Forward Inferences: From Activation to Long-Term Memory.

ERIC Educational Resources Information Center

Klin, Celia M.; Murray, John D.; Levine, William H.; Guzman, Alexandria E.

1999-01-01

Investigates the extent to which forward inferences are activated and encoded during reading, as well as their prevalence and their time course. Finds that inferences were encoded and retained in working memory in both high- and low-predictability conditions, and that high-predictability forward inferences were encoded into long-term memory.…

Working memory component processes: isolating BOLD signal changes.

PubMed

Motes, Michael A; Rypma, Bart

2010-01-15

The chronology of the component processes subserving working memory (WM) and hemodynamic response lags has hindered the use of fMRI for exploring neural substrates of WM. In the present study, however, participants completed full trials that involved encoding two or six letters, maintaining the memory set over a delay, and then deciding whether a probe was in the memory set or not. Additionally, they completed encode-only, encode-and-maintain, and encode-and-decide partial trials intermixed with the full trials. The inclusion of partial trials allowed for the isolation of BOLD signal changes to the different trial periods. The results showed that only lateral and medial prefrontal cortex regions differentially responded to the 2- and 6-letter memory sets over the trial periods, showing greater activation to 6-letter sets during the encode and maintain trial periods. Thus, the data showed the differential involvement of PFC in the encoding and maintenance of supra- and sub-capacity memory sets and show the efficacy of using fMRI partial trial methods to study WM component processes.

Working Memory Component Processes: Isolating BOLD Signal-Changes

PubMed Central

Motes, Michael A.; Rypma, Bart

2009-01-01

The chronology of the component processes subserving working memory (WM) and hemodynamic response lags have hindered the use of fMRI for exploring neural substrates of WM. In the present study, however, participants completed full trials that involved encoding two or six letters, maintaining the memory-set over a delay, and then deciding whether a probe was in the memory-set or not. Additionally, they completed encode only, encode and maintain, and encode and decide partial-trials intermixed with the full-trials. The inclusion of partial-trials allowed for the isolation of BOLD signal-changes to the different trial-periods. The results showed that only lateral and medial prefrontal cortex regions differentially responded to the 2- and 6-letter memory-sets over the trial-periods, showing greater activation to 6-letter sets during the encode and maintain trial-periods. Thus, the data showed the differential involvement of PFC in the encoding and maintenance of supra- and sub-capacity memory-sets and show the efficacy of using fMRI partial-trial methods to study WM component processes. PMID:19732840

The neuropsychology of emerging psychosis and the role of working memory in episodic memory encoding.

PubMed

Pflueger, Marlon O; Calabrese, Pasquale; Studerus, Erich; Zimmermann, Ronan; Gschwandtner, Ute; Borgwardt, Stefan; Aston, Jacqueline; Stieglitz, Rolf-Dieter; Riecher-Rössler, Anita

2018-01-01

Episodic memory encoding and working memory (WM) deficits are among the first cognitive signs and symptoms in the course of schizophrenia spectrum disorders. However, it is not clear whether the deficit pattern is generalized or specific in nature. We hypothesized that encoding deficits at an early stage of the disease might be due to the more fundamental WM deficits. We examined episodic memory encoding and WM by administering the California Verbal Learning Test, a 2-back task, and the Wisconsin Card Sorting Test in 90 first-episode psychosis (FE) patients and 116 individuals with an at-risk mental state for psychosis (ARMS) compared to 57 healthy subjects. Learning progress, but not span of apprehension, was diminished to a similar extent in both the ARMS and the FE. We showed that this was due to WM impairment by applying a structural equation approach. Thus, we conclude that verbal memory encoding deficits are secondary to primary WM impairment in emerging psychosis.

Age-related changes in working memory and the ability to ignore distraction.

PubMed

McNab, Fiona; Zeidman, Peter; Rutledge, Robb B; Smittenaar, Peter; Brown, Harriet R; Adams, Rick A; Dolan, Raymond J

2015-05-19

A weakened ability to effectively resist distraction is a potential basis for reduced working memory capacity (WMC) associated with healthy aging. Exploiting data from 29,631 users of a smartphone game, we show that, as age increases, working memory (WM) performance is compromised more by distractors presented during WM maintenance than distractors presented during encoding. However, with increasing age, the ability to exclude distraction at encoding is a better predictor of WMC in the absence of distraction. A significantly greater contribution of distractor filtering at encoding represents a potential compensation for reduced WMC in older age.

Episodic and working memory deficits in alcoholic Korsakoff patients: the continuity theory revisited.

PubMed

Pitel, Anne Lise; Beaunieux, Hélène; Witkowski, Thomas; Vabret, François; de la Sayette, Vincent; Viader, Fausto; Desgranges, Béatrice; Eustache, Francis

2008-07-01

The exact nature of episodic and working memory impairments in alcoholic Korsakoff patients (KS) remains unclear, as does the specificity of these neuropsychological deficits compared with those of non-Korsakoff alcoholics (AL). The goals of the present study were therefore to (1) specify the nature of episodic and working memory impairments in KS, (2) determine the specificity of the KS neuropsychological profile compared with the AL profile, and (3) observe the distribution of individual performances within the 2 patient groups. We investigated episodic memory (encoding and retrieval abilities, contextual memory and state of consciousness associated with memories), the slave systems of working memory (phonological loop, visuospatial sketchpad and episodic buffer) and executive functions (inhibition, flexibility, updating and integration abilities) in 14 strictly selected KS, 40 AL and 55 control subjects (CS). Compared with CS, KS displayed impairments of episodic memory encoding and retrieval, contextual memory, recollection, the slave systems of working memory and executive functions. Although episodic memory was more severely impaired in KS than in AL, the single specificity of the KS profile was a disproportionately large encoding deficit. Apart from organizational and updating abilities, the slave systems of working memory and inhibition, flexibility and integration abilities were impaired to the same extent in both alcoholic groups. However, some KS were unable to complete the most difficult executive tasks. There was only a partial overlap of individual performances by KS and AL for episodic memory and a total mixture of the 2 groups for working memory. Korsakoff's syndrome encompasses impairments of the different episodic and working memory components. AL and KS displayed similar profiles of episodic and working memory deficits, in accordance with neuroimaging investigations showing similar patterns of brain damage in both alcoholic groups.

Neutral details associated with emotional events are encoded: evidence from a cued recall paradigm.

PubMed

Mickley Steinmetz, Katherine R; Knight, Aubrey G; Kensinger, Elizabeth A

2016-11-01

Enhanced emotional memory often comes at the cost of memory for surrounding background information. Narrowed-encoding theories suggest that this is due to narrowed attention for emotional information at encoding, leading to impaired encoding of background information. Recent work has suggested that an encoding-based theory may be insufficient. Here, we examined whether cued recall-instead of previously used recognition memory tasks-would reveal evidence that non-emotional information associated with emotional information was effectively encoded. Participants encoded positive, negative, or neutral objects on neutral backgrounds. At retrieval, they were given either the item or the background as a memory cue and were asked to recall the associated scene element. Counter to narrowed-encoding theories, emotional items were more likely than neutral items to trigger recall of the associated background. This finding suggests that there is a memory trace of this contextual information and that emotional cues may facilitate retrieval of this information.

Self-initiated encoding facilitates object working memory in schizophrenia: implications for the etiology of working memory deficit.

PubMed

Kim, Jejoong; Park, Sohee; Shin, Yong-Wook; Jin Lee, Kyung; Kwon, Jun Soo

2006-02-15

Working memory (WM) deficit is present in a majority of patients with schizophrenia but it is unclear which components of WM are impaired. Past studies suggest that encoding may be compromised. One important determinant of encoding is the deployment of selective attention to the target stimulus. In addition, attention and encoding are modulated by motivational factors. In this study, we investigated the effects of self-initiated encoding (i.e., voluntary attention) on WM. 19 patients with schizophrenia and 19 matched control subjects participated in visual WM and control tasks. Encoding was manipulated by asking subjects to select from two face targets and memorize 1) one of the two identical faces (Non-preference condition), 2) one that is marked (Non-choice condition), and 3) one they prefer (Preference condition). WM accuracy for both location (spatial) and identity (object) was measured. Overall, patients with schizophrenia were less accurate and slower than the control subjects but the deficit was greater for object WM. However, patients were more accurate in object WM when they selected a preferred face as their target during encoding (preference condition) compared with the other two conditions. This effect was not significant for spatial WM. These results suggest that voluntary, self-initiated attention may facilitate object encoding especially if the selection of the target involves affective choice, and that attention may play different roles in encoding 'what' versus 'where' in WM. Since encoding affects all forms of memory, these results may have a more general implication for memory.

ERP Correlates of Encoding Success and Encoding Selectivity in Attention Switching

PubMed Central

Yeung, Nick

2016-01-01

Long-term memory encoding depends critically on effective processing of incoming information. The degree to which participants engage in effective encoding can be indexed in electroencephalographic (EEG) data by studying event-related potential (ERP) subsequent memory effects. The current study investigated ERP correlates of memory success operationalised with two different measures—memory selectivity and global memory—to assess whether previously observed ERP subsequent memory effects reflect focused encoding of task-relevant information (memory selectivity), general encoding success (global memory), or both. Building on previous work, the present study combined an attention switching paradigm—in which participants were presented with compound object-word stimuli and switched between attending to the object or the word across trials—with a later recognition memory test for those stimuli, while recording their EEG. Our results provided clear evidence that subsequent memory effects resulted from selective attentional focusing and effective top-down control (memory selectivity) in contrast to more general encoding success effects (global memory). Further analyses addressed the question of whether successful encoding depended on similar control mechanisms to those involved in attention switching. Interestingly, differences in the ERP correlates of attention switching and successful encoding, particularly during the poststimulus period, indicated that variability in encoding success occurred independently of prestimulus demands for top-down cognitive control. These results suggest that while effects of selective attention and selective encoding co-occur behaviourally their ERP correlates are at least partly dissociable. PMID:27907075

Working memory accuracy for multiple targets is driven by reward expectation and stimulus contrast with different time-courses.

PubMed

Klink, P Christiaan; Jeurissen, Danique; Theeuwes, Jan; Denys, Damiaan; Roelfsema, Pieter R

2017-08-22

The richness of sensory input dictates that the brain must prioritize and select information for further processing and storage in working memory. Stimulus salience and reward expectations influence this prioritization but their relative contributions and underlying mechanisms are poorly understood. Here we investigate how the quality of working memory for multiple stimuli is determined by priority during encoding and later memory phases. Selective attention could, for instance, act as the primary gating mechanism when stimuli are still visible. Alternatively, observers might still be able to shift priorities across memories during maintenance or retrieval. To distinguish between these possibilities, we investigated how and when reward cues determine working memory accuracy and found that they were only effective during memory encoding. Previously learned, but currently non-predictive, color-reward associations had a similar influence, which gradually weakened without reinforcement. Finally, we show that bottom-up salience, manipulated through varying stimulus contrast, influences memory accuracy during encoding with a fundamentally different time-course than top-down reward cues. While reward-based effects required long stimulus presentation, the influence of contrast was strongest with brief presentations. Our results demonstrate how memory resources are distributed over memory targets and implicates selective attention as a main gating mechanism between sensory and memory systems.

Control of information in working memory: Encoding and removal of distractors in the complex-span paradigm.

PubMed

Oberauer, Klaus; Lewandowsky, Stephan

2016-11-01

The article reports four experiments with complex-span tasks in which encoding of memory items alternates with processing of distractors. The experiments test two assumptions of a computational model of complex span, SOB-CS: (1) distractor processing impairs memory because distractors are encoded into working memory, thereby interfering with memoranda; and (2) free time following distractors is used to remove them from working memory by unbinding their representations from list context. Experiment 1 shows that distractors are erroneously chosen for recall more often than not-presented stimuli, demonstrating that distractors are encoded into memory. Distractor intrusions declined with longer free time, as predicted by distractor removal. Experiment 2 shows these effects even when distractors precede the memory list, ruling out an account based on selective rehearsal of memoranda during free time. Experiments 3 and 4 test the notion that distractors decay over time. Both experiments show that, contrary to the notion of distractor decay, the chance of a distractor intruding at test does not decline with increasing time since encoding of that distractor. Experiment 4 provides additional evidence against the prediction from distractor decay that distractor intrusions decline over an unfilled retention interval. Taken together, the results support SOB-CS and rule out alternative explanations. Data and simulation code are available on Open Science Framework: osf.io/3ewh7. Copyright © 2016 Elsevier B.V. All rights reserved.

Working memory is not fixed-capacity: More active storage capacity for real-world objects than for simple stimuli

PubMed Central

Brady, Timothy F.; Störmer, Viola S.; Alvarez, George A.

2016-01-01

Visual working memory is the cognitive system that holds visual information active to make it resistant to interference from new perceptual input. Information about simple stimuli—colors and orientations—is encoded into working memory rapidly: In under 100 ms, working memory ‟fills up,” revealing a stark capacity limit. However, for real-world objects, the same behavioral limits do not hold: With increasing encoding time, people store more real-world objects and do so with more detail. This boost in performance for real-world objects is generally assumed to reflect the use of a separate episodic long-term memory system, rather than working memory. Here we show that this behavioral increase in capacity with real-world objects is not solely due to the use of separate episodic long-term memory systems. In particular, we show that this increase is a result of active storage in working memory, as shown by directly measuring neural activity during the delay period of a working memory task using EEG. These data challenge fixed-capacity working memory models and demonstrate that working memory and its capacity limitations are dependent upon our existing knowledge. PMID:27325767

Working memory is not fixed-capacity: More active storage capacity for real-world objects than for simple stimuli.

PubMed

Brady, Timothy F; Störmer, Viola S; Alvarez, George A

2016-07-05

Visual working memory is the cognitive system that holds visual information active to make it resistant to interference from new perceptual input. Information about simple stimuli-colors and orientations-is encoded into working memory rapidly: In under 100 ms, working memory ‟fills up," revealing a stark capacity limit. However, for real-world objects, the same behavioral limits do not hold: With increasing encoding time, people store more real-world objects and do so with more detail. This boost in performance for real-world objects is generally assumed to reflect the use of a separate episodic long-term memory system, rather than working memory. Here we show that this behavioral increase in capacity with real-world objects is not solely due to the use of separate episodic long-term memory systems. In particular, we show that this increase is a result of active storage in working memory, as shown by directly measuring neural activity during the delay period of a working memory task using EEG. These data challenge fixed-capacity working memory models and demonstrate that working memory and its capacity limitations are dependent upon our existing knowledge.

The impact of threat of shock-induced anxiety on memory encoding and retrieval

PubMed Central

Bolton, Sorcha

2017-01-01

Anxiety disorders are the most common mental health disorders, and daily transient feelings of anxiety (or “stress”) are ubiquitous. However, the precise impact of both transient and pathological anxiety on higher-order cognitive functions, including short- and long-term memory, is poorly understood. A clearer understanding of the anxiety–memory relationship is important as one of the core symptoms of anxiety, most prominently in post-traumatic stress disorder (PTSD), is intrusive reexperiencing of traumatic events in the form of vivid memories. This study therefore aimed to examine the impact of induced anxiety (threat of shock) on memory encoding and retrieval. Eighty-six healthy participants completed tasks assessing: visuospatial working memory, verbal recognition, face recognition, and associative memory. Critically, anxiety was manipulated within-subjects: information was both encoded and retrieved under threat of shock and safe (no shock) conditions. Results revealed that visuospatial working memory was enhanced when information was encoded and subsequently retrieved under threat, and that threat impaired the encoding of faces regardless of the condition in which it was retrieved. Episodic memory and verbal short-term recognition were, however, unimpaired. These findings indicate that transient anxiety in healthy individuals has domain-specific, rather than domain-general, impacts on memory. Future studies would benefit from expanding these findings into anxiety disorder patients to delineate the differences between adaptive and maladaptive responding. PMID:28916628

Visuospatial declarative learning despite profound verbal declarative amnesia in Korsakoff's syndrome.

PubMed

Oudman, Erik; Postma, Albert; Nijboer, Tanja C W; Wijnia, Jan W; Van der Stigchel, Stefan

2017-03-20

Korsakoff's syndrome (KS) is a neuropsychiatric disorder characterised by severe amnesia. Although the presence of impairments in memory has long been acknowledged, there is a lack of knowledge about the precise characteristics of declarative memory capacities in order to implement memory rehabilitation. In this study, we investigated the extent to which patients diagnosed with KS have preserved declarative memory capacities in working memory, long-term memory encoding or long-term memory recall operations, and whether these capacities are most preserved for verbal or visuospatial content. The results of this study demonstrate that patients with KS have compromised declarative memory functioning on all memory indices. Performance was lowest for the encoding operation compared to the working memory and delayed recall operation. With respect to the content, visuospatial memory was relatively better preserved than verbal memory. All memory operations functioned suboptimally, although the most pronounced disturbance was found in verbal memory encoding. Based on the preserved declarative memory capacities in patients, visuospatial memory can form a more promising target for compensatory memory rehabilitation than verbal memory. It is therefore relevant to increase the number of spatial cues in memory rehabilitation for KS patients.

Putting the Pieces Together: The Role of Dorsolateral Prefrontal Cortex in Relational Memory Encoding

ERIC Educational Resources Information Center

Blumenfeld, Robert S.; Parks, Colleen M.; Yonelinas, Andrew P.; Ranganath, Charan

2011-01-01

Results from fMRI have strongly supported the idea that the ventrolateral PFC (VLPFC) contributes to successful memory formation, but the role the dorsolateral PFC (DLPFC) in memory encoding is more controversial. Some findings suggest that the DLPFC is recruited when one is processing relationships between items in working memory, and this…

Minimal-memory realization of pearl-necklace encoders of general quantum convolutional codes

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

Houshmand, Monireh; Hosseini-Khayat, Saied

2011-02-15

Quantum convolutional codes, like their classical counterparts, promise to offer higher error correction performance than block codes of equivalent encoding complexity, and are expected to find important applications in reliable quantum communication where a continuous stream of qubits is transmitted. Grassl and Roetteler devised an algorithm to encode a quantum convolutional code with a ''pearl-necklace'' encoder. Despite their algorithm's theoretical significance as a neat way of representing quantum convolutional codes, it is not well suited to practical realization. In fact, there is no straightforward way to implement any given pearl-necklace structure. This paper closes the gap between theoretical representation andmore » practical implementation. In our previous work, we presented an efficient algorithm to find a minimal-memory realization of a pearl-necklace encoder for Calderbank-Shor-Steane (CSS) convolutional codes. This work is an extension of our previous work and presents an algorithm for turning a pearl-necklace encoder for a general (non-CSS) quantum convolutional code into a realizable quantum convolutional encoder. We show that a minimal-memory realization depends on the commutativity relations between the gate strings in the pearl-necklace encoder. We find a realization by means of a weighted graph which details the noncommutative paths through the pearl necklace. The weight of the longest path in this graph is equal to the minimal amount of memory needed to implement the encoder. The algorithm has a polynomial-time complexity in the number of gate strings in the pearl-necklace encoder.« less

Male veterans with PTSD exhibit aberrant neural dynamics during working memory processing: an MEG study

PubMed Central

McDermott, Timothy J.; Badura-Brack, Amy S.; Becker, Katherine M.; Ryan, Tara J.; Khanna, Maya M.; Heinrichs-Graham, Elizabeth; Wilson, Tony W.

2016-01-01

Background Posttraumatic stress disorder (PTSD) is associated with executive functioning deficits, including disruptions in working memory. In this study, we examined the neural dynamics of working memory processing in veterans with PTSD and a matched healthy control sample using magnetoencephalography (MEG). Methods Our sample of recent combat veterans with PTSD and demographically matched participants without PTSD completed a working memory task during a 306-sensor MEG recording. The MEG data were preprocessed and transformed into the time-frequency domain. Significant oscillatory brain responses were imaged using a beamforming approach to identify spatiotemporal dynamics. Results Fifty-one men were included in our analyses: 27 combat veterans with PTSD and 24 controls. Across all participants, a dynamic wave of neural activity spread from posterior visual cortices to left frontotemporal regions during encoding, consistent with a verbal working memory task, and was sustained throughout maintenance. Differences related to PTSD emerged during early encoding, with patients exhibiting stronger α oscillatory responses than controls in the right inferior frontal gyrus (IFG). Differences spread to the right supramarginal and temporal cortices during later encoding where, along with the right IFG, they persisted throughout the maintenance period. Limitations This study focused on men with combat-related PTSD using a verbal working memory task. Future studies should evaluate women and the impact of various traumatic experiences using diverse tasks. Conclusion Posttraumatic stress disorder is associated with neurophysiological abnormalities during working memory encoding and maintenance. Veterans with PTSD engaged a bilateral network, including the inferior prefrontal cortices and supramarginal gyri. Right hemispheric neural activity likely reflects compensatory processing, as veterans with PTSD work to maintain accurate performance despite known cognitive deficits associated with the disorder. PMID:26645740

Working memory encoding delays top-down attention to visual cortex.

PubMed

Scalf, Paige E; Dux, Paul E; Marois, René

2011-09-01

The encoding of information from one event into working memory can delay high-level, central decision-making processes for subsequent events [e.g., Jolicoeur, P., & Dell'Acqua, R. The demonstration of short-term consolidation. Cognitive Psychology, 36, 138-202, 1998, doi:10.1006/cogp.1998.0684]. Working memory, however, is also believed to interfere with the deployment of top-down attention [de Fockert, J. W., Rees, G., Frith, C. D., & Lavie, N. The role of working memory in visual selective attention. Science, 291, 1803-1806, 2001, doi:10.1126/science.1056496]. It is, therefore, possible that, in addition to delaying central processes, the engagement of working memory encoding (WME) also postpones perceptual processing as well. Here, we tested this hypothesis with time-resolved fMRI by assessing whether WME serially postpones the action of top-down attention on low-level sensory signals. In three experiments, participants viewed a skeletal rapid serial visual presentation sequence that contained two target items (T1 and T2) separated by either a short (550 msec) or long (1450 msec) SOA. During single-target runs, participants attended and responded only to T1, whereas in dual-target runs, participants attended and responded to both targets. To determine whether T1 processing delayed top-down attentional enhancement of T2, we examined T2 BOLD response in visual cortex by subtracting the single-task waveforms from the dual-task waveforms for each SOA. When the WME demands of T1 were high (Experiments 1 and 3), T2 BOLD response was delayed at the short SOA relative to the long SOA. This was not the case when T1 encoding demands were low (Experiment 2). We conclude that encoding of a stimulus into working memory delays the deployment of attention to subsequent target representations in visual cortex.

Neutral Details Associated with Emotional Events are Encoded: Evidence from a Cued Recall Paradigm

PubMed Central

Steinmetz, Katherine R. Mickley; Knight, Aubrey G.; Kensinger, Elizabeth A.

2015-01-01

Enhanced emotional memory often comes at the cost of memory for surrounding background information. Narrowed-encoding theories suggest that this is due to narrowed attention for emotional information at encoding, leading to impaired encoding of background information. Recent work has suggested that an encoding-based theory may be insufficient. Here, we examined whether cued recall – instead of previously used recognition memory tasks - would reveal evidence that non-emotional information associated with emotional information was effectively encoded. Participants encoded positive, negative, or neutral objects on neutral backgrounds. At retrieval, they were given either the item or the background as a memory cue and were asked to recall the associated scene element. Counter to narrowed-encoding theories, emotional items were more likely than neutral items to trigger recall of the associated background. This finding suggests that there is a memory trace of this contextual information and that emotional cues may facilitate retrieval of this information. PMID:26220708

Applicability of the Compensatory Encoding Model in Foreign Language Reading: An Investigation with Chinese College English Language Learners

PubMed Central

Han, Feifei

2017-01-01

While some first language (L1) reading models suggest that inefficient word recognition and small working memory tend to inhibit higher-level comprehension processes; the Compensatory Encoding Model maintains that slow word recognition and small working memory do not normally hinder reading comprehension, as readers are able to operate metacognitive strategies to compensate for inefficient word recognition and working memory limitation as long as readers process a reading task without time constraint. Although empirical evidence is accumulated for support of the Compensatory Encoding Model in L1 reading, there is lack of research for testing of the Compensatory Encoding Model in foreign language (FL) reading. This research empirically tested the Compensatory Encoding Model in English reading among Chinese college English language learners (ELLs). Two studies were conducted. Study one focused on testing whether reading condition varying time affects the relationship between word recognition, working memory, and reading comprehension. Students were tested on a computerized English word recognition test, a computerized Operation Span task, and reading comprehension in time constraint and non-time constraint reading. The correlation and regression analyses showed that the strength of association was much stronger between word recognition, working memory, and reading comprehension in time constraint than that in non-time constraint reading condition. Study two examined whether FL readers were able to operate metacognitive reading strategies as a compensatory way of reading comprehension for inefficient word recognition and working memory limitation in non-time constraint reading. The participants were tested on the same computerized English word recognition test and Operation Span test. They were required to think aloud while reading and to complete the comprehension questions. The think-aloud protocols were coded for concurrent use of reading strategies, classified into language-oriented strategies, content-oriented strategies, re-reading, pausing, and meta-comment. The correlation analyses showed that while word recognition and working memory were only significantly related to frequency of language-oriented strategies, re-reading, and pausing, but not with reading comprehension. Jointly viewed, the results of the two studies, complimenting each other, supported the applicability of the Compensatory Encoding Model in FL reading with Chinese college ELLs. PMID:28522984

Applicability of the Compensatory Encoding Model in Foreign Language Reading: An Investigation with Chinese College English Language Learners.

PubMed

Han, Feifei

2017-01-01

While some first language (L1) reading models suggest that inefficient word recognition and small working memory tend to inhibit higher-level comprehension processes; the Compensatory Encoding Model maintains that slow word recognition and small working memory do not normally hinder reading comprehension, as readers are able to operate metacognitive strategies to compensate for inefficient word recognition and working memory limitation as long as readers process a reading task without time constraint. Although empirical evidence is accumulated for support of the Compensatory Encoding Model in L1 reading, there is lack of research for testing of the Compensatory Encoding Model in foreign language (FL) reading. This research empirically tested the Compensatory Encoding Model in English reading among Chinese college English language learners (ELLs). Two studies were conducted. Study one focused on testing whether reading condition varying time affects the relationship between word recognition, working memory, and reading comprehension. Students were tested on a computerized English word recognition test, a computerized Operation Span task, and reading comprehension in time constraint and non-time constraint reading. The correlation and regression analyses showed that the strength of association was much stronger between word recognition, working memory, and reading comprehension in time constraint than that in non-time constraint reading condition. Study two examined whether FL readers were able to operate metacognitive reading strategies as a compensatory way of reading comprehension for inefficient word recognition and working memory limitation in non-time constraint reading. The participants were tested on the same computerized English word recognition test and Operation Span test. They were required to think aloud while reading and to complete the comprehension questions. The think-aloud protocols were coded for concurrent use of reading strategies, classified into language-oriented strategies, content-oriented strategies, re-reading, pausing, and meta-comment. The correlation analyses showed that while word recognition and working memory were only significantly related to frequency of language-oriented strategies, re-reading, and pausing, but not with reading comprehension. Jointly viewed, the results of the two studies, complimenting each other, supported the applicability of the Compensatory Encoding Model in FL reading with Chinese college ELLs.

Hippocampal-targeted Theta-burst Stimulation Enhances Associative Memory Formation.

PubMed

Tambini, Arielle; Nee, Derek Evan; D'Esposito, Mark

2018-06-19

The hippocampus plays a critical role in episodic memory, among other cognitive functions. However, few tools exist to causally manipulate hippocampal function in healthy human participants. Recent work has targeted hippocampal-cortical networks by performing TMS to a region interconnected with the hippocampus, posterior inferior parietal cortex (pIPC). Such hippocampal-targeted TMS enhances associative memory and influences hippocampal functional connectivity. However, it is currently unknown which stages of mnemonic processing (encoding or retrieval) are affected by hippocampal-targeted TMS. Here, we examined whether hippocampal-targeted TMS influences the initial encoding of associations (vs. items) into memory. To selectively influence encoding and not retrieval, we performed continuous theta-burst TMS before participants encoded object-location associations and assessed memory after the direct effect of stimulation dissipated. Relative to control TMS and baseline memory, pIPC TMS enhanced associative memory success and confidence. Item memory was unaffected, demonstrating a selective influence on associative versus item memory. The strength of hippocampal-pIPC functional connectivity predicted TMS-related memory benefits, which was mediated by parahippocampal and retrosplenial cortices. Our findings indicate that hippocampal-targeted TMS can specifically modulate the encoding of new associations into memory without directly influencing retrieval processes and suggest that the ability to influence associative memory may be related to the fidelity of hippocampal TMS targeting. Our results support the notion that pIPC TMS may serve as a potential tool for manipulating hippocampal function in healthy participants. Nonetheless, future work combining hippocampal-targeted continuous theta-burst TMS with neuroimaging is needed to better understand the neural basis of TMS-induced memory changes.

Prefrontal Engagement during Source Memory Retrieval Depends on the Prior Encoding Task

PubMed Central

Kuo, Trudy Y.; Van Petten, Cyma

2008-01-01

The prefrontal cortex is strongly engaged by some, but not all, episodic memory tests. Prior work has shown that source recognition tests—those that require memory for conjunctions of studied attributes—yield deficient performance in patients with prefrontal damage and greater prefrontal activity in healthy subjects, as compared to simple recognition tests. Here, we tested the hypothesis that there is no intrinsic relationship between the prefrontal cortex and source memory, but that the prefrontal cortex is engaged by the demand to retrieve weakly encoded relationships. Subjects attempted to remember object/color conjunctions after an encoding task that focused on object identity alone, and an integrative encoding task that encouraged attention to object/color relationships. After the integrative encoding task, the late prefrontal brain electrical activity that typically occurs in source memory tests was eliminated. Earlier brain electrical activity related to successful recognition of the objects was unaffected by the nature of prior encoding. PMID:16839287

What–where–when memory and encoding strategies in healthy aging

PubMed Central

2016-01-01

Older adults exhibit disproportionate impairments in memory for item-associations. These impairments may stem from an inability to self-initiate deep encoding strategies. The present study investigates this using the “treasure-hunt task”; a what–where–when style episodic memory test that requires individuals to “hide” items around complex scenes. This task separately assesses memory for item, location, and temporal order, as well as bound what–where–when information. The results suggest that older adults are able to ameliorate integration memory deficits by using self-initiated encoding strategies when these are externally located and therefore place reduced demands on working memory and attentional resources. PMID:26884230

Prefrontal responses to digit span memory phases in patients with post-traumatic stress disorder (PTSD): a functional near infrared spectroscopy study.

PubMed

Tian, Fenghua; Yennu, Amarnath; Smith-Osborne, Alexa; Gonzalez-Lima, F; North, Carol S; Liu, Hanli

2014-01-01

Neuroimaging studies of post-traumatic stress disorder (PTSD)-related memory impairments have consistently implicated abnormal activities in the frontal and parietal lobes. However, most studies have used block designs and could not dissociate the multiple phases of working memory. In this study, the involvement of the prefrontal cortex in working memory phases was assessed among veterans with PTSD and age-/gender-matched healthy controls. Multichannel functional near infrared spectroscopy (fNIRS) was utilized to measure prefrontal cortex hemodynamic activations during memory of neutral (i.e., not trauma-related) forward and backward digit span tasks. An event-related experimental design was utilized to dissociate the different phases (i.e., encoding, maintenance and retrieval) of working memory. The healthy controls showed robust hemodynamic activations during the encoding and retrieval processes. In contrast, the veterans with PTSD were found to have activations during the encoding process, but followed by distinct deactivations during the retrieval process. The PTSD participants, but not the controls, appeared to suppress prefrontal activity during memory retrieval. This deactivation was more pronounced in the right dorsolateral prefrontal cortex during the retrieval phase. These deactivations in PTSD patients might implicate an active inhibition of dorsolateral prefrontal neural activity during retrieval of working memory.

Compromised encoding of proprioceptively determined joint angles in older adults: the role of working memory and attentional load.

PubMed

Goble, Daniel J; Mousigian, Marianne A; Brown, Susan H

2012-01-01

Perceiving the positions and movements of one's body segments (i.e., proprioception) is critical for movement control. However, this ability declines with older age as has been demonstrated by joint angle matching paradigms in the absence of vision. The aim of the present study was to explore the extent to which reduced working memory and attentional load influence older adult proprioceptive matching performance. Older adults with relatively HIGH versus LOW working memory ability as determined by backward digit span and healthy younger adults, performed memory-based elbow position matching with and without attentional load (i.e., counting by 3 s) during target position encoding. Even without attentional load, older adults with LOW digit spans (i.e., 4 digits or less) had larger matching errors than younger adults. Further, LOW older adults made significantly greater errors when attentional loads were present during proprioceptive target encoding as compared to both younger and older adults with HIGH digit span scores (i.e., 5 digits or greater). These results extend previous position matching results that suggested greater errors in older adults were due to degraded input signals from peripheral mechanoreceptors. Specifically, the present work highlights the role cognitive factors play in the assessment of older adult proprioceptive acuity using memory-based matching paradigms. Older adults with LOW working memory appear prone to compromised proprioceptive encoding, especially when secondary cognitive tasks must be concurrently executed. This may ultimately result in poorer performance on various activities of daily living.

The list-composition effect in memory for emotional and neutral pictures: Differential contribution of ventral and dorsal attention networks to successful encoding.

PubMed

Barnacle, Gemma E; Montaldi, Daniela; Talmi, Deborah; Sommer, Tobias

2016-09-01

The Emotional enhancement of memory (EEM) is observed in immediate free-recall memory tests when emotional and neutral stimuli are encoded and tested together ("mixed lists"), but surprisingly, not when they are encoded and tested separately ("pure lists"). Here our aim was to investigate whether the effect of list-composition (mixed versus pure lists) on the EEM is due to differential allocation of attention. We scanned participants with fMRI during encoding of semantically-related emotional (negative valence only) and neutral pictures. Analysis of memory performance data replicated previous work, demonstrating an interaction between list composition and emotional valence. In mixed lists, neural subsequent memory effects in the dorsal attention network were greater for neutral stimulus encoding, while neural subsequent memory effects for emotional stimuli were found in a region associated with the ventral attention network. These results imply that when life experiences include both emotional and neutral elements, memory for the latter is more highly correlated with neural activity representing goal-directed attention processing at encoding. Copyright © 2016. Published by Elsevier Ltd.

Dissecting contributions of prefrontal cortex and fusiform face area to face working memory.

PubMed

Druzgal, T Jason; D'Esposito, Mark

2003-08-15

Interactions between prefrontal cortex (PFC) and stimulus-specific visual cortical association areas are hypothesized to mediate visual working memory in behaving monkeys. To clarify the roles for homologous regions in humans, event-related fMRI was used to assess neural activity in PFC and fusiform face area (FFA) of subjects performing a delay-recognition task for faces. In both PFC and FFA, activity increased parametrically with memory load during encoding and maintenance of face stimuli, despite quantitative differences in the magnitude of activation. Moreover, timing differences in PFC and FFA activation during memory encoding and retrieval implied a context dependence in the flow of neural information. These results support existing neurophysiological models of visual working memory developed in the nonhuman primate.

Brain activity related to working memory for temporal order and object information.

PubMed

Roberts, Brooke M; Libby, Laura A; Inhoff, Marika C; Ranganath, Charan

2017-06-08

Maintaining items in an appropriate sequence is important for many daily activities; however, remarkably little is known about the neural basis of human temporal working memory. Prior work suggests that the prefrontal cortex (PFC) and medial temporal lobe (MTL), including the hippocampus, play a role in representing information about temporal order. The involvement of these areas in successful temporal working memory, however, is less clear. Additionally, it is unknown whether regions in the PFC and MTL support temporal working memory across different timescales, or at coarse or fine levels of temporal detail. To address these questions, participants were scanned while completing 3 working memory task conditions (Group, Position and Item) that were matched in terms of difficulty and the number of items to be actively maintained. Group and Position trials probed temporal working memory processes, requiring the maintenance of hierarchically organized coarse and fine temporal information, respectively. To isolate activation related to temporal working memory, Group and Position trials were contrasted against Item trials, which required detailed working memory maintenance of visual objects. Results revealed that working memory encoding and maintenance of temporal information relative to visual information was associated with increased activation in dorsolateral PFC (DLPFC), and perirhinal cortex (PRC). In contrast, maintenance of visual details relative to temporal information was characterized by greater activation of parahippocampal cortex (PHC), medial and anterior PFC, and retrosplenial cortex. In the hippocampus, a dissociation along the longitudinal axis was observed such that the anterior hippocampus was more active for working memory encoding and maintenance of visual detail information relative to temporal information, whereas the posterior hippocampus displayed the opposite effect. Posterior parietal cortex was the only region to show sensitivity to temporal working memory across timescales, and was particularly involved in the encoding and maintenance of fine temporal information relative to maintenance of temporal information at more coarse timescales. Collectively, these results highlight the involvement of PFC and MTL in temporal working memory processes, and suggest a dissociation in the type of working memory information represented along the longitudinal axis of the hippocampus. Copyright © 2017 Elsevier B.V. All rights reserved.

Remembering faces and scenes: The mixed-category advantage in visual working memory.

PubMed

Jiang, Yuhong V; Remington, Roger W; Asaad, Anthony; Lee, Hyejin J; Mikkalson, Taylor C

2016-09-01

We examined the mixed-category memory advantage for faces and scenes to determine how domain-specific cortical resources constrain visual working memory. Consistent with previous findings, visual working memory for a display of 2 faces and 2 scenes was better than that for a display of 4 faces or 4 scenes. This pattern was unaffected by manipulations of encoding duration. However, the mixed-category advantage was carried solely by faces: Memory for scenes was not better when scenes were encoded with faces rather than with other scenes. The asymmetry between faces and scenes was found when items were presented simultaneously or sequentially, centrally, or peripherally, and when scenes were drawn from a narrow category. A further experiment showed a mixed-category advantage in memory for faces and bodies, but not in memory for scenes and objects. The results suggest that unique category-specific interactions contribute significantly to the mixed-category advantage in visual working memory. (PsycINFO Database Record (c) 2016 APA, all rights reserved).

Randomized Controlled Trial Considering Varied Exercises for Reducing Proactive Memory Interference.

PubMed

Frith, Emily; Sng, Eveleen; Loprinzi, Paul D

2018-06-11

We evaluated the effects of exercise on proactive memory interference. Study 1 ( n = 88) employed a 15-min treadmill walking protocol, while Study 2 ( n = 88) included a 15-min bout of progressive maximal exertion treadmill exercise. Each study included four distinct groups, in which groups of 22 participants each were randomly assigned to: (a) exercise before memory encoding, (b) a control group with no exercise, (c) exercise during memory encoding, and (d) exercise after memory encoding (i.e., during memory consolidation). We used the Rey Auditory Verbal Learning Test (RAVLT) to assess proactive memory interference. In both studies, the group that exercised prior to memory encoding recalled the most words from list B (distractor list) of the RAVLT, though group differences were not statistically significant for Study 1 (walking exercise) ( p = 0.521) or Study 2 (high-intensity exercise) ( p = 0.068). In this sample of young adults, high intensity exercise prior to memory encoding showed a non-significant tendency to attenuate impairments in recall attributable to proactive memory interference. Thus, future work with larger samples is needed to clarify potential beneficial effects of exercise for reducing proactive memory interference.

The Benefit of Surface Uniformity for Encoding Boundary Features in Visual Working Memory

ERIC Educational Resources Information Center

Kim, Sung-Ho; Kim, Jung-Oh

2011-01-01

Using a change detection paradigm, the present study examined an object-based encoding benefit in visual working memory (VWM) for two boundary features (two orientations in Experiments 1-2 and two shapes in Experiments 3-4) assigned to a single object. Participants remembered more boundary features when they were conjoined into a single object of…

Fine-grained versus categorical: Pupil size differentiates between strategies for spatial working memory performance.

PubMed

Starc, Martina; Anticevic, Alan; Repovš, Grega

2017-05-01

Pupillometry provides an accessible option to track working memory processes with high temporal resolution. Several studies showed that pupil size increases with the number of items held in working memory; however, no study has explored whether pupil size also reflects the quality of working memory representations. To address this question, we used a spatial working memory task to investigate the relationship of pupil size with spatial precision of responses and indicators of reliance on generalized spatial categories. We asked 30 participants (15 female, aged 19-31) to remember the position of targets presented at various locations along a hidden radial grid. After a delay, participants indicated the remembered location with a high-precision joystick providing a parametric measure of trial-to-trial accuracy. We recorded participants' pupil dilations continuously during task performance. Results showed a significant relation between pupil dilation during preparation/early encoding and the precision of responses, possibly reflecting the attentional resources devoted to memory encoding. In contrast, pupil dilation at late maintenance and response predicted larger shifts of responses toward prototypical locations, possibly reflecting larger reliance on categorical representation. On an intraindividual level, smaller pupil dilations during encoding predicted larger dilations during late maintenance and response. On an interindividual level, participants relying more on categorical representation also produced larger precision errors. The results confirm the link between pupil size and the quality of spatial working memory representation. They suggest compensatory strategies of spatial working memory performance-loss of precise spatial representation likely increases reliance on generalized spatial categories. © 2017 Society for Psychophysiological Research.

Spatiotemporal encoding of search strategies by prefrontal neurons.

PubMed

Chiang, Feng-Kuei; Wallis, Joni D

2018-05-08

Working memory is capacity-limited. In everyday life we rarely notice this limitation, in part because we develop behavioral strategies that help mitigate the capacity limitation. How behavioral strategies are mediated at the neural level is unclear, but a likely locus is lateral prefrontal cortex (LPFC). Neurons in LPFC play a prominent role in working memory and have been shown to encode behavioral strategies. To examine the role of LPFC in overcoming working-memory limitations, we recorded the activity of LPFC neurons in animals trained to perform a serial self-ordered search task. This task measured the ability to prospectively plan the selection of unchosen spatial search targets while retrospectively tracking which targets were previously visited. We found that individual LPFC neurons encoded the spatial location of the current search target but also encoded the spatial location of targets up to several steps away in the search sequence. Neurons were more likely to encode prospective than retrospective targets. When subjects used a behavioral strategy of stereotyped target selection, mitigating the working-memory requirements of the task, not only did the number of selection errors decrease but there was a significant reduction in the strength of spatial encoding in LFPC. These results show that LPFC neurons have spatiotemporal mnemonic fields, in that their firing rates are modulated both by the spatial location of future selection behaviors and the temporal organization of that behavior. Furthermore, the strength of this tuning can be dynamically modulated by the demands of the task.

Modality-specific alpha modulations facilitate long-term memory encoding in the presence of distracters.

PubMed

Jiang, Haiteng; van Gerven, Marcel A J; Jensen, Ole

2015-03-01

It has been proposed that long-term memory encoding is not only dependent on engaging task-relevant regions but also on disengaging task-irrelevant regions. In particular, oscillatory alpha activity has been shown to be involved in shaping the functional architecture of the working brain because it reflects the functional disengagement of specific regions in attention and memory tasks. We here ask if such allocation of resources by alpha oscillations generalizes to long-term memory encoding in a cross-modal setting in which we acquired the ongoing brain activity using magnetoencephalography. Participants were asked to encode pictures while ignoring simultaneously presented words and vice versa. We quantified the brain activity during rehearsal reflecting subsequent memory in the different attention conditions. The key finding was that successful long-term memory encoding is reflected by alpha power decreases in the sensory region of the to-be-attended modality and increases in the sensory region of the to-be-ignored modality to suppress distraction during rehearsal period. Our results corroborate related findings from attention studies by demonstrating that alpha activity is also important for the allocation of resources during long-term memory encoding in the presence of distracters.

The Relationship between Visual Attention and Visual Working Memory Encoding: A Dissociation between Covert and Overt Orienting

PubMed Central

Tas, A. Caglar; Luck, Steven J.; Hollingworth, Andrew

2016-01-01

There is substantial debate over whether visual working memory (VWM) and visual attention constitute a single system for the selection of task-relevant perceptual information or whether they are distinct systems that can be dissociated when their representational demands diverge. In the present study, we focused on the relationship between visual attention and the encoding of objects into visual working memory (VWM). Participants performed a color change-detection task. During the retention interval, a secondary object, irrelevant to the memory task, was presented. Participants were instructed either to execute an overt shift of gaze to this object (Experiments 1–3) or to attend it covertly (Experiments 4 and 5). Our goal was to determine whether these overt and covert shifts of attention disrupted the information held in VWM. We hypothesized that saccades, which typically introduce a memorial demand to bridge perceptual disruption, would lead to automatic encoding of the secondary object. However, purely covert shifts of attention, which introduce no such demand, would not result in automatic memory encoding. The results supported these predictions. Saccades to the secondary object produced substantial interference with VWM performance, but covert shifts of attention to this object produced no interference with VWM performance. These results challenge prevailing theories that consider attention and VWM to reflect a common mechanism. In addition, they indicate that the relationship between attention and VWM is dependent on the memorial demands of the orienting behavior. PMID:26854532

Age-Related Differences in Recognition Memory for Items and Associations: Contribution of Individual Differences in Working Memory and Metamemory

PubMed Central

Bender, Andrew R.; Raz, Naftali

2012-01-01

Ability to form new associations between unrelated items is particularly sensitive to aging, but the reasons for such differential vulnerability are unclear. In this study, we examined the role of objective and subjective factors (working memory and beliefs about memory strategies) on differential relations of age with recognition of items and associations. Healthy adults (N = 100, age 21 to 79) studied word pairs, completed item and association recognition tests, and rated the effectiveness of shallow (e.g., repetition) and deep (e.g., imagery or sentence generation) encoding strategies. Advanced age was associated with reduced working memory (WM) capacity and poorer associative recognition. In addition, reduced WM capacity, beliefs in the utility of ineffective encoding strategies, and lack of endorsement of effective ones were independently associated with impaired associative memory. Thus, maladaptive beliefs about memory in conjunction with reduced cognitive resources account in part for differences in associative memory commonly attributed to aging. PMID:22251381

Neural mechanisms of interference control in working memory capacity.

PubMed

Bomyea, Jessica; Taylor, Charles T; Spadoni, Andrea D; Simmons, Alan N

2018-02-01

The extent to which one can use cognitive resources to keep information in working memory is known to rely on (1) active maintenance of target representations and (2) downregulation of interference from irrelevant representations. Neurobiologically, the global capacity of working memory is thought to depend on the prefrontal and parietal cortices; however, the neural mechanisms involved in controlling interference specifically in working memory capacity tasks remain understudied. In this study, 22 healthy participants completed a modified complex working memory capacity task (Reading Span) with trials of varying levels of interference control demands while undergoing functional MRI. Neural activity associated with interference control demands was examined separately during encoding and recall phases of the task. Results suggested a widespread network of regions in the prefrontal, parietal, and occipital cortices, and the cingulate and cerebellum associated with encoding, and parietal and occipital regions associated with recall. Results align with prior findings emphasizing the importance of frontoparietal circuits for working memory performance, including the role of the inferior frontal gyrus, cingulate, occipital cortex, and cerebellum in regulation of interference demands. © 2017 Wiley Periodicals, Inc.

Working memory and the strategic control of attention in older and younger adults.

PubMed

Hayes, Melissa G; Kelly, Andrew J; Smith, Anderson D

2013-03-01

The objective of this study was to investigate the effects of aging on the strategic control of attention and the extent to which this relationship is mediated by working memory capacity (WMC). This study also sought to investigate boundary conditions wherein age differences in selectivity may occur. Across 2 studies, the value-directed remembering task used by Castel and colleagues (Castel, A. D., Balota, D. A., & McCabe, D. P. (2009). Memory efficiency and the strategic control of attention at encoding: Impairments of value-directed remembering in Alzheimer's Disease. Neuropsychology, 23, 297-306) was modified to include value-directed forgetting. Study 2 incorporated valence as an additional task demand, and age differences were predicted in both studies due to increased demands of controlled processing. Automated operation span and Stroop span were included as working memory measures, and working memory was predicted to mediate performance. Results confirmed these predictions, as older adults were less efficient in maximizing selectivity scores when high demands were placed on selectivity processes, and working memory was found to mediate performance on this task. When list length was increased from previous studies and participants were required to actively forget negative-value words, older adults were not able to selectively encode high-value information to the same degree as younger adults. Furthermore, WMC appears to support the ability to selectively encode information.

Developing a hippocampal neural prosthetic to facilitate human memory encoding and recall.

PubMed

Hampson, Robert E; Song, Dong; Robinson, Brian S; Fetterhoff, Dustin; Dakos, Alexander S; Roeder, Brent M; She, Xiwei; Wicks, Robert T; Witcher, Mark R; Couture, Daniel E; Laxton, Adrian W; Munger-Clary, Heidi; Popli, Gautam; Sollman, Myriam J; Whitlow, Christopher T; Marmarelis, Vasilis Z; Berger, Theodore W; Deadwyler, Sam A

2018-06-01

We demonstrate here the first successful implementation in humans of a proof-of-concept system for restoring and improving memory function via facilitation of memory encoding using the patient's own hippocampal spatiotemporal neural codes for memory. Memory in humans is subject to disruption by drugs, disease and brain injury, yet previous attempts to restore or rescue memory function in humans typically involved only nonspecific, modulation of brain areas and neural systems related to memory retrieval. We have constructed a model of processes by which the hippocampus encodes memory items via spatiotemporal firing of neural ensembles that underlie the successful encoding of short-term memory. A nonlinear multi-input, multi-output (MIMO) model of hippocampal CA3 and CA1 neural firing is computed that predicts activation patterns of CA1 neurons during the encoding (sample) phase of a delayed match-to-sample (DMS) human short-term memory task. MIMO model-derived electrical stimulation delivered to the same CA1 locations during the sample phase of DMS trials facilitated short-term/working memory by 37% during the task. Longer term memory retention was also tested in the same human subjects with a delayed recognition (DR) task that utilized images from the DMS task, along with images that were not from the task. Across the subjects, the stimulated trials exhibited significant improvement (35%) in both short-term and long-term retention of visual information. These results demonstrate the facilitation of memory encoding which is an important feature for the construction of an implantable neural prosthetic to improve human memory.

Developing a hippocampal neural prosthetic to facilitate human memory encoding and recall

NASA Astrophysics Data System (ADS)

Hampson, Robert E.; Song, Dong; Robinson, Brian S.; Fetterhoff, Dustin; Dakos, Alexander S.; Roeder, Brent M.; She, Xiwei; Wicks, Robert T.; Witcher, Mark R.; Couture, Daniel E.; Laxton, Adrian W.; Munger-Clary, Heidi; Popli, Gautam; Sollman, Myriam J.; Whitlow, Christopher T.; Marmarelis, Vasilis Z.; Berger, Theodore W.; Deadwyler, Sam A.

2018-06-01

Objective. We demonstrate here the first successful implementation in humans of a proof-of-concept system for restoring and improving memory function via facilitation of memory encoding using the patient’s own hippocampal spatiotemporal neural codes for memory. Memory in humans is subject to disruption by drugs, disease and brain injury, yet previous attempts to restore or rescue memory function in humans typically involved only nonspecific, modulation of brain areas and neural systems related to memory retrieval. Approach. We have constructed a model of processes by which the hippocampus encodes memory items via spatiotemporal firing of neural ensembles that underlie the successful encoding of short-term memory. A nonlinear multi-input, multi-output (MIMO) model of hippocampal CA3 and CA1 neural firing is computed that predicts activation patterns of CA1 neurons during the encoding (sample) phase of a delayed match-to-sample (DMS) human short-term memory task. Main results. MIMO model-derived electrical stimulation delivered to the same CA1 locations during the sample phase of DMS trials facilitated short-term/working memory by 37% during the task. Longer term memory retention was also tested in the same human subjects with a delayed recognition (DR) task that utilized images from the DMS task, along with images that were not from the task. Across the subjects, the stimulated trials exhibited significant improvement (35%) in both short-term and long-term retention of visual information. Significance. These results demonstrate the facilitation of memory encoding which is an important feature for the construction of an implantable neural prosthetic to improve human memory.

Role of prefrontal cortex and the midbrain dopamine system in working memory updating

PubMed Central

D’Ardenne, Kimberlee; Eshel, Neir; Luka, Joseph; Lenartowicz, Agatha; Nystrom, Leigh E.; Cohen, Jonathan D.

2012-01-01

Humans are adept at switching between goal-directed behaviors quickly and effectively. The prefrontal cortex (PFC) is thought to play a critical role by encoding, updating, and maintaining internal representations of task context in working memory. It has also been hypothesized that the encoding of context representations in PFC is regulated by phasic dopamine gating signals. Here we use multimodal methods to test these hypotheses. First we used functional MRI (fMRI) to identify regions of PFC associated with the representation of context in a working memory task. Next we used single-pulse transcranial magnetic stimulation (TMS), guided spatially by our fMRI findings and temporally by previous event-related EEG recordings, to disrupt context encoding while participants performed the same working memory task. We found that TMS pulses to the right dorsolateral PFC (DLPFC) immediately after context presentation, and well in advance of the response, adversely impacted context-dependent relative to context-independent responses. This finding causally implicates right DLPFC function in context encoding. Finally, using the same paradigm, we conducted high-resolution fMRI measurements in brainstem dopaminergic nuclei (ventral tegmental area and substantia nigra) and found phasic responses after presentation of context stimuli relative to other stimuli, consistent with the timing of a gating signal that regulates the encoding of representations in PFC. Furthermore, these responses were positively correlated with behavior, as well as with responses in the same region of right DLPFC targeted in the TMS experiment, lending support to the hypothesis that dopamine phasic signals regulate encoding, and thereby the updating, of context representations in PFC. PMID:23086162

Age 60 Study, Part 2: Airline Pilot Age and Performance - A Review of the Scientific Literature

DTIC Science & Technology

1994-10-01

It is clear that increasing age 14 differentially affects different memory processes. Hultsch and Dixon (1990) draw the following conclusions about...tasks involving retrieval from secondary memory that may also reflect age differences in initial encoding processes. Hultsch and Dixon (1990) also...working memory ( Hultsch & Dixon, 1990). These age-related declines in working memory are important because of working memory’s contribution to

Ensemble clustering in visual working memory biases location memories and reduces the Weber noise of relative positions.

