioned stimulus not paired with an unconditioned stimulus. The results indicate that the neural state reflected by the hippocampal theta ratio is specifically linked to forming associations between stimuli rather than to the learning of inhibitory associations needed for successful discrimination. This is in line with the view that the hippocampus is responsible for contingency detection in the early phase of learning in eyeblink conditioning. (c) 2009 Wiley-Liss, Inc.

A Novel QKD-based Secure Edge Router Architecture Design for Burst Confidentiality in Optical Burst Switched Networks

NASA Astrophysics Data System (ADS)

Balamurugan, A. M.; Sivasubramanian, A.

2014-06-01

The Optical Burst Switching (OBS) is an emergent result to the technology issue that could achieve a viable network in future. They have the ability to meet the bandwidth requisite of those applications that call for intensive bandwidth. The field of optical transmission has undergone numerous advancements and is still being researched mainly due to the fact that optical data transmission can be done at enormous speeds. The concept of OBS is still far from perfection facing issues in case of security threat. The transfer of optical switching paradigm to optical burst switching faces serious downfall in the fields of burst aggregation, routing, authentication, dispute resolution and quality of service (QoS). This paper proposes a framework based on QKD based secure edge router architecture design to provide burst confidentiality. The QKD protocol offers high level of confidentiality as it is indestructible. The design architecture was implemented in FPGA using diverse models and the results were taken. The results show that the proposed model is suitable for real time secure routing applications of the Optical burst switched networks.

3rd Interplanetary Network Gamma-Ray Burst Website

NASA Astrophysics Data System (ADS)

Hurley, Kevin

1998-05-01

We announce the opening of the 3rd Interplanetary Network web site at http://ssl.berkeley.edu/ipn3/index.html This site presently has four parts: 1. A bibliography of over 3000 publications on gamma-ray bursts, 2. IPN data on all bursts triangulated up to February 1998, 3. A master list showing which spacecraft observed which bursts, 4. Preliminary IPN data on the latest bursts observed.

GRB 081029: A Gamma-Ray Burst with a Multi-Component Afterglow

NASA Technical Reports Server (NTRS)

Holland, Stephen T.; De Pasquale, Massimiliano; Mao, Jirong; Sakamoto, Takanori; Schady, Patricia; Covino, Stefano; Fan, Yi-Zhong; Jin, Zhi-Ping; D'Avanzo, Paolo; Antonelli, Angelo;

GRB 081029: A Gamma-Ray Burst with a Multi-Component Afterglow

NASA Technical Reports Server (NTRS)

Holland, Stephen T.; DePasquale, Massimiliano; Mao, Jirong; Sakamoto, Taka; Shady, Patricia; Covino, Stefano; Yi-Zhong, Fan; Zhi-Ping, Jin; D'Avanzo, Paolo; Antonelli, Angelo;

Theta and Alpha Oscillation Impairments in Autistic Spectrum Disorder Reflect Working Memory Deficit.

PubMed

Larrain-Valenzuela, Josefina; Zamorano, Francisco; Soto-Icaza, Patricia; Carrasco, Ximena; Herrera, Claudia; Daiber, Francisca; Aboitiz, Francisco; Billeke, Pablo

2017-10-30

A dysfunction in the excitatory-inhibitory (E/I) coordination in neuronal assembly has been proposed as a possible neurobiological mechanism of Autistic Spectrum Disorder (ASD). However, the potential impact of this mechanism in cognitive performance is not fully explored. Since the main consequence of E/I dysfunction is an impairment in oscillatory activity and its underlying cognitive computations, we assessed the electroencephalographic activity of ASD and typically developing (TD) subjects during a working-memory task. We found that ASD subjects committed more errors than TD subjects. Moreover, TD subjects demonstrated a parametric modulation in the power of alpha and theta band while ASD subjects did not demonstrate significant modulations. The preceding leads to significant differences between the groups in both the alpha power placed on the occipital cortex and the theta power placed on the left premotor and the right prefrontal cortex. The impaired theta modulation correlated with autistic symptoms. The results indicated that ASD may present an alteration in the recruitment of the oscillatory activity during working-memory, and this alteration could be related to the physiopathology of the disorder.

Interstellar absorption along the line of sight to Theta Carinae using Copernicus observations

NASA Technical Reports Server (NTRS)

Allen, M. M.; Jenkins, E. B.; Snow, T. P.

1992-01-01

A profile fitting technique is employed to identify the velocities and Doppler b values for H I and H II clouds along the line of sight to Theta Car. Total abundances and depletions for 12 elements, plus column densities for the J = 0 to J = 5 rotational levels of H2 are obtained. Electron densities for both clouds are calculated from the ratios of the fine-structure levels of C II and N II, obtaining 0.08/cu cm and 1.2/cu cm. The fine-structure levels of C I, which led to 120/cu cm, are used to calculate the neutral hydrogen density for the H I region. D I is also present in the data from the Theta Car line of sight, yielding a D/H ratio of 5 x 10 exp -6. Elemental depletions are calculated for the H I region as well. Comparison of the results for Theta Car and those for Zeta Oph and Alpha Vir shows that the absolute depletions are different; however, the relative depletions are remarkably stable for different physical conditions.

Observational properties of decameter type IV bursts

NASA Astrophysics Data System (ADS)

Melnik, Valentin; Brazhenko, Anatoly; Rucker, Helmut; Konovalenko, Alexander; Briand, Carine; Dorovskyy, Vladimir; Zarka, Philippe; Frantzusenko, Anatoly; Panchenko, Michael; Poedts, Stefan; Zaqarashvili, Teimuraz; Shergelashvili, Bidzina

2013-04-01

Oscillations of decameter type IV bursts were registered during observations of solar radio emission by UTR-2, URAN-2 and NDA in 2011-2012. Large majority of these bursts were accompanied by coronal mass ejections (CMEs), which were observed by SOHO and STEREO in the visible light. Only in some cases decameter type IV bursts were not associated with CMEs. The largest periods of oscillations P were some tens of minutes. There were some modes of long periods of oscillations simultaneously. Periods of oscillations in flux and in polarization profiles were close. Detailed properties of oscillations at different frequencies were analyzed on the example of two type IV bursts. One of them was observed on April 7, 2011 when a CME happened. Another one (August 1, 2011) was registered without any CME. The 7 April type IV burst had two periods in the frames 75-85 and 35-85 minutes. Interesting feature of these oscillations is decreasing periods with time. The observed decreasing rates dP/dt equaled 0.03-0.07. Concerning type IV burst observed on August 1, 2011 the period of its oscillations increases from 17 min. at 30 MHz to 44 min. at 10 MHz. Connection of type IV burst oscillations with oscillations of magnetic arches and CMEs at corresponding altitudes are discussed. The work is fulfilled in the frame of FP7 project "SOLSPANET".