PubMed

Lew, Timothy F; Vul, Edward

2015-01-01

People seem to compute the ensemble statistics of objects and use this information to support the recall of individual objects in visual working memory. However, there are many different ways that hierarchical structure might be encoded. We examined the format of structured memories by asking subjects to recall the locations of objects arranged in different spatial clustering structures. Consistent with previous investigations of structured visual memory, subjects recalled objects biased toward the center of their clusters. Subjects also recalled locations more accurately when they were arranged in fewer clusters containing more objects, suggesting that subjects used the clustering structure of objects to aid recall. Furthermore, subjects had more difficulty recalling larger relative distances, consistent with subjects encoding the positions of objects relative to clusters and recalling them with magnitude-proportional (Weber) noise. Our results suggest that clustering improved the fidelity of recall by biasing the recall of locations toward cluster centers to compensate for uncertainty and by reducing the magnitude of encoded relative distances.

Greater Working Memory Load Results in Greater Medial Temporal Activity at Retrieval

PubMed Central

Quiroz, Yakeel T.; Hasselmo, Michael E.; Stern, Chantal E.

2009-01-01

Most functional magnetic resonance imaging (fMRI) studies examining working memory (WM) load have focused on the prefrontal cortex (PFC) and have demonstrated increased prefrontal activity with increased load. Here we examined WM load effects in the medial temporal lobe (MTL) using an fMRI Sternberg task with novel complex visual scenes. Trials consisted of 3 sequential events: 1) sample presentation (encoding), 2) delay period (maintenance), and 3) probe period (retrieval). During sample encoding, subjects saw either 2 or 4 pictures consecutively. During retrieval, subjects indicated whether the probe picture matched one of the sample pictures. Results revealed that activity in the left anterior hippocampal formation, bilateral retrosplenial area, and left amygdala was greater at retrieval for trials with larger memory load, whereas activity in the PFC was greater at encoding for trials with larger memory load. There was no load effect during the delay. When encoding, maintenance, and retrieval periods were compared with fixation, activity was present in the hippocampal body/tail and fusiform gyrus bilaterally during encoding and retrieval, but not maintenance. Bilateral dorsolateral prefrontal activity was present during maintenance, but not during encoding or retrieval. The results support models of WM predicting that activity in the MTL should be modulated by WM load. PMID:19224975

Memorization and recall of very long lists accounted for within the Long-Term Working Memory framework.

PubMed

Hu, Yi; Ericsson, K Anders

2012-06-01

In a recent paper, Hu, Ericsson, Yang, and Lu (2009) found that an ability to memorize very long lists of digits is not mediated by the same mechanisms as exceptional memory for rapidly presented lists, which has been the traditional focus of laboratory research. Chao Lu is the holder of the Guinness World Record for reciting the most decimal positions of pi, yet he lacks an exceptional memory span for digits. In the first part of this paper we analyzed the reliability and structure of his reported encodings for lists of 300 digits and his application of the story mnemonic. Next, his study and recall times for lists of digits were analyzed to test hypotheses about his detailed encoding processes, and cued-recall performance was used to assess the structure of his encodings. Three experiments were then designed to interfere with the uniqueness of Chao Lu's story encodings, and evidence was found for his remarkable ability to adapt his encoding processes to reduce the interference. Finally, we show how his skills for encoding and recalling long lists can be accounted for within the theoretical framework of Ericsson and Kintsch's (1995) Long-Term Working Memory. Copyright © 2012 Elsevier Inc. All rights reserved.

Translating working memory into action: behavioral and neural evidence for using motor representations in encoding visuo-spatial sequences.

PubMed

Langner, Robert; Sternkopf, Melanie A; Kellermann, Tanja S; Grefkes, Christian; Kurth, Florian; Schneider, Frank; Zilles, Karl; Eickhoff, Simon B

2014-07-01

The neurobiological organization of action-oriented working memory is not well understood. To elucidate the neural correlates of translating visuo-spatial stimulus sequences into delayed (memory-guided) sequential actions, we measured brain activity using functional magnetic resonance imaging while participants encoded sequences of four to seven dots appearing on fingers of a left or right schematic hand. After variable delays, sequences were to be reproduced with the corresponding fingers. Recall became less accurate with longer sequences and was initiated faster after long delays. Across both hands, encoding and recall activated bilateral prefrontal, premotor, superior and inferior parietal regions as well as the basal ganglia, whereas hand-specific activity was found (albeit to a lesser degree during encoding) in contralateral premotor, sensorimotor, and superior parietal cortex. Activation differences after long versus short delays were restricted to motor-related regions, indicating that rehearsal during long delays might have facilitated the conversion of the memorandum into concrete motor programs at recall. Furthermore, basal ganglia activity during encoding selectively predicted correct recall. Taken together, the results suggest that to-be-reproduced visuo-spatial sequences are encoded as prospective action representations (motor intentions), possibly in addition to retrospective sensory codes. Overall, our study supports and extends multi-component models of working memory, highlighting the notion that sensory input can be coded in multiple ways depending on what the memorandum is to be used for. Copyright © 2013 Wiley Periodicals, Inc.

Selective attention neutralizes the adverse effects of low socioeconomic status on memory in 9-month-old infants

PubMed Central

Markant, Julie; Ackerman, Laura K.; Nussenbaum, Kate; Amso, Dima

2015-01-01

Socioeconomic status (SES) has a documented impact on brain and cognitive development. We demonstrate that engaging spatial selective attention mechanisms may counteract this negative influence of impoverished environments on early learning. We previously used a spatial cueing task to compare target object encoding in the context of basic orienting (“facilitation”) versus a spatial selective attention orienting mechanism that engages distractor suppression (“IOR”). This work showed that object encoding in the context of IOR boosted 9-month-old infants’ recognition memory relative to facilitation (Markant and Amso, 2013). Here we asked whether this attention-memory links further interacted with SES in infancy. Results indicated that SES was related to memory but not attention orienting efficacy. However, the correlation between SES and memory performance was moderated by the attention mechanism engaged during encoding. SES predicted memory performance when objects were encoded with basic orienting processes, with infants from low-SES environments showing poorer memory than those from high-SES environments. However, SES did not predict memory performance among infants who engaged selective attention during encoding. Spatial selective attention engagement mitigated the effects of SES on memory and may offer an effective mechanism for promoting learning among infants at risk for poor cognitive outcomes related to SES. PMID:26597046

Strategic trade-offs between quality and quantity in working memory

PubMed Central

Fougnie, Daryl; Cormiea, Sarah M.; Kanabar, Anish; Alvarez, George A.

2016-01-01

Is working memory capacity determined by an immutable limit—e.g. four memory storage slots? The fact that performance is typically unaffected by task instructions has been taken as support for such structural models of memory. Here, we modified a standard working memory task to incentivize participants to remember more items. Participants were asked to remember a set of colors over a short retention interval. In one condition, participants reported a random item’s color using a color wheel. In the modified task, participants responded to all items and their response was only considered correct if all responses were on the correct half of the color wheel. We looked for a trade-off between quantity and quality—participants storing more items, but less precisely, when required to report them all. This trade-off was observed when tasks were blocked, when task-type was cued after encoding, but not when task-type was cued during the response, suggesting that task differences changed how items were actively encoded and maintained. This strategic control over the contents of working memory challenges models that assume inflexible limits on memory storage. PMID:26950383

Cognitive Behavioral Performance of Untreated Depressed Patients with Mild Depressive Symptoms

PubMed Central

Li, Mi; Zhong, Ning; Lu, Shengfu; Wang, Gang; Feng, Lei; Hu, Bin

2016-01-01

This study evaluated the working memory performance of 18 patients experiencing their first onset of mild depression without treatment and 18 healthy matched controls. The results demonstrated that working memory impairment in patients with mild depression occurred when memorizing the position of a picture but not when memorizing the pictures themselves. There was no significant difference between the two groups in the emotional impact on the working memory, indicating that the attenuation of spatial working memory was not affected by negative emotion; however, cognitive control selectively affected spatial working memory. In addition, the accuracy of spatial working memory in the depressed patients was not significantly reduced, but the reaction time was significantly extended compared with the healthy controls. This finding indicated that there was no damage to memory encoding and function maintenance in the patients but rather only impaired memory retrieval, suggesting that the extent of damage to the working memory system and cognitive control abilities was associated with the corresponding depressive symptoms. The development of mild to severe depressive symptoms may be accompanied by spatial working memory damage from the impaired memory retrieval function extending to memory encoding and memory retention impairments. In addition, the impaired cognitive control began with an inadequate capacity to automatically process internal negative emotions and further extended to impairment of the ability to regulate and suppress external emotions. The results of the mood-congruent study showed that the memory of patients with mild symptoms of depression was associated with a mood-congruent memory effect, demonstrating that mood-congruent memory was a typical feature of depression, regardless of the severity of depression. This study provided important information for understanding the development of cognitive dysfunction. PMID:26730597

Impairment of working memory maintenance and response in schizophrenia: functional magnetic resonance imaging evidence.

PubMed

Driesen, Naomi R; Leung, Hoi-Chung; Calhoun, Vincent D; Constable, R Todd; Gueorguieva, Ralitza; Hoffman, Ralph; Skudlarski, Pawel; Goldman-Rakic, Patricia S; Krystal, John H

2008-12-15

Comparing prefrontal cortical activity during particular phases of working memory in healthy subjects and individuals diagnosed with schizophrenia might help to define the phase-specific deficits in cortical function that contribute to cognitive impairments associated with schizophrenia. This study featured a spatial working memory task, similar to that used in nonhuman primates, that was designed to facilitate separating brain activation into encoding, maintenance, and response phases. Fourteen patients with schizophrenia (4 medication-free) and 12 healthy comparison participants completed functional magnetic resonance imaging while performing a spatial working memory task with two levels of memory load. Task accuracy was similar in patients and healthy participants. However, patients showed reductions in brain activation during maintenance and response phases but not during the encoding phase. The reduced prefrontal activity during the maintenance phase of working memory was attributed to a greater rate of decay of prefrontal activity over time in patients. Cortical deficits in patients did not appear to be related to antipsychotic treatment. In patients and in healthy subjects, the time-dependent reduction in prefrontal activity during working memory maintenance correlated with poorer performance on the memory task. Overall, these data highlight that basic research insights into the distinct neurobiologies of the maintenance and response phases of working memory are of potential importance for understanding the neurobiology of cognitive impairment in schizophrenia and advancing its treatment.

Memory skills mediating superior memory in a world-class memorist.

PubMed

Ericsson, K Anders; Cheng, Xiaojun; Pan, Yafeng; Ku, Yixuan; Ge, Yi; Hu, Yi

2017-10-01

Laboratory studies have investigated how individuals with normal memory spans attained digit spans over 80 digits after hundreds of hours of practice. Experimental analyses of their memory skills suggested that their attained memory spans were constrained by the encoding time, for the time needed will increase if the length of digit sequences to be memorised becomes longer. These constraints seemed to be violated by a world-class memorist, Feng Wang (FW), who won the World Memory Championship by recalling 300 digits presented at 1 digit/s. In several studies we examined FW's memory skills underlying his exceptional performance. First FW reproduced his superior memory span of 200 digits under laboratory condition, and we obtained his retrospective reports describing his encoding/retrieval processes (Experiment 1). Further experiments used self-paced memorisation to identify temporal characteristics of encoding of digits in 4-digit clusters (Experiment 2), and explored memory encoding at presentation speeds much faster than 1 digit/s (Experiment 3). FW's superiority over previous digit span experts is explained by his acquisition of well-known mnemonic techniques and his training that focused on rapid memorisation. His memory performance supports the feasibility of acquiring memory skills for improved working memory based on storage in long-term memory.

Following Instructions in Patients With Schizophrenia: The Benefits of Actions at Encoding and Recall.

PubMed

Lui, Simon S Y; Yang, Tian-Xiao; Ng, Chris L Y; Wong, Peony T Y; Wong, Jessica O Y; Ettinger, Ulrich; Cheung, Eric F C; Chan, Raymond C K

2018-01-13

The ability to follow spoken instructions is important to everyday functioning but has seldom been studied in patients with schizophrenia (SZ). Recent evidence suggests that action-based processing may facilitate the ability to follow instructions, which relies largely on working memory. In this study, we tested the hypothesis that SZ patients may also benefit from action-based advantages in following instructions. Forty-eight clinically stable SZ patients and 48 demographic- and IQ-matched controls completed a following spoken instruction span task involving varied encoding and recall conditions. While SZ patients were impaired in the overall performance of following spoken instructions, this deficit could be attributed to working memory impairment. More importantly, SZ patients showed action-based advantages both at the encoding and retrieval stage to the same extent as healthy controls. Specifically, both healthy controls and SZ patients showed improved memory performance when they additionally performed the actions, or watched the experimenter carrying out the actions compared with simply listening to spoken instructions during the encoding stage. During the retrieval stage, memory was improved when they recalled the instructions by physical enactment compared with oral repetition. The present study provides the first empirical evidence for the impairment in the ability to follow instructions in SZ. We have shown that involving action-based processing in the encoding and retrieval stage facilitated memory of instructions, indicating that the enactment advantage in working memory also applies to SZ patients. These findings provide useful insights for clinical interventions and cognitive remediation for SZ patients. © The Author(s) 2017. Published by Oxford University Press on behalf of the Maryland Psychiatric Research Center. All rights reserved. For permissions, please email: journals.permissions@oup.com.

Salience of working-memory maintenance and manipulation deficits in schizophrenia

PubMed Central

Hill, S. K.; Griffin, G. B.; Miura, T. Kazuto; Herbener, E. S.; Sweeney, J. A.

2011-01-01

Background Encoding and maintenance of information in working memory, followed by internal manipulation of that information for planning adaptive behavior, are two key components of working-memory systems. Both processes have been reported to be impaired in schizophrenia, but few studies have directly compared the relative severity of these abnormalities, or the degree to which manipulation deficits might be secondary to alterations in maintenance processes. Method Clinically stable schizophrenia patients (n=25) and a demographically similar healthy comparison group (n=24) were administered a verbal span task with three levels of working-memory load. Maintenance was assessed using sequential position questions. Manipulation processes were assessed by requiring comparison of the relative sequential position of test items, which entailed simultaneous serial search strategies regarding item order. Results Both groups showed reduced accuracy and increased reaction time for manipulation compared with maintenance processing. There were significant patient impairments across working-memory loads. There was no differential deficit in manipulation processing, and effect sizes of relative deficit in the patient group were higher for maintenance than manipulation processing. Conclusions The strong correlation for maintenance and manipulation deficits suggest that impairments in the ability to internally manipulate information stored in working-memory systems are not greater than alterations in the encoding and maintaining of information in working memory and that disturbances in maintenance processing may contribute to deficits in higher-order working-memory operations. PMID:20214839

The Focus of Spatial Attention Determines the Number and Precision of Face Representations in Working Memory.

PubMed

Towler, John; Kelly, Maria; Eimer, Martin

2016-06-01

The capacity of visual working memory for faces is extremely limited, but the reasons for these limitations remain unknown. We employed event-related brain potential measures to demonstrate that individual faces have to be focally attended in order to be maintained in working memory, and that attention is allocated to only a single face at a time. When 2 faces have to be memorized simultaneously in a face identity-matching task, the focus of spatial attention during encoding predicts which of these faces can be successfully maintained in working memory and matched to a subsequent test face. We also show that memory representations of attended faces are maintained in a position-dependent fashion. These findings demonstrate that the limited capacity of face memory is directly linked to capacity limits of spatial attention during the encoding and maintenance of individual face representations. We suggest that the capacity and distribution of selective spatial attention is a dynamic resource that constrains the capacity and fidelity of working memory for faces. © The Author 2015. Published by Oxford University Press. All rights reserved. For Permissions, please e-mail: journals.permissions@oup.com.

Low-Density Parity-Check Code Design Techniques to Simplify Encoding

NASA Astrophysics Data System (ADS)

Perez, J. M.; Andrews, K.

2007-11-01

This work describes a method for encoding low-density parity-check (LDPC) codes based on the accumulate-repeat-4-jagged-accumulate (AR4JA) scheme, using the low-density parity-check matrix H instead of the dense generator matrix G. The use of the H matrix to encode allows a significant reduction in memory consumption and provides the encoder design a great flexibility. Also described are new hardware-efficient codes, based on the same kind of protographs, which require less memory storage and area, allowing at the same time a reduction in the encoding delay.

The Astrocentric Hypothesis: proposed role of astrocytes in consciousness and memory formation.

PubMed

Robertson, James M

2002-01-01

Consciousness is self-awareness. This process is closely associated with attention and working memory, a special form of short-term memory, which is vital when solving explicit task. Edelman has equated consciousness as the "remembered present" to highlight the importance of this form of memory (G.M. Edelman, Bright Air, Brilliant Fire, Basic Books, New York, 1992). The majority of other memories are recollections of past events that are encoded, stored, and brought back into consciousness if appropriate for solving new problems. Encoding prior experiences into memories is based on the salience of each event (A.R. Damasio, Descartes' Error, G.P. Putnam's Sons, New York, 1994; G.M. Edelman, Bright Air, Brilliant Fire, Basic Books, New York, 1992). It is proposed that protoplasmic astrocytes bind attended sensory information into consciousness and store encoded memories. This conclusion is supported by research conducted by gliobiologist over the past 15 years. Copyright 2002 Elsevier Science Ltd.

Removal of irrelevant information from working memory: sometimes fast, sometimes slow, and sometimes not at all.

PubMed

Oberauer, Klaus

2018-03-12

To function properly, working memory must be rapidly updated. Updating requires the removal of information no longer relevant. I present six experiments designed to explore the boundary conditions and the time course of removal. A condition in which three out of six memory items can be removed was compared to two baseline conditions in which either three or six items were encoded and maintained in working memory. The time for removal was varied. In experiment 1, in the removal condition, a distinct subset of three words was cued to be irrelevant after encoding all six words. With longer removal time, response times in the removal condition approximated those in the set-size 3 baseline, but accuracies stayed at the set-size 6 level. In experiment 2, in which a random subset of three words was cued as irrelevant, there was no evidence for removal. Experiments 3 and 4 showed that when each item is cued as relevant or irrelevant after its encoding, irrelevant items can be removed rapidly and completely. Experiments 5 and 6 showed that complete removal was no longer possible when words had to be processed before being cued as irrelevant. The pattern of findings can be explained by distinguishing two forms of removal: deactivation removes working-memory contents from the set of competitors for retrieval; unbinding contents from their contexts removes them from working memory entirely, so that they also cease to compete for limited capacity. © 2018 New York Academy of Sciences.

Event-related rTMS at encoding affects differently deep and shallow memory traces.

PubMed

Innocenti, Iglis; Giovannelli, Fabio; Cincotta, Massimo; Feurra, Matteo; Polizzotto, Nicola R; Bianco, Giovanni; Cappa, Stefano F; Rossi, Simone

2010-10-15

The "level of processing" effect is a classical finding of the experimental psychology of memory. Actually, the depth of information processing at encoding predicts the accuracy of the subsequent episodic memory performance. When the incoming stimuli are analyzed in terms of their meaning (semantic, or deep, encoding), the memory performance is superior with respect to the case in which the same stimuli are analyzed in terms of their perceptual features (shallow encoding). As suggested by previous neuroimaging studies and by some preliminary findings with transcranial magnetic stimulation (TMS), the left prefrontal cortex may play a role in semantic processing requiring the allocation of working memory resources. However, it still remains unclear whether deep and shallow encoding share or not the same cortical networks, as well as how these networks contribute to the "level of processing" effect. To investigate the brain areas casually involved in this phenomenon, we applied event-related repetitive TMS (rTMS) during deep (semantic) and shallow (perceptual) encoding of words. Retrieval was subsequently tested without rTMS interference. RTMS applied to the left dorsolateral prefrontal cortex (DLPFC) abolished the beneficial effect of deep encoding on memory performance, both in terms of accuracy (decrease) and reaction times (increase). Neither accuracy nor reaction times were instead affected by rTMS to the right DLPFC or to an additional control site excluded by the memory process (vertex). The fact that online measures of semantic processing at encoding were unaffected suggests that the detrimental effect on memory performance for semantically encoded items took place in the subsequent consolidation phase. These results highlight the specific causal role of the left DLPFC among the wide left-lateralized cortical network engaged by long-term memory, suggesting that it probably represents a crucial node responsible for the improved memory performance induced by semantic processing. Copyright 2010 Elsevier Inc. All rights reserved.

Age Differences in Visual Working Memory Capacity: Not Based on Encoding Limitations

ERIC Educational Resources Information Center

Cowan, Nelson; AuBuchon, Angela M.; Gilchrist, Amanda L.; Ricker, Timothy J.; Saults, J. Scott

2011-01-01

Why does visual working memory performance increase with age in childhood? One recent study (Cowan et al., 2010b) ruled out the possibility that the basic cause is a tendency in young children to clutter working memory with less-relevant items (within a concurrent array, colored items presented in one of two shapes). The age differences in memory…

When plausibility manipulations work: an examination of their role in the development of false beliefs and memories.

PubMed

Bays, Rebecca B; Zabrucky, Karen M; Gagne, Phill

2012-01-01

In the current study we examined whether prevalence information and imagery encoding influence participants' general plausibility, personal plausibility, belief, and memory ratings for suggested childhood events. Results showed decreases in general and personal plausibility ratings for low prevalence events when encoding instructions were not elaborate; however, instructions to repeatedly imagine suggested events elicited personal plausibility increases for low-prevalence events, evidence that elaborate imagery negated the effect of our prevalence manipulation. We found no evidence of imagination inflation or false memory construction. We discuss critical differences in researchers' manipulations of plausibility and imagery that may influence results of false memory studies in the literature. In future research investigators should focus on the specific nature of encoding instructions when examining the development of false memories.

Does Contralateral Delay Activity Reflect Working Memory Storage or the Current Focus of Spatial Attention within Visual Working Memory?

PubMed

Berggren, Nick; Eimer, Martin

2016-12-01

During the retention of visual information in working memory, event-related brain potentials show a sustained negativity over posterior visual regions contralateral to the side where memorized stimuli were presented. This contralateral delay activity (CDA) is generally believed to be a neural marker of working memory storage. In two experiments, we contrasted this storage account of the CDA with the alternative hypothesis that the CDA reflects the current focus of spatial attention on a subset of memorized items set up during the most recent encoding episode. We employed a sequential loading procedure where participants memorized four task-relevant items that were presented in two successive memory displays (M1 and M2). In both experiments, CDA components were initially elicited contralateral to task-relevant items in M1. Critically, the CDA switched polarity when M2 displays appeared on the opposite side. In line with the attentional activation account, these reversed CDA components exclusively reflected the number of items that were encoded from M2 displays, irrespective of how many M1 items were already held in working memory. On trials where M1 and M2 displays were presented on the same side and on trials where M2 displays appeared nonlaterally, CDA components elicited in the interval after M2 remained sensitive to a residual trace of M1 items, indicating that some activation of previously stored items was maintained across encoding episodes. These results challenge the hypothesis that CDA amplitudes directly reflect the total number of stored objects and suggest that the CDA is primarily sensitive to the activation of a subset of working memory representations within the current focus of spatial attention.

Visuospatial bootstrapping: implicit binding of verbal working memory to visuospatial representations in children and adults.

PubMed

Darling, Stephen; Parker, Mary-Jane; Goodall, Karen E; Havelka, Jelena; Allen, Richard J

2014-03-01

When participants carry out visually presented digit serial recall, their performance is better if they are given the opportunity to encode extra visuospatial information at encoding-a phenomenon that has been termed visuospatial bootstrapping. This bootstrapping is the result of integration of information from different modality-specific short-term memory systems and visuospatial knowledge in long term memory, and it can be understood in the context of recent models of working memory that address multimodal binding (e.g., models incorporating an episodic buffer). Here we report a cross-sectional developmental study that demonstrated visuospatial bootstrapping in adults (n=18) and 9-year-old children (n=15) but not in 6-year-old children (n=18). This is the first developmental study addressing visuospatial bootstrapping, and results demonstrate that the developmental trajectory of bootstrapping is different from that of basic verbal and visuospatial working memory. This pattern suggests that bootstrapping (and hence integrative functions such as those associated with the episodic buffer) emerge independent of the development of basic working memory slave systems during childhood. Copyright © 2013 Elsevier Inc. All rights reserved.

The influence of encoding strategy on episodic memory and cortical activity in schizophrenia.

PubMed

Bonner-Jackson, Aaron; Haut, Kristen; Csernansky, John G; Barch, Deanna M

2005-07-01

Recent work suggests that episodic memory deficits in schizophrenia may be related to disturbances of encoding or retrieval. Schizophrenia patients appear to benefit from instruction in episodic memory strategies. We tested the hypothesis that providing effective encoding strategies to schizophrenia patients enhances encoding-related brain activity and recognition performance. Seventeen schizophrenia patients and 26 healthy comparison subjects underwent functional magnetic resonance imaging scans while performing incidental encoding tasks of words and faces. Subjects were required to make either deep (abstract/concrete) or shallow (alphabetization) judgments for words and deep (gender) judgments for faces, followed by subsequent recognition tests. Schizophrenia and comparison subjects recognized significantly more words encoded deeply than shallowly, activated regions in inferior frontal cortex (Brodmann area 45/47) typically associated with deep and successful encoding of words, and showed greater left frontal activation for the processing of words compared with faces. However, during deep encoding and material-specific processing (words vs. faces), participants with schizophrenia activated regions not activated by control subjects, including several in prefrontal cortex. Our findings suggest that a deficit in use of effective strategies influences episodic memory performance in schizophrenia and that abnormalities in functional brain activation persist even when such strategies are applied.

Memory Skills of Deaf Learners: Implications and Applications

ERIC Educational Resources Information Center

Hamilton, Harley

2011-01-01

This paper will review research on working memory and short-term memory abilities of deaf individuals delineating strengths and weaknesses. The areas of memory reviewed include weaknesses such as sequential recall, processing speed, attention, and memory load. Strengths include free recall, visuospatial recall, imagery and dual encoding.…

Selective attention neutralizes the adverse effects of low socioeconomic status on memory in 9-month-old infants.

PubMed

Markant, Julie; Ackerman, Laura K; Nussenbaum, Kate; Amso, Dima

2016-04-01

Socioeconomic status (SES) has a documented impact on brain and cognitive development. We demonstrate that engaging spatial selective attention mechanisms may counteract this negative influence of impoverished environments on early learning. We previously used a spatial cueing task to compare target object encoding in the context of basic orienting ("facilitation") versus a spatial selective attention orienting mechanism that engages distractor suppression ("IOR"). This work showed that object encoding in the context of IOR boosted 9-month-old infants' recognition memory relative to facilitation (Markant and Amso, 2013). Here we asked whether this attention-memory link further interacted with SES in infancy. Results indicated that SES was related to memory but not attention orienting efficacy. However, the correlation between SES and memory performance was moderated by the attention mechanism engaged during encoding. SES predicted memory performance when objects were encoded with basic orienting processes, with infants from low-SES environments showing poorer memory than those from high-SES environments. However, SES did not predict memory performance among infants who engaged selective attention during encoding. Spatial selective attention engagement mitigated the effects of SES on memory and may offer an effective mechanism for promoting learning among infants at risk for poor cognitive outcomes related to SES. Copyright © 2015 The Authors. Published by Elsevier Ltd.. All rights reserved.

Collaborative Encoding and Memory Accuracy: Examining the Effects of Interactive Components of Co-Construction Processes

ERIC Educational Resources Information Center

Foley, Mary Ann; Fried, Adina Rachel; Cowan, Emily; Bays, Rebecca Brooke

2014-01-01

In 2 experiments, the effect of collaborative encoding on memory was examined by testing 2 interactive components of co-construction processes. One component focused on the nature of the interactive exchange between collaborators: As the partners worked together to create descriptions about ways to interact with familiar objects, constraints were…

Memory skills of deaf learners: implications and applications.

PubMed

Hamilton, Harley

2011-01-01

The author reviews research on working memory and short-term memory abilities of deaf individuals, delineating strengths and weaknesses. Among the areas of weakness that are reviewed are sequential recall, processing speed, attention, and memory load. Areas of strengths include free recall, visuospatial recall, imagery, and dual encoding. Phonological encoding and rehearsal appear to be strengths when these strategies are employed. The implications of the strengths and weaknesses for language learning and educational achievement are discussed. Research questions are posed, and remedial and compensatory classroom applications are suggested.

Your brain on speed: cognitive performance of a spatial working memory task is not affected by walking speed

PubMed Central

Kline, Julia E.; Poggensee, Katherine; Ferris, Daniel P.

2014-01-01

When humans walk in everyday life, they typically perform a range of cognitive tasks while they are on the move. Past studies examining performance changes in dual cognitive-motor tasks during walking have produced a variety of results. These discrepancies may be related to the type of cognitive task chosen, differences in the walking speeds studied, or lack of controlling for walking speed. The goal of this study was to determine how young, healthy subjects performed a spatial working memory task over a range of walking speeds. We used high-density electroencephalography to determine if electrocortical activity mirrored changes in cognitive performance across speeds. Subjects stood (0.0 m/s) and walked (0.4, 0.8, 1.2, and 1.6 m/s) with and without performing a Brooks spatial working memory task. We hypothesized that performance of the spatial working memory task and the associated electrocortical activity would decrease significantly with walking speed. Across speeds, the spatial working memory task caused subjects to step more widely compared with walking without the task. This is typically a sign that humans are adapting their gait dynamics to increase gait stability. Several cortical areas exhibited power fluctuations time-locked to memory encoding during the cognitive task. In the somatosensory association cortex, alpha power increased prior to stimulus presentation and decreased during memory encoding. There were small significant reductions in theta power in the right superior parietal lobule and the posterior cingulate cortex around memory encoding. However, the subjects did not show a significant change in cognitive task performance or electrocortical activity with walking speed. These findings indicate that in young, healthy subjects walking speed does not affect performance of a spatial working memory task. These subjects can devote adequate cortical resources to spatial cognition when needed, regardless of walking speed. PMID:24847239

More than a filter: Feature-based attention regulates the distribution of visual working memory resources.

PubMed

Dube, Blaire; Emrich, Stephen M; Al-Aidroos, Naseem

2017-10-01

Across 2 experiments we revisited the filter account of how feature-based attention regulates visual working memory (VWM). Originally drawing from discrete-capacity ("slot") models, the filter account proposes that attention operates like the "bouncer in the brain," preventing distracting information from being encoded so that VWM resources are reserved for relevant information. Given recent challenges to the assumptions of discrete-capacity models, we investigated whether feature-based attention plays a broader role in regulating memory. Both experiments used partial report tasks in which participants memorized the colors of circle and square stimuli, and we provided a feature-based goal by manipulating the likelihood that 1 shape would be probed over the other across a range of probabilities. By decomposing participants' responses using mixture and variable-precision models, we estimated the contributions of guesses, nontarget responses, and imprecise memory representations to their errors. Consistent with the filter account, participants were less likely to guess when the probed memory item matched the feature-based goal. Interestingly, this effect varied with goal strength, even across high probabilities where goal-matching information should always be prioritized, demonstrating strategic control over filter strength. Beyond this effect of attention on which stimuli were encoded, we also observed effects on how they were encoded: Estimates of both memory precision and nontarget errors varied continuously with feature-based attention. The results offer support for an extension to the filter account, where feature-based attention dynamically regulates the distribution of resources within working memory so that the most relevant items are encoded with the greatest precision. (PsycINFO Database Record (c) 2017 APA, all rights reserved).

Working Memory Capacity and Recall from Long-Term Memory: Examining the Influences of Encoding Strategies, Study Time Allocation, Search Efficiency, and Monitoring Abilities

ERIC Educational Resources Information Center

Unsworth, Nash

2016-01-01

The relation between working memory capacity (WMC) and recall from long-term memory (LTM) was examined in the current study. Participants performed multiple measures of delayed free recall varying in presentation duration and self-reported their strategy usage after each task. Participants also performed multiple measures of WMC. The results…

Strategic trade-offs between quantity and quality in working memory.

PubMed

Fougnie, Daryl; Cormiea, Sarah M; Kanabar, Anish; Alvarez, George A

2016-08-01

Is working memory capacity determined by an immutable limit-for example, 4 memory storage slots? The fact that performance is typically unaffected by task instructions has been taken as support for such structural models of memory. Here, we modified a standard working memory task to incentivize participants to remember more items. Participants were asked to remember a set of colors over a short retention interval. In 1 condition, participants reported a random item's color using a color wheel. In the modified task, participants responded to all items and their response was only considered correct if all responses were on the correct half of the color wheel. We looked for a trade-off between quantity and quality-participants storing more items, but less precisely, when required to report them all. This trade-off was observed when tasks were blocked and when task-type was cued after encoding, but not when task-type was cued during the response, suggesting that task differences changed how items were actively encoded and maintained. This strategic control over the contents of working memory challenges models that assume inflexible limits on memory storage. (PsycINFO Database Record (c) 2016 APA, all rights reserved).

Parietal cortex integrates contextual and saliency signals during the encoding of natural scenes in working memory.

PubMed

Santangelo, Valerio; Di Francesco, Simona Arianna; Mastroberardino, Serena; Macaluso, Emiliano

2015-12-01

The Brief presentation of a complex scene entails that only a few objects can be selected, processed indepth, and stored in memory. Both low-level sensory salience and high-level context-related factors (e.g., the conceptual match/mismatch between objects and scene context) contribute to this selection process, but how the interplay between these factors affects memory encoding is largely unexplored. Here, during fMRI we presented participants with pictures of everyday scenes. After a short retention interval, participants judged the position of a target object extracted from the initial scene. The target object could be either congruent or incongruent with the context of the scene, and could be located in a region of the image with maximal or minimal salience. Behaviourally, we found a reduced impact of saliency on visuospatial working memory performance when the target was out-of-context. Encoding-related fMRI results showed that context-congruent targets activated dorsoparietal regions, while context-incongruent targets de-activated the ventroparietal cortex. Saliency modulated activity both in dorsal and ventral regions, with larger context-related effects for salient targets. These findings demonstrate the joint contribution of knowledge-based and saliency-driven attention for memory encoding, highlighting a dissociation between dorsal and ventral parietal regions. © 2015 Wiley Periodicals, Inc.

Obligatory encoding of task-irrelevant features depletes working memory resources.

PubMed

Marshall, Louise; Bays, Paul M

2013-02-18

Selective attention is often considered the "gateway" to visual working memory (VWM). However, the extent to which we can voluntarily control which of an object's features enter memory remains subject to debate. Recent research has converged on the concept of VWM as a limited commodity distributed between elements of a visual scene. Consequently, as memory load increases, the fidelity with which each visual feature is stored decreases. Here we used changes in recall precision to probe whether task-irrelevant features were encoded into VWM when individuals were asked to store specific feature dimensions. Recall precision for both color and orientation was significantly enhanced when task-irrelevant features were removed, but knowledge of which features would be probed provided no advantage over having to memorize both features of all items. Next, we assessed the effect an interpolated orientation-or color-matching task had on the resolution with which orientations in a memory array were stored. We found that the presence of orientation information in the second array disrupted memory of the first array. The cost to recall precision was identical whether the interfering features had to be remembered, attended to, or could be ignored. Therefore, it appears that storing, or merely attending to, one feature of an object is sufficient to promote automatic encoding of all its features, depleting VWM resources. However, the precision cost was abolished when the match task preceded the memory array. So, while encoding is automatic, maintenance is voluntary, allowing resources to be reallocated to store new visual information.

Working Memory in the Service of Executive Control Functions.

PubMed

Mansouri, Farshad A; Rosa, Marcello G P; Atapour, Nafiseh

2015-01-01

Working memory is a type of short-term memory which has a crucial cognitive function that supports ongoing and upcoming behaviors, allowing storage of information across delay periods. The content of this memory may typically include tangible information about features such as the shape, color or texture of an object, and its location and motion relative to the body, as well as phonological information. The neural correlate of working memory has been found in different brain areas that are involved in organizing perceptual or motor functions. In particular, neuronal activity in prefrontal areas encodes task-related information corresponding to working memory across delay periods, and lesions in the prefrontal cortex severely affect the ability to retain this type of memory. Recent studies have further expanded the scope and possible role of working memory by showing that information of a more abstract nature (including a behavior-guiding rule, or the occurrence of a conflict in information processing) can also be maintained in short-term memory, and used for adjusting the allocation of executive control in dynamic environments. It has also been shown that neuronal activity in the prefrontal cortex encodes and maintains information about such abstract entities. These findings suggest that the prefrontal cortex plays crucial roles in the organization of goal-directed behavior by supporting many different mnemonic processes, which maintain a wide range of information required for the executive control of ongoing and upcoming behaviors.

Load-sensitive impairment of working memory for biological motion in schizophrenia.

PubMed

Lee, Hannah; Kim, Jejoong

2017-01-01

Impaired working memory (WM) is a core cognitive deficit in schizophrenia. Nevertheless, past studies have reported that patients may also benefit from increasing salience of memory stimuli. Such efficient encoding largely depends upon precise perception. Thus an investigation on the relationship between perceptual processing and WM would be worthwhile. Here, we used biological motion (BM), a socially relevant stimulus that schizophrenics have difficulty discriminating from similar meaningless motions, in a delayed-response task. Non-BM stimuli and static polygons were also used for comparison. In each trial, one of the three types of stimuli was presented followed by two probes, with a short delay in between. Participants were asked to indicate whether one of them was identical to the memory item or both were novel. The number of memory items was one or two. Healthy controls were more accurate in recognizing BM than non-BM regardless of memory loads. Patients with schizophrenia exhibited similar accuracy patterns to those of controls in the Load 1 condition only. These results suggest that information contained in BM could facilitate WM encoding in general, but the effect is vulnerable to the increase of cognitive load in schizophrenia, implying inefficient encoding driven by imprecise perception.

The default mode network and the working memory network are not anti-correlated during all phases of a working memory task.

PubMed

Piccoli, Tommaso; Valente, Giancarlo; Linden, David E J; Re, Marta; Esposito, Fabrizio; Sack, Alexander T; Di Salle, Francesco

2015-01-01

The default mode network and the working memory network are known to be anti-correlated during sustained cognitive processing, in a load-dependent manner. We hypothesized that functional connectivity among nodes of the two networks could be dynamically modulated by task phases across time. To address the dynamic links between default mode network and the working memory network, we used a delayed visuo-spatial working memory paradigm, which allowed us to separate three different phases of working memory (encoding, maintenance, and retrieval), and analyzed the functional connectivity during each phase within and between the default mode network and the working memory network networks. We found that the two networks are anti-correlated only during the maintenance phase of working memory, i.e. when attention is focused on a memorized stimulus in the absence of external input. Conversely, during the encoding and retrieval phases, when the external stimulation is present, the default mode network is positively coupled with the working memory network, suggesting the existence of a dynamically switching of functional connectivity between "task-positive" and "task-negative" brain networks. Our results demonstrate that the well-established dichotomy of the human brain (anti-correlated networks during rest and balanced activation-deactivation during cognition) has a more nuanced organization than previously thought and engages in different patterns of correlation and anti-correlation during specific sub-phases of a cognitive task. This nuanced organization reinforces the hypothesis of a direct involvement of the default mode network in cognitive functions, as represented by a dynamic rather than static interaction with specific task-positive networks, such as the working memory network.

The Default Mode Network and the Working Memory Network Are Not Anti-Correlated during All Phases of a Working Memory Task

PubMed Central

Piccoli, Tommaso; Valente, Giancarlo; Linden, David E. J.; Re, Marta; Esposito, Fabrizio; Sack, Alexander T.; Salle, Francesco Di

2015-01-01

Introduction The default mode network and the working memory network are known to be anti-correlated during sustained cognitive processing, in a load-dependent manner. We hypothesized that functional connectivity among nodes of the two networks could be dynamically modulated by task phases across time. Methods To address the dynamic links between default mode network and the working memory network, we used a delayed visuo-spatial working memory paradigm, which allowed us to separate three different phases of working memory (encoding, maintenance, and retrieval), and analyzed the functional connectivity during each phase within and between the default mode network and the working memory network networks. Results We found that the two networks are anti-correlated only during the maintenance phase of working memory, i.e. when attention is focused on a memorized stimulus in the absence of external input. Conversely, during the encoding and retrieval phases, when the external stimulation is present, the default mode network is positively coupled with the working memory network, suggesting the existence of a dynamically switching of functional connectivity between “task-positive” and “task-negative” brain networks. Conclusions Our results demonstrate that the well-established dichotomy of the human brain (anti-correlated networks during rest and balanced activation-deactivation during cognition) has a more nuanced organization than previously thought and engages in different patterns of correlation and anti-correlation during specific sub-phases of a cognitive task. This nuanced organization reinforces the hypothesis of a direct involvement of the default mode network in cognitive functions, as represented by a dynamic rather than static interaction with specific task-positive networks, such as the working memory network. PMID:25848951

Impaired Contingent Attentional Capture Predicts Reduced Working Memory Capacity in Schizophrenia

PubMed Central

Mayer, Jutta S.; Fukuda, Keisuke; Vogel, Edward K.; Park, Sohee

2012-01-01

Although impairments in working memory (WM) are well documented in schizophrenia, the specific factors that cause these deficits are poorly understood. In this study, we hypothesized that a heightened susceptibility to attentional capture at an early stage of visual processing would result in working memory encoding problems. 30 patients with schizophrenia and 28 demographically matched healthy participants were presented with a search array and asked to report the orientation of the target stimulus. In some of the trials, a flanker stimulus preceded the search array that either matched the color of the target (relevant-flanker capture) or appeared in a different color (irrelevant-flanker capture). Working memory capacity was determined in each individual using the visual change detection paradigm. Patients needed considerably more time to find the target in the no-flanker condition. After adjusting the individual exposure time, both groups showed equivalent capture costs in the irrelevant-flanker condition. However, in the relevant-flanker condition, capture costs were increased in patients compared to controls when the stimulus onset asynchrony between the flanker and the search array was high. Moreover, the increase in relevant capture costs correlated negatively with working memory capacity. This study demonstrates preserved stimulus-driven attentional capture but impaired contingent attentional capture associated with low working memory capacity in schizophrenia. These findings suggest a selective impairment of top-down attentional control in schizophrenia, which may impair working memory encoding. PMID:23152783

Impaired contingent attentional capture predicts reduced working memory capacity in schizophrenia.

PubMed

Mayer, Jutta S; Fukuda, Keisuke; Vogel, Edward K; Park, Sohee

2012-01-01

Although impairments in working memory (WM) are well documented in schizophrenia, the specific factors that cause these deficits are poorly understood. In this study, we hypothesized that a heightened susceptibility to attentional capture at an early stage of visual processing would result in working memory encoding problems. 30 patients with schizophrenia and 28 demographically matched healthy participants were presented with a search array and asked to report the orientation of the target stimulus. In some of the trials, a flanker stimulus preceded the search array that either matched the color of the target (relevant-flanker capture) or appeared in a different color (irrelevant-flanker capture). Working memory capacity was determined in each individual using the visual change detection paradigm. Patients needed considerably more time to find the target in the no-flanker condition. After adjusting the individual exposure time, both groups showed equivalent capture costs in the irrelevant-flanker condition. However, in the relevant-flanker condition, capture costs were increased in patients compared to controls when the stimulus onset asynchrony between the flanker and the search array was high. Moreover, the increase in relevant capture costs correlated negatively with working memory capacity. This study demonstrates preserved stimulus-driven attentional capture but impaired contingent attentional capture associated with low working memory capacity in schizophrenia. These findings suggest a selective impairment of top-down attentional control in schizophrenia, which may impair working memory encoding.

Compression in visual working memory: using statistical regularities to form more efficient memory representations.

PubMed

Brady, Timothy F; Konkle, Talia; Alvarez, George A

2009-11-01

The information that individuals can hold in working memory is quite limited, but researchers have typically studied this capacity using simple objects or letter strings with no associations between them. However, in the real world there are strong associations and regularities in the input. In an information theoretic sense, regularities introduce redundancies that make the input more compressible. The current study shows that observers can take advantage of these redundancies, enabling them to remember more items in working memory. In 2 experiments, covariance was introduced between colors in a display so that over trials some color pairs were more likely to appear than other color pairs. Observers remembered more items from these displays than from displays where the colors were paired randomly. The improved memory performance cannot be explained by simply guessing the high-probability color pair, suggesting that observers formed more efficient representations to remember more items. Further, as observers learned the regularities, their working memory performance improved in a way that is quantitatively predicted by a Bayesian learning model and optimal encoding scheme. These results suggest that the underlying capacity of the individuals' working memory is unchanged, but the information they have to remember can be encoded in a more compressed fashion. Copyright 2009 APA

Visual working memory buffers information retrieved from visual long-term memory.

PubMed

Fukuda, Keisuke; Woodman, Geoffrey F

2017-05-16

Human memory is thought to consist of long-term storage and short-term storage mechanisms, the latter known as working memory. Although it has long been assumed that information retrieved from long-term memory is represented in working memory, we lack neural evidence for this and need neural measures that allow us to watch this retrieval into working memory unfold with high temporal resolution. Here, we show that human electrophysiology can be used to track information as it is brought back into working memory during retrieval from long-term memory. Specifically, we found that the retrieval of information from long-term memory was limited to just a few simple objects' worth of information at once, and elicited a pattern of neurophysiological activity similar to that observed when people encode new information into working memory. Our findings suggest that working memory is where information is buffered when being retrieved from long-term memory and reconcile current theories of memory retrieval with classic notions about the memory mechanisms involved.

Visual working memory buffers information retrieved from visual long-term memory

PubMed Central

Fukuda, Keisuke; Woodman, Geoffrey F.

2017-01-01

Human memory is thought to consist of long-term storage and short-term storage mechanisms, the latter known as working memory. Although it has long been assumed that information retrieved from long-term memory is represented in working memory, we lack neural evidence for this and need neural measures that allow us to watch this retrieval into working memory unfold with high temporal resolution. Here, we show that human electrophysiology can be used to track information as it is brought back into working memory during retrieval from long-term memory. Specifically, we found that the retrieval of information from long-term memory was limited to just a few simple objects’ worth of information at once, and elicited a pattern of neurophysiological activity similar to that observed when people encode new information into working memory. Our findings suggest that working memory is where information is buffered when being retrieved from long-term memory and reconcile current theories of memory retrieval with classic notions about the memory mechanisms involved. PMID:28461479

Behavioral Functions of the CA3 Subregion of the Hippocampus

ERIC Educational Resources Information Center

Kesner, Raymond P.

2007-01-01

From a behavioral perspective, the CA3a,b subregion of the hippocampus plays an important role in the encoding of new spatial information within short-term memory with a duration of seconds and minutes. This can easily be observed in tasks that require rapid encoding, novelty detection, one-trial short-term or working memory, and one-trial cued…

Medial prefrontal cortex supports source memory accuracy for self-referenced items.

PubMed

Leshikar, Eric D; Duarte, Audrey

2012-01-01

Previous behavioral work suggests that processing information in relation to the self enhances subsequent item recognition. Neuroimaging evidence further suggests that regions along the cortical midline, particularly those of the medial prefrontal cortex (PFC), underlie this benefit. There has been little work to date, however, on the effects of self-referential encoding on source memory accuracy or whether the medial PFC might contribute to source memory for self-referenced materials. In the current study, we used fMRI to measure neural activity while participants studied and subsequently retrieved pictures of common objects superimposed on one of two background scenes (sources) under either self-reference or self-external encoding instructions. Both item recognition and source recognition were better for objects encoded self-referentially than self-externally. Neural activity predictive of source accuracy was observed in the medial PFC (Brodmann area 10) at the time of study for self-referentially but not self-externally encoded objects. The results of this experiment suggest that processing information in relation to the self leads to a mnemonic benefit for source level features, and that activity in the medial PFC contributes to this source memory benefit. This evidence expands the purported role that the medial PFC plays in self-referencing.

Transcranial direct current stimulation of dorsolateral prefrontal cortex during encoding improves recall but not recognition memory

DOE PAGES

Leshikar, Eric D.; Leach, Ryan C.; McCurdy, Matthew P.; ...

2017-10-19

Prior work demonstrates that application of transcranial direct current stimulation (tDCS) improves memory. In this study, we investigated tDCS effects on face-name associative memory using both recall and recognition tests. Participants encoded face-name pairs under either active (1.5 mA) or sham (.1 mA) stimulation applied to the scalp adjacent to the left dorsolateral prefrontal cortex (dlPFC), an area known to support associative memory. Participants’ memory was then tested after study (day one) and then again after a 24-h delay (day two), to assess both immediate and delayed stimulation effects on memory. Results indicated that active relative to sham stimulation ledmore » to substantially improved recall (more than 50%) at both day one and day two. Recognition memory performance did not differ between stimulation groups at either time point. These results suggest that stimulation at encoding improves memory performance by enhancing memory for details that enable a rich recollective experience, but that these improvements are evident only under some testing conditions, especially those that rely on recollection. Altogether, stimulation of the dlPFC could have led to recall improvement through enhanced encoding from stimulation or from carryover effects of stimulation that influenced retrieval processes, or both.« less

Transcranial direct current stimulation of dorsolateral prefrontal cortex during encoding improves recall but not recognition memory

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

Leshikar, Eric D.; Leach, Ryan C.; McCurdy, Matthew P.

Prior work demonstrates that application of transcranial direct current stimulation (tDCS) improves memory. In this study, we investigated tDCS effects on face-name associative memory using both recall and recognition tests. Participants encoded face-name pairs under either active (1.5 mA) or sham (.1 mA) stimulation applied to the scalp adjacent to the left dorsolateral prefrontal cortex (dlPFC), an area known to support associative memory. Participants’ memory was then tested after study (day one) and then again after a 24-h delay (day two), to assess both immediate and delayed stimulation effects on memory. Results indicated that active relative to sham stimulation ledmore » to substantially improved recall (more than 50%) at both day one and day two. Recognition memory performance did not differ between stimulation groups at either time point. These results suggest that stimulation at encoding improves memory performance by enhancing memory for details that enable a rich recollective experience, but that these improvements are evident only under some testing conditions, especially those that rely on recollection. Altogether, stimulation of the dlPFC could have led to recall improvement through enhanced encoding from stimulation or from carryover effects of stimulation that influenced retrieval processes, or both.« less

Memory on time

PubMed Central

Eichenbaum, Howard

2013-01-01

Considerable recent work has shown that the hippocampus is critical for remembering the order of events in distinct experiences, a defining feature of episodic memory. Correspondingly, hippocampal neuronal activity can ‘replay’ sequential events in memories and hippocampal neuronal ensembles represent a gradually changing temporal context signal. Most strikingly, single hippocampal neurons – called time cells – encode moments in temporally structured experiences much as the well-known place cells encode locations in spatially structured experiences. These observations bridge largely disconnected literatures on the role of the hippocampus in episodic memory and spatial mapping, and suggest that the fundamental function of the hippocampus is to establish spatio-temporal frameworks for organizing memories. PMID:23318095

No Evidence for an Item Limit in Change Detection (Open Access)

DTIC Science & Technology

2013-02-28

memory : a reconsideration of mental storage capacity. Behav Brain Sci 24: 87–114. 17. Eng HY, Chen D, Jiang Y (2005) Visual working memory for simple...working memory can hold no more than a fixed number of items (‘‘item-limit models’’). Recent findings force us to consider the alternative view that working... memory is limited by the precision in stimulus encoding, with mean precision decreasing with increasing set size (‘‘continuous-resource models

The attentional blink reveals serial working memory encoding: evidence from virtual and human event-related potentials.

PubMed

Craston, Patrick; Wyble, Brad; Chennu, Srivas; Bowman, Howard

2009-03-01

Observers often miss a second target (T2) if it follows an identified first target item (T1) within half a second in rapid serial visual presentation (RSVP), a finding termed the attentional blink. If two targets are presented in immediate succession, however, accuracy is excellent (Lag 1 sparing). The resource sharing hypothesis proposes a dynamic distribution of resources over a time span of up to 600 msec during the attentional blink. In contrast, the ST(2) model argues that working memory encoding is serial during the attentional blink and that, due to joint consolidation, Lag 1 is the only case where resources are shared. Experiment 1 investigates the P3 ERP component evoked by targets in RSVP. The results suggest that, in this context, P3 amplitude is an indication of bottom-up strength rather than a measure of cognitive resource allocation. Experiment 2, employing a two-target paradigm, suggests that T1 consolidation is not affected by the presentation of T2 during the attentional blink. However, if targets are presented in immediate succession (Lag 1 sparing), they are jointly encoded into working memory. We use the ST(2) model's neural network implementation, which replicates a range of behavioral results related to the attentional blink, to generate "virtual ERPs" by summing across activation traces. We compare virtual to human ERPs and show how the results suggest a serial nature of working memory encoding as implied by the ST(2) model.

Iconic Decay in Schizophrenia

PubMed Central

Hahn, Britta; Kappenman, Emily S.; Robinson, Benjamin M.; Fuller, Rebecca L.; Luck, Steven J.; Gold, James M.

2011-01-01

Working memory impairment is considered a core deficit in schizophrenia, but the precise nature of this deficit has not been determined. Multiple lines of evidence implicate deficits at the encoding stage. During encoding, information is held in a precategorical sensory store termed iconic memory, a literal image of the stimulus with high capacity but rapid decay. Pathologically increased iconic decay could reduce the number of items that can be transferred into working memory before the information is lost and could thus contribute to the working memory deficit seen in the illness. The current study used a partial report procedure to test the hypothesis that patients with schizophrenia (n = 37) display faster iconic memory decay than matched healthy control participants (n = 28). Six letters, arranged in a circle, were presented for 50 ms. Following a variable delay of 0–1000 ms, a central arrow cue indicated the item to be reported. In both patients and control subjects, recall accuracy decreased with increasing cue delay, reflecting decay of the iconic representation of the stimulus array. Patients displayed impaired memory performance across all cue delays, consistent with an impairment in working memory, but the rate of iconic memory decay did not differ between patients and controls. This provides clear evidence against faster loss of iconic memory representations in schizophrenia, ruling out iconic decay as an underlying source of the working memory impairment in this population. Thus, iconic decay rate can be added to a growing list of unimpaired cognitive building blocks in schizophrenia. PMID:20053864

Iconic decay in schizophrenia.

PubMed

Hahn, Britta; Kappenman, Emily S; Robinson, Benjamin M; Fuller, Rebecca L; Luck, Steven J; Gold, James M

2011-09-01

Working memory impairment is considered a core deficit in schizophrenia, but the precise nature of this deficit has not been determined. Multiple lines of evidence implicate deficits at the encoding stage. During encoding, information is held in a precategorical sensory store termed iconic memory, a literal image of the stimulus with high capacity but rapid decay. Pathologically increased iconic decay could reduce the number of items that can be transferred into working memory before the information is lost and could thus contribute to the working memory deficit seen in the illness. The current study used a partial report procedure to test the hypothesis that patients with schizophrenia (n = 37) display faster iconic memory decay than matched healthy control participants (n = 28). Six letters, arranged in a circle, were presented for 50 ms. Following a variable delay of 0-1000 ms, a central arrow cue indicated the item to be reported. In both patients and control subjects, recall accuracy decreased with increasing cue delay, reflecting decay of the iconic representation of the stimulus array. Patients displayed impaired memory performance across all cue delays, consistent with an impairment in working memory, but the rate of iconic memory decay did not differ between patients and controls. This provides clear evidence against faster loss of iconic memory representations in schizophrenia, ruling out iconic decay as an underlying source of the working memory impairment in this population. Thus, iconic decay rate can be added to a growing list of unimpaired cognitive building blocks in schizophrenia.

Leveling the playing field: attention mitigates the effects of intelligence on memory.

PubMed

Markant, Julie; Amso, Dima

2014-05-01

Effective attention and memory skills are fundamental to typical development and essential for achievement during the formal education years. It is critical to identify the specific mechanisms linking efficiency of attentional selection of an item and the quality of its memory retention. The present study capitalized on the spatial cueing paradigm to examine the role of selection via suppression in modulating children and adolescents' memory encoding. By varying a single parameter, the spatial cueing task can elicit either a simple orienting mechanism (i.e., facilitation) or one that involves both target selection and simultaneous suppression of competing information (i.e., IOR). We modified this paradigm to include images of common items in target locations. Participants were not instructed to learn the items and were not told they would be completing a memory test later. Following the cueing task, we imposed a 7-min delay and then asked participants to complete a recognition memory test. Results indicated that selection via suppression promoted recognition memory among 7-17year-olds. Moreover, individual differences in the extent of suppression during encoding predicted recognition memory accuracy. When basic cueing facilitated orienting to target items during encoding, IQ was the best predictor of recognition memory performance for the attended items. In contrast, engaging suppression (i.e., IOR) during encoding counteracted individual differences in intelligence, effectively improving recognition memory performance among children with lower IQs. This work demonstrates that engaging selection via suppression during learning and encoding improves memory retention and has broad implications for developing effective educational techniques. Copyright © 2014 Elsevier B.V. All rights reserved.

Leveling the playing field: Attention mitigates the effects of intelligence on memory

PubMed Central

Markant, Julie; Amso, Dima

2014-01-01

Effective attention and memory skills are fundamental to typical development and essential for achievement during the formal education years. It is critical to identify the specific mechanisms linking efficiency of attentional selection of an item and the quality of its memory retention. The present study capitalized on the spatial cueing paradigm to examine the role of selection via suppression in modulating children and adolescents’ memory encoding. By varying a single parameter, the spatial cueing task can elicit either a simple orienting mechanism (i.e., facilitation) or one that involves both target selection and simultaneous suppression of competing information (i.e., IOR). We modified this paradigm to include images of common items in target locations. Participants were not instructed to learn the items and were not told they would be completing a memory test later. Following the cueing task, we imposed a seven-minute delay and then asked participants to complete a recognition memory test. Results indicated that selection via suppression promoted recognition memory among 7-17 year-olds. Moreover, individual differences in the extent of suppression during encoding predicted recognition memory accuracy. When basic cueing facilitated orienting to target items during encoding, IQ was the best predictor of recognition memory performance for the attended items. In contrast, engaging suppression (i.e, IOR) during encoding counteracted individual differences in intelligence, effectively improving recognition memory performance among children with lower IQs. This work demonstrates that engaging selection via suppression during learning and encoding improves memory retention and has broad implications for developing effective educational techniques. PMID:24549142

Memory Skills of Deaf Learners: Implications and Applications

ERIC Educational Resources Information Center

Hamilton, Harley

2011-01-01

The author reviews research on working memory and short-term memory abilities of deaf individuals, delineating strengths and weaknesses. Among the areas of weakness that are reviewed are sequential recall, processing speed, attention, and memory load. Areas of strengths include free recall, visuospatial recall, imagery, and dual encoding.…

Individual Differences in Working Memory Capacity Predict Sleep-Dependent Memory Consolidation

ERIC Educational Resources Information Center

Fenn, Kimberly M.; Hambrick, David Z.

2012-01-01

Decades of research have established that "online" cognitive processes, which operate during conscious encoding and retrieval of information, contribute substantially to individual differences in memory. Furthermore, it is widely accepted that "offline" processes during sleep also contribute to memory performance. However, the question of whether…

Task-selective memory effects for successfully implemented encoding strategies.

PubMed

Leshikar, Eric D; Duarte, Audrey; Hertzog, Christopher

2012-01-01

Previous behavioral evidence suggests that instructed strategy use benefits associative memory formation in paired associate tasks. Two such effective encoding strategies--visual imagery and sentence generation--facilitate memory through the production of different types of mediators (e.g., mental images and sentences). Neuroimaging evidence suggests that regions of the brain support memory reflecting the mental operations engaged at the time of study. That work, however, has not taken into account self-reported encoding task success (i.e., whether participants successfully generated a mediator). It is unknown, therefore, whether task-selective memory effects specific to each strategy might be found when encoding strategies are successfully implemented. In this experiment, participants studied pairs of abstract nouns under either visual imagery or sentence generation encoding instructions. At the time of study, participants reported their success at generating a mediator. Outside of the scanner, participants further reported the quality of the generated mediator (e.g., images, sentences) for each word pair. We observed task-selective memory effects for visual imagery in the left middle occipital gyrus, the left precuneus, and the lingual gyrus. No such task-selective effects were observed for sentence generation. Intriguingly, activity at the time of study in the left precuneus was modulated by the self-reported quality (vividness) of the generated mental images with greater activity for trials given higher ratings of quality. These data suggest that regions of the brain support memory in accord with the encoding operations engaged at the time of study.

Task-Selective Memory Effects for Successfully Implemented Encoding Strategies

PubMed Central

Leshikar, Eric D.; Duarte, Audrey; Hertzog, Christopher

2012-01-01

Previous behavioral evidence suggests that instructed strategy use benefits associative memory formation in paired associate tasks. Two such effective encoding strategies–visual imagery and sentence generation–facilitate memory through the production of different types of mediators (e.g., mental images and sentences). Neuroimaging evidence suggests that regions of the brain support memory reflecting the mental operations engaged at the time of study. That work, however, has not taken into account self-reported encoding task success (i.e., whether participants successfully generated a mediator). It is unknown, therefore, whether task-selective memory effects specific to each strategy might be found when encoding strategies are successfully implemented. In this experiment, participants studied pairs of abstract nouns under either visual imagery or sentence generation encoding instructions. At the time of study, participants reported their success at generating a mediator. Outside of the scanner, participants further reported the quality of the generated mediator (e.g., images, sentences) for each word pair. We observed task-selective memory effects for visual imagery in the left middle occipital gyrus, the left precuneus, and the lingual gyrus. No such task-selective effects were observed for sentence generation. Intriguingly, activity at the time of study in the left precuneus was modulated by the self-reported quality (vividness) of the generated mental images with greater activity for trials given higher ratings of quality. These data suggest that regions of the brain support memory in accord with the encoding operations engaged at the time of study. PMID:22693593

Social memory engram in the hippocampus.

PubMed

Okuyama, Teruhiro

2018-04-01

Social memory is one of the crucial components of episodic memories. Gregarious animals living in societies utilize social memory to exhibit the appropriate social behaviors such as aggression, avoidance, cooperative behavior, and even mating behavior. However, the neural mechanisms underlying social memory in the hippocampus remains mysterious. Here, I review some evidence from work done in rodents and primates on the brain region(s) and circuits encoding and/or retrieving social memory, as well as a storage for social memory (i.e. social memory engram neurons). Based on our recent findings that neural ensemble in ventral CA1 sub-region of the hippocampus possesses social memory engram, I would discuss the neural network for social information processing in order to encode social memory; and its evolutionary conservation between rodents and human. Copyright © 2017 Elsevier Ireland Ltd and Japan Neuroscience Society. All rights reserved.

The Influence of Encoding Strategy on Episodic Memory and Cortical Activity in Schizophrenia

PubMed Central

Haut, Kristen; Csernansky, John G.; Barch, Deanna M.

2005-01-01

Background: Recent work suggests that episodic memory deficits in schizophrenia may be related to disturbances of encoding or retrieval. Schizophrenia patients appear to benefit from instruction in episodic memory strategies. We tested the hypothesis that providing effective encoding strategies to schizophrenia patients enhances encoding-related brain activity and recognition performance. Methods: Seventeen schizophrenia patients and 26 healthy comparison subjects underwent functional magnetic resonance imaging scans while performing incidental encoding tasks of words and faces. Subjects were required to make either deep (abstract/concrete) or shallow (alphabetization) judgments for words and deep (gender) judgments for faces, followed by subsequent recognition tests. Results: Schizophrenia and comparison subjects recognized significantly more words encoded deeply than shallowly, activated regions in inferior frontal cortex (Brodmann area 45/47) typically associated with deep and successful encoding of words, and showed greater left frontal activation for the processing of words compared with faces. However, during deep encoding and material-specific processing (words vs. faces), participants with schizophrenia activated regions not activated by control subjects, including several in prefrontal cortex. Conclusions: Our findings suggest that a deficit in use of effective strategies influences episodic memory performance in schizophrenia and that abnormalities in functional brain activation persist even when such strategies are applied. PMID:15992522

Monkey prefrontal neurons during Sternberg task performance: full contents of working memory or most recent item?

PubMed

Konecky, R O; Smith, M A; Olson, C R

2017-06-01

To explore the brain mechanisms underlying multi-item working memory, we monitored the activity of neurons in the dorsolateral prefrontal cortex while macaque monkeys performed spatial and chromatic versions of a Sternberg working-memory task. Each trial required holding three sequentially presented samples in working memory so as to identify a subsequent probe matching one of them. The monkeys were able to recall all three samples at levels well above chance, exhibiting modest load and recency effects. Prefrontal neurons signaled the identity of each sample during the delay period immediately following its presentation. However, as each new sample was presented, the representation of antecedent samples became weak and shifted to an anomalous code. A linear classifier operating on the basis of population activity during the final delay period was able to perform at approximately the level of the monkeys on trials requiring recall of the third sample but showed a falloff in performance on trials requiring recall of the first or second sample much steeper than observed in the monkeys. We conclude that delay-period activity in the prefrontal cortex robustly represented only the most recent item. The monkeys apparently based performance of this classic working-memory task on some storage mechanism in addition to the prefrontal delay-period firing rate. Possibilities include delay-period activity in areas outside the prefrontal cortex and changes within the prefrontal cortex not manifest at the level of the firing rate. NEW & NOTEWORTHY It has long been thought that items held in working memory are encoded by delay-period activity in the dorsolateral prefrontal cortex. Here we describe evidence contrary to that view. In monkeys performing a serial multi-item working memory task, dorsolateral prefrontal neurons encode almost exclusively the identity of the sample presented most recently. Information about earlier samples must be encoded outside the prefrontal cortex or represented within the prefrontal cortex in a cryptic code. Copyright © 2017 the American Physiological Society.

Object perception is selectively slowed by a visually similar working memory load.

PubMed

Robinson, Alan; Manzi, Alberto; Triesch, Jochen

2008-12-22

The capacity of visual working memory has been extensively characterized, but little work has investigated how occupying visual memory influences other aspects of cognition and perception. Here we show a novel effect: maintaining an item in visual working memory slows processing of similar visual stimuli during the maintenance period. Subjects judged the gender of computer rendered faces or the naturalness of body postures while maintaining different visual memory loads. We found that when stimuli of the same class (faces or bodies) were maintained in memory, perceptual judgments were slowed. Interestingly, this is the opposite of what would be predicted from traditional priming. Our results suggest there is interference between visual working memory and perception, caused by visual similarity between new perceptual input and items already encoded in memory.

Misremembering what you see or hear: Dissociable effects of modality on short- and long-term false recognition.

PubMed

Olszewska, Justyna M; Reuter-Lorenz, Patricia A; Munier, Emily; Bendler, Sara A

2015-09-01

False working memories readily emerge using a visual item-recognition variant of the converging associates task. Two experiments, manipulating study and test modality, extended prior working memory results by demonstrating a reliable false recognition effect (more false alarms to associatively related lures than to unrelated lures) within seconds of encoding in either the visual or auditory modality. However, false memories were nearly twice as frequent when study lists were seen than when they were heard, regardless of test modality, although study-test modality mismatch was generally disadvantageous (consistent with encoding specificity). A final experiment that varied study-test modality using a hybrid short- and long-term memory test (Flegal, Atkins & Reuter-Lorenz, 2010) replicated the auditory advantage in the short term but revealed a reversal in the long term: The false memory effect was greater in the auditory study-test condition than in the visual study-test condition. Thus, the same encoding conditions gave rise to an opposite modality advantage depending on whether recognition was tested under short-term or long-term memory conditions. Although demonstrating continuity in associative processing across delay, the results indicate that delay condition affects the availability of modality-dependent features of the memory trace and, thus, distinctiveness, leading to dissociable patterns of short- and long-term memory performance. (c) 2015 APA, all rights reserved).

Mental reinstatement of encoding context improves episodic remembering.

PubMed

Bramão, Inês; Karlsson, Anna; Johansson, Mikael

2017-09-01

This study investigates context-dependent memory retrieval. Previous work has shown that physically re-experiencing the encoding context at retrieval improves memory accessibility. The current study examined if mental reconstruction of the original encoding context would yield parallel memory benefits. Participants performed a cued-recall memory task, preceded either by a mental or by a physical context reinstatement task, and we manipulated whether the context reinstated at retrieval overlapped with the context of the target episode. Both behavioral and electrophysiological measures of brain activity showed strong encoding-retrieval (E-R) overlap effects, with facilitated episodic retrieval when the encoding and retrieval contexts overlapped. The electrophysiological E-R overlap effect was more sustained and involved more posterior regions when context was mentally compared with physically reinstated. Additionally, a time-frequency analysis revealed that context reinstatement alone engenders recollection of the target episode. However, while recollection of the target memory is readily prompted by a physical reinstatement, target recollection during mental reinstatement is delayed and depends on the gradual reconstruction of the context. Taken together, our results show facilitated episodic remembering also when mentally reinstating the encoding context; and that such benefits are supported by both shared and partially non-overlapping neural mechanisms when the encoding context is mentally reconstructed as compared with physically presented at the time of retrieval. Copyright © 2017 Elsevier Ltd. All rights reserved.

The relationship between visual attention and visual working memory encoding: A dissociation between covert and overt orienting.

PubMed

Tas, A Caglar; Luck, Steven J; Hollingworth, Andrew

2016-08-01

There is substantial debate over whether visual working memory (VWM) and visual attention constitute a single system for the selection of task-relevant perceptual information or whether they are distinct systems that can be dissociated when their representational demands diverge. In the present study, we focused on the relationship between visual attention and the encoding of objects into VWM. Participants performed a color change-detection task. During the retention interval, a secondary object, irrelevant to the memory task, was presented. Participants were instructed either to execute an overt shift of gaze to this object (Experiments 1-3) or to attend it covertly (Experiments 4 and 5). Our goal was to determine whether these overt and covert shifts of attention disrupted the information held in VWM. We hypothesized that saccades, which typically introduce a memorial demand to bridge perceptual disruption, would lead to automatic encoding of the secondary object. However, purely covert shifts of attention, which introduce no such demand, would not result in automatic memory encoding. The results supported these predictions. Saccades to the secondary object produced substantial interference with VWM performance, but covert shifts of attention to this object produced no interference with VWM performance. These results challenge prevailing theories that consider attention and VWM to reflect a common mechanism. In addition, they indicate that the relationship between attention and VWM is dependent on the memorial demands of the orienting behavior. (PsycINFO Database Record (c) 2016 APA, all rights reserved).

Working Memory Encoding and False Memory in Schizophrenia and Bipolar Disorder in a Spatial Delayed Response Task

PubMed Central

Mayer, Jutta S.; Park, Sohee

2014-01-01

Working memory (WM) impairment is a core feature of schizophrenia, but the contributions of different WM components are not yet specified. Here, we investigated the potential role of inefficient encoding in reduced WM performance in patients with schizophrenia (PSZ). Twenty-eight PSZ, 16 patients with bipolar disorder (PBP), 16 unaffected and unmedicated relatives of PSZ (REL), and 29 demographically matched healthy controls (HC) performed a spatial delayed response task with either low or high WM demands. The demands on attentional selection were also manipulated by presenting distractor stimuli during encoding in some of the trials. After each trial, participants rated their level of response confidence. This allowed us to analyze different types of WM responses. WM was severely impaired in PSZ compared to HC; this reduction was mainly due to an increase in the amount of false memory responses (incorrect responses that were given with high confidence) rather than an increase in the amount of incorrect and not-confident responses. Although PBP showed WM impairments, they did not have increased false memory errors. In contrast, reduced WM in REL was also accompanied by an increase in false memory errors. The presentation of distractors led to a decline in WM performance, which was comparable across groups indicating that attentional selection was intact in PSZ. These findings suggest that inefficient WM encoding is responsible for impaired WM in schizophrenia and point to differential mechanisms underlying WM impairments in PSZ and PBP. PMID:22708888

Regional brain activity that determines successful and unsuccessful working memory formation.

PubMed

Teramoto, Shohei; Inaoka, Tsubasa; Ono, Yumie

2016-08-01

Using EEG source reconstruction with Multiple Sparse Priors (MSP), we investigated the regional brain activity that determines successful memory encoding in two participant groups of high and low accuracy rates. Eighteen healthy young adults performed a sequential fashion of visual Sternberg memory task. The 32-channel EEG was continuously measured during participants performed two 70 trials of memory task. The regional brain activity corresponding to the oscillatory EEG activity in the alpha band (8-13 Hz) during encoding period was analyzed by MSP implemented in SPM8. We divided the data of all participants into 2 groups (low- and highperformance group) and analyzed differences in regional brain activity between trials in which participants answered correctly and incorrectly within each of the group. Participants in low-performance group showed significant activity increase in the visual cortices in their successful trials compared to unsuccessful ones. On the other hand, those in high-performance group showed a significant activity increase in widely distributed cortical regions in the frontal, temporal, and parietal areas including those suggested as Baddeley's working memory model. Further comparison of activated cortical volumes and mean current source intensities within the cortical regions of Baddeley's model during memory encoding demonstrated that participants in high-performance group showed enhanced activity in the right premotor cortex, which plays an important role in maintaining visuospatial attention, compared to those in low performance group. Our results suggest that better ability in memory encoding is associated with distributed and stronger regional brain activities including the premotor cortex, possibly indicating efficient allocation of cognitive load and maintenance of attention.

Effects of Stress and Task Difficulty on Working Memory and Cortical Networking.

PubMed

Kim, Yujin; Woo, Jihwan; Woo, Minjung

2017-12-01

This study investigated interactive effects of stress and task difficulty on working memory and cortico-cortical communication during memory encoding. Thirty-eight adolescent participants (mean age of 15.7 ± 1.5 years) completed easy and hard working memory tasks under low- and high-stress conditions. We analyzed the accuracy and reaction time (RT) of working memory performance and inter- and intrahemispheric electroencephalogram coherences during memory encoding. Working memory accuracy was higher, and RT shorter, in the easy versus the hard task. RT was shorter under the high-stress (TENS) versus low-stress (no-TENS) condition, while there was no difference in memory accuracy between the two stress conditions. For electroencephalogram coherence, we found higher interhemispheric coherence in all bands but only at frontal electrode sites in the easy versus the hard task. On the other hand, intrahemispheric coherence was higher in the left hemisphere in the easy (versus hard task) and higher in the right hemisphere (with one exception) in the hard (versus easy task). Inter- and intracoherences were higher in the low- versus high-stress condition. Significant interactions between task difficulty and stress condition were observed in coherences of the beta frequency band. The difference in coherence between low- and high-stress conditions was greater in the hard compared with the easy task, with lower coherence under the high-stress condition relative to the low-stress condition. Stress seemed to cause a decrease in cortical network communications between memory-relevant cortical areas as task difficulty increased.

Brain systems underlying attentional control and emotional distraction during working memory encoding.

PubMed

Ziaei, Maryam; Peira, Nathalie; Persson, Jonas

2014-02-15

Goal-directed behavior requires that cognitive operations can be protected from emotional distraction induced by task-irrelevant emotional stimuli. The brain processes involved in attending to relevant information while filtering out irrelevant information are still largely unknown. To investigate the neural and behavioral underpinnings of attending to task-relevant emotional stimuli while ignoring irrelevant stimuli, we used fMRI to assess brain responses during attentional instructed encoding within an emotional working memory (WM) paradigm. We showed that instructed attention to emotion during WM encoding resulted in enhanced performance, by means of increased memory performance and reduced reaction time, compared to passive viewing. A similar performance benefit was also demonstrated for recognition memory performance, although for positive pictures only. Functional MRI data revealed a network of regions involved in directed attention to emotional information for both positive and negative pictures that included medial and lateral prefrontal cortices, fusiform gyrus, insula, the parahippocampal gyrus, and the amygdala. Moreover, we demonstrate that regions in the striatum, and regions associated with the default-mode network were differentially activated for emotional distraction compared to neutral distraction. Activation in a sub-set of these regions was related to individual differences in WM and recognition memory performance, thus likely contributing to performing the task at an optimal level. The present results provide initial insights into the behavioral and neural consequences of instructed attention and emotional distraction during WM encoding. © 2013.

The Integration of Realistic Episodic Memories Relies on Different Working Memory Processes: Evidence from Virtual Navigation.

PubMed

Plancher, Gaën; Gyselinck, Valérie; Piolino, Pascale

2018-01-01

Memory is one of the most important cognitive functions in a person's life as it is essential for recalling personal memories and performing many everyday tasks. Although a huge number of studies have been conducted in the field, only a few of them investigated memory in realistic situations, due to methodological issues. The various tools that have been developed using virtual environments (VEs) have gained popularity in cognitive psychology and neuropsychology because they enable to create naturalistic and controlled situations, and are thus particularly adapted to the study of episodic memory (EM), for which an ecological evaluation is of prime importance. EM is the conscious recollection of personal events combined with their phenomenological and spatiotemporal encoding contexts. Using an original paradigm in a VE, the objective of the present study was to characterize the construction of episodic memories. While the concept of working memory has become central in the understanding of a wide range of cognitive functions, its role in the integration of episodic memories has seldom been assessed in an ecological context. This experiment aimed at filling this gap by studying how EM is affected by concurrent tasks requiring working memory resources in a realistic situation. Participants navigated in a virtual town and had to memorize as many elements in their spatiotemporal context as they could. During learning, participants had either to perform a concurrent task meant to prevent maintenance through the phonological loop, or a task aimed at preventing maintenance through the visuospatial sketchpad, or no concurrent task. EM was assessed in a recall test performed after learning through various scores measuring the what, where and when of the memories. Results showed that, compared to the control condition with no concurrent task, the prevention of maintenance through the phonological loop had a deleterious impact only on the encoding of central elements. By contrast, the prevention of visuo-spatial maintenance interfered both with the encoding of the temporal context and with the binding. These results suggest that the integration of realistic episodic memories relies on different working memory processes that depend on the nature of the traces.

A case of hyperthymesia: Rethinking the role of the amygdala in autobiographical memory

PubMed Central

Ally, Brandon A.; Hussey, Erin P.; Donahue, Manus J.

2012-01-01

Much controversy has been focused on the extent to which the amygdala belongs to the autobiographical memory core network. Early evidence suggested the amygdala played a vital role in emotional processing, likely helping to encode emotionally charged stimuli. However, recent work has highlighted the amygdala’s role in social and self-referential processing, leading to speculation that the amygdala likely supports the encoding and retrieval of autobiographical memory. Here, cognitive as well as structural and functional magnetic resonance imaging data was collected from an extremely rare individual with near-perfect autobiographical memory, or hyperthymesia. Right amygdala hypertrophy (approximately 20%) and enhanced amygdala-to-hippocampus connectivity (> 10 standard deviations) was observed in this volunteer relative to controls. Based on these findings and previous literature, we speculate that the amygdala likely charges autobiographical memories with emotional, social, and self-relevance. In heightened memory, this system may be hyperactive, allowing for many types of autobiographical information, including emotionally benign, to be more efficiently processed as self-relevant for encoding and storage. PMID:22519463

Hippocampal place cell and inhibitory neuron activity in disrupted-in-schizophrenia-1 mutant mice: implications for working memory deficits

PubMed Central

Mesbah-Oskui, Lia; Georgiou, John; Roder, John C

2015-01-01

Background: Despite the prevalence of working memory deficits in schizophrenia, the neuronal mechanisms mediating these deficits are not fully understood. Importantly, deficits in spatial working memory are identified in numerous mouse models that exhibit schizophrenia-like endophenotypes. The hippocampus is one of the major brain regions that actively encodes spatial location, possessing pyramidal neurons, commonly referred to as ‘place cells’, that fire in a location-specific manner. This study tests the hypothesis that mice with a schizophrenia-like endophenotype exhibit impaired encoding of spatial location in the hippocampus. Aims: To characterize hippocampal place cell activity in mice that exhibit a schizophrenia-like endophenotype. Methods: We recorded CA1 place cell activity in six control mice and six mice that carry a point mutation in the disrupted-in-schizophrenia-1 gene (Disc1-L100P) and have previously been shown to exhibit deficits in spatial working memory. Results: The spatial specificity and stability of Disc1-L100P place cells were similar to wild-type place cells. Importantly, however, Disc1-L100P place cells exhibited a higher propensity to increase their firing rate in a single, large location of the environment, rather than multiple smaller locations, indicating a generalization in their spatial selectivity. Alterations in the signaling and numbers of CA1 putative inhibitory interneurons and decreased hippocampal theta (5–12 Hz) power were also identified in the Disc1-L100P mice. Conclusions: The generalized spatial selectivity of Disc1-L100P place cells suggests a simplification of the ensemble place codes that encode individual locations and subserve spatial working memory. Moreover, these results suggest that deficient working memory in schizophrenia results from an impaired ability to uniquely code the individual components of a memory sequence. PMID:27280123

Short-Term Memory Stages in Sign vs. Speech: The Source of the Serial Span Discrepancy

PubMed Central

Hall, Matthew L.

2011-01-01

Speakers generally outperform signers when asked to recall a list of unrelated verbal items. This phenomenon is well established, but its source has remained unclear. In this study, we evaluate the relative contribution of the three main processing stages of short-term memory – perception, encoding, and recall – in this effect. The present study factorially manipulates whether American Sign Language (ASL) or English was used for perception, memory encoding, and recall in hearing ASL-English bilinguals. Results indicate that using ASL during both perception and encoding contributes to the serial span discrepancy. Interestingly, performing recall in ASL slightly increased span, ruling out the view that signing is in general a poor choice for short-term memory. These results suggest that despite the general equivalence of sign and speech in other memory domains, speech-based representations are better suited for the specific task of perception and memory encoding of a series of unrelated verbal items in serial order through the phonological loop. This work suggests that interpretation of performance on serial recall tasks in English may not translate straightforwardly to serial tasks in sign language. PMID:21450284

Controlled encoding strategies in memory tests in lithium patients.

PubMed

Opgenoorth, E; Karlick-Bolten, E

1986-03-01

The "levels of processing" theory (Craik and Lockhart) and "dual coding" theory (Paivio) provide new aspects for clinical memory research work. Therefore, an incidental learning paradigm on the basis of these two theoretical approaches was chosen to test aspects of memory performances with lithium therapy. Results of two experiments, with controlled non-semantic processing (rating experiment "comparison of size") and additive semantic processing (rating "living--non-living") indicate a slight reduction in recall (Fig. 1) and recognition performance (Fig. 2) in lithium patients. Effects on encoding strategies are of equal quality in patients and healthy subjects (Tab. 1, 2) but performance differs between both groups: poorer systematic benefit from within code repetitions ("word-word" items, "picture-picture" items) and dual coding (repeated variable item presentation "picture-word") is obtained. The less efficient encoding strategies in the speeded task are discussed with respect to cognitive rigidity and slowing of performance by emotional states. This investigation of so-called "memory deficits" with lithium is an attempt to explore impairments at an early stage of processing; the characterization of the perceptual cognitive analysis seems useful for further clinical research work on this topic.

Evidence against Decay in Verbal Working Memory

ERIC Educational Resources Information Center

Oberauer, Klaus; Lewandowsky, Stephan

2013-01-01

The article tests the assumption that forgetting in working memory for verbal materials is caused by time-based decay, using the complex-span paradigm. Participants encoded 6 letters for serial recall; each letter was preceded and followed by a processing period comprising 4 trials of difficult visual search. Processing duration, during which…

Sex and menstrual cycle phase at encoding influence emotional memory for gist and detail

PubMed Central

Nielsen, Shawn E.; Ahmed, Imran; Cahill, Larry

2013-01-01

Sex influences on emotional memory have received increasing interest over the past decade. However, only a subset of this previous work explored the influence of sex on memory for central information (gist) and peripheral detail in emotional versus neutral contexts. Here we examined the influence of sex and menstrual cycle phase at encoding on memory for either an emotional or neutral story, specifically with respect to the retention of gist and peripheral detail. Healthy naturally cycling women and men viewed a brief, narrated, three-phase story containing neutral or emotionally arousing elements. One week later, participants received a surprise free recall test for story elements. The results indicate that naturally cycling women in the luteal (high hormone) phase of the menstrual cycle at encoding show enhanced memory for peripheral details, but not gist, when in the emotional compared with neutral stories (p<.05). In contrast, naturally cycling women in the follicular (low hormone) phase of the menstrual cycle at encoding did not show enhanced memory for gist or peripheral details in the emotional compared with neutral stories. Men show enhanced memory for gist, but not peripheral details, in the emotional versus neutral stories (p<.05). In addition, these sex influences on memory cannot be attributed to differences in attention or arousal; luteal women, follicular women, and men performed similarly on measures of attention (fixation time percentage) and arousal (pupil diameter changes) during the most arousing phase of the emotional story. These findings suggest that sex and menstrual cycle phase at encoding influence long term memory for different types of emotional information. PMID:23891713

VERBAL AND SPATIAL WORKING MEMORY LOAD HAVE SIMILARLY MINIMAL EFFECTS ON SPEECH PRODUCTION.

PubMed

Lee, Ogyoung; Redford, Melissa A

2015-08-10

The goal of the present study was to test the effects of working memory on speech production. Twenty American-English speaking adults produced syntactically complex sentences in tasks that taxed either verbal or spatial working memory. Sentences spoken under load were produced with more errors, fewer prosodic breaks, and at faster rates than sentence produced in the control conditions, but other acoustic correlates of rhythm and intonation did not change. Verbal and spatial working memory had very similar effects on production, suggesting that the different span tasks used to tax working memory merely shifted speakers' attention away from the act of speaking. This finding runs contra the hypothesis of incremental phonological/phonetic encoding, which predicts the manipulation of information in verbal working memory during speech production.

Role of the hippocampus and orbitofrontal cortex during the disambiguation of social cues in working memory

PubMed Central

Ross, Robert S.; LoPresti, Matthew L.; Schon, Karin; Stern, Chantal E.

2013-01-01

Human social interactions are complex behaviors requiring the concerted effort of multiple neural systems to track and monitor the individuals around us. Cognitively, adjusting our behavior based on changing social cues such as facial expressions relies on working memory and the ability to disambiguate, or separate, representations of overlapping stimuli resulting from viewing the same individual with different facial expressions. We conducted an fMRI experiment examining brain regions contributing to the encoding, maintenance and retrieval of overlapping identity information during working memory using a delayed match-to-sample (DMS) task. In the overlapping condition, two faces from the same individual with different facial expressions were presented at sample. In the non-overlapping condition, the two sample faces were from two different individuals with different expressions. fMRI activity was assessed by contrasting the overlapping and non-overlapping condition at sample, delay, and test. The lateral orbitofrontal cortex showed increased fMRI signal in the overlapping condition in all three phases of the DMS task and increased functional connectivity with the hippocampus when encoding overlapping stimuli. The hippocampus showed increased fMRI signal at test. These data suggest lateral orbitofrontal cortex helps encode and maintain representations of overlapping stimuli in working memory while the orbitofrontal cortex and hippocampus contribute to the successful retrieval of overlapping stimuli. We suggest the lateral orbitofrontal cortex and hippocampus play a role in encoding, maintaining, and retrieving social cues, especially when multiple interactions with an individual need to be disambiguated in a rapidly changing social context in order to make appropriate social responses. PMID:23640112

CA1 subfield contributions to memory integration and inference

PubMed Central

Schlichting, Margaret L.; Zeithamova, Dagmar; Preston, Alison R.

2014-01-01

The ability to combine information acquired at different times to make novel inferences is a powerful function of episodic memory. One perspective suggests that by retrieving related knowledge during new experiences, existing memories can be linked to the new, overlapping information as it is encoded. The resulting memory traces would thus incorporate content across event boundaries, representing important relationships among items encountered during separate experiences. While prior work suggests that the hippocampus is involved in linking memories experienced at different times, the involvement of specific subfields in this process remains unknown. Using both univariate and multivariate analyses of high-resolution functional magnetic resonance imaging (fMRI) data, we localized this specialized encoding mechanism to human CA1. Specifically, right CA1 responses during encoding of events that overlapped with prior experience predicted subsequent success on a test requiring inferences about the relationships among events. Furthermore, we employed neural pattern similarity analysis to show that patterns of activation evoked during overlapping event encoding were later reinstated in CA1 during successful inference. The reinstatement of CA1 patterns during inference was specific to those trials that were performed quickly and accurately, consistent with the notion that linking memories during learning facilitates novel judgments. These analyses provide converging evidence that CA1 plays a unique role in encoding overlapping events and highlight the dynamic interactions between hippocampal-mediated encoding and retrieval processes. More broadly, our data reflect the adaptive nature of episodic memories, in which representations are derived across events in anticipation of future judgments. PMID:24888442

Medial prefrontal cortex supports source memory accuracy for self-referenced items

PubMed Central

Leshikar, Eric D.; Duarte, Audrey

2013-01-01

Previous behavioral work suggests that processing information in relation to the self enhances subsequent item recognition. Neuroimaging evidence further suggests that regions along the cortical midline, particularly those of the medial prefrontal cortex, underlie this benefit. There has been little work to date, however, on the effects of self-referential encoding on source memory accuracy or whether the medial prefrontal cortex might contribute to source memory for self-referenced materials. In the current study, we used fMRI to measure neural activity while participants studied and subsequently retrieved pictures of common objects superimposed on one of two background scenes (sources) under either self-reference or self-external encoding instructions. Both item recognition and source recognition were better for objects encoded self-referentially than self-externally. Neural activity predictive of source accuracy was observed in the medial prefrontal cortex (BA 10) at the time of study for self-referentially but not self-externally encoded objects. The results of this experiment suggest that processing information in relation to the self leads to a mnemonic benefit for source level features, and that activity in the medial prefrontal cortex contributes to this source memory benefit. This evidence expands the purported role that the medial prefrontal cortex plays in self-referencing. PMID:21936739

Imbalance of incidental encoding across tasks: an explanation for non-memory-related hippocampal activations?

PubMed

Reas, Emilie T; Brewer, James B

2013-11-01

Functional neuroimaging studies have increasingly noted hippocampal activation associated with a variety of cognitive functions--such as decision making, attention, perception, incidental learning, prediction, and working memory--that have little apparent relation to declarative memory. Such findings might be difficult to reconcile with classical hippocampal lesion studies that show remarkable sparing of cognitive functions outside the realm of declarative memory. Even the oft-reported hippocampal activations during confident episodic retrieval are not entirely congruent with evidence that hippocampal lesions reliably impair encoding but inconsistently affect retrieval. Here we explore the conditions under which the hippocampus responds during episodic recall and recognition. Our findings suggest that anterior hippocampal activity may be related to the imbalance of incidental encoding across tasks and conditions rather than due to retrieval per se. Incidental encoding and hippocampal activity may be reduced during conditions where retrieval requires greater attentional engagement. During retrieval, anterior hippocampal activity decreases with increasing search duration and retrieval effort, and this deactivation corresponds with a coincident impaired encoding of the external environment (Israel, Seibert, Black, & Brewer, 2010; Reas & Brewer, 2013; Reas, Gimbel, Hales, & Brewer, 2011). In light of this emerging evidence, we discuss the proposal that some hippocampal activity observed during memory retrieval, or other non-memory conditions, may in fact be attributable to concomitant encoding activity that is regulated by the attentional demands of the principal task. PsycINFO Database Record (c) 2013 APA, all rights reserved.

A Spiking Working Memory Model Based on Hebbian Short-Term Potentiation.

PubMed

Fiebig, Florian; Lansner, Anders

2017-01-04

A dominant theory of working memory (WM), referred to as the persistent activity hypothesis, holds that recurrently connected neural networks, presumably located in the prefrontal cortex, encode and maintain WM memory items through sustained elevated activity. Reexamination of experimental data has shown that prefrontal cortex activity in single units during delay periods is much more variable than predicted by such a theory and associated computational models. Alternative models of WM maintenance based on synaptic plasticity, such as short-term nonassociative (non-Hebbian) synaptic facilitation, have been suggested but cannot account for encoding of novel associations. Here we test the hypothesis that a recently identified fast-expressing form of Hebbian synaptic plasticity (associative short-term potentiation) is a possible mechanism for WM encoding and maintenance. Our simulations using a spiking neural network model of cortex reproduce a range of cognitive memory effects in the classical multi-item WM task of encoding and immediate free recall of word lists. Memory reactivation in the model occurs in discrete oscillatory bursts rather than as sustained activity. We relate dynamic network activity as well as key synaptic characteristics to electrophysiological measurements. Our findings support the hypothesis that fast Hebbian short-term potentiation is a key WM mechanism. Working memory (WM) is a key component of cognition. Hypotheses about the neural mechanism behind WM are currently under revision. Reflecting recent findings of fast Hebbian synaptic plasticity in cortex, we test whether a cortical spiking neural network model with such a mechanism can learn a multi-item WM task (word list learning). We show that our model can reproduce human cognitive phenomena and achieve comparable memory performance in both free and cued recall while being simultaneously compatible with experimental data on structure, connectivity, and neurophysiology of the underlying cortical tissue. These findings are directly relevant to the ongoing paradigm shift in the WM field. Copyright © 2017 Fiebig and Lansner.

A Spiking Working Memory Model Based on Hebbian Short-Term Potentiation

PubMed Central

Fiebig, Florian

2017-01-01

A dominant theory of working memory (WM), referred to as the persistent activity hypothesis, holds that recurrently connected neural networks, presumably located in the prefrontal cortex, encode and maintain WM memory items through sustained elevated activity. Reexamination of experimental data has shown that prefrontal cortex activity in single units during delay periods is much more variable than predicted by such a theory and associated computational models. Alternative models of WM maintenance based on synaptic plasticity, such as short-term nonassociative (non-Hebbian) synaptic facilitation, have been suggested but cannot account for encoding of novel associations. Here we test the hypothesis that a recently identified fast-expressing form of Hebbian synaptic plasticity (associative short-term potentiation) is a possible mechanism for WM encoding and maintenance. Our simulations using a spiking neural network model of cortex reproduce a range of cognitive memory effects in the classical multi-item WM task of encoding and immediate free recall of word lists. Memory reactivation in the model occurs in discrete oscillatory bursts rather than as sustained activity. We relate dynamic network activity as well as key synaptic characteristics to electrophysiological measurements. Our findings support the hypothesis that fast Hebbian short-term potentiation is a key WM mechanism. SIGNIFICANCE STATEMENT Working memory (WM) is a key component of cognition. Hypotheses about the neural mechanism behind WM are currently under revision. Reflecting recent findings of fast Hebbian synaptic plasticity in cortex, we test whether a cortical spiking neural network model with such a mechanism can learn a multi-item WM task (word list learning). We show that our model can reproduce human cognitive phenomena and achieve comparable memory performance in both free and cued recall while being simultaneously compatible with experimental data on structure, connectivity, and neurophysiology of the underlying cortical tissue. These findings are directly relevant to the ongoing paradigm shift in the WM field. PMID:28053032

Neural activity reveals perceptual grouping in working memory.

PubMed

Rabbitt, Laura R; Roberts, Daniel M; McDonald, Craig G; Peterson, Matthew S

2017-03-01

There is extensive evidence that the contralateral delay activity (CDA), a scalp recorded event-related brain potential, provides a reliable index of the number of objects held in visual working memory. Here we present evidence that the CDA not only indexes visual object working memory, but also the number of locations held in spatial working memory. In addition, we demonstrate that the CDA can be predictably modulated by the type of encoding strategy employed. When individual locations were held in working memory, the pattern of CDA modulation mimicked previous findings for visual object working memory. Specifically, CDA amplitude increased monotonically until working memory capacity was reached. However, when participants were instructed to group individual locations to form a constellation, the CDA was prolonged and reached an asymptote at two locations. This result provides neural evidence for the formation of a unitary representation of multiple spatial locations. Published by Elsevier B.V.

Working memory in Farsi-speaking children with normal development and cochlear implant.

PubMed

Soleymani, Zahra; Amidfar, Meysam; Dadgar, Hooshang; Jalaie, Shohre

2014-04-01

Working memory has an important role in language acquisition and development of cognition skills. The ability of encoding, storage and retrieval of phonological codes, as activities of working memory, acquired by audition sense. Children with cochlear implant experience a period that they are not able to perceive sounds. In order to assess the effect of hearing on working memory, we investigated working memory as a cognition skill in children with normal development and cochlear implant. Fifty students with normal hearing and 50 students with cochlear implant aged 5-7 years participated in this study. Children educated in the preschool, the first and second grades. Children with normal development were matched based on age, gender, and grade of education with cochlear implant. Two components of working memory including phonological loop and central executive were compared between two groups. Phonological loop assessed by nonword repetition task and forward digit span. To assess central executive component backward digit span was used. The developmental trend was studied in children with normal development and cochlear implant as well. The effect of age at implantation in children with cochlear implants on components of working memory was investigated. There are significant differences between children with normal development and cochlear implant in all tasks that assess working memory (p < 0.001). The children's age at implantation was negatively correlated with all tasks (p < 0.001). In contrast, duration of usage of cochlear implant set was positively correlated with all tasks (p < 0.001). The comparison of working memory between different grades showed significant differences both in children with normal development and in children with cochlear implant (p < 0.05). These results implied that children with cochlear implant may experience difficulties in working memory. Therefore, these children have problems in encoding, practicing, and repeating phonological units. The results also suggested working memory develops when the child grows up. In cochlear implant children, with decreasing age at implantation and increasing their experience in perceiving sound, working memory skills improved. Copyright © 2014 Elsevier Ireland Ltd. All rights reserved.

Dual-task interference in visual working memory: A limitation in storage capacity but not in encoding or retrieval

PubMed Central

Fougnie, Daryl; Marois, René

2009-01-01

The concurrent maintenance of two visual working memory (VWM) arrays can lead to profound interference. It is unclear, however, whether these costs arise from limitations in VWM storage capacity (Fougnie & Marois, 2006), or from interference between the storage of one visual array and encoding or retrieval of another visual array (Cowan & Morey, 2007). Here, we show that encoding a VWM array does not interfere with maintenance of another VWM array unless the two displays exceed maintenance capacity (Experiments 1 and 2). Moreover, manipulating the extent to which encoding and maintenance can interfere with one another had no discernable effect on dual-task performance (Experiment 2). Finally, maintenance of a VWM array was not affected by retrieval of information from another VWM array (Experiment 3). Taken together, these findings demonstrate that dual-task interference between two concurrent VWM tasks is due to a capacity-limited store that is independent from encoding and retrieval processes. PMID:19933566

Not All Attention Orienting is Created Equal: Recognition Memory is Enhanced When Attention Orienting Involves Distractor Suppression

PubMed Central

Markant, Julie; Worden, Michael S.; Amso, Dima

2015-01-01

Learning through visual exploration often requires orienting of attention to meaningful information in a cluttered world. Previous work has shown that attention modulates visual cortex activity, with enhanced activity for attended targets and suppressed activity for competing inputs, thus enhancing the visual experience. Here we examined the idea that learning may be engaged differentially with variations in attention orienting mechanisms that drive driving eye movements during visual search and exploration. We hypothesized that attention orienting mechanisms that engaged suppression of a previously attended location will boost memory encoding of the currently attended target objects to a greater extent than those that involve target enhancement alone To test this hypothesis we capitalized on the classic spatial cueing task and the inhibition of return (IOR) mechanism (Posner, Rafal, & Choate, 1985; Posner, 1980) to demonstrate that object images encoded in the context of concurrent suppression at a previously attended location were encoded more effectively and remembered better than those encoded without concurrent suppression. Furthermore, fMRI analyses revealed that this memory benefit was driven by attention modulation of visual cortex activity, as increased suppression of the previously attended location in visual cortex during target object encoding predicted better subsequent recognition memory performance. These results suggest that not all attention orienting impacts learning and memory equally. PMID:25701278

Similarity, Not Complexity, Determines Visual Working Memory Performance

ERIC Educational Resources Information Center

Jackson, Margaret C.; Linden, David E. J.; Roberts, Mark V.; Kriegeskorte, Nikolaus; Haenschel, Corinna

2015-01-01

A number of studies have shown that visual working memory (WM) is poorer for complex versus simple items, traditionally accounted for by higher information load placing greater demands on encoding and storage capacity limits. Other research suggests that it may not be complexity that determines WM performance per se, but rather increased…

Propofol and midazolam inhibit conscious memory processes very soon after encoding: an event-related potential study of familiarity and recollection in volunteers.

PubMed

Veselis, Robert A; Pryor, Kane O; Reinsel, Ruth A; Li, Yuelin; Mehta, Meghana; Johnson, Ray

2009-02-01

Intravenous drugs active via gamma-aminobutyric acid receptors to produce memory impairment during conscious sedation. Memory function was assessed using event-related potentials (ERPs) while drug was present. The continuous recognition task measured recognition of photographs from working (6 s) and long-term (27 s) memory while ERPs were recorded from Cz (familiarity recognition) and Pz electrodes (recollection recognition). Volunteer participants received sequential doses of one of placebo (n = 11), 0.45 and 0.9 microg/ml propofol (n = 10), 20 and 40 ng/ml midazolam (n = 12), 1.5 and 3 microg/ml thiopental (n = 11), or 0.25 and 0.4 ng/ml dexmedetomidine (n = 11). End-of-day yes/no recognition 225 min after the end of drug infusion tested memory retention of pictures encoded on the continuous recognition tasks. Active drugs increased reaction times and impaired memory on the continuous recognition task equally, except for a greater effect of midazolam (P < 0.04). Forgetting from continuous recognition tasks to end of day was similar for all drugs (P = 0.40), greater than placebo (P < 0.001). Propofol and midazolam decreased the area between first presentation (new) and recognized (old, 27 s later) ERP waveforms from long-term memory for familiarity (P = 0.03) and possibly for recollection processes (P = 0.12). Propofol shifted ERP amplitudes to smaller voltages (P < 0.002). Dexmedetomidine may have impaired familiarity more than recollection processes (P = 0.10). Thiopental had no effect on ERPs. Propofol and midazolam impaired recognition ERPs from long-term memory but not working memory. ERP measures of memory revealed different pathways to end-of-day memory loss as early as 27 s after encoding.

Striatal contributions to declarative memory retrieval

PubMed Central

Scimeca, Jason M.; Badre, David

2012-01-01

Declarative memory is known to depend on the medial temporal lobe memory system. Recently, there has been renewed focus on the relationship between the basal ganglia and declarative memory, including the involvement of striatum. However, the contribution of striatum to declarative memory retrieval remains unknown. Here, we review neuroimaging and neuropsychological evidence for the involvement of the striatum in declarative memory retrieval. From this review, we propose that, along with the prefrontal cortex (PFC), the striatum primarily supports cognitive control of memory retrieval. We conclude by proposing three hypotheses for the specific role of striatum in retrieval: (1) Striatum modulates the re-encoding of retrieved items in accord with their expected utility (adaptive encoding), (2) striatum selectively admits information into working memory that is expected to increase the likelihood of successful retrieval (adaptive gating), and (3) striatum enacts adjustments in cognitive control based on the outcome of retrieval (reinforcement learning). PMID:22884322

Encoding vs. retention: differential effects of cue manipulation on working memory performance in schizophrenia.

PubMed

Javitt, Daniel C; Rabinowicz, Esther; Silipo, Gail; Dias, Elisa C

2007-03-01

Deficits in working memory performance are among the most widely replicated findings in schizophrenia. Roles of encoding vs. memory retention in working memory remain unresolved. The present study evaluated working memory performance in schizophrenia using an AX-type continuous performance test (AX-CPT) paradigm. Participants included 48 subjects with schizophrenia and 27 comparison subjects. Behavior was obtained in 3 versions of the task, which differed based upon ease of cue interoperability. In a simple cue version of the task, cue letters were replaced with red or green circles. In the complex cue version, letter/color conjunctions served as cues. In the base version of the task, patients showed increased rates of false alarms to invalidly cued targets, similar to prior reports. However, when the cue stimuli were replaced with green or red circles to ease interpretation, patients showed similar false alarm rates to controls. When feature conjunction cues were used, patients were also disproportionately affected relative to controls. No significant group by interstimulus interval interaction effects were observed in either the simple or complex cue conditions, suggesting normal retention of information even in the presence of overall performance decrements. These findings suggest first, that cue manipulation disproportionately affects AX-CPT performance in schizophrenia and, second, that substantial behavioral deficits may be observed on working memory tasks even in the absence of disturbances in mnemonic retention.

The neural fate of neutral information in emotion-enhanced memory.

PubMed

Watts, Sarah; Buratto, Luciano G; Brotherhood, Emilie V; Barnacle, Gemma E; Schaefer, Alexandre

2014-07-01

In this study, we report evidence that neural activity reflecting the encoding of emotionally neutral information in memory is reduced when neutral and emotional stimuli are intermixed during encoding. Specifically, participants studied emotional and neutral pictures organized in mixed lists (in which emotional and neutral pictures were intermixed) or in pure lists (only-neutral or only-emotional pictures) and performed a recall test. To estimate encoding efficiency, we used the Dm effect, measured with event-related potentials. Recall for neutral items was lower in mixed compared to pure lists and posterior Dm activity for neutral items was reduced in mixed lists, whereas it remained robust in pure lists. These findings might be caused by an asymmetrical competition for attentional and working memory resources between emotional and neutral information, which could be a major determinant of emotional memory effects. Copyright © 2014 Society for Psychophysiological Research.

Sleep can eliminate list-method directed forgetting.

PubMed

Abel, Magdalena; Bäuml, Karl-Heinz T

2013-05-01

Recent work suggests a link between sleep and memory consolidation, indicating that sleep in comparison to wakefulness stabilizes memories. However, relatively little is known about how sleep affects forgetting. Here we examined whether sleep influences directed forgetting, the finding that people can intentionally forget obsolete memories when cued to do so. We applied the list-method directed forgetting task and assessed memory performance after 3 delay intervals. Directed forgetting was present after a short 20-min delay and after a 12-hr delay filled with diurnal wakefulness; in contrast, the forgetting was absent after a 12-hr delay that included regular nocturnal sleep. Successful directed forgetting after a delay thus can depend on whether sleep or wakefulness follows upon encoding: When wakefulness follows upon encoding, the forgetting can be successful; when sleep follows upon encoding, no forgetting may arise. Connections of the results to recent studies on the interplay between forgetting and sleep are discussed.

Working memory capacity predicts listwise directed forgetting in adults and children.

PubMed

Aslan, Alp; Zellner, Martina; Bäuml, Karl-Heinz T

2010-05-01

In listwise directed forgetting, participants are cued to forget previously studied material and to learn new material instead. Such cueing typically leads to forgetting of the first set of material and to memory enhancement of the second. The present study examined the role of working memory capacity in adults' and children's listwise directed forgetting. Working memory capacity was assessed with complex span tasks. In Experiment 1 working memory capacity predicted young adults' directed-forgetting performance, demonstrating a positive relationship between working memory capacity and each of the two directed-forgetting effects. In Experiment 2 we replicated the finding with a sample of first and a sample of fourth-grade children, and additionally showed that working memory capacity can account for age-related increases in directed-forgetting efficiency between the two age groups. Following the view that directed forgetting is mediated by inhibition of the first encoded list, the results support the proposal of a close link between working memory capacity and inhibitory function.

Effects of strategy on visual working memory capacity

PubMed Central

Bengson, Jesse J.; Luck, Steven J.

2015-01-01

Substantial evidence suggests that individual differences in estimates of working memory capacity reflect differences in how effectively people use their intrinsic storage capacity. This suggests that estimated capacity could be increased by instructions that encourage more effective encoding strategies. The present study tested this by giving different participants explicit strategy instructions in a change detection task. Compared to a condition in which participants were simply told to do their best, we found that estimated capacity was increased for participants who were instructed to remember the entire visual display, even at set sizes beyond their capacity. However, no increase in estimated capacity was found for a group that was told to focus on a subset of the items in supracapacity arrays. This finding confirms the hypothesis that encoding strategies may influence visual working memory performance, and it is contrary to the hypothesis that the optimal strategy is to filter out any items beyond the storage capacity. PMID:26139356

Effects of strategy on visual working memory capacity.

PubMed

Bengson, Jesse J; Luck, Steven J

2016-02-01

Substantial evidence suggests that individual differences in estimates of working memory capacity reflect differences in how effectively people use their intrinsic storage capacity. This suggests that estimated capacity could be increased by instructions that encourage more effective encoding strategies. The present study tested this by giving different participants explicit strategy instructions in a change detection task. Compared to a condition in which participants were simply told to do their best, we found that estimated capacity was increased for participants who were instructed to remember the entire visual display, even at set sizes beyond their capacity. However, no increase in estimated capacity was found for a group that was told to focus on a subset of the items in supracapacity arrays. This finding confirms the hypothesis that encoding strategies may influence visual working memory performance, and it is contrary to the hypothesis that the optimal strategy is to filter out any items beyond the storage capacity.

Configural Representations in Spatial Working Memory: Modulation by Perceptual Segregation and Voluntary Attention

PubMed Central

Gmeindl, Leon; Nelson, James K.; Wiggin, Timothy; Reuter-Lorenz, Patricia A.

2011-01-01

In what form are multiple spatial locations represented in working memory? The current study revealed that people often maintain the configural properties (inter-item relationships) of visuospatial stimuli even when this information is explicitly task-irrelevant. However, results also indicate that the voluntary allocation of selective attention prior to stimulus presentation, as well as feature-based perceptual segregation of relevant from irrelevant stimuli, can eliminate the influences of stimulus configuration on location change detection performance. In contrast, voluntary attention cued to the relevant target location following presentation of the stimulus array failed to attenuate these influences. Thus, whereas voluntary selective attention can isolate or prevent the encoding of irrelevant stimulus locations and configural properties, people, perhaps due to limitations in attentional resources, reliably fail to isolate or suppress configural representations that have been encoded into working memory. PMID:21761373

Executive control processes underlying multi-item working memory

PubMed Central

Lara, Antonio H.; Wallis, Jonathan D.

2014-01-01

A dominant view of prefrontal cortex (PFC) function is that it stores task-relevant information in working memory. To examine this and determine how it applies when multiple pieces of information must be stored, we trained two macaque monkeys to perform a multi-item color change-detection task and recorded activity of neurons in PFC. Few neurons encoded the color of the items. Instead, the predominant encoding was spatial: a static signal reflecting the item's position and a dynamic signal reflecting the animal's covert attention. These findings challenge the notion that PFC stores task-relevant information. Instead, we suggest that the contribution of PFC is in controlling the allocation of resources to support working memory. In support of this, we found that increased power in the alpha and theta bands of PFC local field potentials, which are thought to reflect long-range communication with other brain areas, was correlated with more precise color representations. PMID:24747574

Divided attention interferes with fulfilling activity-based intentions.

PubMed

Brewer, Gene A; Ball, B Hunter; Knight, Justin B; Dewitt, Michael R; Marsh, Richard L

2011-09-01

Two experiments were conducted to examine the effects of divided attention on activity-based prospective memory. After establishing a goal to fulfill an intention upon completion of an ongoing activity, successful completion of the intention generally suffered when attention was being devoted to an additional task (Experiment 1). Forming an implementation intention at encoding ameliorated the negative effects of divided attention (Experiment 2). The results from the present experiments demonstrate that activity-based prospective memory is susceptible to distraction and that implementing encoding strategies that enhance prospective memory performance can reduce this interference. The current work raises interesting questions about the similarities and differences between event- and activity-based prospective memories. Published by Elsevier B.V.

Encoding of physics concepts: concreteness and presentation modality reflected by human brain dynamics.

PubMed

Lai, Kevin; She, Hsiao-Ching; Chen, Sheng-Chang; Chou, Wen-Chi; Huang, Li-Yu; Jung, Tzyy-Ping; Gramann, Klaus

2012-01-01

Previous research into working memory has focused on activations in different brain areas accompanying either different presentation modalities (verbal vs. non-verbal) or concreteness (abstract vs. concrete) of non-science concepts. Less research has been conducted investigating how scientific concepts are learned and further processed in working memory. To bridge this gap, the present study investigated human brain dynamics associated with encoding of physics concepts, taking both presentation modality and concreteness into account. Results of this study revealed greater theta and low-beta synchronization in the anterior cingulate cortex (ACC) during encoding of concrete pictures as compared to the encoding of both high and low imageable words. In visual brain areas, greater theta activity accompanying stimulus onsets was observed for words as compared to pictures while stronger alpha suppression was observed in responses to pictures as compared to words. In general, the EEG oscillation patterns for encoding words of different levels of abstractness were comparable but differed significantly from encoding of pictures. These results provide insights into the effects of modality of presentation on human encoding of scientific concepts and thus might help in developing new ways to better teach scientific concepts in class.

Effects of load and maintenance duration on the time course of information encoding and retrieval in working memory: from perceptual analysis to post-categorization processes.

PubMed

Pinal, Diego; Zurrón, Montserrat; Díaz, Fernando

2014-01-01

information encoding, maintenance, and retrieval; these are supported by brain activity in a network of frontal, parietal and temporal regions. Manipulation of WM load and duration of the maintenance period can modulate this activity. Although such modulations have been widely studied using the event-related potentials (ERP) technique, a precise description of the time course of brain activity during encoding and retrieval is still required. Here, we used this technique and principal component analysis to assess the time course of brain activity during encoding and retrieval in a delayed match to sample task. We also investigated the effects of memory load and duration of the maintenance period on ERP activity. Brain activity was similar during information encoding and retrieval and comprised six temporal factors, which closely matched the latency and scalp distribution of some ERP components: P1, N1, P2, N2, P300, and a slow wave. Changes in memory load modulated task performance and yielded variations in frontal lobe activation. Moreover, the P300 amplitude was smaller in the high than in the low load condition during encoding and retrieval. Conversely, the slow wave amplitude was higher in the high than in the low load condition during encoding, and the same was true for the N2 amplitude during retrieval. Thus, during encoding, memory load appears to modulate the processing resources for context updating and post-categorization processes, and during retrieval it modulates resources for stimulus classification and context updating. Besides, despite the lack of differences in task performance related to duration of the maintenance period, larger N2 amplitude and stronger activation of the left temporal lobe after long than after short maintenance periods were found during information retrieval. Thus, results regarding the duration of maintenance period were complex, and future work is required to test the time-based decay theory predictions.

Aging affects the interaction between attentional control and source memory: an fMRI study.

PubMed

Dulas, Michael R; Duarte, Audrey

2014-12-01

Age-related source memory impairments may be due, at least in part, to deficits in executive processes mediated by the PFC at both study and test. Behavioral work suggests that providing environmental support at encoding, such as directing attention toward item-source associations, may improve source memory and reduce age-related deficits in the recruitment of these executive processes. The present fMRI study investigated the effects of directed attention and aging on source memory encoding and retrieval. At study, participants were shown pictures of objects. They were either asked to attend to the objects and their color (source) or to their size. At test, participants determined if objects were seen before, and if so, whether they were the same color as previously. Behavioral results showed that direction of attention improved source memory for both groups; however, age-related deficits persisted. fMRI results revealed that, across groups, direction of attention facilitated medial temporal lobe-mediated contextual binding processes during study and attenuated right PFC postretrieval monitoring effects at test. However, persistent age-related source memory deficits may be related to increased recruitment of medial anterior PFC during encoding, indicative of self-referential processing, as well as underrecruitment of lateral anterior PFC-mediated relational processes. Taken together, this study suggests that, even when supported, older adults may fail to selectively encode goal-relevant contextual details supporting source memory performance.

Electrophysiological evidence for strategically orienting retrieval toward the specific age of a memory.

PubMed

Johnson, Jeffrey D; McGhee, Anna K

2015-11-01

For over a century, memory researchers have extensively studied the differences between retrieving memories that were encoded in the remote past as opposed to recently. Although this work has largely focused on the changes that these memory traces undergo over time, an unexplored issue is whether retrieval attempts and other strategic processes might be differentially oriented in order to effectively access memories of different ages. The current study addressed this issue by instructing participants to retrieve words that were encoded either one week (remote) or about 30 minutes earlier (recent). To maximize the possibility that participants adopted distinct retrieval orientations, separate blocks of the memory test employed exclusion task procedures in which the words from only one encoding period were targeted at a given time, in the face of distractors from the other period. Event-related potentials (ERPs) elicited by correctly-rejected new items were contrasted to minimize confounding effects of retrieval success. The new-item ERPs revealed differences according to the targeted week, such that the ERPs over posterior scalp were more positive-going for the recent compared to remote blocks. Furthermore, using multiple methods, these ERP effects were dissociated from differences in difficulty across the two conditions. The findings provide novel evidence that knowledge about when a memory was initially encoded leads to differences in the adoption of retrieval processing strategies. Copyright © 2015 Elsevier Inc. All rights reserved.

Selective memory retrieval in social groups: When silence is golden and when it is not.

PubMed

Abel, Magdalena; Bäuml, Karl-Heinz T

2015-07-01

Previous research has shown that the selective remembering of a speaker and the resulting silences can cause forgetting of related, but unmentioned information by a listener (Cuc, Koppel, & Hirst, 2007). Guided by more recent work that demonstrated both detrimental and beneficial effects of selective memory retrieval in individuals, the present research explored the effects of selective remembering in social groups when access to the encoding context at retrieval was maintained or impaired. In each of three experiments, selective retrieval by the speaker impaired recall of the listener when access to the encoding context was maintained, but it improved recall of the listener when context access was impaired. The results suggest the existence of two faces of selective memory retrieval in social groups, with a detrimental face when the encoding context is still active at retrieval and a beneficial face when it is not. The role of silence in social recall thus seems to be more complex than was indicated in prior work, and mnemonic silences on the part of a speaker can be "golden" for the memories of a listener under some circumstances, but not be "golden" under others. Copyright © 2015 Elsevier B.V. All rights reserved.

Movement Interferes with Visuospatial Working Memory during the Encoding: An ERP Study

PubMed Central

Gunduz Can, Rumeysa; Schack, Thomas; Koester, Dirk

2017-01-01

The present study focuses on the functional interactions of cognition and manual action control. Particularly, we investigated the neurophysiological correlates of the dual-task costs of a manual-motor task (requiring grasping an object, holding it, and subsequently placing it on a target) for working memory (WM) domains (verbal and visuospatial) and processes (encoding and retrieval). Thirty participants were tested in a cognitive-motor dual-task paradigm, in which a single block (a verbal or visuospatial WM task) was compared with a dual block (concurrent performance of a WM task and a motor task). Event-related potentials (ERPs) were analyzed separately for the encoding and retrieval processes of verbal and visuospatial WM domains both in single and dual blocks. The behavioral analyses show that the motor task interfered with WM and decreased the memory performance. The performance decrease was larger for the visuospatial task compared with the verbal task, i.e., domain-specific memory costs were obtained. The ERP analyses show the domain-specific interference also at the neurophysiological level, which is further process-specific to encoding. That is, comparing the patterns of WM-related ERPs in the single block and dual block, we showed that visuospatial ERPs changed only for the encoding process when a motor task was performed at the same time. Generally, the present study provides evidence for domain- and process-specific interactions of a prepared manual-motor movement with WM (visuospatial domain during the encoding process). This study, therefore, provides an initial neurophysiological characterization of functional interactions of WM and manual actions in a cognitive-motor dual-task setting, and contributes to a better understanding of the neuro-cognitive mechanisms of motor action control. PMID:28611714

Differential verbal, visual, and spatial working memory in written language production.

PubMed

Raulerson, Bascom A; Donovan, Michael J; Whiteford, Alison P; Kellogg, Ronald T

2010-02-01

The contributions of verbal, visual, and spatial working memory to written language production were investigated. Participants composed definitions for nouns while concurrently performing a task which required updating, storing, and retrieving information coded either verbally, visually, or spatially. The present study extended past findings by showing the linguistic encoding of planned conceptual content makes its largest demand on verbal working memory for both low and high frequency nouns. Kellogg, Olive, and Piolat in 2007 found that concrete nouns place substantial demands on visual working memory when imaging the nouns' referents during planning, whereas abstract nouns make no demand. The current study further showed that this pattern was not an artifact of visual working memory being sensitive to manipulation of just any lexical property of the noun prompts. In contrast to past results, writing made a small but detectible demand on spatial working memory.

The influence of emotional cues on prospective memory: a systematic review with meta-analyses.

PubMed

Hostler, Thomas J; Wood, Chantelle; Armitage, Christopher J

2018-01-10

Remembering to perform a behaviour in the future, prospective memory, is essential to ensuring that people fulfil their intentions. Prospective memory involves committing to memory a cue to action (encoding), and later recognising and acting upon the cue in the environment (retrieval). Prospective memory performance is believed to be influenced by the emotionality of the cues, however the literature is fragmented and inconsistent. We conducted a systematic search to synthesise research on the influence of emotion on prospective memory. Sixty-seven effect sizes were extracted from 17 articles and hypothesised effects tested using three meta-analyses. Overall, prospective memory was enhanced when positively-valenced rather than neutral cues were presented (d = 0.32). In contrast, negatively-valenced cues did not enhance prospective memory overall (d = 0.07), but this effect was moderated by the timing of the emotional manipulation. Prospective memory performance was improved when negatively-valenced cues were presented during both encoding and retrieval (d = 0.40), but undermined when presented only during encoding (d = -0.25). Moderating effects were also found for cue-focality and whether studies controlled for the arousal level of the cues. The principal finding is that positively-valenced cues improve prospective memory performance and that timing of the manipulation can moderate emotional effects on prospective memory. We offer a new agenda for future empirical work and theorising in this area.

Temporal dynamics of attention during encoding vs. maintenance of working memory: complementary views from event-related potentials and alpha-band oscillations

PubMed Central

Myers, Nicholas E.; Walther, Lena; Wallis, George; Stokes, Mark G.; Nobre, Anna C.

2015-01-01

Working memory (WM) is strongly influenced by attention. In visual working-memory tasks, recall performance can be improved by an attention-guiding cue presented before encoding (precue) or during maintenance (retrocue). Although precues and retrocues recruit a similar fronto-parietal control network, the two are likely to exhibit some processing differences, since precues invite anticipation of upcoming information, while retrocues may guide prioritisation, protection, and selection of information already in mind. Here we explored the behavioral and electrophysiological differences between precueing and retrocueing in a new visual working-memory task designed to permit a direct comparison between cueing conditions. We found marked differences in event-related potential (ERP) profiles between the precue and retrocue conditions. In line with precues primarily generating an anticipatory shift of attention toward the location of an upcoming item, we found a robust lateralization in late cue-evoked potentials associated with target anticipation. Retrocues elicited a different pattern of ERPs that was compatible with an early selection mechanism, but not with stimulus anticipation. In contrast to the distinct ERP patterns, alpha band (8-14 Hz) lateralization was indistinguishable between cue types (reflecting, in both conditions, the location of the cued item). We speculate that whereas alpha-band lateralization after a precue is likely to enable anticipatory attention, lateralization after a retrocue may instead enable the controlled spatiotopic access to recently encoded visual information. PMID:25244118

Not all attention orienting is created equal: recognition memory is enhanced when attention orienting involves distractor suppression.

PubMed

Markant, Julie; Worden, Michael S; Amso, Dima

2015-04-01

Learning through visual exploration often requires orienting of attention to meaningful information in a cluttered world. Previous work has shown that attention modulates visual cortex activity, with enhanced activity for attended targets and suppressed activity for competing inputs, thus enhancing the visual experience. Here we examined the idea that learning may be engaged differentially with variations in attention orienting mechanisms that drive eye movements during visual search and exploration. We hypothesized that attention orienting mechanisms that engaged suppression of a previously attended location would boost memory encoding of the currently attended target objects to a greater extent than those that involve target enhancement alone. To test this hypothesis we capitalized on the classic spatial cueing task and the inhibition of return (IOR) mechanism (Posner, 1980; Posner, Rafal, & Choate, 1985) to demonstrate that object images encoded in the context of concurrent suppression at a previously attended location were encoded more effectively and remembered better than those encoded without concurrent suppression. Furthermore, fMRI analyses revealed that this memory benefit was driven by attention modulation of visual cortex activity, as increased suppression of the previously attended location in visual cortex during target object encoding predicted better subsequent recognition memory performance. These results suggest that not all attention orienting impacts learning and memory equally. Copyright © 2015 Elsevier Inc. All rights reserved.

The memory that’s right and the memory that’s left: Event-related potentials reveal hemispheric asymmetries in the encoding and retention of verbal information

PubMed Central

Evans, Karen M.; Federmeier, Kara D.

2009-01-01

We examined the nature and timecourse of hemispheric asymmetries in verbal memory by recording event-related potentials (ERPs) in a continuous recognition task. Participants made overt recognition judgments to test words presented in central vision that were either novel (new words) or had been previously presented in the left or right visual field (old words). An ERP memory effect linked to explicit retrieval revealed no asymmetries for words repeated at short and medium retention intervals, but at longer repetition lags (20–50 intervening words) this ‘old/new effect’ was more pronounced for words whose study presentation had been biased to the right hemisphere (RH). Additionally, a repetition effect linked to more implicit recognition processes (P2 amplitude changes) was observed at all lags for words preferentially encoded by the RH but was not observed for left hemisphere (LH)-encoded words. These results are consistent with theories that the RH encodes verbal stimuli more veridically whereas the LH encodes in a more abstract manner. The current findings provide a critical link between prior work on memory asymmetries, which has emphasized general LH advantages for verbal material, and on language comprehension, which has pointed to an important role for the RH in language processes that require the retention and integration of verbal information over long time spans. PMID:17291547

Reward associations impact both iconic and visual working memory.

PubMed

Infanti, Elisa; Hickey, Clayton; Turatto, Massimo

2015-02-01

Reward plays a fundamental role in human behavior. A growing number of studies have shown that stimuli associated with reward become salient and attract attention. The aim of the present study was to extend these results into the investigation of iconic memory and visual working memory. In two experiments we asked participants to perform a visual-search task where different colors of the target stimuli were paired with high or low reward. We then tested whether the pre-established feature-reward association affected performance on a subsequent visual memory task, in which no reward was provided. In this test phase participants viewed arrays of 8 objects, one of which had unique color that could match the color associated with reward during the previous visual-search task. A probe appeared at varying intervals after stimulus offset to identify the to-be-reported item. Our results suggest that reward biases the encoding of visual information such that items characterized by a reward-associated feature interfere with mnemonic representations of other items in the test display. These results extend current knowledge regarding the influence of reward on early cognitive processes, suggesting that feature-reward associations automatically interact with the encoding and storage of visual information, both in iconic memory and visual working memory. Copyright © 2014 Elsevier Ltd. All rights reserved.

Effect of emotional valence on retrieval-related recapitulation of encoding activity in the ventral visual stream

PubMed Central

Kark, Sarah M.; Kensinger, Elizabeth A.

2015-01-01

While prior work has shown greater retrieval-related reactivation in the ventral visual stream for emotional stimuli compared to neutral stimuli, the effects of valence on retrieval-related recapitulation of successful encoding processes (Dm effects) have yet to be investigated. Here, seventeen participants (aged 19–35) studied line drawings of negative, positive, or neutral images followed immediately by the complete photo. After a 20-minute delay, participants performed a challenging recognition memory test, distinguishing the studied line drawing outlines from novel ones. First, results replicated earlier work by demonstrating that negative and positive hits elicited greater ventral occipito-temporal cortex (VOTC) activity than neutral hits during both encoding and retrieval. Moreover, the amount of activation in portions of the VOTC correlated with the magnitude of participants’ emotional memory enhancement. Second, results revealed significant retrieval-related recapitulation of Dm effects (Hits > Misses) in VOTC (anterior inferior temporal gyri) only for negative stimuli. Third, connectivity between the amygdala and fusiform gyrus during the encoding of negative stimuli increased the likelihood of fusiform activation during successful retrieval. Together, these results suggest that recapitulation in posterior VOTC reflects memory for the affective dimension of the stimuli (Emotional Hits > Neutral Hits) and the magnitude of activation in some of these regions is related to superior emotional memory. Moreover, for negative stimuli, recapitulation in more anterior portions of the VOTC is greater for remembered than forgotten items. The current study offers new evidence for effects of emotion on recapitulation of activity and functional connectivity in support of memory. PMID:26459096

Effect of emotional valence on retrieval-related recapitulation of encoding activity in the ventral visual stream.

PubMed

Kark, Sarah M; Kensinger, Elizabeth A

2015-11-01

While prior work has shown greater retrieval-related reactivation in the ventral visual stream for emotional stimuli compared to neutral stimuli, the effects of valence on retrieval-related recapitulation of successful encoding processes (Dm effects) have yet to be investigated. Here, seventeen participants (aged 19-35) studied line drawings of negative, positive, or neutral images followed immediately by the complete photo. After a 20-min delay, participants performed a challenging recognition memory test, distinguishing the studied line drawing outlines from novel ones. First, results replicated earlier work by demonstrating that negative and positive hits elicited greater ventral occipito-temporal cortex (VOTC) activity than neutral hits during both encoding and retrieval. Moreover, the amount of activation in portions of the VOTC correlated with the magnitude of participants' emotional memory enhancement. Second, results revealed significant retrieval-related recapitulation of Dm effects (Hits>Misses) in VOTC (anterior inferior temporal gyri) only for negative stimuli. Third, connectivity between the amygdala and fusiform gyrus during the encoding of negative stimuli increased the likelihood of fusiform activation during successful retrieval. Together, these results suggest that recapitulation in posterior VOTC reflects memory for the affective dimension of the stimuli (Emotional Hits>Neutral Hits) and the magnitude of activation in some of these regions is related to superior emotional memory. Moreover, for negative stimuli, recapitulation in more anterior portions of the VOTC is greater for remembered than forgotten items. The current study offers new evidence for effects of emotion on recapitulation of activity and functional connectivity in support of memory. Copyright © 2015 Elsevier Ltd. All rights reserved.

What makes deeply encoded items memorable? Insights into the levels of processing framework from neuroimaging and neuromodulation.

PubMed

Galli, Giulia

2014-01-01

When we form new memories, their mnestic fate largely depends upon the cognitive operations set in train during encoding. A typical observation in experimental as well as everyday life settings is that if we learn an item using semantic or "deep" operations, such as attending to its meaning, memory will be better than if we learn the same item using more "shallow" operations, such as attending to its structural features. In the psychological literature, this phenomenon has been conceptualized within the "levels of processing" framework and has been consistently replicated since its original proposal by Craik and Lockhart in 1972. However, the exact mechanisms underlying the memory advantage for deeply encoded items are not yet entirely understood. A cognitive neuroscience perspective can add to this field by clarifying the nature of the processes involved in effective deep and shallow encoding and how they are instantiated in the brain, but so far there has been little work to systematically integrate findings from the literature. This work aims to fill this gap by reviewing, first, some of the key neuroimaging findings on the neural correlates of deep and shallow episodic encoding and second, emerging evidence from studies using neuromodulatory approaches such as psychopharmacology and non-invasive brain stimulation. Taken together, these studies help further our understanding of levels of processing. In addition, by showing that deep encoding can be modulated by acting upon specific brain regions or systems, the reviewed studies pave the way for selective enhancements of episodic encoding processes.

What Makes Deeply Encoded Items Memorable? Insights into the Levels of Processing Framework from Neuroimaging and Neuromodulation

PubMed Central

Galli, Giulia

2014-01-01

When we form new memories, their mnestic fate largely depends upon the cognitive operations set in train during encoding. A typical observation in experimental as well as everyday life settings is that if we learn an item using semantic or “deep” operations, such as attending to its meaning, memory will be better than if we learn the same item using more “shallow” operations, such as attending to its structural features. In the psychological literature, this phenomenon has been conceptualized within the “levels of processing” framework and has been consistently replicated since its original proposal by Craik and Lockhart in 1972. However, the exact mechanisms underlying the memory advantage for deeply encoded items are not yet entirely understood. A cognitive neuroscience perspective can add to this field by clarifying the nature of the processes involved in effective deep and shallow encoding and how they are instantiated in the brain, but so far there has been little work to systematically integrate findings from the literature. This work aims to fill this gap by reviewing, first, some of the key neuroimaging findings on the neural correlates of deep and shallow episodic encoding and second, emerging evidence from studies using neuromodulatory approaches such as psychopharmacology and non-invasive brain stimulation. Taken together, these studies help further our understanding of levels of processing. In addition, by showing that deep encoding can be modulated by acting upon specific brain regions or systems, the reviewed studies pave the way for selective enhancements of episodic encoding processes. PMID:24904444

Incidental Biasing of Attention from Visual Long-Term Memory

ERIC Educational Resources Information Center

Fan, Judith E.; Turk-Browne, Nicholas B.

2016-01-01

Holding recently experienced information in mind can help us achieve our current goals. However, such immediate and direct forms of guidance from working memory are less helpful over extended delays or when other related information in long-term memory is useful for reaching these goals. Here we show that information that was encoded in the past…

Neural network communication facilitates verbal working memory.

PubMed

Kustermann, Thomas; Rockstroh, Brigitte; Miller, Gregory A; Popov, Tzvetan

2018-05-28

Oscillatory brain activity in the theta, alpha, and gamma frequency ranges has been associated with working memory (WM). In addition to alpha and theta activity associated with WM retention, and gamma band activity with item encoding, activity in the alpha band is related to the deployment of attention resources and information. The present study sought to specify distinct roles of neuromagnetic 4-7 Hz theta, 9-13 Hz alpha, and 50-70 Hz gamma power modulation and communication in fronto-parietal networks during cued, hemifield-specific item presentation in a modified Sternberg verbal WM task in 14 student volunteers. Lateralized posterior alpha and gamma power during encoding suggest a preparatory role of alpha oscillations. Bilateral alpha power increases during maintenance reflect information retention for the non-lateralized probe response. Lateralized alpha power increase during encoding was apparently driven by a monotonic increase in fronto-parietal 6 Hz phase, suggesting a mechanism facilitating WM encoding and successful performance. Copyright © 2018 Elsevier B.V. All rights reserved.

Dissociation of verbal working memory system components using a delayed serial recall task.

PubMed

Chein, J M; Fiez, J A

2001-11-01

Functional magnetic resonance imaging (fMRI) was used to investigate the neural substrates of component processes in verbal working memory. Based on behavioral research using manipulations of verbal stimulus type to dissociate storage, rehearsal, and executive components of verbal working memory, we designed a delayed serial recall task requiring subjects to encode, maintain, and overtly recall sets of verbal items for which phonological similarity, articulatory length, and lexical status were manipulated. By using a task with temporally extended trials, we were able to exploit the temporal resolution afforded by fMRI to partially isolate neural contributions to encoding, maintenance, and retrieval stages of task performance. Several regions commonly associated with maintenance, including supplementary motor, premotor, and inferior frontal areas, were found to be active across all three trial stages. Additionally, we found that left inferior frontal and supplementary motor regions showed patterns of stimulus and temporal sensitivity implicating them in distinct aspects of articulatory rehearsal, while no regions showed a pattern of sensitivity consistent with a role in phonological storage. Regional modulation by task difficulty was further investigated as a measure of executive processing. We interpret our findings as they relate to notions about the cognitive architecture underlying verbal working memory performance.

Normative shifts of cortical mechanisms of encoding contribute to adult age differences in visual-spatial working memory.

PubMed

Störmer, Viola S; Li, Shu-Chen; Heekeren, Hauke R; Lindenberger, Ulman

2013-06-01

The capacity of visual-spatial working memory (WM) declines from early to late adulthood. Recent attempts at identifying neural correlates of WM capacity decline have focused on the maintenance phase of WM. Here, we investigate neural mechanisms during the encoding phase as another potential mechanism contributing to adult age differences in WM capacity. We used electroencephalography to track neural activity during encoding and maintenance on a millisecond timescale in 35 younger and 35 older adults performing a visual-spatial WM task. As predicted, we observed pronounced age differences in ERP indicators of WM encoding: Younger adults showed attentional selection during item encoding (N2pc component), but this selection mechanism was greatly attenuated in older adults. Conversely, older adults showed more pronounced signs of early perceptual stimulus processing (N1 component) than younger adults. The amplitude modulation of the N1 component predicted WM capacity in older adults, whereas the attentional amplitude modulation of the N2pc component predicted WM capacity in younger adults. Our findings suggest that adult age differences in mechanisms of WM encoding contribute to adult age differences in limits of visual-spatial WM capacity. Copyright © 2013 Elsevier Inc. All rights reserved.

Event-related Potentials Reveal Age Differences in the Encoding and Recognition of Scenes

PubMed Central

Gutchess, Angela H.; Ieuji, Yoko; Federmeier, Kara D.

2009-01-01

The present study used event-related potentials (ERPs) to investigate how the encoding and recognition of complex scenes change with normal aging. Although functional magnetic resonance imaging (fMRI) studies have identified more drastic age impairments at encoding than at recognition, ERP studies accumulate more evidence for age differences at retrieval. However, stimulus type and paradigm differences across the two literatures have made direct comparisons difficult. Here, we collected young and elderly adults’ encoding- and recognition-phase ERPs using the same materials and paradigm as a previous fMRI study. Twenty young and 20 elderly adults incidentally encoded and then recognized photographs of outdoor scenes. During encoding, young adults showed a frontocentral subsequent memory effect, with high-confidence hits exhibiting greater positivity than misses. Elderly adults showed a similar subsequent memory effect, which, however, did not differ as a function of confidence. During recognition, young adults elicited a widespread old/new effect, and high-confidence hits were distinct from both low-confidence hits and false alarms. Elderly adults elicited a smaller and later old/new effect, which was unaffected by confidence, and hits and false alarms were indistinguishable in the waveforms. Consistent with prior ERP work, these results point to important age-related changes in recognition-phase brain activity, even when behavioral measures of memory and confidence pattern similarly across groups. We speculate that memory processes with different time signatures contribute to the apparent differences across encoding and retrieval stages, and across methods. PMID:17583986

Enhanced dimension-specific visual working memory in grapheme–color synesthesia☆

PubMed Central

Terhune, Devin Blair; Wudarczyk, Olga Anna; Kochuparampil, Priya; Cohen Kadosh, Roi

2013-01-01

There is emerging evidence that the encoding of visual information and the maintenance of this information in a temporarily accessible state in working memory rely on the same neural mechanisms. A consequence of this overlap is that atypical forms of perception should influence working memory. We examined this by investigating whether having grapheme–color synesthesia, a condition characterized by the involuntary experience of color photisms when reading or representing graphemes, would confer benefits on working memory. Two competing hypotheses propose that superior memory in synesthesia results from information being coded in two information channels (dual-coding) or from superior dimension-specific visual processing (enhanced processing). We discriminated between these hypotheses in three n-back experiments in which controls and synesthetes viewed inducer and non-inducer graphemes and maintained color or grapheme information in working memory. Synesthetes displayed superior color working memory than controls for both grapheme types, whereas the two groups did not differ in grapheme working memory. Further analyses excluded the possibilities of enhanced working memory among synesthetes being due to greater color discrimination, stimulus color familiarity, or bidirectionality. These results reveal enhanced dimension-specific visual working memory in this population and supply further evidence for a close relationship between sensory processing and the maintenance of sensory information in working memory. PMID:23892185

Interregional synaptic maps among engram cells underlie memory formation.

PubMed

Choi, Jun-Hyeok; Sim, Su-Eon; Kim, Ji-Il; Choi, Dong Il; Oh, Jihae; Ye, Sanghyun; Lee, Jaehyun; Kim, TaeHyun; Ko, Hyoung-Gon; Lim, Chae-Seok; Kaang, Bong-Kiun

2018-04-27

Memory resides in engram cells distributed across the brain. However, the site-specific substrate within these engram cells remains theoretical, even though it is generally accepted that synaptic plasticity encodes memories. We developed the dual-eGRASP (green fluorescent protein reconstitution across synaptic partners) technique to examine synapses between engram cells to identify the specific neuronal site for memory storage. We found an increased number and size of spines on CA1 engram cells receiving input from CA3 engram cells. In contextual fear conditioning, this enhanced connectivity between engram cells encoded memory strength. CA3 engram to CA1 engram projections strongly occluded long-term potentiation. These results indicate that enhanced structural and functional connectivity between engram cells across two directly connected brain regions forms the synaptic correlate for memory formation. Copyright © 2018 The Authors, some rights reserved; exclusive licensee American Association for the Advancement of Science. No claim to original U.S. Government Works.

Does visual working memory represent the predicted locations of future target objects? An event-related brain potential study.

PubMed

Grubert, Anna; Eimer, Martin

2015-11-11

During the maintenance of task-relevant objects in visual working memory, the contralateral delay activity (CDA) is elicited over the hemisphere opposite to the visual field where these objects are presented. The presence of this lateralised CDA component demonstrates the existence of position-dependent object representations in working memory. We employed a change detection task to investigate whether the represented object locations in visual working memory are shifted in preparation for the known location of upcoming comparison stimuli. On each trial, bilateral memory displays were followed after a delay period by bilateral test displays. Participants had to encode and maintain three visual objects on one side of the memory display, and to judge whether they were identical or different to three objects in the test display. Task-relevant memory and test stimuli were located in the same visual hemifield in the no-shift task, and on opposite sides in the horizontal shift task. CDA components of similar size were triggered contralateral to the memorized objects in both tasks. The absence of a polarity reversal of the CDA in the horizontal shift task demonstrated that there was no preparatory shift of memorized object location towards the side of the upcoming comparison stimuli. These results suggest that visual working memory represents the locations of visual objects during encoding, and that the matching of memorized and test objects at different locations is based on a comparison process that can bridge spatial translations between these objects. This article is part of a Special Issue entitled SI: Prediction and Attention. Copyright © 2014 Elsevier B.V. All rights reserved.

Divided attention selectively impairs memory for self-relevant information.

PubMed

Turk, David J; Brady-van den Bos, Mirjam; Collard, Philip; Gillespie-Smith, Karri; Conway, Martin A; Cunningham, Sheila J

2013-05-01

Information that is relevant to oneself tends to be remembered more than information that relates to other people, but the role of attention in eliciting this "self-reference effect" is unclear. In the present study, we assessed the importance of attention in self-referential encoding using an ownership paradigm, which required participants to encode items under conditions of imagined ownership by themselves or by another person. Previous work has established that this paradigm elicits a robust self-reference effect, with more "self-owned" items being remembered than "other-owned" items. Access to attentional resources was manipulated using divided-attention tasks at encoding. A significant self-reference effect emerged under full-attention conditions and was related to an increase in episodic recollection for self-owned items, but dividing attention eliminated this memory advantage. These findings are discussed in relation to the nature of self-referential cognition and the importance of attentional resources at encoding in the manifestation of the self-reference effect in memory.

Design and construction of a double inversion recombination switch for heritable sequential genetic memory.

PubMed

Ham, Timothy S; Lee, Sung K; Keasling, Jay D; Arkin, Adam P

2008-07-30

Inversion recombination elements present unique opportunities for computing and information encoding in biological systems. They provide distinct binary states that are encoded into the DNA sequence itself, allowing us to overcome limitations posed by other biological memory or logic gate systems. Further, it is in theory possible to create complex sequential logics by careful positioning of recombinase recognition sites in the sequence. In this work, we describe the design and synthesis of an inversion switch using the fim and hin inversion recombination systems to create a heritable sequential memory switch. We have integrated the two inversion systems in an overlapping manner, creating a switch that can have multiple states. The switch is capable of transitioning from state to state in a manner analogous to a finite state machine, while encoding the state information into DNA. This switch does not require protein expression to maintain its state, and "remembers" its state even upon cell death. We were able to demonstrate transition into three out of the five possible states showing the feasibility of such a switch. We demonstrate that a heritable memory system that encodes its state into DNA is possible, and that inversion recombination system could be a starting point for more complex memory circuits. Although the circuit did not fully behave as expected, we showed that a multi-state, temporal memory is achievable.

Design and Construction of a Double Inversion Recombination Switch for Heritable Sequential Genetic Memory

PubMed Central

Ham, Timothy S.; Lee, Sung K.; Keasling, Jay D.; Arkin, Adam P.

2008-01-01

Background Inversion recombination elements present unique opportunities for computing and information encoding in biological systems. They provide distinct binary states that are encoded into the DNA sequence itself, allowing us to overcome limitations posed by other biological memory or logic gate systems. Further, it is in theory possible to create complex sequential logics by careful positioning of recombinase recognition sites in the sequence. Methodology/Principal Findings In this work, we describe the design and synthesis of an inversion switch using the fim and hin inversion recombination systems to create a heritable sequential memory switch. We have integrated the two inversion systems in an overlapping manner, creating a switch that can have multiple states. The switch is capable of transitioning from state to state in a manner analogous to a finite state machine, while encoding the state information into DNA. This switch does not require protein expression to maintain its state, and “remembers” its state even upon cell death. We were able to demonstrate transition into three out of the five possible states showing the feasibility of such a switch. Conclusions/Significance We demonstrate that a heritable memory system that encodes its state into DNA is possible, and that inversion recombination system could be a starting point for more complex memory circuits. Although the circuit did not fully behave as expected, we showed that a multi-state, temporal memory is achievable. PMID:18665232

Working memory deficits in boys with attention-deficit/hyperactivity disorder (ADHD): the contribution of central executive and subsystem processes.

PubMed

Rapport, Mark D; Alderson, R Matt; Kofler, Michael J; Sarver, Dustin E; Bolden, Jennifer; Sims, Valerie

2008-08-01

The current study investigated contradictory findings from recent experimental and meta-analytic studies concerning working memory deficits in ADHD. Working memory refers to the cognitive ability to temporarily store and mentally manipulate limited amounts of information for use in guiding behavior. Phonological (verbal) and visuospatial (nonverbal) working memory were assessed across four memory load conditions in 23 boys (12 ADHD, 11 typically developing) using tasks based on Baddeley's (Working memory, thought, and action, Oxford University Press, New York, 2007) working memory model. The model posits separate phonological and visuospatial storage and rehearsal components that are controlled by a single attentional controller (CE: central executive). A latent variable approach was used to partial task performance related to three variables of interest: phonological buffer/rehearsal loop, visuospatial buffer/rehearsal loop, and the CE attentional controller. ADHD-related working memory deficits were apparent across all three cognitive systems--with the largest magnitude of deficits apparent in the CE--even after controlling for reading speed, nonverbal visual encoding, age, IQ, and SES.

Instructional Design and Directed Cognitive Processing.

ERIC Educational Resources Information Center

Bovy, Ruth Colvin

This paper argues that the information processing model provides a promising basis on which to build a comprehensive theory of instruction. Characteristics of the major information processing constructs are outlined including attention, encoding and rehearsal, working memory, long term memory, retrieval, and metacognitive processes, and a unifying…

Working memory capacity and recall from long-term memory: Examining the influences of encoding strategies, study time allocation, search efficiency, and monitoring abilities.

PubMed

Unsworth, Nash

2016-01-01

The relation between working memory capacity (WMC) and recall from long-term memory (LTM) was examined in the current study. Participants performed multiple measures of delayed free recall varying in presentation duration and self-reported their strategy usage after each task. Participants also performed multiple measures of WMC. The results suggested that WMC and LTM recall were related, and part of this relation was due to effective strategy use. However, adaptive changes in strategy use and study time allocation were not related to WMC. Examining multiple variables with structural equation modeling suggested that the relation between WMC and LTM recall was due to variation in effective strategy use, search efficiency, and monitoring abilities. Furthermore, all variables were shown to account for individual differences in LTM recall. These results suggest that the relation between WMC and recall from LTM is due to multiple strategic factors operating at both encoding and retrieval. (PsycINFO Database Record (c) 2016 APA, all rights reserved).

Decoding complex flow-field patterns in visual working memory.

PubMed

Christophel, Thomas B; Haynes, John-Dylan

2014-05-01

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

Negative affect promotes encoding of and memory for details at the expense of the gist: affect, encoding, and false memories.

PubMed

Storbeck, Justin

2013-01-01

I investigated whether negative affective states enhance encoding of and memory for item-specific information reducing false memories. Positive, negative, and neutral moods were induced, and participants then completed a Deese-Roediger-McDermott (DRM) false-memory task. List items were presented in unique spatial locations or unique fonts to serve as measures for item-specific encoding. The negative mood conditions had more accurate memories for item-specific information, and they also had fewer false memories. The final experiment used a manipulation that drew attention to distinctive information, which aided learning for DRM words, but also promoted item-specific encoding. For the condition that promoted item-specific encoding, false memories were reduced for positive and neutral mood conditions to a rate similar to that of the negative mood condition. These experiments demonstrated that negative affective cues promote item-specific processing reducing false memories. People in positive and negative moods encode events differently creating different memories for the same event.

Stress as a mnemonic filter: Interactions between medial temporal lobe encoding processes and post-encoding stress

PubMed Central

Ritchey, Maureen; McCullough, Andrew M.; Ranganath, Charan; Yonelinas, Andrew P.

2016-01-01

Acute stress has been shown to modulate memory for recently learned information, an effect attributed to the influence of stress hormones on medial temporal lobe (MTL) consolidation processes. However, little is known about which memories will be affected when stress follows encoding. One possibility is that stress interacts with encoding processes to selectively protect memories that had elicited responses in the hippocampus and amygdala, two MTL structures important for memory formation. There is limited evidence for interactions between encoding processes and consolidation effects in humans, but recent studies of consolidation in rodents have emphasized the importance of encoding “tags” for determining the impact of consolidation manipulations on memory. Here, we used fMRI in humans to test the hypothesis that the effects of post-encoding stress depend on MTL processes observed during encoding. We found that changes in stress hormone levels were associated with an increase in the contingency of memory outcomes on hippocampal and amygdala encoding responses. That is, for participants showing high cortisol reactivity, memories became more dependent on MTL activity observed during encoding, thereby shifting the distribution of recollected events toward those that had elicited relatively high activation. Surprisingly, this effect was generally larger for neutral, compared to emotionally negative, memories. The results suggest that stress does not uniformly enhance memory, but instead selectively preserves memories tagged during encoding, effectively acting as mnemonic filter. PMID:27774683

Emotional arousal and memory after deep encoding.

PubMed

Leventon, Jacqueline S; Camacho, Gabriela L; Ramos Rojas, Maria D; Ruedas, Angelica

2018-05-22

Emotion often enhances long-term memory. One mechanism for this enhancement is heightened arousal during encoding. However, reducing arousal, via emotion regulation (ER) instructions, has not been associated with reduced memory. In fact, the opposite pattern has been observed: stronger memory for emotional stimuli encoded with an ER instruction to reduce arousal. This pattern may be due to deeper encoding required by ER instructions. In the current research, we examine the effects of emotional arousal and deep-encoding on memory across three studies. In Study 1, adult participants completed a writing task (deep-encoding) for encoding negative, neutral, and positive picture stimuli, whereby half the emotion stimuli had the ER instruction to reduce the emotion. Memory was strong across conditions, and no memory enhancement was observed for any condition. In Study 2, adult participants completed the same writing task as Study 1, as well as a shallow-encoding task for one-third of negative, neutral, and positive trials. Memory was strongest for deep vs. shallow encoding trials, with no effects of emotion or ER instruction. In Study 3, adult participants completed a shallow-encoding task for negative, neutral, and positive stimuli, with findings indicating enhanced memory for negative emotional stimuli. Findings suggest that deep encoding must be acknowledged as a source of memory enhancement when examining manipulations of emotion-related arousal. Copyright © 2018. Published by Elsevier B.V.

The Importance of Encoding-Related Neural Dynamics in the Prediction of Inter-Individual Differences in Verbal Working Memory Performance

PubMed Central

Majerus, Steve; Salmon, Eric; Attout, Lucie

2013-01-01

Studies of brain-behaviour interactions in the field of working memory (WM) have associated WM success with activation of a fronto-parietal network during the maintenance stage, and this mainly for visuo-spatial WM. Using an inter-individual differences approach, we demonstrate here the equal importance of neural dynamics during the encoding stage, and this in the context of verbal WM tasks which are characterized by encoding phases of long duration and sustained attentional demands. Participants encoded and maintained 5-word lists, half of them containing an unexpected word intended to disturb WM encoding and associated task-related attention processes. We observed that inter-individual differences in WM performance for lists containing disturbing stimuli were related to activation levels in a region previously associated with task-related attentional processing, the left intraparietal sulcus (IPS), and this during stimulus encoding but not maintenance; functional connectivity strength between the left IPS and lateral prefrontal cortex (PFC) further predicted WM performance. This study highlights the critical role, during WM encoding, of neural substrates involved in task-related attentional processes for predicting inter-individual differences in verbal WM performance, and, more generally, provides support for attention-based models of WM. PMID:23874935

Post-encoding emotional arousal enhances consolidation of item memory, but not reality-monitoring source memory.

PubMed

Wang, Bo; Sun, Bukuan

2017-03-01

The current study examined whether the effect of post-encoding emotional arousal on item memory extends to reality-monitoring source memory and, if so, whether the effect depends on emotionality of learning stimuli and testing format. In Experiment 1, participants encoded neutral words and imagined or viewed their corresponding object pictures. Then they watched a neutral, positive, or negative video. The 24-hour delayed test showed that emotional arousal had little effect on both item memory and reality-monitoring source memory. Experiment 2 was similar except that participants encoded neutral, positive, and negative words and imagined or viewed their corresponding object pictures. The results showed that positive and negative emotional arousal induced after encoding enhanced consolidation of item memory, but not reality-monitoring source memory, regardless of emotionality of learning stimuli. Experiment 3, identical to Experiment 2 except that participants were tested only on source memory for all the encoded items, still showed that post-encoding emotional arousal had little effect on consolidation of reality-monitoring source memory. Taken together, regardless of emotionality of learning stimuli and regardless of testing format of source memory (conjunction test vs. independent test), the facilitatory effect of post-encoding emotional arousal on item memory does not generalize to reality-monitoring source memory.

Attention and implicit memory: priming-induced benefits and costs have distinct attentional requirements.

PubMed

Keane, Margaret M; Cruz, Matt E; Verfaellie, Mieke

2015-02-01

Attention at encoding plays a critical and ubiquitous role in explicit memory performance, but its role in implicit memory performance (i.e., priming) is more variable: some, but not all, priming effects are reduced by division of attention at encoding. A wealth of empirical and theoretical work has aimed to define the critical features of priming effects that do or do not require attention at encoding. This work, however, has focused exclusively on priming effects that are beneficial in nature (wherein performance is enhanced by prior exposure to task stimuli), and has overlooked priming effects that are costly in nature (wherein performance is harmed by prior exposure to task stimuli). The present study takes up this question by examining the effect of divided attention on priming-induced costs and benefits in a speeded picture-naming task. Experiment 1 shows that the costs, but not the benefits, are eliminated by division of attention at encoding. Experiment 2 shows that the costs (as well as the benefits) in this task are intact in amnesic participants, demonstrating that the elimination of the cost in the divided attention condition in Experiment 1 was not an artifact of the reduced availability of explicit memory in that condition. We suggest that the differential role of attention in priming-induced performance costs and benefits is linked to differences in response competition associated with these effects. This interpretation situates the present findings within a theoretical framework that has been applied to a broad range of facilitatory priming effects.

Effects of Age, Acoustic Challenge, and Verbal Working Memory on Recall of Narrative Speech.

PubMed

Ward, Caitlin M; Rogers, Chad S; Van Engen, Kristin J; Peelle, Jonathan E

2016-01-01

A common goal during speech comprehension is to remember what we have heard. Encoding speech into long-term memory frequently requires processes such as verbal working memory that may also be involved in processing degraded speech. Here the authors tested whether young and older adult listeners' memory for short stories was worse when the stories were acoustically degraded, or whether the additional contextual support provided by a narrative would protect against these effects. The authors tested 30 young adults (aged 18-28 years) and 30 older adults (aged 65-79 years) with good self-reported hearing. Participants heard short stories that were presented as normal (unprocessed) speech or acoustically degraded using a noise vocoding algorithm with 24 or 16 channels. The degraded stories were still fully intelligible. Following each story, participants were asked to repeat the story in as much detail as possible. Recall was scored using a modified idea unit scoring approach, which included separately scoring hierarchical levels of narrative detail. Memory for acoustically degraded stories was significantly worse than for normal stories at some levels of narrative detail. Older adults' memory for the stories was significantly worse overall, but there was no interaction between age and acoustic clarity or level of narrative detail. Verbal working memory (assessed by reading span) significantly correlated with recall accuracy for both young and older adults, whereas hearing ability (better ear pure tone average) did not. The present findings are consistent with a framework in which the additional cognitive demands caused by a degraded acoustic signal use resources that would otherwise be available for memory encoding for both young and older adults. Verbal working memory is a likely candidate for supporting both of these processes.

Regulation of Cognitive Resources During an N-Back Task in Youth-Onset Psychosis and Attention-Deficit/Hyperactivity Disorder (ADHD)

PubMed Central

Karatekin, Canan; Bingham, Christopher; White, Tonya

2009-01-01

The goals of the current study were to use behavioral and pupillary measures to examine working memory on a spatial n-back task in 8-20-year-olds with youth-onset psychosis or ADHD (Combined subtype) and healthy controls to determine the contribution of different attentional factors to spatial working memory impairments, and to examine if age-related changes in performance differed across groups. Although both clinical groups had lower perceptual sensitivity on both 0- and 1-back, there was no evidence of an impairment in spatial working memory or differential order effects on the 0-back. Instead, results suggest that both clinical groups had difficulty encoding the stimuli. They also appeared to have difficulty maintaining attention and/or readiness to respond, and, to a lesser extent, recruiting resources on a trial-to-trial basis. It is likely that these attentional problems prevented the clinical groups from encoding the stimuli effectively and contributed to their general performance deficits. PMID:19427339

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.

The contribution of encoding and retrieval processes to proactive interference.

PubMed

Kliegl, Oliver; Pastötter, Bernhard; Bäuml, Karl-Heinz T

2015-11-01

Proactive interference (PI) refers to the finding that memory for recently studied (target) material can be impaired by the prior study of other (nontarget) material. Previous accounts of PI differed in whether they attributed PI to impaired retrieval or impaired encoding. Here, we suggest an integrated encoding-retrieval account, which assigns a role for each of the 2 types of processes in buildup of PI. Employing a typical PI task, we examined (a) the role of encoding processes in PI by recording scalp EEG during study of nontarget and target lists, and (b) the role of retrieval processes in PI by measuring recall totals and response latencies in target list recall. In addition, we measured subjects' working memory capacity (WMC). Behaviorally, the PI effect arose in both recall totals and response latencies, indicating PI at the sampling and the recovery stage of recall. Neurally, we found an increase in electrophysiological activities in the theta frequency band (5-8 Hz) from nontarget to target list encoding, indicating an increase in memory load during target list encoding. The results demonstrate that impaired retrieval and impaired encoding can contribute to PI. They also show that WMC affects PI. For both encoding and retrieval processes, PI was reduced in high-WMC subjects, suggesting that these subjects are able to separate target from nontarget information and create stronger focus on the target material. (c) 2015 APA, all rights reserved).

The benefit of forgetting.

PubMed

Williams, Melonie; Hong, Sang W; Kang, Min-Suk; Carlisle, Nancy B; Woodman, Geoffrey F

2013-04-01

Recent research using change-detection tasks has shown that a directed-forgetting cue, indicating that a subset of the information stored in memory can be forgotten, significantly benefits the other information stored in visual working memory. How do these directed-forgetting cues aid the memory representations that are retained? We addressed this question in the present study by using a recall paradigm to measure the nature of the retained memory representations. Our results demonstrated that a directed-forgetting cue leads to higher-fidelity representations of the remaining items and a lower probability of dropping these representations from memory. Next, we showed that this is made possible by the to-be-forgotten item being expelled from visual working memory following the cue, allowing maintenance mechanisms to be focused on only the items that remain in visual working memory. Thus, the present findings show that cues to forget benefit the remaining information in visual working memory by fundamentally improving their quality relative to conditions in which just as many items are encoded but no cue is provided.

Memory for a single object has differently variable precisions for relevant and irrelevant features.

PubMed

Swan, Garrett; Collins, John; Wyble, Brad

2016-01-01

Working memory is a limited resource. To further characterize its limitations, it is vital to understand exactly what is encoded about a visual object beyond the "relevant" features probed in a particular task. We measured the memory quality of a task-irrelevant feature of an attended object by coupling a delayed estimation task with a surprise test. Participants were presented with a single colored arrow and were asked to retrieve just its color for the first half of the experiment before unexpectedly being asked to report its direction. Mixture modeling of the data revealed that participants had highly variable precision on the surprise test, indicating a coarse-grained memory for the irrelevant feature. Following the surprise test, all participants could precisely recall the arrow's direction; however, this improvement in direction memory came at a cost in precision for color memory even though only a single object was being remembered. We attribute these findings to varying levels of attention to different features during memory encoding.

Effects of noise and working memory capacity on memory processing of speech for hearing-aid users.

PubMed

Ng, Elaine Hoi Ning; Rudner, Mary; Lunner, Thomas; Pedersen, Michael Syskind; Rönnberg, Jerker

2013-07-01

It has been shown that noise reduction algorithms can reduce the negative effects of noise on memory processing in persons with normal hearing. The objective of the present study was to investigate whether a similar effect can be obtained for persons with hearing impairment and whether such an effect is dependent on individual differences in working memory capacity. A sentence-final word identification and recall (SWIR) test was conducted in two noise backgrounds with and without noise reduction as well as in quiet. Working memory capacity was measured using a reading span (RS) test. Twenty-six experienced hearing-aid users with moderate to moderately severe sensorineural hearing loss. Noise impaired recall performance. Competing speech disrupted memory performance more than speech-shaped noise. For late list items the disruptive effect of the competing speech background was virtually cancelled out by noise reduction for persons with high working memory capacity. Noise reduction can reduce the adverse effect of noise on memory for speech for persons with good working memory capacity. We argue that the mechanism behind this is faster word identification that enhances encoding into working memory.

The synaptic plasticity and memory hypothesis: encoding, storage and persistence

PubMed Central

Takeuchi, Tomonori; Duszkiewicz, Adrian J.; Morris, Richard G. M.

2014-01-01

The synaptic plasticity and memory hypothesis asserts that activity-dependent synaptic plasticity is induced at appropriate synapses during memory formation and is both necessary and sufficient for the encoding and trace storage of the type of memory mediated by the brain area in which it is observed. Criteria for establishing the necessity and sufficiency of such plasticity in mediating trace storage have been identified and are here reviewed in relation to new work using some of the diverse techniques of contemporary neuroscience. Evidence derived using optical imaging, molecular-genetic and optogenetic techniques in conjunction with appropriate behavioural analyses continues to offer support for the idea that changing the strength of connections between neurons is one of the major mechanisms by which engrams are stored in the brain. PMID:24298167

Differences in Memory Functioning between Children with Attention-Deficit/Hyperactivity Disorder and/or Focal Epilepsy

PubMed Central

Lee, Sylvia E.; Kibby, Michelle Y.; Cohen, Morris J.; Stanford, Lisa; Park, Yong; Strickland, Suzanne

2016-01-01

Prior research has shown that attention-deficit/hyperactivity disorder (ADHD) and epilepsy are frequently comorbid and that both disorders are associated with various attention and memory problems. Nonetheless, limited research has been conducted comparing the two disorders in one sample to determine unique versus shared deficits. Hence, we investigated differences in working memory and short-term and delayed recall between children with ADHD, focal epilepsy of mixed foci, comorbid ADHD/epilepsy and controls. Participants were compared on the Core subtests and the Picture Locations subtest of the Children’s Memory Scale (CMS). Results indicated that children with ADHD displayed intact verbal working memory and long-term memory (LTM), as well as intact performance on most aspects of short-term memory (STM). They performed worse than controls on Numbers Forward and Picture Locations, suggesting problems with focused attention and simple span for visual-spatial material. Conversely, children with epilepsy displayed poor focused attention and STM regardless of modality assessed, which affected encoding into LTM. The only loss over time was found for passages (Stories). Working memory was intact. Children with comorbid ADHD/epilepsy displayed focused attention and STM/LTM problems consistent with both disorders, having the lowest scores across the four groups. Hence, focused attention and visual-spatial span appear to be affected in both disorders, whereas additional STM/encoding problems are specific to epilepsy. Children with comorbid ADHD/epilepsy have deficits consistent with both disorders, with slight additive effects. This study suggests that attention and memory testing should be a regular part of the evaluation of children with epilepsy and ADHD. PMID:26156331

The neural correlates of gist-based true and false recognition

PubMed Central

Gutchess, Angela H.; Schacter, Daniel L.

2012-01-01

When information is thematically related to previously studied information, gist-based processes contribute to false recognition. Using functional MRI, we examined the neural correlates of gist-based recognition as a function of increasing numbers of studied exemplars. Sixteen participants incidentally encoded small, medium, and large sets of pictures, and we compared the neural response at recognition using parametric modulation analyses. For hits, regions in middle occipital, middle temporal, and posterior parietal cortex linearly modulated their activity according to the number of related encoded items. For false alarms, visual, parietal, and hippocampal regions were modulated as a function of the encoded set size. The present results are consistent with prior work in that the neural regions supporting veridical memory also contribute to false memory for related information. The results also reveal that these regions respond to the degree of relatedness among similar items, and implicate perceptual and constructive processes in gist-based false memory. PMID:22155331

Exploration of depth modeling mode one lossless wedgelets storage strategies for 3D-high efficiency video coding

NASA Astrophysics Data System (ADS)

Sanchez, Gustavo; Marcon, César; Agostini, Luciano Volcan

2018-01-01

The 3D-high efficiency video coding has introduced tools to obtain higher efficiency in 3-D video coding, and most of them are related to the depth maps coding. Among these tools, the depth modeling mode-1 (DMM-1) focuses on better encoding edges regions of depth maps. The large memory required for storing all wedgelet patterns is one of the bottlenecks in the DMM-1 hardware design of both encoder and decoder since many patterns must be stored. Three algorithms to reduce the DMM-1 memory requirements and a hardware design targeting the most efficient among these algorithms are presented. Experimental results demonstrate that the proposed solutions surpass related works reducing up to 78.8% of the wedgelet memory, without degrading the encoding efficiency. Synthesis results demonstrate that the proposed algorithm reduces almost 75% of the power dissipation when compared to the standard approach.

Modality specificity and integration in working memory: Insights from visuospatial bootstrapping.

PubMed

Allen, Richard J; Havelka, Jelena; Falcon, Thomas; Evans, Sally; Darling, Stephen

2015-05-01

The question of how meaningful associations between verbal and spatial information might be utilized to facilitate working memory performance is potentially highly instructive for models of memory function. The present study explored how separable processing capacities within specialized domains might each contribute to this, by examining the disruptive impacts of simple verbal and spatial concurrent tasks on young adults' recall of visually presented digit sequences encountered either in a single location or within a meaningful spatial "keypad" configuration. The previously observed advantage for recall in the latter condition (the "visuospatial bootstrapping effect") consistently emerged across 3 experiments, indicating use of familiar spatial information in boosting verbal memory. The magnitude of this effect interacted with concurrent activity; articulatory suppression during encoding disrupted recall to a greater extent when digits were presented in single locations (Experiment 1), while spatial tapping during encoding had a larger impact on the keypad condition and abolished the visuospatial bootstrapping advantage (Experiment 2). When spatial tapping was performed during recall (Experiment 3), no task by display interaction was observed. Outcomes are discussed within the context of the multicomponent model of working memory, with a particular emphasis on cross-domain storage in the episodic buffer (Baddeley, 2000). (c) 2015 APA, all rights reserved).

Enhanced dimension-specific visual working memory in grapheme-color synesthesia.

PubMed

Terhune, Devin Blair; Wudarczyk, Olga Anna; Kochuparampil, Priya; Cohen Kadosh, Roi

2013-10-01

There is emerging evidence that the encoding of visual information and the maintenance of this information in a temporarily accessible state in working memory rely on the same neural mechanisms. A consequence of this overlap is that atypical forms of perception should influence working memory. We examined this by investigating whether having grapheme-color synesthesia, a condition characterized by the involuntary experience of color photisms when reading or representing graphemes, would confer benefits on working memory. Two competing hypotheses propose that superior memory in synesthesia results from information being coded in two information channels (dual-coding) or from superior dimension-specific visual processing (enhanced processing). We discriminated between these hypotheses in three n-back experiments in which controls and synesthetes viewed inducer and non-inducer graphemes and maintained color or grapheme information in working memory. Synesthetes displayed superior color working memory than controls for both grapheme types, whereas the two groups did not differ in grapheme working memory. Further analyses excluded the possibilities of enhanced working memory among synesthetes being due to greater color discrimination, stimulus color familiarity, or bidirectionality. These results reveal enhanced dimension-specific visual working memory in this population and supply further evidence for a close relationship between sensory processing and the maintenance of sensory information in working memory. Copyright © 2013 The Authors. Published by Elsevier B.V. All rights reserved.

Hierarchical Chunking of Sequential Memory on Neuromorphic Architecture with Reduced Synaptic Plasticity

PubMed Central

Li, Guoqi; Deng, Lei; Wang, Dong; Wang, Wei; Zeng, Fei; Zhang, Ziyang; Li, Huanglong; Song, Sen; Pei, Jing; Shi, Luping

2016-01-01

Chunking refers to a phenomenon whereby individuals group items together when performing a memory task to improve the performance of sequential memory. In this work, we build a bio-plausible hierarchical chunking of sequential memory (HCSM) model to explain why such improvement happens. We address this issue by linking hierarchical chunking with synaptic plasticity and neuromorphic engineering. We uncover that a chunking mechanism reduces the requirements of synaptic plasticity since it allows applying synapses with narrow dynamic range and low precision to perform a memory task. We validate a hardware version of the model through simulation, based on measured memristor behavior with narrow dynamic range in neuromorphic circuits, which reveals how chunking works and what role it plays in encoding sequential memory. Our work deepens the understanding of sequential memory and enables incorporating it for the investigation of the brain-inspired computing on neuromorphic architecture. PMID:28066223

Visual Memory in Methamphetamine Dependent Individuals: Deficient Strategic Control of Encoding and Retrieval

PubMed Central

Morgan, Erin E.; Woods, Steven Paul; Poquette, Amelia J.; Vigil, Ofilio; Heaton, Robert K.; Grant, Igor

2012-01-01

Objective Chronic use of methamphetamine (MA) has moderate effects on neurocognitive functions associated with frontal systems, including the executive aspects of verbal episodic memory. Extending this literature, the current study examined the effects of MA on visual episodic memory with the hypothesis that a profile of deficient strategic encoding and retrieval processes would be revealed for visuospatial information (i.e., simple geometric designs), including possible differential effects on source versus item recall. Method The sample comprised 114 MA-dependent (MA+) and 110 demographically-matched MA-nondependent comparison participants (MA−) who completed the Brief Visuospatial Memory Test – Revised (BVMT-R), which was scored for standard learning and memory indices, as well as novel item (i.e., figure) and source (i.e., location) memory indices. Results Results revealed a profile of impaired immediate and delayed free recall (p < .05) in the context of preserved learning slope, retention, and recognition discriminability in the MA+ group. The MA+ group also performed more poorly than MA− participants on Item visual memory (p < .05) but not Source visual memory (p > .05), and no group by task-type interaction was observed (p > .05). Item visual memory demonstrated significant associations with executive dysfunction, deficits in working memory, and shorter length of abstinence from MA use (p < 0.05). Conclusions These visual memory findings are commensurate with studies reporting deficient strategic verbal encoding and retrieval in MA users that are posited to reflect the vulnerability of frontostriatal circuits to the neurotoxic effects of MA. Potential clinical implications of these visual memory deficits are discussed. PMID:22311530

Large-scale network integration in the human brain tracks temporal fluctuations in memory encoding performance.

PubMed

Keerativittayayut, Ruedeerat; Aoki, Ryuta; Sarabi, Mitra Taghizadeh; Jimura, Koji; Nakahara, Kiyoshi

2018-06-18

Although activation/deactivation of specific brain regions have been shown to be predictive of successful memory encoding, the relationship between time-varying large-scale brain networks and fluctuations of memory encoding performance remains unclear. Here we investigated time-varying functional connectivity patterns across the human brain in periods of 30-40 s, which have recently been implicated in various cognitive functions. During functional magnetic resonance imaging, participants performed a memory encoding task, and their performance was assessed with a subsequent surprise memory test. A graph analysis of functional connectivity patterns revealed that increased integration of the subcortical, default-mode, salience, and visual subnetworks with other subnetworks is a hallmark of successful memory encoding. Moreover, multivariate analysis using the graph metrics of integration reliably classified the brain network states into the period of high (vs. low) memory encoding performance. Our findings suggest that a diverse set of brain systems dynamically interact to support successful memory encoding. © 2018, Keerativittayayut et al.

Source and destination memory: two sides of the same coin?

PubMed

Lindner, Isabel; Drouin, Héloïse; Tanguay, Annick F N; Stamenova, Vessela; Davidson, Patrick S R

2015-01-01

Whereas source memory involves remembering from whom you have heard something, destination memory involves remembering to whom you have told something. Despite its practical relevance, destination memory has been studied little. Recently, two reports suggested that generally destination memory should be poorer than source memory, and that it should be particularly difficult for older people. We tested these predictions by having young and older participants read sentences to two examiners (destination encoding) and listen to sentences read by two examiners (source encoding), under intentional (Experiment 1) or incidental encoding (Experiments 2 and 3). Only in Experiment 3 (in which cognitive demands during destination encoding were increased) was destination memory significantly poorer than source memory. In none of the experiments were older adults inferior to the young on destination or source memory. Destination- and source-memory scores were significantly correlated. Item memory was consistently superior for sentences that had been read out loud (during destination encoding) versus those that had been heard (during source encoding). Destination memory needs not always be poorer than source memory, appears not to be particularly impaired by normal ageing and may depend on similar processes to those supporting source memory.

The Asymmetrical Effects of Divided Attention on Encoding and Retrieval Processes: A Different View Based on an Interference with the Episodic Register

PubMed Central

Guez, Jonathan; Naveh-Benjamin, Moshe

2013-01-01

In this study, we evaluate the conceptualization of encoding and retrieval processes established in previous studies that used a divided attention (DA) paradigm. These studies indicated that there were considerable detrimental effects of DA at encoding on later memory performance, but only minimal effects, if any, on divided attention at retrieval. We suggest that this asymmetry in the effects of DA on memory can be due, at least partially, to a confound between the memory phase (encoding and retrieval) and the memory requirements of the task (memory “for” encoded information versus memory “at” test). To control for this confound, we tested memory for encoded information and for retrieved information by introducing a second test that assessed memory for the retrieved information from the first test. We report the results of four experiments that use measures of memory performance, retrieval latency, and performance on the concurrent task, all of which consistently show that DA at retrieval strongly disrupts later memory for the retrieved episode, similarly to the effects of DA at encoding. We suggest that these symmetrical disruptive effects of DA at encoding and retrieval on later retrieval reflect a disruption of an episodic buffer (EB) or episodic register component (ER), rather than a failure of encoding or retrieval operations per se. PMID:24040249

The asymmetrical effects of divided attention on encoding and retrieval processes: a different view based on an interference with the episodic register.

PubMed

Guez, Jonathan; Naveh-Benjamin, Moshe

2013-01-01

In this study, we evaluate the conceptualization of encoding and retrieval processes established in previous studies that used a divided attention (DA) paradigm. These studies indicated that there were considerable detrimental effects of DA at encoding on later memory performance, but only minimal effects, if any, on divided attention at retrieval. We suggest that this asymmetry in the effects of DA on memory can be due, at least partially, to a confound between the memory phase (encoding and retrieval) and the memory requirements of the task (memory "for" encoded information versus memory "at" test). To control for this confound, we tested memory for encoded information and for retrieved information by introducing a second test that assessed memory for the retrieved information from the first test. We report the results of four experiments that use measures of memory performance, retrieval latency, and performance on the concurrent task, all of which consistently show that DA at retrieval strongly disrupts later memory for the retrieved episode, similarly to the effects of DA at encoding. We suggest that these symmetrical disruptive effects of DA at encoding and retrieval on later retrieval reflect a disruption of an episodic buffer (EB) or episodic register component (ER), rather than a failure of encoding or retrieval operations per se.

Learning terms and definitions: Drawing and the role of elaborative encoding.

PubMed

Wammes, Jeffrey D; Meade, Melissa E; Fernandes, Myra A

2017-09-01

Traditionally, students adopt the strategy of taking written notes when attending a class or learning from a textbook in educational settings. Informed by previous work showing that learning by doing improves memory performance, we examined whether drawing to-be-remembered definitions from university textbooks would improve later memory, relative to a more typical strategy of rote transcription. Participants were asked to either write out the definition, or to draw a picture representative of the definition. Results indicated that drawing, relative to verbatim writing, conferred a reliable memorial benefit that was robust, even when participants' preexisting familiarity with the terms was included as a covariate (in Experiment 1) or when the to-be-remembered terms and definitions were fictitious, thus removing the influence of familiarity (in Experiment 2). We reasoned that drawing likely facilitates retention at least in part because at encoding, participants must retain and elaborate upon information regarding the meaning of the definition, to translate it into a new form (a picture). This is not the case when participants write out the definitions verbatim. In Experiment 3 we showed that paraphrasing during encoding, which, like drawing and in contrast with verbatim writing, requires self-generated elaboration, led to memory performance that was comparable to drawing. Taken together, results suggest that drawing is a powerful tool which improves memory, and that drawing produces a similar level of retention as does paraphrasing. This suggests that elaborative encoding plays a critical role in the memorial benefit that drawing confers to memory for definitions of academic terms. Copyright © 2017 Elsevier B.V. All rights reserved.

Increase in posterior alpha activity during rehearsal predicts successful long-term memory formation of word sequences.

PubMed

Meeuwissen, Esther B; Takashima, Atsuko; Fernández, Guillén; Jensen, Ole

2011-12-01

It is becoming increasingly clear that demanding cognitive tasks rely on an extended network engaging task-relevant areas and, importantly, disengaging task-irrelevant areas. Given that alpha activity (8-12 Hz) has been shown to reflect the disengagement of task-irrelevant regions in attention and working memory tasks, we here ask if alpha activity plays a related role for long-term memory formation. Subjects were instructed to encode and maintain the order of word sequences while the ongoing brain activity was recorded using magnetoencephalography (MEG). In each trial, three words were presented followed by a 3.4 s rehearsal interval. Considering the good temporal resolution of MEG this allowed us to investigate the word presentation and rehearsal interval separately. The sequences were grouped in trials where word order either could be tested immediately (working memory trials; WM) or later (LTM trials) according to instructions. Subjects were tested on their ability to retrieve the order of the three words. The data revealed that alpha power in parieto-occipital regions was lower during word presentation compared to rehearsal. Our key finding was that parieto-occipital alpha power during the rehearsal period was markedly stronger for successfully than unsuccessfully encoded LTM sequences. This subsequent memory effect demonstrates that high posterior alpha activity creates an optimal brain state for successful LTM formation possibly by actively reducing parieto-occipital activity that might interfere with sequence encoding. Copyright © 2010 Wiley Periodicals, Inc.

Does learning to read shape verbal working memory?

PubMed

Demoulin, Catherine; Kolinsky, Régine

2016-06-01

Many experimental studies have investigated the relationship between the acquisition of reading and working memory in a unidirectional way, attempting to determine to what extent individual differences in working memory can predict reading achievement. In contrast, very little attention has been dedicated to the converse possibility that learning to read shapes the development of verbal memory processes. In this paper, we present available evidence that advocates a more prominent role for reading acquisition on verbal working memory and then discuss the potential mechanisms of such literacy effects. First, the early decoding activities might bolster the development of subvocal rehearsal, which, in turn, would enhance serial order performance in immediate memory tasks. In addition, learning to read and write in an alphabetical system allows the emergence of phonemic awareness and finely tuned phonological representations, as well as of orthographic representations. This could improve the quality, strength, and precision of lexical representations, and hence offer better support for the temporary encoding of memory items and/or for their retrieval.

Reactivation in Working Memory: An Attractor Network Model of Free Recall

PubMed Central

Lansner, Anders; Marklund, Petter; Sikström, Sverker; Nilsson, Lars-Göran

2013-01-01

The dynamic nature of human working memory, the general-purpose system for processing continuous input, while keeping no longer externally available information active in the background, is well captured in immediate free recall of supraspan word-lists. Free recall tasks produce several benchmark memory phenomena, like the U-shaped serial position curve, reflecting enhanced memory for early and late list items. To account for empirical data, including primacy and recency as well as contiguity effects, we propose here a neurobiologically based neural network model that unifies short- and long-term forms of memory and challenges both the standard view of working memory as persistent activity and dual-store accounts of free recall. Rapidly expressed and volatile synaptic plasticity, modulated intrinsic excitability, and spike-frequency adaptation are suggested as key cellular mechanisms underlying working memory encoding, reactivation and recall. Recent findings on the synaptic and molecular mechanisms behind early LTP and on spiking activity during delayed-match-to-sample tasks support this view. PMID:24023690

Reactivation in working memory: an attractor network model of free recall.

PubMed

Lansner, Anders; Marklund, Petter; Sikström, Sverker; Nilsson, Lars-Göran

2013-01-01

The dynamic nature of human working memory, the general-purpose system for processing continuous input, while keeping no longer externally available information active in the background, is well captured in immediate free recall of supraspan word-lists. Free recall tasks produce several benchmark memory phenomena, like the U-shaped serial position curve, reflecting enhanced memory for early and late list items. To account for empirical data, including primacy and recency as well as contiguity effects, we propose here a neurobiologically based neural network model that unifies short- and long-term forms of memory and challenges both the standard view of working memory as persistent activity and dual-store accounts of free recall. Rapidly expressed and volatile synaptic plasticity, modulated intrinsic excitability, and spike-frequency adaptation are suggested as key cellular mechanisms underlying working memory encoding, reactivation and recall. Recent findings on the synaptic and molecular mechanisms behind early LTP and on spiking activity during delayed-match-to-sample tasks support this view.

The neural substrates of memory suppression: a FMRI exploration of directed forgetting.

PubMed

Bastin, Christine; Feyers, Dorothée; Majerus, Steve; Balteau, Evelyne; Degueldre, Christian; Luxen, André; Maquet, Pierre; Salmon, Eric; Collette, Fabienne

2012-01-01

The directed forgetting paradigm is frequently used to determine the ability to voluntarily suppress information. However, little is known about brain areas associated with information to forget. The present study used functional magnetic resonance imaging to determine brain activity during the encoding and retrieval phases of an item-method directed forgetting recognition task with neutral verbal material in order to apprehend all processing stages that information to forget and to remember undergoes. We hypothesized that regions supporting few selective processes, namely recollection and familiarity memory processes, working memory, inhibitory and selection processes should be differentially activated during the processing of to-be-remembered and to-be-forgotten items. Successful encoding and retrieval of items to remember engaged the entorhinal cortex, the hippocampus, the anterior medial prefrontal cortex, the left inferior parietal cortex, the posterior cingulate cortex and the precuneus; this set of regions is well known to support deep and associative encoding and retrieval processes in episodic memory. For items to forget, encoding was associated with higher activation in the right middle frontal and posterior parietal cortex, regions known to intervene in attentional control. Items to forget but nevertheless correctly recognized at retrieval yielded activation in the dorsomedial thalamus, associated with familiarity-based memory processes and in the posterior intraparietal sulcus and the anterior cingulate cortex, involved in attentional processes.

Long-Term Memory and the Control of Attentional Control

PubMed Central

Mayr, Ulrich; Kuhns, David; Hubbard, Jason

2014-01-01

Task-switch costs and in particular the switch-cost asymmetry (i.e., the larger costs of switching to a dominant than a non-dominant task) are usually explained in terms of trial-to-trial carry-over of task-specific control settings. Here we argue that task switches are just one example of situations that trigger a transition from working-memory maintenance to updating, thereby opening working memory to interference from long-term memory. We used a new paradigm that requires selecting a spatial location either on the basis of a central cue (i.e., endogenous control of attention) or a peripheral, sudden onset (i.e., exogenous control of attention). We found a strong cost asymmetry that occurred even after short interruptions of otherwise single-task blocks (Exp. 1-3), but that was much stronger when participants had experienced the competing task under conditions of conflict (Exp. 1-2). Experiment 3 showed that the asymmetric costs were due to interruptions per se, rather than to associative interference tied to specific interruption activities. Experiment 4 generalized the basic pattern across interruptions varying in length or control demands and Experiment 5 across primary tasks with response-selection conflict rather than attentional conflict. Combined, the results support a model in which costs of selecting control settings arise when (a) potentially interfering memory traces have been encoded in long-term memory and (b) working-memory is forced from a maintenance mode into an updating mode (e.g., through task interruptions), thereby allowing unwanted retrieval of the encoded memory traces. PMID:24650696

Rapid formation and flexible expression of memories of subliminal word pairs.

PubMed

Reber, Thomas P; Henke, Katharina

2011-01-01

Our daily experiences are incidentally and rapidly encoded as episodic memories. Episodic memories consist of numerous associations (e.g., who gave what to whom where and when) that can be expressed flexibly in new situations. Key features of episodic memory are speed of encoding, its associative nature, and its representational flexibility. Another defining feature of human episodic memory has been consciousness of encoding/retrieval. Here, we show that humans can rapidly form associations between subliminal words and minutes later retrieve these associations even if retrieval words were conceptually related to, but different from encoding words. Because encoding words were presented subliminally, associative encoding, and retrieval were unconscious. Unconscious association formation and retrieval were dependent on a preceding understanding of task principles. We conclude that key computations underlying episodic memory - rapid encoding and flexible expression of associations - can operate outside consciousness.

Attention and Implicit Memory: Priming-Induced Benefits and Costs Have Distinct Attentional Requirements

PubMed Central

Keane, Margaret M.; Cruz, Matt E.; Verfaellie, Mieke

2014-01-01

Attention at encoding plays a critical and ubiquitous role in explicit memory performance, but its role in implicit memory performance (i.e., priming) is more variable: Some, but not all, priming effects are reduced by division of attention at encoding. A wealth of empirical and theoretical work has aimed to define the critical features of priming effects that do or do not require attention at encoding. This work, however, has focused exclusively on priming effects that are beneficial in nature (wherein performance is enhanced by prior exposure to task stimuli), and has overlooked priming effects that are costly in nature (wherein performance is harmed by prior exposure to task stimuli). The present study takes up this question by examining the effect of divided attention on priming-induced costs and benefits in a speeded picture-naming task. Experiment 1 shows that the costs, but not the benefits, are eliminated by division of attention at encoding. Experiment 2 shows that the costs (as well as the benefits) in this task are intact in amnesic participants, demonstrating that the elimination of the cost in the divided attention condition in Experiment 1 was not an artifact of the reduced availability of explicit memory in that condition. We suggest that the differential role of attention in priming-induced performance costs and benefits is linked to differences in response competition associated with these effects. This interpretation situates the present findings within a theoretical framework that has been applied to a broad range of facilitatory priming effects. PMID:25257650

Acute Effects of Alcohol on Encoding and Consolidation of Memory for Emotional Stimuli

PubMed Central

Weafer, Jessica; Gallo, David A.; De Wit, Harriet

2016-01-01

Objective: Acute doses of alcohol impair memory when administered before encoding of emotionally neutral stimuli but enhance memory when administered immediately after encoding, potentially by affecting memory consolidation. Here, we examined whether alcohol produces similar biphasic effects on memory for positive or negative emotional stimuli. Method: The current study examined memory for emotional stimuli after alcohol (0.8 g/kg) was administered either before stimulus viewing (encoding group; n = 20) or immediately following stimulus viewing (consolidation group; n = 20). A third group received placebo both before and after stimulus viewing (control group; n = 19). Participants viewed the stimuli on one day, and their retrieval was assessed exactly 48 hours later, when they performed a surprise cued recollection and recognition test of the stimuli in a drug-free state. Results: As in previous studies, alcohol administered before encoding impaired memory accuracy, whereas alcohol administered after encoding enhanced memory accuracy. Critically, alcohol effects on cued recollection depended on the valence of the emotional stimuli: Its memory-impairing effects during encoding were greatest for emotional stimuli, whereas its memory-enhancing effects during consolidation were greatest for emotionally neutral stimuli. Effects of alcohol on recognition were not related to stimulus valence. Conclusions: This study extends previous findings with memory for neutral stimuli, showing that alcohol differentially affects the encoding and consolidation of memory for emotional stimuli. These effects of alcohol on memory for emotionally salient material may contribute to the development of alcohol-related problems, perhaps by dampening memory for adverse consequences of alcohol consumption. PMID:26751358

Ghosts in the Machine II: Neural Correlates of Memory Interference from the Previous Trial.

PubMed

Papadimitriou, Charalampos; White, Robert L; Snyder, Lawrence H

2017-04-01

Previous memoranda interfere with working memory. For example, spatial memories are biased toward locations memorized on the previous trial. We predicted, based on attractor network models of memory, that activity in the frontal eye fields (FEFs) encoding a previous target location can persist into the subsequent trial and that this ghost will then bias the readout of the current target. Contrary to this prediction, we find that FEF memory representations appear biased away from (not toward) the previous target location. The behavioral and neural data can be reconciled by a model in which receptive fields of memory neurons converge toward remembered locations, much as receptive fields converge toward attended locations. Convergence increases the resources available to encode the relevant memoranda and decreases overall error in the network, but the residual convergence from the previous trial can give rise to an attractive behavioral bias on the next trial. © The Author 2016. Published by Oxford University Press. All rights reserved. For Permissions, please e-mail: journals.permissions@oup.com.

Ghrelin modulates encoding-related brain function without enhancing memory formation in humans.

PubMed

Kunath, N; Müller, N C J; Tonon, M; Konrad, B N; Pawlowski, M; Kopczak, A; Elbau, I; Uhr, M; Kühn, S; Repantis, D; Ohla, K; Müller, T D; Fernández, G; Tschöp, M; Czisch, M; Steiger, A; Dresler, M

2016-11-15

Ghrelin regulates energy homeostasis in various species and enhances memory in rodent models. In humans, the role of ghrelin in cognitive processes has yet to be characterized. Here we show in a double-blind randomized crossover design that acute administration of ghrelin alters encoding-related brain activity, however does not enhance memory formation in humans. Twenty-one healthy young male participants had to memorize food- and non-food-related words presented on a background of a virtual navigational route while undergoing fMRI recordings. After acute ghrelin administration, we observed decreased post-encoding resting state fMRI connectivity between the caudate nucleus and the insula, amygdala, and orbitofrontal cortex. In addition, brain activity related to subsequent memory performance was modulated by ghrelin. On the next day, however, no differences were found in free word recall or cued location-word association recall between conditions; and ghrelin's effects on brain activity or functional connectivity were unrelated to memory performance. Further, ghrelin had no effect on a cognitive test battery comprising tests for working memory, fluid reasoning, creativity, mental speed, and attention. In conclusion, in contrast to studies with animal models, we did not find any evidence for the potential of ghrelin acting as a short-term cognitive enhancer in humans. Copyright © 2016 Elsevier Inc. All rights reserved.

A functional magnetic resonance imaging study of working memory abnormalities in schizophrenia.

PubMed

Johnson, Matthew R; Morris, Nicholas A; Astur, Robert S; Calhoun, Vince D; Mathalon, Daniel H; Kiehl, Kent A; Pearlson, Godfrey D

2006-07-01

Previous neuroimaging studies of working memory (WM) in schizophrenia, typically focusing on dorsolateral prefrontal cortex, yield conflicting results, possibly because of varied choice of tasks and analysis techniques. We examined neural function changes at several WM loads to derive a more complete picture of WM dysfunction in schizophrenia. We used a version of the Sternberg Item Recognition Paradigm to test WM function at five distinct loads. Eighteen schizophrenia patients and 18 matched healthy controls were scanned with functional magnetic resonance imaging at 3 Tesla. Patterns of both overactivation and underactivation in patients were observed depending on WM load. Patients' activation was generally less responsive to load changes than control subjects', and different patterns of between-group differences were observed for memory encoding and retrieval. In the specific case of successful retrieval, patients recruited additional neural circuits unused by control subjects. Behavioral effects were generally consistent with these imaging results. Differential findings of overactivation and underactivation may be attributable to patients' decreased ability to focus and allocate neural resources at task-appropriate levels. Additionally, differences between encoding and retrieval suggest that WM dysfunction may be manifested differently during the distinct phases of encoding, maintenance, and retrieval.

Determining the Neural Substrate for Encoding a Memory of Human Pain and the Influence of Anxiety

PubMed Central

Kong, Yazhuo; Tracey, Irene

2017-01-01

To convert a painful stimulus into a briefly maintainable construct when the painful stimulus is no longer accessible is essential to guide human behavior and avoid dangerous situations. Because of the aversive nature of pain, this encoding process might be influenced by emotional aspects and could thus vary across individuals, but we have yet to understand both the basic underlying neural mechanisms as well as potential interindividual differences. Using fMRI in combination with a delayed-discrimination task in healthy volunteers of both sexes, we discovered that brain regions involved in this working memory encoding process were dissociable according to whether the to-be-remembered stimulus was painful or not, with the medial thalamus and the rostral anterior cingulate cortex encoding painful and the primary somatosensory cortex encoding nonpainful stimuli. Encoding of painful stimuli furthermore significantly enhanced functional connectivity between the thalamus and medial prefrontal cortex (mPFC). With regards to emotional aspects influencing encoding processes, we observed that more anxious participants showed significant performance advantages when encoding painful stimuli. Importantly, only during the encoding of pain, the interindividual differences in anxiety were associated with the strength of coupling between medial thalamus and mPFC, which was furthermore related to activity in the amygdala. These results indicate not only that there is a distinct signature for the encoding of a painful experience in humans, but also that this encoding process involves a strong affective component. SIGNIFICANCE STATEMENT To convert the sensation of pain into a briefly maintainable construct is essential to guide human behavior and avoid dangerous situations. Although this working memory encoding process is implicitly contained in the majority of studies, the underlying neural mechanisms remain unclear. Using fMRI in a delayed-discrimination task, we found that the encoding of pain engaged the activation of the medial thalamus and the functional connectivity between the thalamus and medial prefrontal cortex. These fMRI data were directly and indirectly related to participants' self-reported trait and state anxiety. Our findings indicate that the mechanisms responsible for the encoding of noxious stimuli differ from those for the encoding of innocuous stimuli, and that these mechanisms are shaped by an individual's anxiety levels. PMID:29097595

Determining the Neural Substrate for Encoding a Memory of Human Pain and the Influence of Anxiety.

PubMed

Tseng, Ming-Tsung; Kong, Yazhuo; Eippert, Falk; Tracey, Irene

2017-12-06

To convert a painful stimulus into a briefly maintainable construct when the painful stimulus is no longer accessible is essential to guide human behavior and avoid dangerous situations. Because of the aversive nature of pain, this encoding process might be influenced by emotional aspects and could thus vary across individuals, but we have yet to understand both the basic underlying neural mechanisms as well as potential interindividual differences. Using fMRI in combination with a delayed-discrimination task in healthy volunteers of both sexes, we discovered that brain regions involved in this working memory encoding process were dissociable according to whether the to-be-remembered stimulus was painful or not, with the medial thalamus and the rostral anterior cingulate cortex encoding painful and the primary somatosensory cortex encoding nonpainful stimuli. Encoding of painful stimuli furthermore significantly enhanced functional connectivity between the thalamus and medial prefrontal cortex (mPFC). With regards to emotional aspects influencing encoding processes, we observed that more anxious participants showed significant performance advantages when encoding painful stimuli. Importantly, only during the encoding of pain, the interindividual differences in anxiety were associated with the strength of coupling between medial thalamus and mPFC, which was furthermore related to activity in the amygdala. These results indicate not only that there is a distinct signature for the encoding of a painful experience in humans, but also that this encoding process involves a strong affective component. SIGNIFICANCE STATEMENT To convert the sensation of pain into a briefly maintainable construct is essential to guide human behavior and avoid dangerous situations. Although this working memory encoding process is implicitly contained in the majority of studies, the underlying neural mechanisms remain unclear. Using fMRI in a delayed-discrimination task, we found that the encoding of pain engaged the activation of the medial thalamus and the functional connectivity between the thalamus and medial prefrontal cortex. These fMRI data were directly and indirectly related to participants' self-reported trait and state anxiety. Our findings indicate that the mechanisms responsible for the encoding of noxious stimuli differ from those for the encoding of innocuous stimuli, and that these mechanisms are shaped by an individual's anxiety levels. Copyright © 2017 Tseng et al.

A Brain System for Auditory Working Memory.

PubMed

Kumar, Sukhbinder; Joseph, Sabine; Gander, Phillip E; Barascud, Nicolas; Halpern, Andrea R; Griffiths, Timothy D

2016-04-20

The brain basis for auditory working memory, the process of actively maintaining sounds in memory over short periods of time, is controversial. Using functional magnetic resonance imaging in human participants, we demonstrate that the maintenance of single tones in memory is associated with activation in auditory cortex. In addition, sustained activation was observed in hippocampus and inferior frontal gyrus. Multivoxel pattern analysis showed that patterns of activity in auditory cortex and left inferior frontal gyrus distinguished the tone that was maintained in memory. Functional connectivity during maintenance was demonstrated between auditory cortex and both the hippocampus and inferior frontal cortex. The data support a system for auditory working memory based on the maintenance of sound-specific representations in auditory cortex by projections from higher-order areas, including the hippocampus and frontal cortex. In this work, we demonstrate a system for maintaining sound in working memory based on activity in auditory cortex, hippocampus, and frontal cortex, and functional connectivity among them. Specifically, our work makes three advances from the previous work. First, we robustly demonstrate hippocampal involvement in all phases of auditory working memory (encoding, maintenance, and retrieval): the role of hippocampus in working memory is controversial. Second, using a pattern classification technique, we show that activity in the auditory cortex and inferior frontal gyrus is specific to the maintained tones in working memory. Third, we show long-range connectivity of auditory cortex to hippocampus and frontal cortex, which may be responsible for keeping such representations active during working memory maintenance. Copyright © 2016 Kumar et al.

Schematic knowledge changes what judgments of learning predict in a source memory task.

PubMed

Konopka, Agnieszka E; Benjamin, Aaron S

2009-01-01

Source monitoring can be influenced by information that is external to the study context, such as beliefs and general knowledge (Johnson, Hashtroudi, & Lindsay, 1993). We investigated the extent to which metamnemonic judgments predict memory for items and sources when schematic information about the sources is or is not provided at encoding. Participants made judgments of learning (JOLs) to statements presented by two speakers and were informed of the occupation of each speaker either before or after the encoding session. Replicating earlier work, prior knowledge decreased participants' tendency to erroneously attribute statements to schematically consistent but episodically incorrect speakers. The origin of this effect can be understood by examining the relationship between JOLs and performance: JOLs were equally predictive of item and source memory in the absence of prior knowledge, but were exclusively predictive of source memory when participants knew of the relationship between speakers and statements during study. Background knowledge determines the information that people solicit in service of metamnemonic judgments, suggesting that these judgments reflect control processes during encoding that reduce schematic errors.

A test of the reward-value hypothesis.

PubMed

Smith, Alexandra E; Dalecki, Stefan J; Crystal, Jonathon D

2017-03-01

Rats retain source memory (memory for the origin of information) over a retention interval of at least 1 week, whereas their spatial working memory (radial maze locations) decays within approximately 1 day. We have argued that different forgetting functions dissociate memory systems. However, the two tasks, in our previous work, used different reward values. The source memory task used multiple pellets of a preferred food flavor (chocolate), whereas the spatial working memory task provided access to a single pellet of standard chow-flavored food at each location. Thus, according to the reward-value hypothesis, enhanced performance in the source memory task stems from enhanced encoding/memory of a preferred reward. We tested the reward-value hypothesis by using a standard 8-arm radial maze task to compare spatial working memory accuracy of rats rewarded with either multiple chocolate or chow pellets at each location using a between-subjects design. The reward-value hypothesis predicts superior accuracy for high-valued rewards. We documented equivalent spatial memory accuracy for high- and low-value rewards. Importantly, a 24-h retention interval produced equivalent spatial working memory accuracy for both flavors. These data are inconsistent with the reward-value hypothesis and suggest that reward value does not explain our earlier findings that source memory survives unusually long retention intervals.

The Hippocampus Supports Encoding of Between-Domain Associations within Working Memory

ERIC Educational Resources Information Center

Piekema, Carinne; Kessel, Roy P. C.; Rijpkema, Mark; Fernandez, Guillen

2009-01-01

It has been established that the medial temporal lobe, including the hippocampus, is crucial for associative memory. The aim of the current functional magnetic resonance imaging (fMRI) study was to investigate whether the hippocampus is differentially activated for associations between items processed in the same neocortical region (within-domain)…

Visual Working Memory Cannot Trade Quantity for Quality.

PubMed

Ramaty, Ayelet; Luria, Roy

2018-01-01

Two main models have been proposed to describe how visual working memory (WM) allocates its capacity: the slot-model and the continuous resource-model. The purpose of the current study was to test a direct prediction of the resource model suggesting that WM can trade-off between the quantity and quality of the encoded information. Previous research reported equivocal results, with studies that failed to find such a trade-off and other studies that reported a trade-off. Following the design of previous studies, in Experiment 1 we replicated this trade-off, by presenting the memory array for 1200 ms. Experiment 2 failed to observe a trade-off between quantity and quality using a memory array interval of 300 ms (a standard interval for visual WM). Experiment 3 again failed to find this trade-off, when reinstating the 1200 ms memory array interval but adding an articulatory suppression manipulation. We argue that while participants can trade quantity for quality, this pattern depends on verbal encoding and transfer to long-term memory processes that were possible to perform only during the long retention interval. When these processes were eliminated, the trade-off disappeared. Thus, we didn't find any evidence that the trade-off between quantity for quality can occur within visual WM.

Object-based Encoding in Visual Working Memory: Evidence from Memory-driven Attentional Capture.

PubMed

Gao, Zaifeng; Yu, Shixian; Zhu, Chengfeng; Shui, Rende; Weng, Xuchu; Li, Peng; Shen, Mowei

2016-03-09

Visual working memory (VWM) adopts a specific manner of object-based encoding (OBE) to extract perceptual information: Whenever one feature-dimension is selected for entry into VWM, the others are also extracted. Currently most studies revealing OBE probed an 'irrelevant-change distracting effect', where changes of irrelevant-features dramatically affected the performance of the target feature. However, the existence of irrelevant-feature change may affect participants' processing manner, leading to a false-positive result. The current study conducted a strict examination of OBE in VWM, by probing whether irrelevant-features guided the deployment of attention in visual search. The participants memorized an object's colour yet ignored shape and concurrently performed a visual-search task. They searched for a target line among distractor lines, each embedded within a different object. One object in the search display could match the shape, colour, or both dimensions of the memory item, but this object never contained the target line. Relative to a neutral baseline, where there was no match between the memory and search displays, search time was significantly prolonged in all match conditions, regardless of whether the memory item was displayed for 100 or 1000 ms. These results suggest that task-irrelevant shape was extracted into VWM, supporting OBE in VWM.

Conceptualizing and Measuring Working Memory and its Relationship to Aphasia

PubMed Central

Wright, Heather Harris; Fergadiotis, Gerasimos

2011-01-01

Background General agreement exists in the literature that individuals with aphasia can exhibit a working memory deficit that contributes to their language processing impairments. Though conceptualized within different working memory frameworks, researchers have suggested that individuals with aphasia have limited working memory capacity, impaired attention-control processes as well as impaired inhibitory mechanisms. However, across studies investigating working memory ability in individuals with aphasia, different measures have been used to quantify their working memory ability and identify the relationship between working memory and language performance. Aims The primary objectives of this article are to (1) review current working memory theoretical frameworks, (2) review tasks used to measure working memory, and (3) discuss findings from studies that have investigated working memory as they relate to language processing in aphasia. Main Contribution Though findings have been consistent across studies investigating working memory ability in individuals with aphasia, discussion of how working memory is conceptualized and defined is often missing, as is discussion of results within a theoretical framework. This is critical, as working memory is conceptualized differently across the different theoretical frameworks. They differ in explaining what limits capacity and the source of individual differences as well as how information is encoded, maintained, and retrieved. When test methods are considered within a theoretical framework, specific hypotheses can be tested and stronger conclusions that are less susceptible to different interpretations can be made. Conclusions Working memory ability has been investigated in numerous studies with individuals with aphasia. To better understand the underlying cognitive constructs that contribute to the language deficits exhibited by individuals with aphasia, future investigations should operationally define the cognitive constructs of interest and discuss findings within theoretical frameworks. PMID:22639480

Memory for self-generated narration in the elderly.

PubMed

Drevenstedt, J; Bellezza, F S

1993-06-01

The story mnemonic technique, an effective encoding and retrieval strategy for young adults, was used as a procedure to study encoding and recall in elderly women. Experiment 1 (15 undergraduate and 14 elderly women) showed the technique to be reliable over 3 weeks and without practice effects in both age groups. In Experiment 2, 67 elderly women (mean age = 72 years) were found to make up 3 distinctive subgroupings in patterns of narration cohesiveness and recall accuracy, consistent with pilot data on the technique. A stepwise multiple regression equation found narration cohesiveness, an adaptation of the Daneman-Carpenter (1980) working-memory measure and vocabulary to predict word recall. Results suggested that a general memory factor differentiated the 3 elderly subgroups.

Rapid Formation and Flexible Expression of Memories of Subliminal Word Pairs

PubMed Central

Reber, Thomas P.; Henke, Katharina

2011-01-01

Our daily experiences are incidentally and rapidly encoded as episodic memories. Episodic memories consist of numerous associations (e.g., who gave what to whom where and when) that can be expressed flexibly in new situations. Key features of episodic memory are speed of encoding, its associative nature, and its representational flexibility. Another defining feature of human episodic memory has been consciousness of encoding/retrieval. Here, we show that humans can rapidly form associations between subliminal words and minutes later retrieve these associations even if retrieval words were conceptually related to, but different from encoding words. Because encoding words were presented subliminally, associative encoding, and retrieval were unconscious. Unconscious association formation and retrieval were dependent on a preceding understanding of task principles. We conclude that key computations underlying episodic memory – rapid encoding and flexible expression of associations – can operate outside consciousness. PMID:22125545

Face Encoding and Recognition in the Human Brain

NASA Astrophysics Data System (ADS)

Haxby, James V.; Ungerleider, Leslie G.; Horwitz, Barry; Maisog, Jose Ma.; Rapoport, Stanley I.; Grady, Cheryl L.

1996-01-01

A dissociation between human neural systems that participate in the encoding and later recognition of new memories for faces was demonstrated by measuring memory task-related changes in regional cerebral blood flow with positron emission tomography. There was almost no overlap between the brain structures associated with these memory functions. A region in the right hippocampus and adjacent cortex was activated during memory encoding but not during recognition. The most striking finding in neocortex was the lateralization of prefrontal participation. Encoding activated left prefrontal cortex, whereas recognition activated right prefrontal cortex. These results indicate that the hippocampus and adjacent cortex participate in memory function primarily at the time of new memory encoding. Moreover, face recognition is not mediated simply by recapitulation of operations performed at the time of encoding but, rather, involves anatomically dissociable operations.

Factors affecting reorganisation of memory encoding networks in temporal lobe epilepsy

PubMed Central

Sidhu, M.K.; Stretton, J.; Winston, G.P.; Symms, M.; Thompson, P.J.; Koepp, M.J.; Duncan, J.S.

2015-01-01

Summary Aims In temporal lobe epilepsy (TLE) due to hippocampal sclerosis reorganisation in the memory encoding network has been consistently described. Distinct areas of reorganisation have been shown to be efficient when associated with successful subsequent memory formation or inefficient when not associated with successful subsequent memory. We investigated the effect of clinical parameters that modulate memory functions: age at onset of epilepsy, epilepsy duration and seizure frequency in a large cohort of patients. Methods We studied 53 patients with unilateral TLE and hippocampal sclerosis (29 left). All participants performed a functional magnetic resonance imaging memory encoding paradigm of faces and words. A continuous regression analysis was used to investigate the effects of age at onset of epilepsy, epilepsy duration and seizure frequency on the activation patterns in the memory encoding network. Results Earlier age at onset of epilepsy was associated with left posterior hippocampus activations that were involved in successful subsequent memory formation in left hippocampal sclerosis patients. No association of age at onset of epilepsy was seen with face encoding in right hippocampal sclerosis patients. In both left hippocampal sclerosis patients during word encoding and right hippocampal sclerosis patients during face encoding, shorter duration of epilepsy and lower seizure frequency were associated with medial temporal lobe activations that were involved in successful memory formation. Longer epilepsy duration and higher seizure frequency were associated with contralateral extra-temporal activations that were not associated with successful memory formation. Conclusion Age at onset of epilepsy influenced verbal memory encoding in patients with TLE due to hippocampal sclerosis in the speech-dominant hemisphere. Shorter duration of epilepsy and lower seizure frequency were associated with less disruption of the efficient memory encoding network whilst longer duration and higher seizure frequency were associated with greater, inefficient, extra-temporal reorganisation. PMID:25616449

Dysfunction in different phases of working memory in schizophrenia: evidence from ERP recordings.

PubMed

Zhao, Yan Li; Tan, Shu Ping; Yang, Fu De; Wang, Li Li; Feng, Wen Feng; Chan, Raymond C K; Gao, Xiao; Zhou, Dong Feng; Li, Bin Bin; Song, Chong Sheng; Fan, Feng Mei; Tan, Yun Long; Zhang, Jin Guo; Wang, Yun Hui; Zou, Yi Zhuang

2011-12-01

The present study combined a time-locked paradigm and high-time-resolution event-related potential (ERP) recordings to examine different phases of working memory, including early visual processing and late memory-related processes of encoding, maintenance, and retrieval, in 67 adults with schizophrenia and 46 healthy controls. Alterations in ERP components were correlated with task performance. Patients performed significantly worse in the working memory task than healthy subjects, although all subjects' accuracy exceeded 80%. During encoding, the N1 and P2 component amplitudes were lower while the P300 amplitude was higher in schizophrenic patients compared to healthy controls. There were no differences between groups with respect to the mean amplitudes of the negative slow waves in the early stage (the first 400 ms) of the maintenance phase. However, in the next 500-ms time window, the patients exhibited a more negative deflection in the middle fronto-central region than the control group. Likewise, a similar pattern was observed in the second 500-ms period in the middle fronto-central region, although the effect was marginally significant. There were no differences between groups in the remaining 1000 ms. During retrieval, the P1, N1 and P2 amplitudes were lower while the P300 amplitude and latency were higher in schizophrenic patients. The present results indicate early visual deficits in the working memory task in adults with schizophrenia. Impairments in the maintenance phase were confined to the late rehearsal stage. The increased P300 amplitude at the fronto-central electrode sites along with the poorer behavioral performance suggests that schizophrenic patients have an inefficient working memory system. Copyright © 2011 Elsevier B.V. All rights reserved.

GABA level, gamma oscillation, and working memory performance in schizophrenia

PubMed Central

Chen, Chi-Ming A.; Stanford, Arielle D.; Mao, Xiangling; Abi-Dargham, Anissa; Shungu, Dikoma C.; Lisanby, Sarah H.; Schroeder, Charles E.; Kegeles, Lawrence S.

2014-01-01

A relationship between working memory impairment, disordered neuronal oscillations, and abnormal prefrontal GABA function has been hypothesized in schizophrenia; however, in vivo GABA measurements and gamma band neural synchrony have not yet been compared in schizophrenia. This case–control pilot study (N = 24) compared baseline and working memory task-induced neuronal oscillations acquired with high-density electroencephalograms (EEGs) to GABA levels measured in vivo with magnetic resonance spectroscopy. Working memory performance, baseline GABA level in the left dorsolateral prefrontal cortex (DLPFC), and measures of gamma oscillations from EEGs at baseline and during a working memory task were obtained. A major limitation of this study is a relatively small sample size for several analyses due to the integration of diverse methodologies and participant compliance. Working memory performance was significantly lower for patients than for controls. During the working memory task, patients (n = 7) had significantly lower amplitudes in gamma oscillations than controls (n = 9). However, both at rest and across working memory stages, there were significant correlations between gamma oscillation amplitude and left DLPFC GABA level. Peak gamma frequency during the encoding stage of the working memory task (n = 16) significantly correlated with GABA level and working memory performance. Despite gamma band amplitude deficits in patients across working memory stages, both baseline and working memory-induced gamma oscillations showed strong dependence on baseline GABA levels in patients and controls. These findings suggest a critical role for GABA function in gamma band oscillations, even under conditions of system and cognitive impairments as seen in schizophrenia. PMID:24749063

GABA level, gamma oscillation, and working memory performance in schizophrenia.

PubMed

Chen, Chi-Ming A; Stanford, Arielle D; Mao, Xiangling; Abi-Dargham, Anissa; Shungu, Dikoma C; Lisanby, Sarah H; Schroeder, Charles E; Kegeles, Lawrence S

2014-01-01

A relationship between working memory impairment, disordered neuronal oscillations, and abnormal prefrontal GABA function has been hypothesized in schizophrenia; however, in vivo GABA measurements and gamma band neural synchrony have not yet been compared in schizophrenia. This case-control pilot study (N = 24) compared baseline and working memory task-induced neuronal oscillations acquired with high-density electroencephalograms (EEGs) to GABA levels measured in vivo with magnetic resonance spectroscopy. Working memory performance, baseline GABA level in the left dorsolateral prefrontal cortex (DLPFC), and measures of gamma oscillations from EEGs at baseline and during a working memory task were obtained. A major limitation of this study is a relatively small sample size for several analyses due to the integration of diverse methodologies and participant compliance. Working memory performance was significantly lower for patients than for controls. During the working memory task, patients (n = 7) had significantly lower amplitudes in gamma oscillations than controls (n = 9). However, both at rest and across working memory stages, there were significant correlations between gamma oscillation amplitude and left DLPFC GABA level. Peak gamma frequency during the encoding stage of the working memory task (n = 16) significantly correlated with GABA level and working memory performance. Despite gamma band amplitude deficits in patients across working memory stages, both baseline and working memory-induced gamma oscillations showed strong dependence on baseline GABA levels in patients and controls. These findings suggest a critical role for GABA function in gamma band oscillations, even under conditions of system and cognitive impairments as seen in schizophrenia.

The role of rewarding and novel events in facilitating memory persistence in a separate spatial memory task.

PubMed

Salvetti, Beatrice; Morris, Richard G M; Wang, Szu-Han

2014-01-15

Many insignificant events in our daily life are forgotten quickly but can be remembered for longer when other memory-modulating events occur before or after them. This phenomenon has been investigated in animal models in a protocol in which weak memories persist longer if exploration in a novel context is introduced around the time of memory encoding. This study aims to understand whether other types of rewarding or novel tasks, such as rewarded learning in a T-maze and novel object recognition, can also be effective memory-modulating events. Rats were trained in a delayed matching-to-place task to encode and retrieve food locations in an event arena. Weak encoding with only one food pellet at the sample location induced memory encoding but forgetting over 24 h. When this same weak encoding was followed by a rewarded task in a T-maze, the memory persisted for 24 h. Moreover, the same persistence of memory over 24 h could be achieved by exploration in a novel box or by a rewarded T-maze task after a "non-rewarded" weak encoding. When the one-pellet weak encoding was followed by novel object exploration, the memory did not persist at 24 h. Together, the results confirm that place encoding is possible without explicit reward, and that rewarded learning in a separate task lacking novelty can be an effective memory-modulating event. The behavioral and neurobiological implications are discussed.

The first does the work, but the third time's the charm: the effects of massed repetition on episodic encoding of multimodal face-name associations.

PubMed

Mangels, Jennifer A; Manzi, Alberto; Summerfield, Christopher

2010-03-01

In social interactions, it is often necessary to rapidly encode the association between visually presented faces and auditorily presented names. The present study used event-related potentials to examine the neural correlates of associative encoding for multimodal face-name pairs. We assessed study-phase processes leading to high-confidence recognition of correct pairs (and consistent rejection of recombined foils) as compared to lower-confidence recognition of correct pairs (with inconsistent rejection of recombined foils) and recognition failures (misses). Both high- and low-confidence retrieval of face-name pairs were associated with study-phase activity suggestive of item-specific processing of the face (posterior inferior temporal negativity) and name (fronto-central negativity). However, only those pairs later retrieved with high confidence recruited a sustained centro-parietal positivity that an ancillary localizer task suggested may index an association-unique process. Additionally, we examined how these processes were influenced by massed repetition, a mnemonic strategy commonly employed in everyday situations to improve face-name memory. Differences in subsequent memory effects across repetitions suggested that associative encoding was strongest at the initial presentation, and thus, that the initial presentation has the greatest impact on memory formation. Yet, exploratory analyses suggested that the third presentation may have benefited later memory by providing an opportunity for extended processing of the name. Thus, although encoding of the initial presentation was critical for establishing a strong association, the extent to which processing was sustained across subsequent immediate (massed) presentations may provide additional encoding support that serves to differentiate face-name pairs from similar (recombined) pairs by providing additional encoding opportunities for the less dominant stimulus dimension (i.e., name).

Revealing past memories: proactive interference and ketamine-induced memory deficits.

PubMed

Chrobak, James J; Hinman, James R; Sabolek, Helen R

2008-04-23

Memories of events that occur often are sensitive to interference from memories of similar events. Proactive interference plays an important and often unexamined role in memory testing for spatially and temporally unique events ("episodes"). Ketamine (NMDA receptor antagonist) treatment in humans and other mammals induces a constellation of cognitive deficits, including impairments in working and episodic memory. We examined the effects of the ketamine (2.5-100 mg/kg) on the acquisition, retrieval, and retention of memory in a delayed-match-to-place radial water maze task that can be used to assess proactive interference. Ketamine (2.5-25 mg/kg, i.p.) given 20 min before the sample trial, impaired encoding. The first errors made during the test trial were predominantly to arms located spatially adjacent to the goal arm, suggesting an established albeit weakened representation. Ketamine (25-100 mg/kg) given immediately after the sample trial had no effect on retention. Ketamine given before the test trial impaired retrieval. First errors under the influence of ketamine were predominantly to the goal location of the previous session. Thus, ketamine treatment promoted proactive interference. These memory deficits were not state dependent, because ketamine treatment at both encoding and retrieval only increased the number of errors during the test session. These data demonstrate the competing influence of distinct memory representations during the performance of a memory task in the rat. Furthermore, they demonstrate the subtle disruptive effects of the NMDA antagonist ketamine on both encoding and retrieval. Specifically, ketamine treatment disrupted retrieval by promoting proactive interference from previous episodic representations.

Improving prospective memory in persons with Parkinson disease: A randomized controlled trial

PubMed Central

Foster, Erin R.; McDaniel, Mark A.; Rendell, Peter G.

2017-01-01

Background Prospective memory is essential for productive and independent living and necessary for compliance with prescribed health behaviors. Parkinson disease (PD) can cause prospective memory deficits that are associated with activity limitations and reduced quality of life. Forming implementation intentions is an encoding strategy that may improve prospective memory in this population. Objective To determine the effect of implementation intentions on prospective memory performance in PD. Methods This was a laboratory-based randomized controlled trial. Participants with mild to moderate PD without dementia (N = 62) performed a computerized prospective memory test (Virtual Week) under standard instructions. One week later they were randomly allocated to perform it again while using either implementation intentions or a rehearsal encoding strategy. Results Prospective memory performance was better with the use of both strategies relative to standard instructions. This effect was larger for tasks with event-based compared to time-based cues. In addition, implementation intentions resulted in a larger effect than rehearsal for the non-repeated tasks. Conclusions Strategies that support full encoding of prospective memory cues and actions can improve prospective memory performance among people with PD, particularly for tasks with cues that are readily available in the environment. Implementation intentions may be more effective than rehearsal for non-repeated tasks, but this finding warrants verification. Future work should address transfer of strategy use from the laboratory to everyday life. Targeted strategies to manage prospective memory impairment could improve function and quality of life and significantly impact clinical care for people with PD. (NCT01469741) PMID:28176547

Hemispheric encoding/retrieval asymmetry in episodic memory: positron emission tomography findings.

PubMed Central

Tulving, E; Kapur, S; Craik, F I; Moscovitch, M; Houle, S

1994-01-01

Data are reviewed from positron emission tomography studies of encoding and retrieval processes in episodic memory. These data suggest a hemispheric encoding/retrieval asymmetry model of prefrontal involvement in encoding and retrieval of episodic memory. According to this model, the left and right prefrontal lobes are part of an extensive neuronal network that subserves episodic remembering, but the two prefrontal hemispheres play different roles. Left prefrontal cortical regions are differentially more involved in retrieval of information from semantic memory and in simultaneously encoding novel aspects of the retrieved information into episodic memory. Right prefrontal cortical regions, on the other hand, are differentially more involved in episodic memory retrieval. PMID:8134342

Working Memory Maturation: Can We Get at the Essence of Cognitive Growth?

PubMed

Cowan, Nelson

2016-03-01

The theoretical and practical understanding of cognitive development depends on working memory, the limited information temporarily accessible for such daily activities as language processing and problem solving. In this article, I assess many possible reasons that working memory performance improves with development. A first glance at the literature leads to the weird impression that working memory capacity reaches adult levels during infancy but then regresses during childhood. In place of that unlikely explanation, I consider how infant studies may lead to overestimates of capacity if one neglects supports that the tasks provide, compared with adult-level tasks. Further development of working memory during the school years is also considered. Many investigators have come to suspect that working memory capacity may be constant after infancy because of various factors such as developmental increases in knowledge, filtering out of irrelevant distractions, encoding and rehearsal strategies, and pattern formation. With each of these factors controlled, though, working memory still improves during the school years. Suggestions are made for research to bridge the gap between infant and child developmental research, to understand the focus and control of attention in working memory and how these skills develop, and to pinpoint the nature of capacity and its development from infancy forward. © The Author(s) 2016.

Working Memory Maturation: Can We Get At the Essence of Cognitive Growth?

PubMed Central

Cowan, Nelson

2015-01-01

Our theoretical and practical understanding of cognitive development depends on working memory, the limited information temporarily accessible for such daily activities as language processing and problem-solving. Here I assess many possible reasons why working memory performance improves with development. A first glance at the literature leads to the weird impression that working memory capacity reaches adult-like levels during infancy but then regresses during childhood. In place of that unlikely surmise, I consider how infant studies may lead to overestimates of capacity if one neglects supports that the tasks provide, compared to adult-like tasks. Further development of working memory during the school years is also considered. Various confounding factors have led many investigators to suspect that working memory capacity may be constant after infancy; the factors include developmental increases in knowledge, filtering out of irrelevant distractions, encoding and rehearsal strategies, and pattern formation. With each of these factors controlled, though, working memory still improves during the school years. Suggestions are made for research to bridge the gap between infant and child developmental research, to understand the focus and control of attention in working memory and how they develop, and to pinpoint the nature of capacity and its development from infancy on. PMID:26993277

Evidence for Human Fronto-Central Gamma Activity during Long-Term Memory Encoding of Word Sequences

PubMed Central

Meeuwissen, Esther Berendina; Takashima, Atsuko; Fernández, Guillén; Jensen, Ole

2011-01-01

Although human gamma activity (30–80 Hz) associated with visual processing is often reported, it is not clear to what extend gamma activity can be reliably detected non-invasively from frontal areas during complex cognitive tasks such as long term memory (LTM) formation. We conducted a memory experiment composed of 35 blocks each having three parts: LTM encoding, working memory (WM) maintenance and LTM retrieval. In the LTM encoding and WM maintenance parts, participants had to respectively encode or maintain the order of three sequentially presented words. During LTM retrieval subjects had to reproduce these sequences. Using magnetoencephalography (MEG) we identified significant differences in the gamma and beta activity. Robust gamma activity (55–65 Hz) in left BA6 (supplementary motor area (SMA)/pre-SMA) was stronger during LTM rehearsal than during WM maintenance. The gamma activity was sustained throughout the 3.4 s rehearsal period during which a fixation cross was presented. Importantly, the difference in gamma band activity correlated with memory performance over subjects. Further we observed a weak gamma power difference in left BA6 during the first half of the LTM rehearsal interval larger for successfully than unsuccessfully reproduced word triplets. In the beta band, we found a power decrease in left anterior regions during LTM rehearsal compared to WM maintenance. Also this suppression of beta power correlated with memory performance over subjects. Our findings show that an extended network of brain areas, characterized by oscillatory activity in different frequency bands, supports the encoding of word sequences in LTM. Gamma band activity in BA6 possibly reflects memory processes associated with language and timing, and suppression of beta activity at left frontal sensors is likely to reflect the release of inhibition directly associated with the engagement of language functions. PMID:21738641

Effects of emotional content on working memory capacity.

PubMed

Garrison, Katie E; Schmeichel, Brandon J

2018-02-13

Emotional events tend to be remembered better than neutral events, but emotional states and stimuli may also interfere with cognitive processes that underlie memory performance. The current study investigated the effects of emotional content on working memory capacity (WMC), which involves both short term storage and executive attention control. We tested competing hypotheses in a preregistered experiment (N = 297). The emotional enhancement hypothesis predicts that emotional stimuli attract attention and additional processing resources relative to neutral stimuli, thereby making it easier to encode and store emotional information in WMC. The emotional impairment hypothesis, by contrast, predicts that emotional stimuli interfere with attention control and the active maintenance of information in working memory. Participants completed a common measure of WMC (the operation span task; Turner, M. L., & Engle, R. W. [1989]. Is working memory capacity task dependent? Journal of Memory and Language, 28, 127-154) that included either emotional or neutral words. Results revealed that WMC was reduced for emotional words relative to neutral words, consistent with the emotional impairment hypothesis.

Olfactory short-term memory encoding and maintenance - an event-related potential study.

PubMed

Lenk, Steffen; Bluschke, Annet; Beste, Christian; Iannilli, Emilia; Rößner, Veit; Hummel, Thomas; Bender, Stephan

2014-09-01

This study examined whether the memory encoding and short term maintenance of olfactory stimuli is associated with neurophysiological activation patterns which parallel those described for sensory modalities such as vision and auditory. We examined olfactory event-related potentials in an olfactory change detection task in twenty-four healthy adults and compared the measured activation to that found during passive olfactory stimulation. During the early olfactory post-processing phase, we found a sustained negativity over bilateral frontotemporal areas in the passive perception condition which was enhanced in the active memory task. There was no significant lateralization in either experimental condition. During the maintenance interval at the end of the delay period, we still found sustained activation over bilateral frontotemporal areas which was more negative in trials with correct - as compared to incorrect - behavioural responses. This was complemented by a general significantly stronger frontocentral activation. Summarizing, we were able to show that olfactory short term memory involves a parallel sequence of activation as found in other sensory modalities. In addition to olfactory-specific frontotemporal activations in the memory encoding phase, we found slow cortical potentials over frontocentral areas during the memory maintenance phase indicating the activation of a supramodal memory maintenance system. These findings could represent the neurophysiological underpinning of the 'olfactory flacon', the olfactory counter-part to the visual sketchpad and phonological loop embedded in Baddeley's working memory model. Copyright © 2014 Elsevier Inc. All rights reserved.

Isolating Age-Group Differences in Working Memory Load-Related Neural Activity: Assessing the Contribution of Working Memory Capacity Using a Partial-Trial fMRI Method

PubMed Central

Bennett, Ilana J.; Rivera, Hannah G.; Rypma, Bart

2013-01-01

Previous studies examining age-group differences in working memory load-related neural activity have yielded mixed results. When present, age-group differences in working memory capacity are frequently proposed to underlie these neural effects. However, direct relationships between working memory capacity and working memory load-related activity have only been observed in younger adults. These relationships remain untested in healthy aging. Therefore, the present study examined patterns of working memory load-related activity in 22 younger and 20 older adults and assessed the contribution of working memory capacity to these load-related effects. Participants performed a partial-trial delayed response item recognition task during functional magnetic resonance imaging. In this task, participants encoded either 2 or 6 letters, maintained them during a delay, and then indicated whether a probe was present in the memory set. Behavioral results revealed faster and more accurate responses to load 2 versus 6, with age-group differences in this load condition effect for the accuracy measure. Neuroimaging results revealed one region (medial superior frontal gyrus) that showed age-group differences in load-related activity during the retrieval period, with less (greater) neural activity for the low versus high load condition in younger (older) adults. Furthermore, for older adults, load-related activity did not vary as a function of working memory capacity. Thus, working memory-related activity varies with healthy aging, but these patterns are not due solely to working memory capacity. Neurocognitive aging theories that feature capacity will need to account for these results. PMID:23357076

Visual short-term memory: activity supporting encoding and maintenance in retinotopic visual cortex.

PubMed

Sneve, Markus H; Alnæs, Dag; Endestad, Tor; Greenlee, Mark W; Magnussen, Svein

2012-10-15

Recent studies have demonstrated that retinotopic cortex maintains information about visual stimuli during retention intervals. However, the process by which transient stimulus-evoked sensory responses are transformed into enduring memory representations is unknown. Here, using fMRI and short-term visual memory tasks optimized for univariate and multivariate analysis approaches, we report differential involvement of human retinotopic areas during memory encoding of the low-level visual feature orientation. All visual areas show weaker responses when memory encoding processes are interrupted, possibly due to effects in orientation-sensitive primary visual cortex (V1) propagating across extrastriate areas. Furthermore, intermediate areas in both dorsal (V3a/b) and ventral (LO1/2) streams are significantly more active during memory encoding compared with non-memory (active and passive) processing of the same stimulus material. These effects in intermediate visual cortex are also observed during memory encoding of a different stimulus feature (spatial frequency), suggesting that these areas are involved in encoding processes on a higher level of representation. Using pattern-classification techniques to probe the representational content in visual cortex during delay periods, we further demonstrate that simply initiating memory encoding is not sufficient to produce long-lasting memory traces. Rather, active maintenance appears to underlie the observed memory-specific patterns of information in retinotopic cortex. Copyright © 2012 Elsevier Inc. All rights reserved.

Knowledge Cannot Explain the Developmental Growth of Working Memory Capacity

PubMed Central

Cowan, Nelson; Ricker, Timothy J.; Clark, Katherine M.; Hinrichs, Garrett A.; Glass, Bret A.

2014-01-01

According to some views of cognitive growth, the development of working memory capacity can account for increases in the complexity of cognition. It has been difficult to ascertain, though, that there actually is developmental growth in capacity that cannot be attributed to other developing factors. Here we assess the role of item familiarity. We document developmental increases in working memory for visual arrays of English letters versus unfamiliar characters. Although letter knowledge played a special role in development between the ages of 6 to 8 years, children with adequate letter knowledge showed practically the same developmental growth in normalized functions for letters and unfamiliar characters. The results contribute to a growing body of evidence that the developmental improvement in working memory does not wholly stem from supporting processes such as encoding, mnemonic strategies, and knowledge. PMID:24942111

Learning and memory performance in breast cancer survivors 2 to 6 years post-treatment: the role of encoding versus forgetting.

PubMed

Root, James C; Andreotti, Charissa; Tsu, Loretta; Ellmore, Timothy M; Ahles, Tim A

2016-06-01

Our previous retrospective analysis of clinically referred breast cancer survivors' performance on learning and memory measures found a primary weakness in initial encoding of information into working memory with intact retention and recall of this same information at a delay. This suggests that survivors may misinterpret cognitive lapses as being due to forgetting when, in actuality, they were not able to properly encode this information at the time of initial exposure. Our objective in this study was to replicate and extend this pattern of performance to a research sample to increase the generalizability of this finding in a sample in which subjects were not clinically referred for cognitive issues. We contrasted learning and memory performance between breast cancer survivors on endocrine therapy 2 to 6 years post-treatment with age- and education-matched healthy controls. We then stratified lower- and higher-performing breast cancer survivors to examine specific patterns of learning and memory performance. Contrasts were generated for four aggregate visual and verbal memory variables from the California Verbal Learning Test-2 (CVLT-2) and the Brown Location Test (BLT): Single-trial Learning: Trial 1 performance, Multiple-trial Learning: Trial 5 performance, Delayed Recall: Long-delay Recall performance, and Memory Errors: False-positive errors. As predicted, breast cancer survivors' performance as a whole was significantly lower on Single-trial Learning than the healthy control group but exhibited no significant difference in Delayed Recall. In the secondary analysis contrasting lower- and higher-performing survivors on cognitive measures, the same pattern of lower Single-trial Learning performance was exhibited in both groups, with the additional finding of significantly weaker Multiple-trial Learning performance in the lower-performing breast cancer group and intact Delayed Recall performance in both groups. As with our earlier finding of weaker initial encoding with intact recall in a cohort of clinically referred breast cancer survivors, our results indicate this same profile in a research sample of breast cancer survivors. Further, when the breast cancer group was stratified by lower and higher performance, both groups exhibited significantly lower performance on initial encoding, with more pronounced encoding weakness in the lower-performing group. As in our previous research, survivors did not lose successfully encoded information over longer delays, either in the lower- or higher-performing group, again arguing against memory decay in survivors. The finding of weaker initial encoding of information together with intact delayed recall in survivors points to specific treatment interventions in rehabilitation of cognitive dysfunction. The finding of weaker initial encoding of information together with intact delayed recall in survivors points to specific treatment interventions in rehabilitation of cognitive dysfunction and is discussed.

Working memory, long-term memory, and medial temporal lobe function

PubMed Central

Jeneson, Annette; Squire, Larry R.

2012-01-01

Early studies of memory-impaired patients with medial temporal lobe (MTL) damage led to the view that the hippocampus and related MTL structures are involved in the formation of long-term memory and that immediate memory and working memory are independent of these structures. This traditional idea has recently been revisited. Impaired performance in patients with MTL lesions on tasks with short retention intervals, or no retention interval, and neuroimaging findings with similar tasks have been interpreted to mean that the MTL is sometimes needed for working memory and possibly even for visual perception itself. We present a reappraisal of this interpretation. Our main conclusion is that, if the material to be learned exceeds working memory capacity, if the material is difficult to rehearse, or if attention is diverted, performance depends on long-term memory even when the retention interval is brief. This fundamental notion is better captured by the terms subspan memory and supraspan memory than by the terms short-term memory and long-term memory. We propose methods for determining when performance on short-delay tasks must depend on long-term (supraspan) memory and suggest that MTL lesions impair performance only when immediate memory and working memory are insufficient to support performance. In neuroimaging studies, MTL activity during encoding is influenced by the memory load and correlates positively with long-term retention of the material that was presented. The most parsimonious and consistent interpretation of all the data is that subspan memoranda are supported by immediate memory and working memory and are independent of the MTL. PMID:22180053

The costs of changing an intended action: movement planning, but not execution, interferes with verbal working memory.

PubMed

Spiegel, M A; Koester, D; Weigelt, M; Schack, T

2012-02-16

How much cognitive effort does it take to change a movement plan? In previous studies, it has been shown that humans plan and represent actions in advance, but it remains unclear whether or not action planning and verbal working memory share cognitive resources. Using a novel experimental paradigm, we combined in two experiments a grasp-to-place task with a verbal working memory task. Participants planned a placing movement toward one of two target positions and subsequently encoded and maintained visually presented letters. Both experiments revealed that re-planning the intended action reduced letter recall performance; execution time, however, was not influenced by action modifications. The results of Experiment 2 suggest that the action's interference with verbal working memory arose during the planning rather than the execution phase of the movement. Together, our results strongly suggest that movement planning and verbal working memory share common cognitive resources. Copyright © 2011 Elsevier Ireland Ltd. All rights reserved.

Central Executive Dysfunction and Deferred Prefrontal Processing in Veterans with Gulf War Illness.

PubMed

Hubbard, Nicholas A; Hutchison, Joanna L; Motes, Michael A; Shokri-Kojori, Ehsan; Bennett, Ilana J; Brigante, Ryan M; Haley, Robert W; Rypma, Bart

2014-05-01

Gulf War Illness is associated with toxic exposure to cholinergic disruptive chemicals. The cholinergic system has been shown to mediate the central executive of working memory (WM). The current work proposes that impairment of the cholinergic system in Gulf War Illness patients (GWIPs) leads to behavioral and neural deficits of the central executive of WM. A large sample of GWIPs and matched controls (MCs) underwent functional magnetic resonance imaging during a varied-load working memory task. Compared to MCs, GWIPs showed a greater decline in performance as WM-demand increased. Functional imaging suggested that GWIPs evinced separate processing strategies, deferring prefrontal cortex activity from encoding to retrieval for high demand conditions. Greater activity during high-demand encoding predicted greater WM performance. Behavioral data suggest that WM executive strategies are impaired in GWIPs. Functional data further support this hypothesis and suggest that GWIPs utilize less effective strategies during high-demand WM.

Central Executive Dysfunction and Deferred Prefrontal Processing in Veterans with Gulf War Illness

PubMed Central

Hubbard, Nicholas A.; Hutchison, Joanna L.; Motes, Michael A.; Shokri-Kojori, Ehsan; Bennett, Ilana J.; Brigante, Ryan M.; Haley, Robert W.; Rypma, Bart

2015-01-01

Gulf War Illness is associated with toxic exposure to cholinergic disruptive chemicals. The cholinergic system has been shown to mediate the central executive of working memory (WM). The current work proposes that impairment of the cholinergic system in Gulf War Illness patients (GWIPs) leads to behavioral and neural deficits of the central executive of WM. A large sample of GWIPs and matched controls (MCs) underwent functional magnetic resonance imaging during a varied-load working memory task. Compared to MCs, GWIPs showed a greater decline in performance as WM-demand increased. Functional imaging suggested that GWIPs evinced separate processing strategies, deferring prefrontal cortex activity from encoding to retrieval for high demand conditions. Greater activity during high-demand encoding predicted greater WM performance. Behavioral data suggest that WM executive strategies are impaired in GWIPs. Functional data further support this hypothesis and suggest that GWIPs utilize less effective strategies during high-demand WM. PMID:25767746

The Effects of a Distracting N-Back Task on Recognition Memory Are Reduced by Negative Emotional Intensity

PubMed Central

Buratto, Luciano G.; Pottage, Claire L.; Brown, Charity; Morrison, Catriona M.; Schaefer, Alexandre

2014-01-01

Memory performance is usually impaired when participants have to encode information while performing a concurrent task. Recent studies using recall tasks have found that emotional items are more resistant to such cognitive depletion effects than non-emotional items. However, when recognition tasks are used, the same effect is more elusive as recent recognition studies have obtained contradictory results. In two experiments, we provide evidence that negative emotional content can reliably reduce the effects of cognitive depletion on recognition memory only if stimuli with high levels of emotional intensity are used. In particular, we found that recognition performance for realistic pictures was impaired by a secondary 3-back working memory task during encoding if stimuli were emotionally neutral or had moderate levels of negative emotionality. In contrast, when negative pictures with high levels of emotional intensity were used, the detrimental effects of the secondary task were significantly attenuated. PMID:25330251

The effects of a distracting N-back task on recognition memory are reduced by negative emotional intensity.

PubMed

Buratto, Luciano G; Pottage, Claire L; Brown, Charity; Morrison, Catriona M; Schaefer, Alexandre

2014-01-01

Memory performance is usually impaired when participants have to encode information while performing a concurrent task. Recent studies using recall tasks have found that emotional items are more resistant to such cognitive depletion effects than non-emotional items. However, when recognition tasks are used, the same effect is more elusive as recent recognition studies have obtained contradictory results. In two experiments, we provide evidence that negative emotional content can reliably reduce the effects of cognitive depletion on recognition memory only if stimuli with high levels of emotional intensity are used. In particular, we found that recognition performance for realistic pictures was impaired by a secondary 3-back working memory task during encoding if stimuli were emotionally neutral or had moderate levels of negative emotionality. In contrast, when negative pictures with high levels of emotional intensity were used, the detrimental effects of the secondary task were significantly attenuated.

Only "efficient" emotional stimuli affect the content of working memory during free-recollection from natural scenes.

PubMed

Buttafuoco, Arianna; Pedale, Tiziana; Buchanan, Tony W; Santangelo, Valerio

2018-02-01

Emotional events are thought to have privileged access to attention and memory, consuming resources needed to encode competing emotionally neutral stimuli. However, it is not clear whether this detrimental effect is automatic or depends on the successful maintenance of the specific emotional object within working memory. Here, participants viewed everyday scenes including an emotional object among other neutral objects followed by a free-recollection task. Results showed that emotional objects-irrespective of their perceptual saliency-were recollected more often than neutral objects. The probability of being recollected increased as a function of the arousal of the emotional objects, specifically for negative objects. Successful recollection of emotional objects (positive or negative) from a scene reduced the overall number of recollected neutral objects from the same scene. This indicates that only emotional stimuli that are efficient in grabbing (and then consuming) available attentional resources play a crucial role during the encoding of competing information, with a subsequent bias in the recollection of neutral representations.

Early top-down control of visual processing predicts working memory performance

PubMed Central

Rutman, Aaron M.; Clapp, Wesley C.; Chadick, James Z.; Gazzaley, Adam

2009-01-01

Selective attention confers a behavioral benefit for both perceptual and working memory (WM) performance, often attributed to top-down modulation of sensory neural processing. However, the direct relationship between early activity modulation in sensory cortices during selective encoding and subsequent WM performance has not been established. To explore the influence of selective attention on WM recognition, we used electroencephalography (EEG) to study the temporal dynamics of top-down modulation in a selective, delayed-recognition paradigm. Participants were presented with overlapped, “double-exposed” images of faces and natural scenes, and were instructed to either remember the face or the scene while simultaneously ignoring the other stimulus. Here, we present evidence that the degree to which participants modulate the early P100 (97–129 ms) event-related potential (ERP) during selective stimulus encoding significantly correlates with their subsequent WM recognition. These results contribute to our evolving understanding of the mechanistic overlap between attention and memory. PMID:19413473

Dissociating effects of stimulus identity and load on working memory attentional guidance: lengthening encoding time eliminates the effect of load but not identity.

PubMed

Tsvetanov, Kamen A; Arvanitis, Theodoros N; Humphreys, Glyn W

2012-01-01

Effects of the identity and load of items in working memory (WM) on visual attention were examined. With a short interval between the WM item and a subsequent search task, there were effects of both load (slowed overall reaction times, RTs, in a WM condition relative to a mere repetition baseline) and identity (search RTs were affected by re-presentation of the item in WM in the search display). As the time to encode the initial display increased, the effects of load decreased while the effect of identity remained. The data indicate that the identity of stimuli in WM can affect the subsequent deployment of attention even when time is allowed for consolidation of the stimuli in WM, and that the WM effects are not causally related to the presence of cognitive load. The results are consistent with the identity of stimuli in WM modulating attention post the memory consolidation stage.

The cost of misremembering: Inferring the loss function in visual working memory.

PubMed

Sims, Chris R

2015-03-04

Visual working memory (VWM) is a highly limited storage system. A basic consequence of this fact is that visual memories cannot perfectly encode or represent the veridical structure of the world. However, in natural tasks, some memory errors might be more costly than others. This raises the intriguing possibility that the nature of memory error reflects the costs of committing different kinds of errors. Many existing theories assume that visual memories are noise-corrupted versions of afferent perceptual signals. However, this additive noise assumption oversimplifies the problem. Implicit in the behavioral phenomena of visual working memory is the concept of a loss function: a mathematical entity that describes the relative cost to the organism of making different types of memory errors. An optimally efficient memory system is one that minimizes the expected loss according to a particular loss function, while subject to a constraint on memory capacity. This paper describes a novel theoretical framework for characterizing visual working memory in terms of its implicit loss function. Using inverse decision theory, the empirical loss function is estimated from the results of a standard delayed recall visual memory experiment. These results are compared to the predicted behavior of a visual working memory system that is optimally efficient for a previously identified natural task, gaze correction following saccadic error. Finally, the approach is compared to alternative models of visual working memory, and shown to offer a superior account of the empirical data across a range of experimental datasets. © 2015 ARVO.

Neural Repetition Effects in the Medial Temporal Lobe Complex are Modulated by Previous Encoding Experience

PubMed Central

Greene, Ciara M.; Soto, David

2012-01-01

It remains an intriguing question why the medial temporal lobe (MTL) can display either attenuation or enhancement of neural activity following repetition of previously studied items. To isolate the role of encoding experience itself, we assessed neural repetition effects in the absence of any ongoing task demand or intentional orientation to retrieve. Experiment 1 showed that the hippocampus and surrounding MTL regions displayed neural repetition suppression (RS) upon repetition of past items that were merely attended during an earlier study phase but this was not the case following re-occurrence of items that had been encoded into working memory (WM). In this latter case a trend toward neural repetition enhancement (RE) was observed, though this was highly variable across individuals. Interestingly, participants with a higher degree of neural RE in the MTL complex displayed higher memory sensitivity in a later, surprise recognition test. Experiment 2 showed that massive exposure at encoding effected a change in the neural architecture supporting incidental repetition effects, with regions of the posterior parietal and ventral-frontal cortex in addition to the hippocampus displaying neural RE, while no neural RS was observed. The nature of encoding experience therefore modulates the expression of neural repetition effects in the MTL and the neocortex in the absence of memory goals. PMID:22829892

Modality dependence and intermodal transfer in the Corsi Spatial Sequence Task: Screen vs. Floor.

PubMed

Röser, Andrea; Hardiess, Gregor; Mallot, Hanspeter A

2016-07-01

Four versions of the Corsi Spatial Sequence Task (CSST) were tested in a complete within-subject design, investigating whether participants' performance depends on the modality of task presentation and reproduction that put different demands on spatial processing. Presentation of the sequence (encoding phase) and the reproduction (recall phase) were each carried out either on a computer screen or on the floor of a room, involving actual walking in the recall phase. Combinations of the two different encoding and recall procedures result in the modality conditions Screen-Screen, Screen-Floor, Floor-Screen, and Floor-Floor. Results show the expected decrease in performance with increasing sequence length, which is likely due to processing limitations of working memory. We also found differences in performance between the modality conditions indicating different involvements of spatial working memory processes. Participants performed best in the Screen-Screen modality condition. Floor-Screen and Floor-Floor modality conditions require additional working memory resources for reference frame transformation and spatial updating, respectively; the resulting impairment of the performance was about the same in these two conditions. Finally, the Screen-Floor modality condition requires both types of additional spatial demands and led to the poorest performance. Therefore, we suggest that besides the well-known spatial requirements of CSST, additional working memory resources are demanded in walking CSST supporting processes such as spatial updating, mental rotation, reference frame transformation, and the control of walking itself.

Semantic Congruence Accelerates the Onset of the Neural Signals of Successful Memory Encoding.

PubMed

Packard, Pau A; Rodríguez-Fornells, Antoni; Bunzeck, Nico; Nicolás, Berta; de Diego-Balaguer, Ruth; Fuentemilla, Lluís

2017-01-11

As the stream of experience unfolds, our memory system rapidly transforms current inputs into long-lasting meaningful memories. A putative neural mechanism that strongly influences how input elements are transformed into meaningful memory codes relies on the ability to integrate them with existing structures of knowledge or schemas. However, it is not yet clear whether schema-related integration neural mechanisms occur during online encoding. In the current investigation, we examined the encoding-dependent nature of this phenomenon in humans. We showed that actively integrating words with congruent semantic information provided by a category cue enhances memory for words and increases false recall. The memory effect of such active integration with congruent information was robust, even with an interference task occurring right after each encoding word list. In addition, via electroencephalography, we show in 2 separate studies that the onset of the neural signals of successful encoding appeared early (∼400 ms) during the encoding of congruent words. That the neural signals of successful encoding of congruent and incongruent information followed similarly ∼200 ms later suggests that this earlier neural response contributed to memory formation. We propose that the encoding of events that are congruent with readily available contextual semantics can trigger an accelerated onset of the neural mechanisms, supporting the integration of semantic information with the event input. This faster onset would result in a long-lasting and meaningful memory trace for the event but, at the same time, make it difficult to distinguish it from plausible but never encoded events (i.e., related false memories). Conceptual or schema congruence has a strong influence on long-term memory. However, the question of whether schema-related integration neural mechanisms occur during online encoding has yet to be clarified. We investigated the neural mechanisms reflecting how the active integration of words with congruent semantic categories enhances memory for words and increases false recall of semantically related words. We analyzed event-related potentials during encoding and showed that the onset of the neural signals of successful encoding appeared early (∼400 ms) during the encoding of congruent words. Our findings indicate that congruent events can trigger an accelerated onset of neural encoding mechanisms supporting the integration of semantic information with the event input. Copyright © 2017 the authors 0270-6474/17/370291-11$15.00/0.

Top-down modulation: Bridging selective attention and working memory

PubMed Central

Gazzaley, Adam; Nobre, Anna C.

2012-01-01

Selective attention, the ability to focus our cognitive resources on information relevant to our goals, influences working memory (WM) performance. Indeed, attention and working memory are increasingly viewed as overlapping constructs. Here, we review recent evidence from human neurophysiological studies demonstrating that top-down modulation serves as a common neural mechanism underlying these two cognitive operations. The core features include activity modulation in stimulus-selective sensory cortices with concurrent engagement of prefrontal and parietal control regions that function as sources of top-down signals. Notably, top-down modulation is engaged during both stimulus-present and stimulus-absent stages of WM tasks, i.e., expectation of an ensuing stimulus to be remembered, selection and encoding of stimuli, maintenance of relevant information in mind and memory retrieval. PMID:22209601

Accessibility limits recall from visual working memory.

PubMed

Rajsic, Jason; Swan, Garrett; Wilson, Daryl E; Pratt, Jay

2017-09-01

In this article, we demonstrate limitations of accessibility of information in visual working memory (VWM). Recently, cued-recall has been used to estimate the fidelity of information in VWM, where the feature of a cued object is reproduced from memory (Bays, Catalao, & Husain, 2009; Wilken & Ma, 2004; Zhang & Luck, 2008). Response error in these tasks has been largely studied with respect to failures of encoding and maintenance; however, the retrieval operations used in these tasks remain poorly understood. By varying the number and type of object features provided as a cue in a visual delayed-estimation paradigm, we directly assess the nature of retrieval errors in delayed estimation from VWM. Our results demonstrate that providing additional object features in a single cue reliably improves recall, largely by reducing swap, or misbinding, responses. In addition, performance simulations using the binding pool model (Swan & Wyble, 2014) were able to mimic this pattern of performance across a large span of parameter combinations, demonstrating that the binding pool provides a possible mechanism underlying this pattern of results that is not merely a symptom of one particular parametrization. We conclude that accessing visual working memory is a noisy process, and can lead to errors over and above those of encoding and maintenance limitations. (PsycINFO Database Record (c) 2017 APA, all rights reserved).

Memory retrieval of smoking-related images induce greater insula activation as revealed by an fMRI based delayed matching to sample task

PubMed Central

Janes, AC; Ross, RS; Farmer, S; Frederick, BB; Nickerson, L; Lukas, SE; Stern, CE

2013-01-01

Nicotine dependence is a chronic and difficult to treat disorder. While environmental stimuli associated with smoking precipitate craving and relapse, it is unknown whether smoking cues are cognitively processed differently than neutral stimuli. To evaluate working memory differences between smoking-related and neutral stimuli, we conducted a delay-match-to-sample (DMS) task concurrently with functional magnetic resonance imaging (fMRI) in nicotine dependent participants. The DMS task evaluates brain activation during the encoding, maintenance, and retrieval phases of working memory. Smoking images induced significantly more subjective craving, and greater midline cortical activation during encoding in comparison to neutral stimuli that were similar in content yet lacked a smoking component. The insula, which is involved in maintaining nicotine dependence, was active during the successful retrieval of previously viewed smoking vs. neutral images. In contrast, neutral images required more prefrontal cortex-mediated active maintenance during the maintenance period. These findings indicate that distinct brain regions are involved in the different phases of working memory for smoking-related vs. neutral images. Importantly the results implicate the insula in the retrieval of smoking-related stimuli, which is relevant given the insula’s emerging role in addiction. PMID:24261848

Visual perception as retrospective Bayesian decoding from high- to low-level features

PubMed Central

Ding, Stephanie; Cueva, Christopher J.; Tsodyks, Misha; Qian, Ning

2017-01-01

When a stimulus is presented, its encoding is known to progress from low- to high-level features. How these features are decoded to produce perception is less clear, and most models assume that decoding follows the same low- to high-level hierarchy of encoding. There are also theories arguing for global precedence, reversed hierarchy, or bidirectional processing, but they are descriptive without quantitative comparison with human perception. Moreover, observers often inspect different parts of a scene sequentially to form overall perception, suggesting that perceptual decoding requires working memory, yet few models consider how working-memory properties may affect decoding hierarchy. We probed decoding hierarchy by comparing absolute judgments of single orientations and relative/ordinal judgments between two sequentially presented orientations. We found that lower-level, absolute judgments failed to account for higher-level, relative/ordinal judgments. However, when ordinal judgment was used to retrospectively decode memory representations of absolute orientations, striking aspects of absolute judgments, including the correlation and forward/backward aftereffects between two reported orientations in a trial, were explained. We propose that the brain prioritizes decoding of higher-level features because they are more behaviorally relevant, and more invariant and categorical, and thus easier to specify and maintain in noisy working memory, and that more reliable higher-level decoding constrains less reliable lower-level decoding. PMID:29073108

Memory retrieval of smoking-related images induce greater insula activation as revealed by an fMRI-based delayed matching to sample task.

PubMed

Janes, Amy C; Ross, Robert S; Farmer, Stacey; Frederick, Blaise B; Nickerson, Lisa D; Lukas, Scott E; Stern, Chantal E

2015-03-01

Nicotine dependence is a chronic and difficult to treat disorder. While environmental stimuli associated with smoking precipitate craving and relapse, it is unknown whether smoking cues are cognitively processed differently than neutral stimuli. To evaluate working memory differences between smoking-related and neutral stimuli, we conducted a delay-match-to-sample (DMS) task concurrently with functional magnetic resonance imaging (fMRI) in nicotine-dependent participants. The DMS task evaluates brain activation during the encoding, maintenance and retrieval phases of working memory. Smoking images induced significantly more subjective craving, and greater midline cortical activation during encoding in comparison to neutral stimuli that were similar in content yet lacked a smoking component. The insula, which is involved in maintaining nicotine dependence, was active during the successful retrieval of previously viewed smoking versus neutral images. In contrast, neutral images required more prefrontal cortex-mediated active maintenance during the maintenance period. These findings indicate that distinct brain regions are involved in the different phases of working memory for smoking-related versus neutral images. Importantly, the results implicate the insula in the retrieval of smoking-related stimuli, which is relevant given the insula's emerging role in addiction. © 2013 Society for the Study of Addiction.

Cognitive Predictors of Verbal Memory in a Mixed Clinical Pediatric Sample

PubMed Central

Jordan, Lizabeth L.; Tyner, Callie E.; Heaton, Shelley C.

2013-01-01

Verbal memory problems, along with other cognitive difficulties, are common in children diagnosed with neurological and/or psychological disorders. Historically, these “memory problems” have been poorly characterized and often present with a heterogeneous pattern of performance across memory processes, even within a specific diagnostic group. The current study examined archival neuropsychological data from a large mixed clinical pediatric sample in order to understand whether functioning in other cognitive areas (i.e., verbal knowledge, attention, working memory, executive functioning) may explain some of the performance variability seen across verbal memory tasks of the Children’s Memory Scale (CMS). Multivariate analyses revealed that among the cognitive functions examined, only verbal knowledge explained a significant amount of variance in overall verbal memory performance. Further univariate analyses examining the component processes of verbal memory indicated that verbal knowledge is specifically related to encoding, but not the retention or retrieval stages. Future research is needed to replicate these findings in other clinical samples, to examine whether verbal knowledge predicts performance on other verbal memory tasks and to explore whether these findings also hold true for visual memory tasks. Successful replication of the current study findings would indicate that interventions targeting verbal encoding deficits should include efforts to improve verbal knowledge. PMID:25379253

Individual differences in working memory, secondary memory, and fluid intelligence: evidence from the levels-of-processing span task.

PubMed

Rose, Nathan S

2013-12-01

Individual differences in working memory (WM) are related to performance on secondary memory (SM), and fluid intelligence (gF) tests. However, the source of the relation remains unclear, in part because few studies have controlled for the nature of encoding; therefore, it is unclear whether individual variation is due to encoding, maintenance, or retrieval processes. In the current study, participants performed a WM task (the levels-of-processing span task; Rose, Myerson, Roediger III, & Hale, 2010) and a SM test that tested for both targets and the distracting processing words from the initial WM task. Deeper levels of processing at encoding did not benefit WM, but did benefit subsequent SM, although the amount of benefit was smaller for those with lower WM spans. This result suggests that, despite encoding cues that facilitate retrieval from SM, low spans may have engaged in shallower, maintenance-focused processing to maintain the words in WM. Low spans also recalled fewer targets, more distractors, and more extralist intrusions than high spans, although this was partially due to low spans' poorer recall of targets, which resulted in a greater number of opportunities to commit recall errors. Delayed recall of intrusions and commission of source errors (labeling targets as processing words and vice versa) were significant negative predictors of gF. These results suggest that the ability to use source information to recall relevant information and withhold recall of irrelevant information is a critical source of both individual variation in WM and the relation between WM, SM, and gF. (PsycINFO Database Record (c) 2013 APA, all rights reserved).

Insensitivity of visual short-term memory to irrelevant visual information.

PubMed

Andrade, Jackie; Kemps, Eva; Werniers, Yves; May, Jon; Szmalec, Arnaud

2002-07-01

Several authors have hypothesized that visuo-spatial working memory is functionally analogous to verbal working memory. Irrelevant background speech impairs verbal short-term memory. We investigated whether irrelevant visual information has an analogous effect on visual short-term memory, using a dynamic visual noise (DVN) technique known to disrupt visual imagery (Quinn & McConnell, 1996b). Experiment I replicated the effect of DVN on pegword imagery. Experiments 2 and 3 showed no effect of DVN on recall of static matrix patterns, despite a significant effect of a concurrent spatial tapping task. Experiment 4 showed no effect of DVN on encoding or maintenance of arrays of matrix patterns, despite testing memory by a recognition procedure to encourage visual rather than spatial processing. Serial position curves showed a one-item recency effect typical of visual short-term memory. Experiment 5 showed no effect of DVN on short-term recognition of Chinese characters, despite effects of visual similarity and a concurrent colour memory task that confirmed visual processing of the characters. We conclude that irrelevant visual noise does not impair visual short-term memory. Visual working memory may not be functionally analogous to verbal working memory, and different cognitive processes may underlie visual short-term memory and visual imagery.

Human Genomic Signatures of Brain Oscillations During Memory Encoding.

PubMed

Berto, Stefano; Wang, Guang-Zhong; Germi, James; Lega, Bradley C; Konopka, Genevieve

2018-05-01

Memory encoding is an essential step for all learning. However, the genetic and molecular mechanisms underlying human memory encoding remain poorly understood, and how this molecular framework permits the emergence of specific patterns of brain oscillations observed during mnemonic processing is unknown. Here, we directly compare intracranial electroencephalography recordings from the neocortex in individuals performing an episodic memory task with human gene expression from the same areas. We identify genes correlated with oscillatory memory effects across 6 frequency bands. These genes are enriched for autism-related genes and have preferential expression in neurons, in particular genes encoding synaptic proteins and ion channels, supporting the idea that the genes regulating voltage gradients are involved in the modulation of oscillatory patterns during successful memory encoding across brain areas. Memory-related genes are distinct from those correlated with other forms of cognitive processing and resting state fMRI. These data are the first to identify correlations between gene expression and active human brain states as well as provide a molecular window into memory encoding oscillations in the human brain.

Creating a recollection-based memory through drawing.

PubMed

Wammes, Jeffrey D; Meade, Melissa E; Fernandes, Myra A

2018-05-01

Drawing a picture of to-be-remembered information substantially boosts memory performance in free-recall tasks. In the current work, we sought to test the notion that drawing confers its benefit to memory performance by creating a detailed recollection of the encoding context. In Experiments 1 and 2, we demonstrated that for both pictures and words, items that were drawn by the participant at encoding were better recognized in a later test than were words that were written out. Moreover, participants' source memory (in this experiment, correct identification of whether the word was drawn or written) was superior for items drawn relative to written at encoding. In Experiments 3A and 3B, we used a remember-know paradigm to demonstrate again that drawn words were better recognized than written words, and further showed that this effect was driven by a greater proportion of recollection-, rather than familiarity-based responses. Lastly, in Experiment 4 we implemented a response deadline procedure, and showed that when recognition responses were speeded, thereby reducing participants' capacity for recollection, the benefit of drawing was substantially smaller. Taken together, our findings converge on the idea that drawing improves memory as a result of providing vivid contextual information which can be later called upon to aid retrieval. (PsycINFO Database Record (c) 2018 APA, all rights reserved).

The associative memory deficit in aging is related to reduced selectivity of brain activity during encoding

PubMed Central

Saverino, Cristina; Fatima, Zainab; Sarraf, Saman; Oder, Anita; Strother, Stephen C.; Grady, Cheryl L.

2016-01-01

Human aging is characterized by reductions in the ability to remember associations between items, despite intact memory for single items. Older adults also show less selectivity in task-related brain activity, such that patterns of activation become less distinct across multiple experimental tasks. This reduced selectivity, or dedifferentiation, has been found for episodic memory, which is often reduced in older adults, but not for semantic memory, which is maintained with age. We used functional magnetic resonance imaging (fMRI) to investigate whether there is a specific reduction in selectivity of brain activity during associative encoding in older adults, but not during item encoding, and whether this reduction predicts associative memory performance. Healthy young and older adults were scanned while performing an incidental-encoding task for pictures of objects and houses under item or associative instructions. An old/new recognition test was administered outside the scanner. We used agnostic canonical variates analysis and split-half resampling to detect whole brain patterns of activation that predicted item vs. associative encoding for stimuli that were later correctly recognized. Older adults had poorer memory for associations than did younger adults, whereas item memory was comparable across groups. Associative encoding trials, but not item encoding trials, were predicted less successfully in older compared to young adults, indicating less distinct patterns of associative-related activity in the older group. Importantly, higher probability of predicting associative encoding trials was related to better associative memory after accounting for age and performance on a battery of neuropsychological tests. These results provide evidence that neural distinctiveness at encoding supports associative memory and that a specific reduction of selectivity in neural recruitment underlies age differences in associative memory. PMID:27082043

Huffman coding in advanced audio coding standard

NASA Astrophysics Data System (ADS)

Brzuchalski, Grzegorz

2012-05-01

This article presents several hardware architectures of Advanced Audio Coding (AAC) Huffman noiseless encoder, its optimisations and working implementation. Much attention has been paid to optimise the demand of hardware resources especially memory size. The aim of design was to get as short binary stream as possible in this standard. The Huffman encoder with whole audio-video system has been implemented in FPGA devices.

Aerobic Exercise During Encoding Impairs Hippocampus-Dependent Memory.

PubMed

Soga, Keishi; Kamijo, Keita; Masaki, Hiroaki

2017-08-01

We investigated how aerobic exercise during encoding affects hippocampus-dependent memory through a source memory task that assessed hippocampus-independent familiarity and hippocampus-dependent recollection processes. Using a within-participants design, young adult participants performed a memory-encoding task while performing a cycling exercise or being seated. The subsequent retrieval phase was conducted while sitting on a chair. We assessed behavioral and event-related brain potential measures of familiarity and recollection processes during the retrieval phase. Results indicated that source accuracy was lower for encoding with exercise than for encoding in the resting condition. Event-related brain potential measures indicated that the parietal old/new effect, which has been linked to recollection processing, was observed in the exercise condition, whereas it was absent in the rest condition, which is indicative of exercise-induced hippocampal activation. These findings suggest that aerobic exercise during encoding impairs hippocampus-dependent memory, which may be attributed to inefficient source encoding during aerobic exercise.

Effects of Acute Methamphetamine on Emotional Memory Formation in Humans: Encoding vs Consolidation

PubMed Central

Ballard, Michael E.; Weafer, Jessica; Gallo, David A.; de Wit, Harriet

2015-01-01

Understanding how stimulant drugs affect memory is important for understanding their addictive potential. Here we examined the effects of acute d-methamphetamine (METH), administered either before (encoding phase) or immediately after (consolidation phase) study on memory for emotional and neutral images in healthy humans. Young adult volunteers (N = 60) were randomly assigned to either an encoding group (N = 29) or a consolidation group (N = 31). Across three experimental sessions, they received placebo and two doses of METH (10, 20 mg) either 45 min before (encoding) or immediately after (consolidation) viewing pictures of emotionally positive, neutral, and negative scenes. Memory for the pictures was tested two days later, under drug-free conditions. Half of the sample reported sleep disturbances following the high dose of METH, which affected their memory performance. Therefore, participants were classified as poor sleepers (less than 6 hours; n = 29) or adequate sleepers (6 or more hours; n = 31) prior to analyses. For adequate sleepers, METH (20 mg) administered before encoding significantly improved memory accuracy relative to placebo, especially for emotional (positive and negative), compared to neutral, stimuli. For poor sleepers in the encoding group, METH impaired memory. METH did not affect memory in the consolidation group regardless of sleep quality. These results extend previous findings showing that METH can enhance memory for salient emotional stimuli but only if it is present at the time of study, where it can affect both encoding and consolidation. METH does not appear to facilitate consolidation if administered after encoding. The study also demonstrates the important role of sleep in memory studies. PMID:25679982

Not all order memory is equal: Test demands reveal dissociations in memory for sequence information.

PubMed

Jonker, Tanya R; MacLeod, Colin M

2017-02-01

Remembering the order of a sequence of events is a fundamental feature of episodic memory. Indeed, a number of formal models represent temporal context as part of the memory system, and memory for order has been researched extensively. Yet, the nature of the code(s) underlying sequence memory is still relatively unknown. Across 4 experiments that manipulated encoding task, we found evidence for 3 dissociable facets of order memory. Experiment 1 introduced a test requiring a judgment of which of 2 alternatives had immediately followed a word during encoding. This measure revealed better retention of interitem associations following relational encoding (silent reading) than relatively item-specific encoding (judging referent size), a pattern consistent with that observed in previous research using order reconstruction tests. In sharp contrast, Experiment 2 demonstrated the reverse pattern: Memory for the studied order of 2 sequentially presented items was actually better following item-specific encoding than following relational encoding. Experiment 3 reproduced this dissociation in a single experiment using both tests. Experiment 4 extended these findings by further dissociating the roles of relational encoding and item strength in the 2 tests. Taken together, these results indicate that memory for event sequence is influenced by (a) interitem associations, (b) the emphasized directionality of an association, and (c) an item's strength independent of other items. Memory for order is more complicated than has been portrayed in theories of memory and its nuances should be carefully considered when designing tests and models of temporal and relational memory. (PsycINFO Database Record (c) 2017 APA, all rights reserved).

The special role of item-context associations in the direct-access region of working memory.

PubMed

Campoy, Guillermo

2017-09-01

The three-embedded-component model of working memory (WM) distinguishes three representational states corresponding to three WM regions: activated long-term memory, direct-access region (DAR), and focus of attention. Recent neuroimaging research has revealed that access to the DAR is associated with enhanced hippocampal activity. Because the hippocampus mediates the encoding and retrieval of item-context associations, it has been suggested that this hippocampal activation is a consequence of the fact that item-context associations are particularly strong and accessible in the DAR. This study provides behavioral evidence for this view using an item-recognition task to assess the effect of non-intentional encoding and maintenance of item-location associations across WM regions. Five pictures of human faces were sequentially presented in different screen locations followed by a recognition probe. Visual cues immediately preceding the probe indicated the location thereof. When probe stimuli appeared in the same location that they had been presented within the memory set, the presentation of the cue was expected to elicit the activation of the corresponding WM representation through the just-established item-location association, resulting in faster recognition. Results showed this same-location effect, but only for items that, according to their serial position within the memory set, were held in the DAR.

To search or to like: Mapping fixations to differentiate two forms of incidental scene memory.

PubMed

Choe, Kyoung Whan; Kardan, Omid; Kotabe, Hiroki P; Henderson, John M; Berman, Marc G

2017-10-01

We employed eye-tracking to investigate how performing different tasks on scenes (e.g., intentionally memorizing them, searching for an object, evaluating aesthetic preference) can affect eye movements during encoding and subsequent scene memory. We found that scene memorability decreased after visual search (one incidental encoding task) compared to intentional memorization, and that preference evaluation (another incidental encoding task) produced better memory, similar to the incidental memory boost previously observed for words and faces. By analyzing fixation maps, we found that although fixation map similarity could explain how eye movements during visual search impairs incidental scene memory, it could not explain the incidental memory boost from aesthetic preference evaluation, implying that implicit mechanisms were at play. We conclude that not all incidental encoding tasks should be taken to be similar, as different mechanisms (e.g., explicit or implicit) lead to memory enhancements or decrements for different incidental encoding tasks.

Isolating age-group differences in working memory load-related neural activity: assessing the contribution of working memory capacity using a partial-trial fMRI method.

PubMed

Bennett, Ilana J; Rivera, Hannah G; Rypma, Bart

2013-05-15

Previous studies examining age-group differences in working memory load-related neural activity have yielded mixed results. When present, age-group differences in working memory capacity are frequently proposed to underlie these neural effects. However, direct relationships between working memory capacity and working memory load-related activity have only been observed in younger adults. These relationships remain untested in healthy aging. Therefore, the present study examined patterns of working memory load-related activity in 22 younger and 20 older adults and assessed the contribution of working memory capacity to these load-related effects. Participants performed a partial-trial delayed response item recognition task during functional magnetic resonance imaging. In this task, participants encoded either 2 or 6 letters, maintained them during a delay, and then indicated whether a probe was present in the memory set. Behavioral results revealed faster and more accurate responses to load 2 versus 6, with age-group differences in this load condition effect for the accuracy measure. Neuroimaging results revealed one region (medial superior frontal gyrus) that showed age-group differences in load-related activity during the retrieval period, with less (greater) neural activity for the low versus high load condition in younger (older) adults. Furthermore, for older adults, load-related activity did not vary as a function of working memory capacity. Thus, working memory-related activity varies with healthy aging, but these patterns are not due solely to working memory capacity. Neurocognitive aging theories that feature capacity will need to account for these results. Copyright © 2013 Elsevier Inc. All rights reserved.

Females scan more than males: a potential mechanism for sex differences in recognition memory.

PubMed

Heisz, Jennifer J; Pottruff, Molly M; Shore, David I

2013-07-01

Recognition-memory tests reveal individual differences in episodic memory; however, by themselves, these tests provide little information regarding the stage (or stages) in memory processing at which differences are manifested. We used eye-tracking technology, together with a recognition paradigm, to achieve a more detailed analysis of visual processing during encoding and retrieval. Although this approach may be useful for assessing differences in memory across many different populations, we focused on sex differences in face memory. Females outperformed males on recognition-memory tests, and this advantage was directly related to females' scanning behavior at encoding. Moreover, additional exposures to the faces reduced sex differences in face recognition, which suggests that males may be able to improve their recognition memory by extracting more information at encoding through increased scanning. A strategy of increased scanning at encoding may prove to be a simple way to enhance memory performance in other populations with memory impairment.

Remembering with gains and losses: effects of monetary reward and punishment on successful encoding activation of source memories.

PubMed

Shigemune, Yayoi; Tsukiura, Takashi; Kambara, Toshimune; Kawashima, Ryuta

2014-05-01

The motivation of getting rewards or avoiding punishments reinforces learning behaviors. Although the neural mechanisms underlying the effect of rewards on episodic memory have been demonstrated, there is little evidence of the effect of punishments on this memory. Our functional magnetic resonance imaging (fMRI) study investigated the effects of monetary rewards and punishments on activation during the encoding of source memories. During encoding, participants memorized words (item) and locations of presented words (source) under 3 conditions (Reward, Punishment, and Control). During retrieval, participants retrieved item and source memories of the words and were rewarded or penalized according to their performance. Source memories encoded with rewards or punishments were remembered better than those without such encoding. fMRI data demonstrated that the ventral tegmental area and substantia nigra and nucleus accumbens activations reflected both the processes of reward and punishment, whereas insular activation increased as a linear function of punishment. Activation in the hippocampus and parahippocampal cortex predicted subsequent retrieval success of source memories. Additionally, correlations between these reward/punishment-related regions and the hippocampus were significant. The successful encoding of source memories could be enhanced by punishments and rewards, and interactions between reward/punishment-related regions and memory-related regions could contribute to memory enhancement by reward and/or punishment.

Remembering with Gains and Losses: Effects of Monetary Reward and Punishment on Successful Encoding Activation of Source Memories

PubMed Central

Shigemune, Yayoi; Tsukiura, Takashi; Kambara, Toshimune; Kawashima, Ryuta

2014-01-01

The motivation of getting rewards or avoiding punishments reinforces learning behaviors. Although the neural mechanisms underlying the effect of rewards on episodic memory have been demonstrated, there is little evidence of the effect of punishments on this memory. Our functional magnetic resonance imaging (fMRI) study investigated the effects of monetary rewards and punishments on activation during the encoding of source memories. During encoding, participants memorized words (item) and locations of presented words (source) under 3 conditions (Reward, Punishment, and Control). During retrieval, participants retrieved item and source memories of the words and were rewarded or penalized according to their performance. Source memories encoded with rewards or punishments were remembered better than those without such encoding. fMRI data demonstrated that the ventral tegmental area and substantia nigra and nucleus accumbens activations reflected both the processes of reward and punishment, whereas insular activation increased as a linear function of punishment. Activation in the hippocampus and parahippocampal cortex predicted subsequent retrieval success of source memories. Additionally, correlations between these reward/punishment-related regions and the hippocampus were significant. The successful encoding of source memories could be enhanced by punishments and rewards, and interactions between reward/punishment-related regions and memory-related regions could contribute to memory enhancement by reward and/or punishment. PMID:23314939

Aging, Memory Efficiency and the Strategic Control of Attention at Encoding: Impairments of Value-Directed Remembering in Alzheimer's Disease

PubMed Central

Castel, Alan D.; Balota, David A.; McCabe, David P.

2009-01-01

Selecting what is important to remember, attending to this information, and then later recalling it can be thought of in terms of the strategic control of attention and the efficient use of memory. In order to examine whether aging and Alzheimer's disease (AD) influenced this ability, the present study used a selectivity task, where studied items were worth various point values and participants were asked to maximize the value of the items they recalled. Relative to younger adults (N=35) and healthy older adults (N=109), individuals with very mild AD (N=41) and mild AD (N=13) showed impairments in the strategic and efficient encoding and recall of high value items. Although individuals with AD recalled more high value items than low value items, they did not efficiently maximize memory performance (as measured by a selectivity index) relative to healthy older adults. Performance on complex working memory span tasks was related to the recall of the high value items but not low value items. This pattern suggests that relative to healthy aging, AD leads to impairments in strategic control at encoding and value-directed remembering. PMID:19413444

The contribution of attentional lapses to individual differences in visual working memory capacity.

PubMed

Adam, Kirsten C S; Mance, Irida; Fukuda, Keisuke; Vogel, Edward K

2015-08-01

Attentional control and working memory capacity are important cognitive abilities that substantially vary between individuals. Although much is known about how attentional control and working memory capacity relate to each other and to constructs like fluid intelligence, little is known about how trial-by-trial fluctuations in attentional engagement impact trial-by-trial working memory performance. Here, we employ a novel whole-report memory task that allowed us to distinguish between varying levels of attentional engagement in humans performing a working memory task. By characterizing low-performance trials, we can distinguish between models in which working memory performance failures are caused by either (1) complete lapses of attention or (2) variations in attentional control. We found that performance failures increase with set-size and strongly predict working memory capacity. Performance variability was best modeled by an attentional control model of attention, not a lapse model. We examined neural signatures of performance failures by measuring EEG activity while participants performed the whole-report task. The number of items correctly recalled in the memory task was predicted by frontal theta power, with decreased frontal theta power associated with poor performance on the task. In addition, we found that poor performance was not explained by failures of sensory encoding; the P1/N1 response and ocular artifact rates were equivalent for high- and low-performance trials. In all, we propose that attentional lapses alone cannot explain individual differences in working memory performance. Instead, we find that graded fluctuations in attentional control better explain the trial-by-trial differences in working memory that we observe.

The Contribution of Attentional Lapses to Individual Differences in Visual Working Memory Capacity

PubMed Central

Adam, Kirsten C. S.; Mance, Irida; Fukuda, Keisuke; Vogel, Edward K.

2015-01-01

Attentional control and working memory capacity are important cognitive abilities that substantially vary between individuals. Although much is known about how attentional control and working memory capacity relate to each other and to constructs like fluid intelligence, little is known about how trial-by-trial fluctuations in attentional engagement impact trial-by-trial working memory performance. Here, we employ a novel whole-report memory task that allowed us to distinguish between varying levels of attentional engagement in humans performing a working memory task. By characterizing low-performance trials, we can distinguish between models in which working memory performance failures are caused by either (1) complete lapses of attention or (2) variations in attentional control. We found that performance failures increase with set-size and strongly predict working memory capacity. Performance variability was best modeled by an attentional control model of attention, not a lapse model. We examined neural signatures of performance failures by measuring EEG activity while participants performed the whole-report task. The number of items correctly recalled in the memory task was predicted by frontal theta power, with decreased frontal theta power associated with poor performance on the task. In addition, we found that poor performance was not explained by failures of sensory encoding; the P1/N1 response and ocular artifact rates were equivalent for high- and low-performance trials. In all, we propose that attentional lapses alone cannot explain individual differences in working memory performance. Instead, we find that graded fluctuations in attentional control better explain the trial-by-trial differences in working memory that we observe. PMID:25811710

Divided Attention Can Enhance Memory Encoding: The Attentional Boost Effect in Implicit Memory

ERIC Educational Resources Information Center

Spataro, Pietro; Mulligan, Neil W.; Rossi-Arnaud, Clelia

2013-01-01

Distraction during encoding has long been known to disrupt later memory performance. Contrary to this long-standing result, we show that detecting an infrequent target in a dual-task paradigm actually improves memory encoding for a concurrently presented word, above and beyond the performance reached in the full-attention condition. This absolute…

Non-singleton colors are not attended faster than categories, but they are encoded faster: A combined approach of behavior, modeling and ERPs.

PubMed

Callahan-Flintoft, Chloe; Wyble, Brad

2017-11-01

The visual system is able to detect targets according to a variety of criteria, such as by categorical (letter vs digit) or featural attributes (color). These criteria are often used interchangeably in rapid serial visual presentation (RSVP) studies but little is known about how rapidly they are processed. The aim of this work was to compare the time course of attentional selection and memory encoding for different types of target criteria. We conducted two experiments where participants reported one or two targets (T1, T2) presented in lateral RSVP streams. Targets were marked either by being a singleton color (red letter among black letters), being categorically distinct (digits among letters) or non-singleton color (target color letter among heterogeneously colored letters). Using event related potential (ERPs) associated with attention and memory encoding (the N2pc and the P3 respectively), we compared the relative latency of these two processing stages for these three kinds of targets. In addition to these ERP measures, we obtained convergent behavioral measures for attention and memory encoding by presenting two targets in immediate sequence and comparing their relative accuracy and proportion of temporal order errors. Both behavioral and EEG measures revealed that singleton color targets were attended much more quickly than either non-singleton color or categorical targets, and there was very little difference between attention latencies to non-singleton color and categorical targets. There was however a difference in the speed of memory encoding for non-singleton color and category latencies in both behavioral and EEG measures, which shows that encoding latency differences do not always mirror attention latency differences. Copyright © 2017 Elsevier Ltd. All rights reserved.

The Effects of Similarity on High-Level Visual Working Memory Processing.

PubMed

Yang, Li; Mo, Lei

2017-01-01

Similarity has been observed to have opposite effects on visual working memory (VWM) for complex images. How can these discrepant results be reconciled? To answer this question, we used a change-detection paradigm to test visual working memory performance for multiple real-world objects. We found that working memory for moderate similarity items was worse than that for either high or low similarity items. This pattern was unaffected by manipulations of stimulus type (faces vs. scenes), encoding duration (limited vs. self-paced), and presentation format (simultaneous vs. sequential). We also found that the similarity effects differed in strength in different categories (scenes vs. faces). These results suggest that complex real-world objects are represented using a centre-surround inhibition organization . These results support the category-specific cortical resource theory and further suggest that centre-surround inhibition organization may differ by category.

About sleep's role in memory.

PubMed

Rasch, Björn; Born, Jan

2013-04-01

Over more than a century of research has established the fact that sleep benefits the retention of memory. In this review we aim to comprehensively cover the field of "sleep and memory" research by providing a historical perspective on concepts and a discussion of more recent key findings. Whereas initial theories posed a passive role for sleep enhancing memories by protecting them from interfering stimuli, current theories highlight an active role for sleep in which memories undergo a process of system consolidation during sleep. Whereas older research concentrated on the role of rapid-eye-movement (REM) sleep, recent work has revealed the importance of slow-wave sleep (SWS) for memory consolidation and also enlightened some of the underlying electrophysiological, neurochemical, and genetic mechanisms, as well as developmental aspects in these processes. Specifically, newer findings characterize sleep as a brain state optimizing memory consolidation, in opposition to the waking brain being optimized for encoding of memories. Consolidation originates from reactivation of recently encoded neuronal memory representations, which occur during SWS and transform respective representations for integration into long-term memory. Ensuing REM sleep may stabilize transformed memories. While elaborated with respect to hippocampus-dependent memories, the concept of an active redistribution of memory representations from networks serving as temporary store into long-term stores might hold also for non-hippocampus-dependent memory, and even for nonneuronal, i.e., immunological memories, giving rise to the idea that the offline consolidation of memory during sleep represents a principle of long-term memory formation established in quite different physiological systems.

Short-Term Memory Maintenance of Object Locations during Active Navigation: Which Working Memory Subsystem Is Essential?

PubMed Central

Baumann, Oliver; Skilleter, Ashley J.; Mattingley, Jason B.

2011-01-01

The goal of the present study was to examine the extent to which working memory supports the maintenance of object locations during active spatial navigation. Participants were required to navigate a virtual environment and to encode the location of a target object. In the subsequent maintenance period they performed one of three secondary tasks that were designed to selectively load visual, verbal or spatial working memory subsystems. Thereafter participants re-entered the environment and navigated back to the remembered location of the target. We found that while navigation performance in participants with high navigational ability was impaired only by the spatial secondary task, navigation performance in participants with poor navigational ability was impaired equally by spatial and verbal secondary tasks. The visual secondary task had no effect on navigation performance. Our results extend current knowledge by showing that the differential engagement of working memory subsystems is determined by navigational ability. PMID:21629686

The Simple Act of Choosing Influences Declarative Memory

PubMed Central

Murty, Vishnu P.; DuBrow, Sarah

2015-01-01

Individuals value the opportunity to make choices and exert control over their environment. This perceived sense of agency has been shown to have broad influences on cognition, including preference, decision-making, and valuation. However, it is unclear whether perceived control influences memory. Using a combined behavioral and functional magnetic resonance imaging approach, we investigated whether imbuing individuals with a sense of agency over their learning experience influences novel memory encoding. Participants encoded objects during a task that manipulated the opportunity to choose. Critically, unlike previous work on active learning, there was no relationship between individuals' choices and the content of memoranda. Despite this, we found that the opportunity to choose resulted in robust, reliable enhancements in declarative memory. Neuroimaging results revealed that anticipatory activation of the striatum, a region associated with decision-making, valuation, and exploration, correlated with choice-induced memory enhancements in behavior. These memory enhancements were further associated with interactions between the striatum and hippocampus. Specifically, anticipatory signals in the striatum when participants are alerted to the fact that they will have to choose one of two memoranda were associated with encoding success effects in the hippocampus on a trial-by-trial basis. The precedence of the striatal signal in these interactions suggests a modulatory relationship of the striatum over the hippocampus. These findings not only demonstrate enhanced declarative memory when individuals have perceived control over their learning but also support a novel mechanism by which these enhancements emerge. Furthermore, they demonstrate a novel context in which mesolimbic and declarative memory systems interact. PMID:25904779

The simple act of choosing influences declarative memory.

PubMed

Murty, Vishnu P; DuBrow, Sarah; Davachi, Lila

2015-04-22

Individuals value the opportunity to make choices and exert control over their environment. This perceived sense of agency has been shown to have broad influences on cognition, including preference, decision-making, and valuation. However, it is unclear whether perceived control influences memory. Using a combined behavioral and functional magnetic resonance imaging approach, we investigated whether imbuing individuals with a sense of agency over their learning experience influences novel memory encoding. Participants encoded objects during a task that manipulated the opportunity to choose. Critically, unlike previous work on active learning, there was no relationship between individuals' choices and the content of memoranda. Despite this, we found that the opportunity to choose resulted in robust, reliable enhancements in declarative memory. Neuroimaging results revealed that anticipatory activation of the striatum, a region associated with decision-making, valuation, and exploration, correlated with choice-induced memory enhancements in behavior. These memory enhancements were further associated with interactions between the striatum and hippocampus. Specifically, anticipatory signals in the striatum when participants are alerted to the fact that they will have to choose one of two memoranda were associated with encoding success effects in the hippocampus on a trial-by-trial basis. The precedence of the striatal signal in these interactions suggests a modulatory relationship of the striatum over the hippocampus. These findings not only demonstrate enhanced declarative memory when individuals have perceived control over their learning but also support a novel mechanism by which these enhancements emerge. Furthermore, they demonstrate a novel context in which mesolimbic and declarative memory systems interact. Copyright © 2015 the authors 0270-6474/15/356255-10$15.00/0.

Dissociable effects of top-down and bottom-up attention during episodic encoding

PubMed Central

Uncapher, Melina R.; Hutchinson, J. Benjamin; Wagner, Anthony D.

2011-01-01

It is well established that the formation of memories for life’s experiences—episodic memory—is influenced by how we attend to those experiences, yet the neural mechanisms by which attention shapes episodic encoding are still unclear. We investigated how top-down and bottom-up attention contribute to memory encoding of visual objects in humans by manipulating both types of attention during functional magnetic resonance imaging (fMRI) of episodic memory formation. We show that dorsal parietal cortex—specifically, intraparietal sulcus (IPS)—was engaged during top-down attention and was also recruited during the successful formation of episodic memories. By contrast, bottom-up attention engaged ventral parietal cortex—specifically, temporoparietal junction (TPJ)—and was also more active during encoding failure. Functional connectivity analyses revealed further dissociations in how top-down and bottom-up attention influenced encoding: while both IPS and TPJ influenced activity in perceptual cortices thought to represent the information being encoded (fusiform/lateral occipital cortex), they each exerted opposite effects on memory encoding. Specifically, during a preparatory period preceding stimulus presentation, a stronger drive from IPS was associated with a higher likelihood that the subsequently attended stimulus would be encoded. By contrast, during stimulus processing, stronger connectivity with TPJ was associated with a lower likelihood the stimulus would be successfully encoded. These findings suggest that during encoding of visual objects into episodic memory, top-down and bottom-up attention can have opposite influences on perceptual areas that subserve visual object representation, suggesting that one manner in which attention modulates memory is by altering the perceptual processing of to-be-encoded stimuli. PMID:21880922

Turning Simple Span into Complex Span: Time for Decay or Interference from Distractors?

ERIC Educational Resources Information Center

Lewandowsky, Stephan; Geiger, Sonja M.; Morrell, Daniel B.; Oberauer, Klaus

2010-01-01

We investigated the effects of the duration and type of to-be-articulated distractors during encoding of a verbal list into short-term memory (STM). Distractors and to-be-remembered items alternated during list presentation, as in the complex-span task that underlies much of working-memory research. According to an interference model of STM, known…

Binding biological motion and visual features in working memory.

PubMed

Ding, Xiaowei; Zhao, Yangfan; Wu, Fan; Lu, Xiqian; Gao, Zaifeng; Shen, Mowei

2015-06-01

Working memory mechanisms for binding have been examined extensively in the last decade, yet few studies have explored bindings relating to human biological motion (BM). Human BM is the most salient and biologically significant kinetic information encountered in everyday life and is stored independently from other visual features (e.g., colors). The current study explored 3 critical issues of BM-related binding in working memory: (a) how many BM binding units can be retained in working memory, (b) whether involuntarily object-based binding occurs during BM binding, and (c) whether the maintenance of BM bindings in working memory requires attention above and beyond that needed to maintain the constituent dimensions. We isolated motion signals of human BM from non-BM sources by using point-light displays as to-be-memorized BM and presented the participants colored BM in a change detection task. We found that working memory capacity for BM-color bindings is rather low; only 1 or 2 BM-color bindings could be retained in working memory regardless of the presentation manners (Experiments 1-3). Furthermore, no object-based encoding took place for colored BM stimuli regardless of the processed dimensions (Experiments 4 and 5). Central executive attention contributes to the maintenance of BM-color bindings, yet maintaining BM bindings in working memory did not require more central attention than did maintaining the constituent dimensions in working memory (Experiment 6). Overall, these results suggest that keeping BM bindings in working memory is a fairly resource-demanding process, yet central executive attention does not play a special role in this cross-module binding. (c) 2015 APA, all rights reserved).

Prolonged focal attention without binding: Tracking a ball for half a minute without remembering its color.

PubMed

Chen, Hui; Swan, Garrett; Wyble, Brad

2016-02-01

Conventional theories of cognition focus on attention as the primary determinant of working memory contents. However, here we show that about one third of observers could not report the color of a ball that they had just been specifically attending for 5-59 s. This counterintuitive result was obtained when observers repeatedly counted the passes of one of two different colored balls among actors in a video and were then unexpectedly asked to report the color of the ball that they had just tracked. Control trials demonstrated that observers' color report performance increased dramatically once they had an expectation to do so. Critically, most of the incorrect color responses were the distractor ball color, which suggested memory storage without binding. Therefore, these results, together with other recent findings argued against two opposing theories: object-based encoding and feature-based encoding. Instead, we propose a new hypothesis by suggesting that the failure to report color is because participants might only activate the color representation in long-term memory without binding it to object representation in working memory. Copyright © 2015 Elsevier B.V. All rights reserved.

Value conditioning modulates visual working memory processes.

PubMed

Thomas, Paul M J; FitzGibbon, Lily; Raymond, Jane E

2016-01-01

Learning allows the value of motivationally salient events to become associated with stimuli that predict those events. Here, we asked whether value associations could facilitate visual working memory (WM), and whether such effects would be valence dependent. Our experiment was specifically designed to isolate value-based effects on WM from value-based effects on selective attention that might be expected to bias encoding. In a simple associative learning task, participants learned to associate the color of tinted faces with gaining or losing money or neither. Tinted faces then served as memoranda in a face identity WM task for which previously learned color associations were irrelevant and no monetary outcomes were forthcoming. Memory was best for faces with gain-associated tints, poorest for faces with loss-associated tints, and average for faces with no-outcome-associated tints. Value associated with 1 item in the WM array did not modulate memory for other items in the array. Eye movements when studying faces did not depend on the valence of previously learned color associations, arguing against value-based biases being due to differential encoding. This valence-sensitive value-conditioning effect on WM appears to result from modulation of WM maintenance processes. (c) 2015 APA, all rights reserved).

Selective Attention to Auditory Memory Neurally Enhances Perceptual Precision.

PubMed

Lim, Sung-Joo; Wöstmann, Malte; Obleser, Jonas

2015-12-09

Selective attention to a task-relevant stimulus facilitates encoding of that stimulus into a working memory representation. It is less clear whether selective attention also improves the precision of a stimulus already represented in memory. Here, we investigate the behavioral and neural dynamics of selective attention to representations in auditory working memory (i.e., auditory objects) using psychophysical modeling and model-based analysis of electroencephalographic signals. Human listeners performed a syllable pitch discrimination task where two syllables served as to-be-encoded auditory objects. Valid (vs neutral) retroactive cues were presented during retention to allow listeners to selectively attend to the to-be-probed auditory object in memory. Behaviorally, listeners represented auditory objects in memory more precisely (expressed by steeper slopes of a psychometric curve) and made faster perceptual decisions when valid compared to neutral retrocues were presented. Neurally, valid compared to neutral retrocues elicited a larger frontocentral sustained negativity in the evoked potential as well as enhanced parietal alpha/low-beta oscillatory power (9-18 Hz) during memory retention. Critically, individual magnitudes of alpha oscillatory power (7-11 Hz) modulation predicted the degree to which valid retrocues benefitted individuals' behavior. Our results indicate that selective attention to a specific object in auditory memory does benefit human performance not by simply reducing memory load, but by actively engaging complementary neural resources to sharpen the precision of the task-relevant object in memory. Can selective attention improve the representational precision with which objects are held in memory? And if so, what are the neural mechanisms that support such improvement? These issues have been rarely examined within the auditory modality, in which acoustic signals change and vanish on a milliseconds time scale. Introducing a new auditory memory paradigm and using model-based electroencephalography analyses in humans, we thus bridge this gap and reveal behavioral and neural signatures of increased, attention-mediated working memory precision. We further show that the extent of alpha power modulation predicts the degree to which individuals' memory performance benefits from selective attention. Copyright © 2015 the authors 0270-6474/15/3516094-11$15.00/0.

Encoding negative events under stress: high subjective arousal is related to accurate emotional memory despite misinformation exposure.

PubMed

Hoscheidt, Siobhan M; LaBar, Kevin S; Ryan, Lee; Jacobs, W Jake; Nadel, Lynn

2014-07-01

Stress at encoding affects memory processes, typically enhancing, or preserving, memory for emotional information. These effects have interesting implications for eyewitness accounts, which in real-world contexts typically involve encoding an aversive event under stressful conditions followed by potential exposure to misinformation. The present study investigated memory for a negative event encoded under stress and subsequent misinformation endorsement. Healthy young adults participated in a between-groups design with three experimental sessions conducted 48 h apart. Session one consisted of a psychosocial stress induction (or control task) followed by incidental encoding of a negative slideshow. During session two, participants were asked questions about the slideshow, during which a random subgroup was exposed to misinformation. Memory for the slideshow was tested during the third session. Assessment of memory accuracy across stress and no-stress groups revealed that stress induced just prior to encoding led to significantly better memory for the slideshow overall. The classic misinformation effect was also observed - participants exposed to misinformation were significantly more likely to endorse false information during memory testing. In the stress group, however, memory accuracy and misinformation effects were moderated by arousal experienced during encoding of the negative event. Misinformed-stress group participants who reported that the negative slideshow elicited high arousal during encoding were less likely to endorse misinformation for the most aversive phase of the story. Furthermore, these individuals showed better memory for components of the aversive slideshow phase that had been directly misinformed. Results from the current study provide evidence that stress and high subjective arousal elicited by a negative event act concomitantly during encoding to enhance emotional memory such that the most aversive aspects of the event are well remembered and subsequently more resistant to misinformation effects. Copyright © 2013 The Authors. Published by Elsevier Inc. All rights reserved.

Spatial sequences, but not verbal sequences, are vulnerable to general interference during retention in working memory.

PubMed

Morey, Candice C; Miron, Monica D

2016-12-01

Among models of working memory, there is not yet a consensus about how to describe functions specific to storing verbal or visual-spatial memories. We presented aural-verbal and visual-spatial lists simultaneously and sometimes cued one type of information after presentation, comparing accuracy in conditions with and without informative retro-cues. This design isolates interference due specifically to maintenance, which appears most clearly in the uncued trials, from interference due to encoding, which occurs in all dual-task trials. When recall accuracy was comparable between tasks, we found that spatial memory was worse in uncued than in retro-cued trials, whereas verbal memory was not. Our findings bolster proposals that maintenance of spatial serial order, like maintenance of visual materials more broadly, relies on general rather than specialized resources, while maintenance of verbal sequences may rely on domain-specific resources. We argue that this asymmetry should be explicitly incorporated into models of working memory. (PsycINFO Database Record (c) 2016 APA, all rights reserved).

No evidence for enhancements to visual working memory with transcranial direct current stimulation to prefrontal or posterior parietal cortices.

PubMed

Robison, Matthew K; McGuirk, William P; Unsworth, Nash

2017-08-01

The present study examined the relative contributions of the prefrontal cortex (PFC) and posterior parietal cortex (PPC) to visual working memory. Evidence from a number of different techniques has led to the theory that the PFC controls access to working memory (i.e., filtering), determining which information is encoded and maintained for later use whereas the parietal cortex determines how much information is held at 1 given time, regardless of relevance (i.e., capacity; McNab & Klingberg, 2008; Vogel, McCollough, & Machizawa, 2005). To test this theory, we delivered transcranial DC stimulation (tDCS) to the right PFC and right PPC and measured visual working memory capacity and filtering abilities both during and immediately following stimulation. We observed no evidence that tDCS to either the PFC or PPC significantly improved visual working memory. Although the present results did not allow us to make firm theoretical conclusions about the roles of the PFC and PPC in working memory, the results add to the growing body of literature surrounding tDCS and its associated behavioral and neurophysiological effects. (PsycINFO Database Record (c) 2017 APA, all rights reserved).

The Influence of Music on Prefrontal Cortex during Episodic Encoding and Retrieval of Verbal Information: A Multichannel fNIRS Study

PubMed Central

Ferreri, Laura; Bigand, Emmanuel; Bard, Patrick; Bugaiska, Aurélia

2015-01-01

Music can be thought of as a complex stimulus able to enrich the encoding of an event thus boosting its subsequent retrieval. However, several findings suggest that music can also interfere with memory performance. A better understanding of the behavioral and neural processes involved can substantially improve knowledge and shed new light on the most efficient music-based interventions. Based on fNIRS studies on music, episodic encoding, and the dorsolateral prefrontal cortex (PFC), this work aims to extend previous findings by monitoring the entire lateral PFC during both encoding and retrieval of verbal material. Nineteen participants were asked to encode lists of words presented with either background music or silence and subsequently tested during a free recall task. Meanwhile, their PFC was monitored using a 48-channel fNIRS system. Behavioral results showed greater chunking of words under the music condition, suggesting the employment of associative strategies for items encoded with music. fNIRS results showed that music provided a less demanding way of modulating both episodic encoding and retrieval, with a general prefrontal decreased activity under the music versus silence condition. This suggests that music-related memory processes rely on specific neural mechanisms and that music can positively influence both episodic encoding and retrieval of verbal information. PMID:26508813

The Influence of Music on Prefrontal Cortex during Episodic Encoding and Retrieval of Verbal Information: A Multichannel fNIRS Study.

PubMed

Ferreri, Laura; Bigand, Emmanuel; Bard, Patrick; Bugaiska, Aurélia

2015-01-01

Music can be thought of as a complex stimulus able to enrich the encoding of an event thus boosting its subsequent retrieval. However, several findings suggest that music can also interfere with memory performance. A better understanding of the behavioral and neural processes involved can substantially improve knowledge and shed new light on the most efficient music-based interventions. Based on fNIRS studies on music, episodic encoding, and the dorsolateral prefrontal cortex (PFC), this work aims to extend previous findings by monitoring the entire lateral PFC during both encoding and retrieval of verbal material. Nineteen participants were asked to encode lists of words presented with either background music or silence and subsequently tested during a free recall task. Meanwhile, their PFC was monitored using a 48-channel fNIRS system. Behavioral results showed greater chunking of words under the music condition, suggesting the employment of associative strategies for items encoded with music. fNIRS results showed that music provided a less demanding way of modulating both episodic encoding and retrieval, with a general prefrontal decreased activity under the music versus silence condition. This suggests that music-related memory processes rely on specific neural mechanisms and that music can positively influence both episodic encoding and retrieval of verbal information.

Incidental Memory Encoding Assessed with Signal Detection Theory and Functional Magnetic Resonance Imaging (fMRI).

PubMed

Clemens, Benjamin; Regenbogen, Christina; Koch, Kathrin; Backes, Volker; Romanczuk-Seiferth, Nina; Pauly, Katharina; Shah, N Jon; Schneider, Frank; Habel, Ute; Kellermann, Thilo

2015-01-01

In functional magnetic resonance imaging (fMRI) studies that apply a "subsequent memory" approach, successful encoding is indicated by increased fMRI activity during the encoding phase for hits vs. misses, in areas underlying memory encoding such as the hippocampal formation. Signal-detection theory (SDT) can be used to analyze memory-related fMRI activity as a function of the participant's memory trace strength (d(')). The goal of the present study was to use SDT to examine the relationship between fMRI activity during incidental encoding and participants' recognition performance. To implement a new approach, post-experimental group assignment into High- or Low Performers (HP or LP) was based on 29 healthy participants' recognition performance, assessed with SDT. The analyses focused on the interaction between the factors group (HP vs. LP) and recognition performance (hits vs. misses). A whole-brain analysis revealed increased activation for HP vs. LP during incidental encoding for remembered vs. forgotten items (hits > misses) in the insula/temporo-parietal junction (TPJ) and the fusiform gyrus (FFG). Parameter estimates in these regions exhibited a significant positive correlation with d('). As these brain regions are highly relevant for salience detection (insula), stimulus-driven attention (TPJ), and content-specific processing of mnemonic stimuli (FFG), we suggest that HPs' elevated memory performance was associated with enhanced attentional and content-specific sensory processing during the encoding phase. We provide first correlative evidence that encoding-related activity in content-specific sensory areas and content-independent attention and salience detection areas influences memory performance in a task with incidental encoding of facial stimuli. Based on our findings, we discuss whether the aforementioned group differences in brain activity during incidental encoding might constitute the basis of general differences in memory performance between HP and LP.

Motivation enhances visual working memory capacity through the modulation of central cognitive processes.

PubMed

Sanada, Motoyuki; Ikeda, Koki; Kimura, Kenta; Hasegawa, Toshikazu

2013-09-01

Motivation is well known to enhance working memory (WM) capacity, but the mechanism underlying this effect remains unclear. The WM process can be divided into encoding, maintenance, and retrieval, and in a change detection visual WM paradigm, the encoding and retrieval processes can be subdivided into perceptual and central processing. To clarify which of these segments are most influenced by motivation, we measured ERPs in a change detection task with differential monetary rewards. The results showed that the enhancement of WM capacity under high motivation was accompanied by modulations of late central components but not those reflecting attentional control on perceptual inputs across all stages of WM. We conclude that the "state-dependent" shift of motivation impacted the central, rather than the perceptual functions in order to achieve better behavioral performances. Copyright © 2013 Society for Psychophysiological Research.

Implicit memory in music and language.

PubMed

Ettlinger, Marc; Margulis, Elizabeth H; Wong, Patrick C M

2011-01-01

Research on music and language in recent decades has focused on their overlapping neurophysiological, perceptual, and cognitive underpinnings, ranging from the mechanism for encoding basic auditory cues to the mechanism for detecting violations in phrase structure. These overlaps have most often been identified in musicians with musical knowledge that was acquired explicitly, through formal training. In this paper, we review independent bodies of work in music and language that suggest an important role for implicitly acquired knowledge, implicit memory, and their associated neural structures in the acquisition of linguistic or musical grammar. These findings motivate potential new work that examines music and language comparatively in the context of the implicit memory system.

Lateral and medial prefrontal contributions to emotion generation by semantic elaboration during episodic encoding.

PubMed

Kaneda, Takumi; Shigemune, Yayoi; Tsukiura, Takashi

2017-02-01

Memories for emotion-laden stimuli are remembered more accurately than those for neutral stimuli. Although this enhancement reflects stimulus-driven modulation of memory by emotions, functional neuroimaging evidence of the interacting mechanisms between emotions generated by intentional processes, such as semantic elaboration, and memory is scarce. The present fMRI study investigated how encoding-related activation is modulated by emotions generated during the process of semantic elaboration. During encoding with fMRI, healthy young adults viewed neutral (target) pictures either passively or with semantic elaboration. In semantic elaboration, participants imagined background stories related to the pictures. Encoding trials with semantic elaboration were subdivided into conditions in which participants imagined negative, positive, or neutral stories. One week later, memories for target pictures were tested. In behavioral results, memories for target pictures were significantly enhanced by semantic elaboration, compared to passive viewing, and the memory enhancement was more remarkable when negative or positive stories were imagined. fMRI results demonstrated that activations in the left inferior frontal gyrus and dorsal medial prefrontal cortex (dmPFC) were greater during the encoding of target pictures with semantic elaboration than those with passive viewing, and that these activations further increased during encoding with semantic elaboration of emotional stories than of neutral stories. Functional connectivity between the left inferior frontal gyrus and dmPFC/hippocampus during encoding significantly predicted retrieval accuracies of memories encoded with self-generated emotional stories. These findings suggest that networks including the left inferior frontal region, dmPFC, and hippocampus could contribute to the modulation of memories encoded with the emotion generation.

Processing of visual semantic information to concrete words: temporal dynamics and neural mechanisms indicated by event-related brain potentials( ).

PubMed

van Schie, Hein T; Wijers, Albertus A; Mars, Rogier B; Benjamins, Jeroen S; Stowe, Laurie A

2005-05-01

Event-related brain potentials were used to study the retrieval of visual semantic information to concrete words, and to investigate possible structural overlap between visual object working memory and concreteness effects in word processing. Subjects performed an object working memory task that involved 5 s retention of simple 4-angled polygons (load 1), complex 10-angled polygons (load 2), and a no-load baseline condition. During the polygon retention interval subjects were presented with a lexical decision task to auditory presented concrete (imageable) and abstract (nonimageable) words, and pseudowords. ERP results are consistent with the use of object working memory for the visualisation of concrete words. Our data indicate a two-step processing model of visual semantics in which visual descriptive information of concrete words is first encoded in semantic memory (indicated by an anterior N400 and posterior occipital positivity), and is subsequently visualised via the network for object working memory (reflected by a left frontal positive slow wave and a bilateral occipital slow wave negativity). Results are discussed in the light of contemporary models of semantic memory.

Activation and binding in verbal working memory: a dual-process model for the recognition of nonwords.

PubMed

Oberauer, Klaus; Lange, Elke B

2009-02-01

The article presents a mathematical model of short-term recognition based on dual-process models and the three-component theory of working memory [Oberauer, K. (2002). Access to information in working memory: Exploring the focus of attention. Journal of Experimental Psychology: Learning, Memory, and Cognition, 28, 411-421]. Familiarity arises from activated representations in long-term memory, ignoring their relations; recollection retrieves bindings in the capacity-limited component of working memory. In three experiments participants encoded two short lists of nonwords for immediate recognition, one of which was then cued as irrelevant. Probes from the irrelevant list were rejected more slowly than new probes; this was also found with probes recombining letters of irrelevant nonwords, suggesting that familiarity arises from individual letters independent of their relations. When asked to accept probes whose letters were all in the relevant list, regardless of their conjunction, participants accepted probes preserving the original conjunctions faster than recombinations, showing that recollection accessed feature bindings automatically. The model fit the data best when familiarity depended only on matching letters, whereas recollection used binding information.

Brain computer interface to enhance episodic memory in human participants

PubMed Central

Burke, John F.; Merkow, Maxwell B.; Jacobs, Joshua; Kahana, Michael J.

2015-01-01

Recent research has revealed that neural oscillations in the theta (4–8 Hz) and alpha (9–14 Hz) bands are predictive of future success in memory encoding. Because these signals occur before the presentation of an upcoming stimulus, they are considered stimulus-independent in that they correlate with enhanced memory encoding independent of the item being encoded. Thus, such stimulus-independent activity has important implications for the neural mechanisms underlying episodic memory as well as the development of cognitive neural prosthetics. Here, we developed a brain computer interface (BCI) to test the ability of such pre-stimulus activity to modulate subsequent memory encoding. We recorded intracranial electroencephalography (iEEG) in neurosurgical patients as they performed a free recall memory task, and detected iEEG theta and alpha oscillations that correlated with optimal memory encoding. We then used these detected oscillatory changes to trigger the presentation of items in the free recall task. We found that item presentation contingent upon the presence of pre-stimulus theta and alpha oscillations modulated memory performance in more sessions than expected by chance. Our results suggest that an electrophysiological signal may be causally linked to a specific behavioral condition, and contingent stimulus presentation has the potential to modulate human memory encoding. PMID:25653605

Effects of pointing compared with naming and observing during encoding on item and source memory in young and older adults.

PubMed

Ouwehand, Kim; van Gog, Tamara; Paas, Fred

2016-10-01

Research showed that source memory functioning declines with ageing. Evidence suggests that encoding visual stimuli with manual pointing in addition to visual observation can have a positive effect on spatial memory compared with visual observation only. The present study investigated whether pointing at picture locations during encoding would lead to better spatial source memory than naming (Experiment 1) and visual observation only (Experiment 2) in young and older adults. Experiment 3 investigated whether response modality during the test phase would influence spatial source memory performance. Experiments 1 and 2 supported the hypothesis that pointing during encoding led to better source memory for picture locations than naming or observation only. Young adults outperformed older adults on the source memory but not the item memory task in both Experiments 1 and 2. In Experiments 1 and 2, participants manually responded in the test phase. Experiment 3 showed that if participants had to verbally respond in the test phase, the positive effect of pointing compared with naming during encoding disappeared. The results suggest that pointing at picture locations during encoding can enhance spatial source memory in both young and older adults, but only if the response modality is congruent in the test phase.

Post-encoding control of working memory enhances processing of relevant information in rhesus monkeys (Macaca mulatta).

PubMed

Brady, Ryan J; Hampton, Robert R

2018-06-01

Working memory is a system by which a limited amount of information can be kept available for processing after the cessation of sensory input. Because working memory resources are limited, it is adaptive to focus processing on the most relevant information. We used a retro-cue paradigm to determine the extent to which monkey working memory possesses control mechanisms that focus processing on the most relevant representations. Monkeys saw a sample array of images, and shortly after the array disappeared, they were visually cued to a location that had been occupied by one of the sample images. The cue indicated which image should be remembered for the upcoming recognition test. By determining whether the monkeys were more accurate and quicker to respond to cued images compared to un-cued images, we tested the hypothesis that monkey working memory focuses processing on relevant information. We found a memory benefit for the cued image in terms of accuracy and retrieval speed with a memory load of two images. With a memory load of three images, we found a benefit in retrieval speed but only after shortening the onset latency of the retro-cue. Our results demonstrate previously unknown flexibility in the cognitive control of memory in monkeys, suggesting that control mechanisms in working memory likely evolved in a common ancestor of humans and monkeys more than 32 million years ago. Future work should be aimed at understanding the interaction between memory load and the ability to control memory resources, and the role of working memory control in generating differences in cognitive capacity among primates. Copyright © 2018 Elsevier B.V. All rights reserved.

A Psychometric Measure of Working Memory Capacity for Configured Body Movement

PubMed Central

Wu, Ying Choon; Coulson, Seana

2014-01-01

Working memory (WM) models have traditionally assumed at least two domain-specific storage systems for verbal and visuo-spatial information. We review data that suggest the existence of an additional slave system devoted to the temporary storage of body movements, and present a novel instrument for its assessment: the movement span task. The movement span task assesses individuals' ability to remember and reproduce meaningless configurations of the body. During the encoding phase of a trial, participants watch short videos of meaningless movements presented in sets varying in size from one to five items. Immediately after encoding, they are prompted to reenact as many items as possible. The movement span task was administered to 90 participants along with standard tests of verbal WM, visuo-spatial WM, and a gesture classification test in which participants judged whether a speaker's gestures were congruent or incongruent with his accompanying speech. Performance on the gesture classification task was not related to standard measures of verbal or visuo-spatial working memory capacity, but was predicted by scores on the movement span task. Results suggest the movement span task can serve as an assessment of individual differences in WM capacity for body-centric information. PMID:24465437

Kinesthetic working memory and action control within the dorsal stream.

PubMed

Fiehler, Katja; Burke, Michael; Engel, Annerose; Bien, Siegfried; Rösler, Frank

2008-02-01

There is wide agreement that the "dorsal (action) stream" processes visual information for movement control. However, movements depend not only on vision but also on tactile and kinesthetic information (=haptics). Using functional magnetic resonance imaging, the present study investigates to what extent networks within the dorsal stream are also utilized for kinesthetic action control and whether they are also involved in kinesthetic working memory. Fourteen blindfolded participants performed a delayed-recognition task in which right-handed movements had to be encoded, maintained, and later recognized without any visual feedback. Encoding of hand movements activated somatosensory areas, superior parietal lobe (dorsodorsal stream), anterior intraparietal sulcus (aIPS) and adjoining areas (ventrodorsal stream), premotor cortex, and occipitotemporal cortex (ventral stream). Short-term maintenance of kinesthetic information elicited load-dependent activity in the aIPS and adjacent anterior portion of the superior parietal lobe (ventrodorsal stream) of the left hemisphere. We propose that the action representation system of the dorsodorsal and ventrodorsal stream is utilized not only for visual but also for kinesthetic action control. Moreover, the present findings demonstrate that networks within the ventrodorsal stream, in particular the left aIPS and closely adjacent areas, are also engaged in working memory maintenance of kinesthetic information.

Memory Reactivation Predicts Resistance to Retroactive Interference: Evidence from Multivariate Classification and Pattern Similarity Analyses

PubMed Central

Rugg, Michael D.

2016-01-01

Memory reactivation—the reinstatement of processes and representations engaged when an event is initially experienced—is believed to play an important role in strengthening and updating episodic memory. The present study examines how memory reactivation during a potentially interfering event influences memory for a previously experienced event. Participants underwent fMRI during the encoding phase of an AB/AC interference task in which some words were presented twice in association with two different encoding tasks (AB and AC trials) and other words were presented once (DE trials). The later memory test required retrieval of the encoding tasks associated with each of the study words. Retroactive interference was evident for the AB encoding task and was particularly strong when the AC encoding task was remembered rather than forgotten. We used multivariate classification and pattern similarity analysis (PSA) to measure reactivation of the AB encoding task during AC trials. The results demonstrated that reactivation of generic task information measured with multivariate classification predicted subsequent memory for the AB encoding task regardless of whether interference was strong and weak (trials for which the AC encoding task was remembered or forgotten, respectively). In contrast, reactivation of neural patterns idiosyncratic to a given AB trial measured with PSA only predicted memory when the strength of interference was low. These results suggest that reactivation of features of an initial experience shared across numerous events in the same category, but not features idiosyncratic to a particular event, are important in resisting retroactive interference caused by new learning. SIGNIFICANCE STATEMENT Reactivating a previously encoded memory is believed to provide an opportunity to strengthen the memory, but also to return the memory to a labile state, making it susceptible to interference. However, there is debate as to how memory reactivation elicited by a potentially interfering event influences subsequent retrieval of the memory. The findings of the current study indicate that reactivating features idiosyncratic to a particular experience during interference only influences subsequent memory when interference is relatively weak. Critically, reactivation of generic contextual information predicts subsequent source memory when retroactive interference is either strong and weak. The results indicate that reactivation of generic information about a prior episode mitigates forgetting due to retroactive interference. PMID:27076433

Encoding and choice in the task span paradigm.

PubMed

Reiman, Kaitlin M; Weaver, Starla M; Arrington, Catherine M

2015-03-01

Cognitive control during sequences of planned behaviors requires both plan-level processes such as generating, maintaining, and monitoring the plan, as well as task-level processes such as selecting, establishing and implementing specific task sets. The task span paradigm (Logan in J Exp Psychol Gen 133:218-236, 2004) combines two common cognitive control paradigms, task switching and working memory span, to investigate the integration of plan-level and task-level processes during control of sequential behavior. The current study expands past task span research to include measures of encoding processes and choice behavior with volitional sequence generation, using the standard task span as well as a novel voluntary task span paradigm. In two experiments, we consider how sequence complexity, defined separately for plan-level and task-level complexity, influences sequence encoding (Experiment 1), sequence choice (Experiment 2), sequence memory, and task performance of planned sequences of action. Results indicate that participants were sensitive to sequence complexity, but that different aspects of behavior are most strongly influenced by different types of complexity. Hierarchical complexity at the plan level best predicts voluntary sequence generation and memory; while switch frequency at the task level best predicts encoding of externally defined sequences and task performance. Furthermore, performance RTs were similar for externally and internally defined plans, whereas memory was improved for internally defined sequences. Finally, participants demonstrated a significant sequence choice bias in the voluntary task span. Consistent with past research on choice behavior, volitional selection of plans was markedly influenced by both the ease of memory and performance.

Transformed Neural Pattern Reinstatement during Episodic Memory Retrieval.

PubMed

Xiao, Xiaoqian; Dong, Qi; Gao, Jiahong; Men, Weiwei; Poldrack, Russell A; Xue, Gui

2017-03-15

Contemporary models of episodic memory posit that remembering involves the reenactment of encoding processes. Although encoding-retrieval similarity has been consistently reported and linked to memory success, the nature of neural pattern reinstatement is poorly understood. Using high-resolution fMRI on human subjects, our results obtained clear evidence for item-specific pattern reinstatement in the frontoparietal cortex, even when the encoding-retrieval pairs shared no perceptual similarity. No item-specific pattern reinstatement was found in the ventral visual cortex. Importantly, the brain regions and voxels carrying item-specific representation differed significantly between encoding and retrieval, and the item specificity for encoding-retrieval similarity was smaller than that for encoding or retrieval, suggesting different nature of representations between encoding and retrieval. Moreover, cross-region representational similarity analysis suggests that the encoded representation in the ventral visual cortex was reinstated in the frontoparietal cortex during retrieval. Together, these results suggest that, in addition to reinstatement of the originally encoded pattern in the brain regions that perform encoding processes, retrieval may also involve the reinstatement of a transformed representation of the encoded information. These results emphasize the constructive nature of memory retrieval that helps to serve important adaptive functions. SIGNIFICANCE STATEMENT Episodic memory enables humans to vividly reexperience past events, yet how this is achieved at the neural level is barely understood. A long-standing hypothesis posits that memory retrieval involves the faithful reinstatement of encoding-related activity. We tested this hypothesis by comparing the neural representations during encoding and retrieval. We found strong pattern reinstatement in the frontoparietal cortex, but not in the ventral visual cortex, that represents visual details. Critically, even within the same brain regions, the nature of representation during retrieval was qualitatively different from that during encoding. These results suggest that memory retrieval is not a faithful replay of past event but rather involves additional constructive processes to serve adaptive functions. Copyright © 2017 the authors 0270-6474/17/372986-13$15.00/0.

Differences in Brain Activity during a Verbal Associative Memory Encoding Task in High- and Low-fit Adolescents

PubMed Central

Herting, Megan M.; Nagel, Bonnie J.

2013-01-01

Aerobic fitness is associated with better memory performance as well as larger volumes in memory-related brain regions in children, adolescents, and elderly. It is unclear if aerobic exercise also influences learning and memory functional neural circuitry. Here, we examine brain activity in 17 high-fit (HF) and 17 low-fit (LF) adolescents during a subsequent memory encoding paradigm using fMRI. Despite similar memory performance, HF and LF youth displayed a number of differences in memory-related and default mode (DMN) brain regions during encoding later remembered versus forgotten word pairs. Specifically, HF youth displayed robust deactivation in DMN areas, including the ventral medial PFC and posterior cingulate cortex, whereas LF youth did not show this pattern. Furthermore, LF youth showed greater bilateral hippocampal and right superior frontal gyrus activation during encoding of later remembered versus forgotten word pairs. Follow-up task-dependent functional correlational analyses showed differences in hippocampus and DMN activity coupling during successful encoding between the groups, suggesting aerobic fitness during adolescents may impact functional connectivity of the hippocampus and DMN during memory encoding. To our knowledge, this study is the first to examine the influence of aerobic fitness on hippocampal function and memory-related neural circuitry using fMRI. Taken together with previous research, these findings suggest aerobic fitness can influence not only memory-related brain structure, but also brain function. PMID:23249350

Early remodeling of the neocortex upon episodic memory encoding

PubMed Central

Bero, Adam W.; Meng, Jia; Cho, Sukhee; Shen, Abra H.; Canter, Rebecca G.; Ericsson, Maria; Tsai, Li-Huei

2014-01-01

Understanding the mechanisms by which long-term memories are formed and stored in the brain represents a central aim of neuroscience. Prevailing theory suggests that long-term memory encoding involves early plasticity within hippocampal circuits, whereas reorganization of the neocortex is thought to occur weeks to months later to subserve remote memory storage. Here we report that long-term memory encoding can elicit early transcriptional, structural, and functional remodeling of the neocortex. Parallel studies using genome-wide RNA sequencing, ultrastructural imaging, and whole-cell recording in wild-type mice suggest that contextual fear conditioning initiates a transcriptional program in the medial prefrontal cortex (mPFC) that is accompanied by rapid expansion of the synaptic active zone and postsynaptic density, enhanced dendritic spine plasticity, and increased synaptic efficacy. To address the real-time contribution of the mPFC to long-term memory encoding, we performed temporally precise optogenetic inhibition of excitatory mPFC neurons during contextual fear conditioning. Using this approach, we found that real-time inhibition of the mPFC inhibited activation of the entorhinal–hippocampal circuit and impaired the formation of long-term associative memory. These findings suggest that encoding of long-term episodic memory is associated with early remodeling of neocortical circuits, identify the prefrontal cortex as a critical regulator of encoding-induced hippocampal activation and long-term memory formation, and have important implications for understanding memory processing in healthy and diseased brain states. PMID:25071187

The relationship between level of processing and hippocampal-cortical functional connectivity during episodic memory formation in humans.

PubMed

Schott, Björn H; Wüstenberg, Torsten; Wimber, Maria; Fenker, Daniela B; Zierhut, Kathrin C; Seidenbecher, Constanze I; Heinze, Hans-Jochen; Walter, Henrik; Düzel, Emrah; Richardson-Klavehn, Alan

2013-02-01

New episodic memory traces represent a record of the ongoing neocortical processing engaged during memory formation (encoding). Thus, during encoding, deep (semantic) processing typically establishes more distinctive and retrievable memory traces than does shallow (perceptual) processing, as assessed by later episodic memory tests. By contrast, the hippocampus appears to play a processing-independent role in encoding, because hippocampal lesions impair encoding regardless of level of processing. Here, we clarified the neural relationship between processing and encoding by examining hippocampal-cortical connectivity during deep and shallow encoding. Participants studied words during functional magnetic resonance imaging and freely recalled these words after distraction. Deep study processing led to better recall than shallow study processing. For both levels of processing, successful encoding elicited activations of bilateral hippocampus and left prefrontal cortex, and increased functional connectivity between left hippocampus and bilateral medial prefrontal, cingulate and extrastriate cortices. Successful encoding during deep processing was additionally associated with increased functional connectivity between left hippocampus and bilateral ventrolateral prefrontal cortex and right temporoparietal junction. In the shallow encoding condition, on the other hand, pronounced functional connectivity increases were observed between the right hippocampus and the frontoparietal attention network activated during shallow study processing. Our results further specify how the hippocampus coordinates recording of ongoing neocortical activity into long-term memory, and begin to provide a neural explanation for the typical advantage of deep over shallow study processing for later episodic memory. Copyright © 2011 Wiley Periodicals, Inc.

Encoding processes during retrieval tasks.

PubMed

Buckner, R L; Wheeler, M E; Sheridan, M A

2001-04-01

Episodic memory encoding is pervasive across many kinds of task and often arises as a secondary processing effect in tasks that do not require intentional memorization. To illustrate the pervasive nature of information processing that leads to episodic encoding, a form of incidental encoding was explored based on the "Testing" phenomenon: The incidental-encoding task was an episodic memory retrieval task. Behavioral data showed that performing a memory retrieval task was as effective as intentional instructions at promoting episodic encoding. During fMRI imaging, subjects viewed old and new words and indicated whether they remembered them. Relevant to encoding, the fate of the new words was examined using a second, surprise test of recognition after the imaging session. fMRI analysis of those new words that were later remembered revealed greater activity in left frontal regions than those that were later forgotten - the same pattern of results as previously observed for traditional incidental and intentional episodic encoding tasks. This finding may offer a partial explanation for why repeated testing improves memory performance. Furthermore, the observation of correlates of episodic memory encoding during retrieval tasks challenges some interpretations that arise from direct comparisons between "encoding tasks" and "retrieval tasks" in imaging data. Encoding processes and their neural correlates may arise in many tasks, even those nominally labeled as retrieval tasks by the experimenter.

Complementary-encoding holographic associative memory using a photorefractive crystal

NASA Astrophysics Data System (ADS)

Yuan, ShiFu; Wu, Minxian; Yan, Yingbai; Jin, Guofan

1996-06-01

We present a holographic implementation of accurate associative memory with only one holographic memory system. In the implementation, the stored and test images are coded by using complementary-encoding method. The recalled complete image is also a coded image that can be decoded with a decoding mask to get an original image or its complement image. The experiment shows that the complementary encoding can efficiently increase the addressing accuracy in a simple way. Instead of the above complementary-encoding method, a scheme that uses complementary area-encoding method is also proposed for the holographic implementation of gray-level image associative memory with accurate addressing.

Influence of encoding focus and stereotypes on source monitoring event-related-potentials.

PubMed

Leynes, P Andrew; Nagovsky, Irina

2016-01-01

Source memory, memory for the origin of a memory, can be influenced by stereotypes and the information of focus during encoding processes. Participants studied words from two different speakers (male or female) using self-focus or other-focus encoding. Source judgments for the speaker׳s voice and Event-Related Potentials (ERPs) were recorded during test. Self-focus encoding increased dependence on stereotype information and the Late Posterior Negativity (LPN). The results link the LPN with an increase in systematic decision processes such as consulting prior knowledge to support an episodic memory judgment. In addition, other-focus encoding increased conditional source judgments and resulted in weaker old/new recognition relative to the self-focus encoding. The putative correlate of recollection (LPC) was absent during this condition and this was taken as evidence that recollection of partial information supported source judgments. Collectively, the results suggest that other-focus encoding changes source monitoring processing by altering the weight of specific memory features. Copyright © 2015 Elsevier B.V. All rights reserved.

Do transactive memory and participative teamwork improve nurses' quality of work life?

PubMed

Brunault, Paul; Fouquereau, Evelyne; Colombat, Philippe; Gillet, Nicolas; El-Hage, Wissam; Camus, Vincent; Gaillard, Philippe

2014-03-01

Improvement in nurses' quality of work life (QWL) has become a major issue in health care organizations. We hypothesized that the level of transactive memory (defined as the way groups collectively encode, store, and retrieve knowledge) and participative teamwork (an organizational model of care based on vocational training, a specific service's care project, and regular interdisciplinary staffing) positively affect nurses' QWL. This cross-sectional study enrolled 84 ward-based psychiatric nurses. We assessed transactive memory, participative teamwork, perceived organizational justice, perceived organizational support, and QWL using psychometrically reliable and valid scales. Participative teamwork and transactive memory were positively associated with nurses' QWL. Perceived organizational support and organizational justice fully mediated the relationship between participative teamwork and QWL, but not between transactive memory and QWL. Improved transactive memory could directly improve nurses' QWL. Improved participative teamwork could improve nurses' QWL through better perceived organizational support and perceived organizational justice.

Similar patterns of neural activity predict memory function during encoding and retrieval.

PubMed

Kragel, James E; Ezzyat, Youssef; Sperling, Michael R; Gorniak, Richard; Worrell, Gregory A; Berry, Brent M; Inman, Cory; Lin, Jui-Jui; Davis, Kathryn A; Das, Sandhitsu R; Stein, Joel M; Jobst, Barbara C; Zaghloul, Kareem A; Sheth, Sameer A; Rizzuto, Daniel S; Kahana, Michael J

2017-07-15

Neural networks that span the medial temporal lobe (MTL), prefrontal cortex, and posterior cortical regions are essential to episodic memory function in humans. Encoding and retrieval are supported by the engagement of both distinct neural pathways across the cortex and common structures within the medial temporal lobes. However, the degree to which memory performance can be determined by neural processing that is common to encoding and retrieval remains to be determined. To identify neural signatures of successful memory function, we administered a delayed free-recall task to 187 neurosurgical patients implanted with subdural or intraparenchymal depth electrodes. We developed multivariate classifiers to identify patterns of spectral power across the brain that independently predicted successful episodic encoding and retrieval. During encoding and retrieval, patterns of increased high frequency activity in prefrontal, MTL, and inferior parietal cortices, accompanied by widespread decreases in low frequency power across the brain predicted successful memory function. Using a cross-decoding approach, we demonstrate the ability to predict memory function across distinct phases of the free-recall task. Furthermore, we demonstrate that classifiers that combine information from both encoding and retrieval states can outperform task-independent models. These findings suggest that the engagement of a core memory network during either encoding or retrieval shapes the ability to remember the past, despite distinct neural interactions that facilitate encoding and retrieval. Copyright © 2017 Elsevier Inc. All rights reserved.

Common capacity-limited neural mechanisms of selective attention and spatial working memory encoding

PubMed Central

Fusser, Fabian; Linden, David E J; Rahm, Benjamin; Hampel, Harald; Haenschel, Corinna; Mayer, Jutta S

2011-01-01

One characteristic feature of visual working memory (WM) is its limited capacity, and selective attention has been implicated as limiting factor. A possible reason why attention constrains the number of items that can be encoded into WM is that the two processes share limited neural resources. Functional magnetic resonance imaging (fMRI) studies have indeed demonstrated commonalities between the neural substrates of WM and attention. Here we investigated whether such overlapping activations reflect interacting neural mechanisms that could result in capacity limitations. To independently manipulate the demands on attention and WM encoding within one single task, we combined visual search and delayed discrimination of spatial locations. Participants were presented with a search array and performed easy or difficult visual search in order to encode one, three or five positions of target items into WM. Our fMRI data revealed colocalised activation for attention-demanding visual search and WM encoding in distributed posterior and frontal regions. However, further analysis yielded two patterns of results. Activity in prefrontal regions increased additively with increased demands on WM and attention, indicating regional overlap without functional interaction. Conversely, the WM load-dependent activation in visual, parietal and premotor regions was severely reduced during high attentional demand. We interpret this interaction as indicating the sites of shared capacity-limited neural resources. Our findings point to differential contributions of prefrontal and posterior regions to the common neural mechanisms that support spatial WM encoding and attention, providing new imaging evidence for attention-based models of WM encoding. PMID:21781193

Subthalamic nucleus deep brain stimulation affects distractor interference in auditory working memory.

PubMed

Camalier, Corrie R; Wang, Alice Y; McIntosh, Lindsey G; Park, Sohee; Neimat, Joseph S

2017-03-01

Computational and theoretical accounts hypothesize the basal ganglia play a supramodal "gating" role in the maintenance of working memory representations, especially in preservation from distractor interference. There are currently two major limitations to this account. The first is that supporting experiments have focused exclusively on the visuospatial domain, leaving questions as to whether such "gating" is domain-specific. The second is that current evidence relies on correlational measures, as it is extremely difficult to causally and reversibly manipulate subcortical structures in humans. To address these shortcomings, we examined non-spatial, auditory working memory performance during reversible modulation of the basal ganglia, an approach afforded by deep brain stimulation of the subthalamic nucleus. We found that subthalamic nucleus stimulation impaired auditory working memory performance, specifically in the group tested in the presence of distractors, even though the distractors were predictable and completely irrelevant to the encoding of the task stimuli. This study provides key causal evidence that the basal ganglia act as a supramodal filter in working memory processes, further adding to our growing understanding of their role in cognition. Copyright © 2017 Elsevier Ltd. All rights reserved.

The removal of information from working memory.

PubMed

Lewis-Peacock, Jarrod A; Kessler, Yoav; Oberauer, Klaus

2018-05-09

What happens to goal-relevant information in working memory after it is no longer needed? Here, we review evidence for a selective removal process that operates on outdated information to limit working memory load and hence facilitates the maintenance of goal-relevant information. Removal alters the representations of irrelevant content so as to reduce access to it, thereby improving access to the remaining relevant content and also facilitating the encoding of new information. Both behavioral and neural evidence support the existence of a removal process that is separate from forgetting due to decay or interference. We discuss the potential mechanisms involved in removal and characterize the time course and duration of the process. In doing so, we propose the existence of two forms of removal: one is temporary, and reversible, which modifies working memory content without impacting content-to-context bindings, and another is permanent, which unbinds the content from its context in working memory (without necessarily impacting long-term forgetting). Finally, we discuss limitations on removal and prescribe conditions for evaluating evidence for or against this process. © 2018 New York Academy of Sciences.

The cortical basis of true memory and false memory for motion.

PubMed

Karanian, Jessica M; Slotnick, Scott D

2014-02-01

Behavioral evidence indicates that false memory, like true memory, can be rich in sensory detail. By contrast, there is fMRI evidence that true memory for visual information produces greater activity in earlier visual regions than false memory, which suggests true memory is associated with greater sensory detail. However, false memory in previous fMRI paradigms may have lacked sufficient sensory detail to recruit earlier visual processing regions. To investigate this possibility in the present fMRI study, we employed a paradigm that produced feature-specific false memory with a high degree of visual detail. During the encoding phase, moving or stationary abstract shapes were presented to the left or right of fixation. During the retrieval phase, shapes from encoding were presented at fixation and participants classified each item as previously "moving" or "stationary" within each visual field. Consistent with previous fMRI findings, true memory but not false memory for motion activated motion processing region MT+, while both true memory and false memory activated later cortical processing regions. In addition, false memory but not true memory for motion activated language processing regions. The present findings indicate that true memory activates earlier visual regions to a greater degree than false memory, even under conditions of detailed retrieval. Thus, the dissociation between previous behavioral findings and fMRI findings do not appear to be task dependent. Future work will be needed to assess whether the same pattern of true memory and false memory activity is observed for different sensory modalities. Copyright © 2013 Elsevier Ltd. All rights reserved.

Direct Electrical Stimulation of the Human Entorhinal Region and Hippocampus Impairs Memory.

PubMed

Jacobs, Joshua; Miller, Jonathan; Lee, Sang Ah; Coffey, Tom; Watrous, Andrew J; Sperling, Michael R; Sharan, Ashwini; Worrell, Gregory; Berry, Brent; Lega, Bradley; Jobst, Barbara C; Davis, Kathryn; Gross, Robert E; Sheth, Sameer A; Ezzyat, Youssef; Das, Sandhitsu R; Stein, Joel; Gorniak, Richard; Kahana, Michael J; Rizzuto, Daniel S

2016-12-07

Deep brain stimulation (DBS) has shown promise for treating a range of brain disorders and neurological conditions. One recent study showed that DBS in the entorhinal region improved the accuracy of human spatial memory. Based on this line of work, we performed a series of experiments to more fully characterize the effects of DBS in the medial temporal lobe on human memory. Neurosurgical patients with implanted electrodes performed spatial and verbal-episodic memory tasks. During the encoding periods of both tasks, subjects received electrical stimulation at 50 Hz. In contrast to earlier work, electrical stimulation impaired memory performance significantly in both spatial and verbal tasks. Stimulation in both the entorhinal region and hippocampus caused decreased memory performance. These findings indicate that the entorhinal region and hippocampus are causally involved in human memory and suggest that refined methods are needed to use DBS in these regions to improve memory. Copyright © 2016 Elsevier Inc. All rights reserved.

A New Conceptualization of Human Visual Sensory-Memory

PubMed Central

Öğmen, Haluk; Herzog, Michael H.

2016-01-01

Memory is an essential component of cognition and disorders of memory have significant individual and societal costs. The Atkinson–Shiffrin “modal model” forms the foundation of our understanding of human memory. It consists of three stores: Sensory Memory (SM), whose visual component is called iconic memory, Short-Term Memory (STM; also called working memory, WM), and Long-Term Memory (LTM). Since its inception, shortcomings of all three components of the modal model have been identified. While the theories of STM and LTM underwent significant modifications to address these shortcomings, models of the iconic memory remained largely unchanged: A high capacity but rapidly decaying store whose contents are encoded in retinotopic coordinates, i.e., according to how the stimulus is projected on the retina. The fundamental shortcoming of iconic memory models is that, because contents are encoded in retinotopic coordinates, the iconic memory cannot hold any useful information under normal viewing conditions when objects or the subject are in motion. Hence, half-century after its formulation, it remains an unresolved problem whether and how the first stage of the modal model serves any useful function and how subsequent stages of the modal model receive inputs from the environment. Here, we propose a new conceptualization of human visual sensory memory by introducing an additional component whose reference-frame consists of motion-grouping based coordinates rather than retinotopic coordinates. We review data supporting this new model and discuss how it offers solutions to the paradoxes of the traditional model of sensory memory. PMID:27375519

A New Conceptualization of Human Visual Sensory-Memory.

PubMed

Öğmen, Haluk; Herzog, Michael H

2016-01-01

Memory is an essential component of cognition and disorders of memory have significant individual and societal costs. The Atkinson-Shiffrin "modal model" forms the foundation of our understanding of human memory. It consists of three stores: Sensory Memory (SM), whose visual component is called iconic memory, Short-Term Memory (STM; also called working memory, WM), and Long-Term Memory (LTM). Since its inception, shortcomings of all three components of the modal model have been identified. While the theories of STM and LTM underwent significant modifications to address these shortcomings, models of the iconic memory remained largely unchanged: A high capacity but rapidly decaying store whose contents are encoded in retinotopic coordinates, i.e., according to how the stimulus is projected on the retina. The fundamental shortcoming of iconic memory models is that, because contents are encoded in retinotopic coordinates, the iconic memory cannot hold any useful information under normal viewing conditions when objects or the subject are in motion. Hence, half-century after its formulation, it remains an unresolved problem whether and how the first stage of the modal model serves any useful function and how subsequent stages of the modal model receive inputs from the environment. Here, we propose a new conceptualization of human visual sensory memory by introducing an additional component whose reference-frame consists of motion-grouping based coordinates rather than retinotopic coordinates. We review data supporting this new model and discuss how it offers solutions to the paradoxes of the traditional model of sensory memory.

Brain oscillatory subsequent memory effects differ in power and long-range synchronization between semantic and survival processing.

PubMed

Fellner, Marie-Christin; Bäuml, Karl-Heinz T; Hanslmayr, Simon

2013-10-01

Memory crucially depends on the way information is processed during encoding. Differences in processes during encoding not only lead to differences in memory performance but also rely on different brain networks. Although these assumptions are corroborated by several previous fMRI and ERP studies, little is known about how brain oscillations dissociate between different memory encoding tasks. The present study therefore compared encoding related brain oscillatory activity elicited by two very efficient encoding tasks: a typical deep semantic item feature judgment task and a more elaborative survival encoding task. Subjects were asked to judge words either for survival relevance or for animacy, as indicated by a cue presented prior to the item. This allowed dissociating pre-item activity from item-related activity for both tasks. Replicating prior studies, survival processing led to higher recognition performance than semantic processing. Successful encoding in the semantic condition was reflected by a strong decrease in alpha and beta power, whereas successful encoding in the survival condition was related to increased alpha and beta long-range phase synchrony. Moreover, a pre-item subsequent memory effect in theta power was found which did not vary with encoding condition. These results show that measures of local synchrony (power) and global long range-synchrony (phase synchronization) dissociate between memory encoding processes. Whereas semantic encoding was reflected in decreases in local synchrony, increases in global long range synchrony were related to elaborative survival encoding, presumably reflecting the involvement of a more widespread cortical network in this task. Copyright © 2013 Elsevier Inc. All rights reserved.

Amygdala activity at encoding corresponds with memory vividness and with memory for select episodic details.

PubMed

Kensinger, Elizabeth A; Addis, Donna Rose; Atapattu, Ranga K

2011-03-01

It is well known that amygdala activity during encoding corresponds with subsequent memory for emotional information. It is less clear how amygdala activity relates to the subjective and objective qualities of a memory. In the present study, participants viewed emotional and neutral objects while undergoing a functional magnetic resonance imaging scan. Participants then took a memory test, identifying which verbal labels named a studied object and indicating the vividness of their memory for that object. They then retrieved episodic details associated with each object's presentation, selecting which object exemplar had been studied and indicating in which screen quadrant, study list, and with which encoding question the exemplar had been studied. Parametric analysis of the encoding data allowed examination of the processes that tracked with increasing memory vividness or with an increase in the diversity of episodic details remembered. Dissociable networks tracked these two increases, and amygdala activity corresponded with the former but not the latter. Subsequent-memory analyses revealed that amygdala activity corresponded with memory for exemplar type but not for other episodic features. These results emphasize that amygdala activity does not ensure accurate encoding of all types of episodic detail, yet it does support encoding of some item-specific details and leads to the retention of a memory that will feel subjectively vivid. The types of episodic details tied to amygdala engagement may be those that are most important for creating a subjectively vivid memory. Copyright © 2011 Elsevier Ltd. All rights reserved.

Amygdala Activity at Encoding Corresponds with Memory Vividness and with Memory for Select Episodic Details

PubMed Central

Kensinger, Elizabeth A.; Addis, Donna Rose; Atapattu, Ranga K.

2011-01-01

It is well known that amygdala activity during encoding corresponds with subsequent memory for emotional information. It is less clear how amygdala activity relates to the subjective and objective qualities of a memory. In the present study, participants viewed emotional and neutral objects while undergoing a functional magnetic resonance imaging scan. Participants then took a memory test, identifying which verbal labels named a studied object and indicating the vividness of their memory for that object. They then retrieved episodic details associated with each object’s presentation, selecting which object exemplar had been studied and indicating in which screen quadrant, study list, and with which encoding question the exemplar had been studied. Parametric analysis of the encoding data allowed examination of the processes that tracked with increasing memory vividness or with an increase in the diversity of episodic details remembered. Dissociable networks tracked these two increases, and amygdala activity corresponded with the former but not the latter. Subsequent-memory analyses revealed that amygdala activity corresponded with memory for exemplar type but not for other episodic features. These results emphasize that amygdala activity does not ensure accurate encoding of all types of episodic detail, yet it does support encoding of some item-specific details and leads to the retention of a memory that will feel subjectively vivid. The types of episodic details tied to amygdala engagement may be those that are most important for creating a subjectively vivid memory. PMID:21262244

An Approach toward the Development of a Functional Encoding Model of Short Term Memory during Reading.

ERIC Educational Resources Information Center

Herndon, Mary Anne

1978-01-01

In a model of the functioning of short term memory, the encoding of information for subsequent storage in long term memory is simulated. In the encoding process, semantically equivalent paragraphs are detected for recombination into a macro information unit. (HOD)

Modulating the focus of attention for spoken words at encoding affects frontoparietal activation for incidental verbal memory.

PubMed

Christensen, Thomas A; Almryde, Kyle R; Fidler, Lesley J; Lockwood, Julie L; Antonucci, Sharon M; Plante, Elena

2012-01-01

Attention is crucial for encoding information into memory, and current dual-process models seek to explain the roles of attention in both recollection memory and incidental-perceptual memory processes. The present study combined an incidental memory paradigm with event-related functional MRI to examine the effect of attention at encoding on the subsequent neural activation associated with unintended perceptual memory for spoken words. At encoding, we systematically varied attention levels as listeners heard a list of single English nouns. We then presented these words again in the context of a recognition task and assessed the effect of modulating attention at encoding on the BOLD responses to words that were either attended strongly, weakly, or not heard previously. MRI revealed activity in right-lateralized inferior parietal and prefrontal regions, and positive BOLD signals varied with the relative level of attention present at encoding. Temporal analysis of hemodynamic responses further showed that the time course of BOLD activity was modulated differentially by unintentionally encoded words compared to novel items. Our findings largely support current models of memory consolidation and retrieval, but they also provide fresh evidence for hemispheric differences and functional subdivisions in right frontoparietal attention networks that help shape auditory episodic recall.

Modulating the Focus of Attention for Spoken Words at Encoding Affects Frontoparietal Activation for Incidental Verbal Memory

PubMed Central

Christensen, Thomas A.; Almryde, Kyle R.; Fidler, Lesley J.; Lockwood, Julie L.; Antonucci, Sharon M.; Plante, Elena

2012-01-01

Attention is crucial for encoding information into memory, and current dual-process models seek to explain the roles of attention in both recollection memory and incidental-perceptual memory processes. The present study combined an incidental memory paradigm with event-related functional MRI to examine the effect of attention at encoding on the subsequent neural activation associated with unintended perceptual memory for spoken words. At encoding, we systematically varied attention levels as listeners heard a list of single English nouns. We then presented these words again in the context of a recognition task and assessed the effect of modulating attention at encoding on the BOLD responses to words that were either attended strongly, weakly, or not heard previously. MRI revealed activity in right-lateralized inferior parietal and prefrontal regions, and positive BOLD signals varied with the relative level of attention present at encoding. Temporal analysis of hemodynamic responses further showed that the time course of BOLD activity was modulated differentially by unintentionally encoded words compared to novel items. Our findings largely support current models of memory consolidation and retrieval, but they also provide fresh evidence for hemispheric differences and functional subdivisions in right frontoparietal attention networks that help shape auditory episodic recall. PMID:22144982

Posterior parietal cortex and episodic encoding: insights from fMRI subsequent memory effects and dual-attention theory.

PubMed

Uncapher, Melina R; Wagner, Anthony D

2009-02-01

The formation of episodic memories--memories for life events--is affected by attention during event processing. A leading neurobiological model of attention posits two separate yet interacting systems that depend on distinct regions in lateral posterior parietal cortex (PPC). From this dual-attention perspective, dorsal PPC is thought to support the goal-directed allocation of attention, whereas ventral PPC is thought to support reflexive orienting to information that automatically captures attention. To advance understanding of how parietal mechanisms may impact event encoding, we review functional MRI studies that document the relationship between lateral PPC activation during encoding and subsequent memory performance (e.g., later remembering or forgetting). This review reveals that (a) encoding-related activity is frequently observed in human lateral PPC, (b) increased activation in dorsal PPC is associated with later memory success, and (c) increased activation in ventral PPC predominantly correlates with later memory failure. From a dual-attention perspective, these findings suggest that allocating goal-directed attention during event processing increases the probability that the event will be remembered later, whereas the capture of reflexive attention during event processing may have negative consequences for event encoding. The prevalence of encoding-related activation in parietal cortex suggests that neurobiological models of episodic memory should consider how parietal-mediated attentional mechanisms regulate encoding.

Visual perception as retrospective Bayesian decoding from high- to low-level features.

PubMed

Ding, Stephanie; Cueva, Christopher J; Tsodyks, Misha; Qian, Ning

2017-10-24

When a stimulus is presented, its encoding is known to progress from low- to high-level features. How these features are decoded to produce perception is less clear, and most models assume that decoding follows the same low- to high-level hierarchy of encoding. There are also theories arguing for global precedence, reversed hierarchy, or bidirectional processing, but they are descriptive without quantitative comparison with human perception. Moreover, observers often inspect different parts of a scene sequentially to form overall perception, suggesting that perceptual decoding requires working memory, yet few models consider how working-memory properties may affect decoding hierarchy. We probed decoding hierarchy by comparing absolute judgments of single orientations and relative/ordinal judgments between two sequentially presented orientations. We found that lower-level, absolute judgments failed to account for higher-level, relative/ordinal judgments. However, when ordinal judgment was used to retrospectively decode memory representations of absolute orientations, striking aspects of absolute judgments, including the correlation and forward/backward aftereffects between two reported orientations in a trial, were explained. We propose that the brain prioritizes decoding of higher-level features because they are more behaviorally relevant, and more invariant and categorical, and thus easier to specify and maintain in noisy working memory, and that more reliable higher-level decoding constrains less reliable lower-level decoding. Published under the PNAS license.

Linking working memory and long-term memory: a computational model of the learning of new words.

PubMed

Jones, Gary; Gobet, Fernand; Pine, Julian M

2007-11-01

The nonword repetition (NWR) test has been shown to be a good predictor of children's vocabulary size. NWR performance has been explained using phonological working memory, which is seen as a critical component in the learning of new words. However, no detailed specification of the link between phonological working memory and long-term memory (LTM) has been proposed. In this paper, we present a computational model of children's vocabulary acquisition (EPAM-VOC) that specifies how phonological working memory and LTM interact. The model learns phoneme sequences, which are stored in LTM and mediate how much information can be held in working memory. The model's behaviour is compared with that of children in a new study of NWR, conducted in order to ensure the same nonword stimuli and methodology across ages. EPAM-VOC shows a pattern of results similar to that of children: performance is better for shorter nonwords and for wordlike nonwords, and performance improves with age. EPAM-VOC also simulates the superior performance for single consonant nonwords over clustered consonant nonwords found in previous NWR studies. EPAM-VOC provides a simple and elegant computational account of some of the key processes involved in the learning of new words: it specifies how phonological working memory and LTM interact; makes testable predictions; and suggests that developmental changes in NWR performance may reflect differences in the amount of information that has been encoded in LTM rather than developmental changes in working memory capacity.

A neural measure of precision in visual working memory.

PubMed

Ester, Edward F; Anderson, David E; Serences, John T; Awh, Edward

2013-05-01

Recent studies suggest that the temporary storage of visual detail in working memory is mediated by sensory recruitment or sustained patterns of stimulus-specific activation within feature-selective regions of visual cortex. According to a strong version of this hypothesis, the relative "quality" of these patterns should determine the clarity of an individual's memory. Here, we provide a direct test of this claim. We used fMRI and a forward encoding model to characterize population-level orientation-selective responses in visual cortex while human participants held an oriented grating in memory. This analysis, which enables a precise quantitative description of multivoxel, population-level activity measured during working memory storage, revealed graded response profiles whose amplitudes were greatest for the remembered orientation and fell monotonically as the angular distance from this orientation increased. Moreover, interparticipant differences in the dispersion-but not the amplitude-of these response profiles were strongly correlated with performance on a concurrent memory recall task. These findings provide important new evidence linking the precision of sustained population-level responses in visual cortex and memory acuity.

Interactions among emotional attention, encoding, and retrieval of ambiguous information: An eye-tracking study.

PubMed

Everaert, Jonas; Koster, Ernst H W

2015-10-01

Emotional biases in attention modulate encoding of emotional material into long-term memory, but little is known about the role of such attentional biases during emotional memory retrieval. The present study investigated how emotional biases in memory are related to attentional allocation during retrieval. Forty-nine individuals encoded emotionally positive and negative meanings derived from ambiguous information and then searched their memory for encoded meanings in response to a set of retrieval cues. The remember/know/new procedure was used to classify memories as recollection-based or familiarity-based, and gaze behavior was monitored throughout the task to measure attentional allocation. We found that a bias in sustained attention during recollection-based, but not familiarity-based, retrieval predicted subsequent memory bias toward positive versus negative material following encoding. Thus, during emotional memory retrieval, attention affects controlled forms of retrieval (i.e., recollection) but does not modulate relatively automatic, familiarity-based retrieval. These findings enhance understanding of how distinct components of attention regulate the emotional content of memories. Implications for theoretical models and emotion regulation are discussed. (c) 2015 APA, all rights reserved).

Odor Memory and Discrimination Covary as a Function of Delay between Encoding and Recall in Rats.

PubMed

Hackett, Chelsea; Choi, Christina; O'Brien, Brenna; Shin, Philip; Linster, Christiane

2015-06-01

Nonassociative odor learning paradigms are often used to assess memory, social recognition and neuromodulation of olfactory pathways. We here use a modified object recognition paradigm to investigate how an important task parameter, delay between encoding and recall trials, affects the properties of this memory. We show that both memory for a previously investigated odorant and discrimination of a novel odorant decay with delay time and that rats can remember an odorant for up to 45min after a single trial encoding event. The number of odorants that can be encoded, as well as the specificity of the encoded memory, decrease with increased delay and also depend on stimulus concentration. Memory for an odorant and discrimination of a novel odorant decay at approximately the same rate, whereas the specificity of the formed memory decays faster than the memory itself. These results have important implications for the interpretation of behavioral data obtained with this paradigm. © The Author 2015. Published by Oxford University Press. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.

Phonological and Visual Similarity Effects in Chinese and English Language Users: Implications for the Use of Cognitive Resources in Short-Term Memory

ERIC Educational Resources Information Center

Cole, Rachel L.; Pickering, Susan J.

2010-01-01

This study investigated the encoding strategies employed by Chinese and English language users when recalling sequences of pictured objects. The working memory performance of native English participants (n = 14) and Chinese speakers of English as a second language (Chinese ESL; n = 14) was compared using serial recall of visually-presented…

Network analysis of brain activations in working memory: behavior and age relationships.

PubMed

Mencl, W E; Pugh, K R; Shaywitz, S E; Shaywitz, B A; Fulbright, R K; Constable, R T; Skudlarski, P; Katz, L; Marchione, K E; Lacadie, C; Gore, J C

2000-10-01

Forty-six middle-aged female subjects were scanned using functional Magnetic Resonance Imaging (fMRI) during performance of three distinct stages of a working memory task-encoding, rehearsal, and recognition-for both printed pseudowords and visual forms. An expanse of areas, involving the inferior frontal, parietal, and extrastriate cortex, was active in response to stimuli during both the encoding and recognition periods. Additional increases during memory recognition were seen in right prefrontal regions, replicating a now-common finding [for reviews, see Fletcher et al. (1997) Trends Neurosci 20:213-218; MacLeod et al. (1998) NeuroImage 7:41-48], and broadly supporting the Hemispheric Encoding/Retrieval Asymmetry hypothesis [Tulving et al. (1994) Proc Natl Acad Sci USA 91:2016-2020]. Notably, this asymmetry was not qualified by the type of material being processed. A few sites demonstrated higher activity levels during the rehearsal period, in the absence of any new stimuli, including the medial extrastriate, precuneus, and the medial temporal lobe. Further analyses examined relationships among subjects' brain activations, age, and behavioral scores on working memory tests, acquired outside the scanner. Correlations between brain scores and behavior scores indicated that activations in a number of areas, mainly frontal, were associated with performance. A multivariate analysis, Partial Least Squares [McIntosh et al. (1996) NeuroImage 3:143-157, (1997) Hum Brain Map 5:323-327], was then used to extract component effects from this large set of univariate correlations. Results indicated that better memory performance outside the scanner was associated with higher activity at specific sites within the frontal and, additionally, the medial temporal lobes. Analysis of age effects revealed that younger subjects tended to activate more than older subjects in areas of extrastriate cortex, medial frontal cortex, and the right medial temporal lobe; older subjects tended to activate more than younger subjects in the insular cortex, right inferior temporal lobe, and right inferior frontal gyrus. These results extend recent reports indicating that these regions are specifically involved in the memory impairments seen with aging. Copyright 2000 Wiley-Liss, Inc.

Collaborative encoding and memory accuracy: examining the effects of interactive components of co-construction processes.

PubMed

Foley, Mary Ann; Fried, Adina Rachel; Cowan, Emily; Bays, Rebecca Brooke

2014-01-01

In 2 experiments, the effect of collaborative encoding on memory was examined by testing 2 interactive components of co-construction processes. One component focused on the nature of the interactive exchange between collaborators: As the partners worked together to create descriptions about ways to interact with familiar objects, constraints were imposed on the interactions by requiring them to take turns (Experiment 1) or to interact without constraints (Experiment 2). The nature of the relationship between partners was manipulated as well by including 2 pair types, friends or unfamiliar peers (Experiments 1 and 2). Interactive component effects were found to influence spontaneous activations through content analyses of participants' descriptions, the patterns of false recognition errors, and the relationship between content and errors. The findings highlight the value of examining the content of participants' collaborative efforts when assessing the effects of collaborative encoding on memory and point to mechanisms mediating collaboration's effects. Because the interactions occurred within the context of an imagery generation task, the findings are also intriguing because of their implications for the use of guided imagery techniques that incorporate co-construction processes.

Walking through doorways causes forgetting: Further explorations.

PubMed

Radvansky, Gabriel A; Krawietz, Sabine A; Tamplin, Andrea K

2011-08-01

Previous research using virtual environments has revealed a location-updating effect in which there is a decline in memory when people move from one location to another. Here we assess whether this effect reflects the influence of the experienced context, in terms of the degree of immersion of a person in an environment, as suggested by some work in spatial cognition, or by a shift in context. In Experiment 1, the degree of immersion was reduced by using smaller displays. In comparison, in Experiment 2 an actual, rather than a virtual, environment was used, to maximize immersion. Location-updating effects were observed under both of these conditions. In Experiment 3, the original encoding context was reinstated by having a person return to the original room in which objects were first encoded. However, inconsistent with an encoding specificity account, memory did not improve by reinstating this context. Finally, we did a further analysis of the results of this and previous experiments to assess the differential influence of foregrounding and retrieval interference. Overall, these data are interpreted in terms of the event horizon model of event cognition and memory.

Neurogenesis-mediated forgetting minimizes proactive interference.

PubMed

Epp, Jonathan R; Silva Mera, Rudy; Köhler, Stefan; Josselyn, Sheena A; Frankland, Paul W

2016-02-26

Established memories may interfere with the encoding of new memories, particularly when existing and new memories overlap in content. By manipulating levels of hippocampal neurogenesis, here we show that neurogenesis regulates this form of proactive interference. Increasing hippocampal neurogenesis weakens existing memories and, in doing so, facilitates the encoding of new, conflicting (but not non-conflicting) information in mice. Conversely, decreasing neurogenesis stabilizes existing memories, and impedes the encoding of new, conflicting information. These results suggest that reduced proactive interference is an adaptive benefit of neurogenesis-induced forgetting.

A role for CA3 in social recognition memory.

PubMed

Chiang, Ming-Ching; Huang, Arthur J Y; Wintzer, Marie E; Ohshima, Toshio; McHugh, Thomas J

2018-02-02

Social recognition memory is crucial for survival across species, underlying the need to correctly identify conspecifics, mates and potential enemies. In humans the hippocampus is engaged in social and episodic memory, however the circuit mechanisms of social memory in rodent models has only recently come under scrutiny. Work in mice has established that the dorsal CA2 and ventral CA1 regions play critical roles, however a more comprehensive comparative analyses of the circuits and mechanisms required has not been reported. Here we employ conditional genetics to examine the differential contributions of the hippocampal subfields to social memory. We find that the deletion of NMDA receptor subunit 1 gene (NR1), which abolishes NMDA receptor synaptic plasticity, in CA3 pyramidal cells led to deficits in social memory; however, mice lacking the same gene in DG granule cells performed indistinguishable from controls. Further, we use conditional pharmacogenetic inhibition to demonstrate that activity in ventral, but not dorsal, CA3 is necessary for the encoding of a social memory. These findings demonstrated CA3 pyramidal cell plasticity and transmission contribute to the encoding of social stimuli and help further identify the distinct circuits underlying the role of the hippocampus in social memory. Copyright © 2018 Elsevier B.V. All rights reserved.

Orienting attention in visual working memory requires central capacity: decreased retro-cue effects under dual-task conditions.

PubMed

Janczyk, Markus; Berryhill, Marian E

2014-04-01

The retro-cue effect (RCE) describes superior working memory performance for validly cued stimulus locations long after encoding has ended. Importantly, this happens with delays beyond the range of iconic memory. In general, the RCE is a stable phenomenon that emerges under varied stimulus configurations and timing parameters. We investigated its susceptibility to dual-task interference to determine the attentional requirements at the time point of cue onset and encoding. In Experiment 1, we compared single- with dual-task conditions. In Experiment 2, we borrowed from the psychological refractory period paradigm and compared conditions with high and low (dual-) task overlap. The secondary task was always binary tone discrimination requiring a manual response. Across both experiments, an RCE was found, but it was diminished in magnitude in the critical dual-task conditions. A previous study did not find evidence that sustained attention is required in the interval between cue offset and test. Our results apparently contradict these findings and point to a critical time period around cue onset and briefly thereafter during which attention is required.

Orienting attention in visual working memory requires central capacity: Decreased retro-cue effects under dual-task conditions

PubMed Central

Berryhill, Marian E.

2014-01-01

The retro-cue effect (RCE) describes superior working memory performance for validly cued stimulus locations long after encoding has ended. Importantly, this happens with delays beyond the range of iconic memory. In general, the RCE is a stable phenomenon that emerges under varied stimulus configurations and timing parameters. We investigated its susceptibility to dual-task interference to determine the attentional requirements at the time point of cue onset and encoding. In Experiment 1, we compared single- with dual-task conditions. In Experiment 2, we borrowed from the psychological refractory period paradigm and compared conditions with high and low (dual-) task overlap. The secondary task was always binary tone discrimination requiring amanual response. Across both experiments, an RCE was found, but it was diminished in magnitude in the critical dual-task conditions. A previous study did not find evidence that sustained attention is required in the interval between cue offset and test. Our results apparently contradict these findings and point to a critical time period around cue onset and briefly thereafter during which attention is required. PMID:24452383

Transcranial magnetic stimulation of the left angular gyrus during encoding does not impair associative memory performance.

PubMed

Koen, Joshua D; Thakral, Preston P; Rugg, Michael D

2018-06-05

The left angular gyrus (AG) is thought to play a critical role in episodic retrieval and has been implicated in the recollection of specific details of prior episodes. Motivated by recent fMRI studies in which it was reported that elevated neural activity in left AG during study is predictive of subsequent associative memory, the present study investigated whether the region plays a causal role in associative memory encoding. Participants underwent online transcranial magnetic stimulation (TMS) while encoding word pairs prior to an associative memory test. We predicted that TMS to left AG during encoding would result in reduced subsequent memory accuracy, especially for estimates of recollection. The results did not support this prediction: estimates of both recollection and familiarity-driven recognition were essentially identical for words pairs encoded during TMS to left AG relative to a vertex control site. These results suggest that the left AG may not play a necessary role in associative memory encoding. TMS to left AG did however affect confidence for incorrect 'intact' judgments to rearranged pairs and incorrect 'rearranged' judgments to intact pairs. These findings suggest that the left AG supports encoding processes that contribute to aspects of subjective mnemonic experience.

Reconciling findings of emotion-induced memory enhancement and impairment of preceding items

PubMed Central

Knight, Marisa; Mather, Mara

2009-01-01

A large body of work reveals that people remember emotionally arousing information better than neutral information. However, previous research reveals contradictory effects of emotional events on memory for neutral events that precede or follow them: in some studies emotionally arousing items impair memory for immediately preceding or following items and in others arousing items enhance memory for preceding items. By demonstrating both emotion-induced enhancement and impairment, Experiments 1 and 2 clarified the conditions under which these effects are likely to occur. The results suggest that emotion-induced enhancement is most likely to occur for neutral items that: (1) precede (and so are poised to predict the onset of) emotionally arousing items, (2) have high attentional weights at encoding, and (3) are tested after a delay period of a week rather than within the same experiment session. In contrast, emotion-induced impairment is most likely to occur for neutral items near the onset of emotional arousal that are overshadowed by highly activated competing items during encoding. PMID:20001121

Visual short-term memory for oriented, colored objects.

PubMed

Shin, Hongsup; Ma, Wei Ji

2017-08-01

A central question in the study of visual short-term memory (VSTM) has been whether its basic units are objects or features. Most studies addressing this question have used change detection tasks in which the feature value before the change is highly discriminable from the feature value after the change. This approach assumes that memory noise is negligible, which recent work has shown not to be the case. Here, we investigate VSTM for orientation and color within a noisy-memory framework, using change localization with a variable magnitude of change. A specific consequence of the noise is that it is necessary to model the inference (decision) stage. We find that (a) orientation and color have independent pools of memory resource (consistent with classic results); (b) an irrelevant feature dimension is either encoded but ignored during decision-making, or encoded with low precision and taken into account during decision-making; and (c) total resource available in a given feature dimension is lower in the presence of task-relevant stimuli that are neutral in that feature dimension. We propose a framework in which feature resource comes both in packaged and in targeted form.

Directed Forgetting and Directed Remembering in Visual Working Memory

PubMed Central

Williams, Melonie; Woodman, Geoffrey F.

2013-01-01

A defining characteristic of visual working memory is its limited capacity. This means that it is crucial to maintain only the most relevant information in visual working memory. However, empirical research is mixed as to whether it is possible to selectively maintain a subset of the information previously encoded into visual working memory. Here we examined the ability of subjects to use cues to either forget or remember a subset of the information already stored in visual working memory. In Experiment 1, participants were cued to either forget or remember one of two groups of colored squares during a change-detection task. We found that both types of cues aided performance in the visual working memory task, but that observers benefited more from a cue to remember than a cue to forget a subset of the objects. In Experiment 2, we show that the previous findings, which indicated that directed-forgetting cues are ineffective, were likely due to the presence of invalid cues that appear to cause observers to disregard such cues as unreliable. In Experiment 3, we recorded event-related potentials (ERPs) and show that an electrophysiological index of focused maintenance is elicited by cues that indicate which subset of information in visual working memory needs to be remembered, ruling out alternative explanations of the behavioral effects of retention-interval cues. The present findings demonstrate that observers can focus maintenance mechanisms on specific objects in visual working memory based on cues indicating future task relevance. PMID:22409182

Recognition memory strength is predicted by pupillary responses at encoding while fixation patterns distinguish recollection from familiarity.

PubMed

Kafkas, Alexandros; Montaldi, Daniela

2011-10-01

Thirty-five healthy participants incidentally encoded a set of man-made and natural object pictures, while their pupil response and eye movements were recorded. At retrieval, studied and new stimuli were rated as novel, familiar (strong, moderate, or weak), or recollected. We found that both pupil response and fixation patterns at encoding predict later recognition memory strength. The extent of pupillary response accompanying incidental encoding was found to be predictive of subsequent memory. In addition, the number of fixations was also predictive of later recognition memory strength, suggesting that the accumulation of greater visual detail, even for single objects, is critical for the creation of a strong memory. Moreover, fixation patterns at encoding distinguished between recollection and familiarity at retrieval, with more dispersed fixations predicting familiarity and more clustered fixations predicting recollection. These data reveal close links between the autonomic control of pupil responses and eye movement patterns on the one hand and memory encoding on the other. Moreover, the data illustrate quantitative as well as qualitative differences in the incidental visual processing of stimuli, which are differentially predictive of the strength and the kind of memory experienced at recognition.

Goal-directed mechanisms that constrain retrieval predict subsequent memory for new "foil" information.

PubMed

Vogelsang, David A; Bonnici, Heidi M; Bergström, Zara M; Ranganath, Charan; Simons, Jon S

2016-08-01

To remember a previous event, it is often helpful to use goal-directed control processes to constrain what comes to mind during retrieval. Behavioral studies have demonstrated that incidental learning of new "foil" words in a recognition test is superior if the participant is trying to remember studied items that were semantically encoded compared to items that were non-semantically encoded. Here, we applied subsequent memory analysis to fMRI data to understand the neural mechanisms underlying the "foil effect". Participants encoded information during deep semantic and shallow non-semantic tasks and were tested in a subsequent blocked memory task to examine how orienting retrieval towards different types of information influences the incidental encoding of new words presented as foils during the memory test phase. To assess memory for foils, participants performed a further surprise old/new recognition test involving foil words that were encountered during the previous memory test blocks as well as completely new words. Subsequent memory effects, distinguishing successful versus unsuccessful incidental encoding of foils, were observed in regions that included the left inferior frontal gyrus and posterior parietal cortex. The left inferior frontal gyrus exhibited disproportionately larger subsequent memory effects for semantic than non-semantic foils, and significant overlap in activity during semantic, but not non-semantic, initial encoding and foil encoding. The results suggest that orienting retrieval towards different types of foils involves re-implementing the neurocognitive processes that were involved during initial encoding. Copyright © 2016 The Authors. Published by Elsevier Ltd.. All rights reserved.

Dissociative detachment and memory impairment: reversible amnesia or encoding failure?

PubMed

Allen, J G; Console, D A; Lewis, L

1999-01-01

The authors propose that clinicians endeavor to differentiate between reversible and irreversible memory failures in patients with dissociative symptoms who report "memory gaps" and "lost time." The classic dissociative disorders, such as dissociative amnesia and dissociative identity disorder, entail reversible memory failures associated with encoding experience in altered states. The authors propose another realm of memory failures associated with severe dissociative detachment that may preclude the level of encoding of ongoing experience needed to support durable autobiographical memories. They describe how dissociative detachment may be intertwined with neurobiological factors that impair memory, and they spell out the significance of distinguishing reversible and irreversible memory impairment for diagnosis, patient education, psychotherapy, and research.

Time-dependent effects of cortisol on the contextualization of emotional memories.

PubMed

van Ast, Vanessa A; Cornelisse, Sandra; Meeter, Martijn; Joëls, Marian; Kindt, Merel

2013-12-01

The inability to store fearful memories into their original encoding context is considered to be an important vulnerability factor for the development of anxiety disorders like posttraumatic stress disorder. Altered memory contextualization most likely involves effects of the stress hormone cortisol, acting via receptors located in the memory neurocircuitry. Cortisol via these receptors induces rapid nongenomic effects followed by slower genomic effects, which are thought to modulate cognitive function in opposite, complementary ways. Here, we targeted these time-dependent effects of cortisol during memory encoding and tested subsequent contextualization of emotional and neutral memories. In a double-blind, placebo-controlled design, 64 men were randomly assigned to one of three groups: 1) received 10 mg hydrocortisone 30 minutes (rapid cortisol effects) before a memory encoding task; 2) received 10 mg hydrocortisone 210 minutes (slow cortisol) before a memory encoding task; or 3) received placebo at both times. During encoding, participants were presented with neutral and emotional words in unique background pictures. Approximately 24 hours later, context dependency of their memories was assessed. Recognition data revealed that cortisol's rapid effects impair emotional memory contextualization, while cortisol's slow effects enhance it. Neutral memory contextualization remained unaltered by cortisol, irrespective of the timing of the drug. This study shows distinct time-dependent effects of cortisol on the contextualization of specifically emotional memories. The results suggest that rapid effects of cortisol may lead to impaired emotional memory contextualization, while slow effects of cortisol may confer protection against emotional memory generalization. © 2013 Society of Biological Psychiatry.

Encoding-related brain activity during deep processing of verbal materials: a PET study.

PubMed

Fujii, Toshikatsu; Okuda, Jiro; Tsukiura, Takashi; Ohtake, Hiroya; Suzuki, Maki; Kawashima, Ryuta; Itoh, Masatoshi; Fukuda, Hiroshi; Yamadori, Atsushi

2002-12-01

The recent advent of neuroimaging techniques provides an opportunity to examine brain regions related to a specific memory process such as episodic memory encoding. There is, however, a possibility that areas active during an assumed episodic memory encoding task, compared with a control task, involve not only areas directly relevant to episodic memory encoding processes but also areas associated with other cognitive processes for on-line information. We used positron emission tomography (PET) to differentiate these two kinds of regions. Normal volunteers were engaged in deep (semantic) or shallow (phonological) processing of new or repeated words during PET. Results showed that deep processing, compared with shallow processing, resulted in significantly better recognition performance and that this effect was associated with activation of various brain areas. Further analyses revealed that there were regions directly relevant to episodic memory encoding in the anterior part of the parahippocampal gyrus, inferior frontal gyrus, supramarginal gyrus, anterior cingulate gyrus, and medial frontal lobe in the left hemisphere. Our results demonstrated that several regions, including the medial temporal lobe, play a role in episodic memory encoding.

THE COGNITIVE NEUROSCIENCE OF WORKING MEMORY

PubMed Central

D’Esposito, Mark; Postle, Bradley R.

2015-01-01

For over 50 years, psychologists and neuroscientists have recognized the importance of a “working memory” to coordinate processing when multiple goals are active, and to guide behavior with information that is not present in the immediate environment. In recent years, psychological theory and cognitive neuroscience data have converged on the idea that information is encoded into working memory via the allocation of attention to internal representations – be they semantic long-term memory (e.g., letters, digits, words), sensory, or motoric. Thus, information-based multivariate analyses of human functional MRI data typically find evidence for the temporary representation of stimuli in regions that also process this information in nonworking-memory contexts. The prefrontal cortex, on the other hand, exerts control over behavior by biasing the salience of mnemonic representations, and adjudicating among competing, context-dependent rules. The “control of the controller” emerges from a complex interplay between PFC and striatal circuits, and ascending dopaminergic neuromodulatory signals. PMID:25251486

Flexibility in Visual Working Memory: Accurate Change Detection in the Face of Irrelevant Variations in Position

PubMed Central

Woodman, Geoffrey F.; Vogel, Edward K.; Luck, Steven J.

2012-01-01

Many recent studies of visual working memory have used change-detection tasks in which subjects view sequential displays and are asked to report whether they are identical or if one object has changed. A key question is whether the memory system used to perform this task is sufficiently flexible to detect changes in object identity independent of spatial transformations, but previous research has yielded contradictory results. To address this issue, the present study compared standard change-detection tasks with tasks in which the objects varied in size or position between successive arrays. Performance was nearly identical across the standard and transformed tasks unless the task implicitly encouraged spatial encoding. These results resolve the discrepancies in prior studies and demonstrate that the visual working memory system can detect changes in object identity across spatial transformations. PMID:22287933

Association of auditory-verbal and visual hallucinations with impaired and improved recognition of colored pictures.

PubMed

Brébion, Gildas; Stephan-Otto, Christian; Usall, Judith; Huerta-Ramos, Elena; Perez del Olmo, Mireia; Cuevas-Esteban, Jorge; Haro, Josep Maria; Ochoa, Susana

2015-09-01

A number of cognitive underpinnings of auditory hallucinations have been established in schizophrenia patients, but few have, as yet, been uncovered for visual hallucinations. In previous research, we unexpectedly observed that auditory hallucinations were associated with poor recognition of color, but not black-and-white (b/w), pictures. In this study, we attempted to replicate and explain this finding. Potential associations with visual hallucinations were explored. B/w and color pictures were presented to 50 schizophrenia patients and 45 healthy individuals under 2 conditions of visual context presentation corresponding to 2 levels of visual encoding complexity. Then, participants had to recognize the target pictures among distractors. Auditory-verbal hallucinations were inversely associated with the recognition of the color pictures presented under the most effortful encoding condition. This association was fully mediated by working-memory span. Visual hallucinations were associated with improved recognition of the color pictures presented under the less effortful condition. Patients suffering from visual hallucinations were not impaired, relative to the healthy participants, in the recognition of these pictures. Decreased working-memory span in patients with auditory-verbal hallucinations might impede the effortful encoding of stimuli. Visual hallucinations might be associated with facilitation in the visual encoding of natural scenes, or with enhanced color perception abilities. (c) 2015 APA, all rights reserved).

The effects of aging on ERP correlates of source memory retrieval for self-referential information.

PubMed

Dulas, Michael R; Newsome, Rachel N; Duarte, Audrey

2011-03-04

Numerous behavioral studies have suggested that normal aging negatively affects source memory accuracy for various kinds of associations. Neuroimaging evidence suggests that less efficient retrieval processing (temporally delayed and attenuated) may contribute to these impairments. Previous aging studies have not compared source memory accuracy and corresponding neural activity for different kinds of source details; namely, those that have been encoded via a more or less effective strategy. Thus, it is not yet known whether encoding source details in a self-referential manner, a strategy suggested to promote successful memory in the young and old, may enhance source memory accuracy and reduce the commonly observed age-related changes in neural activity associated with source memory retrieval. Here, we investigated these issues by using event-related potentials (ERPs) to measure the effects of aging on the neural correlates of successful source memory retrieval ("old-new effects") for objects encoded either self-referentially or self-externally. Behavioral results showed that both young and older adults demonstrated better source memory accuracy for objects encoded self-referentially. ERP results showed that old-new effects onsetted earlier for self-referentially encoded items in both groups and that age-related differences in the onset latency of these effects were reduced for self-referentially, compared to self-externally, encoded items. These results suggest that the implementation of an effective encoding strategy, like self-referential processing, may lead to more efficient retrieval, which in turn may improve source memory accuracy in both young and older adults. Published by Elsevier B.V.

About Sleep's Role in Memory

PubMed Central

2013-01-01

Over more than a century of research has established the fact that sleep benefits the retention of memory. In this review we aim to comprehensively cover the field of “sleep and memory” research by providing a historical perspective on concepts and a discussion of more recent key findings. Whereas initial theories posed a passive role for sleep enhancing memories by protecting them from interfering stimuli, current theories highlight an active role for sleep in which memories undergo a process of system consolidation during sleep. Whereas older research concentrated on the role of rapid-eye-movement (REM) sleep, recent work has revealed the importance of slow-wave sleep (SWS) for memory consolidation and also enlightened some of the underlying electrophysiological, neurochemical, and genetic mechanisms, as well as developmental aspects in these processes. Specifically, newer findings characterize sleep as a brain state optimizing memory consolidation, in opposition to the waking brain being optimized for encoding of memories. Consolidation originates from reactivation of recently encoded neuronal memory representations, which occur during SWS and transform respective representations for integration into long-term memory. Ensuing REM sleep may stabilize transformed memories. While elaborated with respect to hippocampus-dependent memories, the concept of an active redistribution of memory representations from networks serving as temporary store into long-term stores might hold also for non-hippocampus-dependent memory, and even for nonneuronal, i.e., immunological memories, giving rise to the idea that the offline consolidation of memory during sleep represents a principle of long-term memory formation established in quite different physiological systems. PMID:23589831

Short-Term and Working Memory Impairments in Early-Implanted, Long-Term Cochlear Implant Users Are Independent of Audibility and Speech Production

PubMed Central

AuBuchon, Angela M.; Pisoni, David B.; Kronenberger, William G.

2015-01-01

OBJECTIVES Determine if early-implanted, long-term cochlear implant (CI) users display delays in verbal short-term and working memory capacity when processes related to audibility and speech production are eliminated. DESIGN Twenty-three long-term CI users and 23 normal-hearing controls each completed forward and backward digit span tasks under testing conditions which differed in presentation modality (auditory or visual) and response output (spoken recall or manual pointing). RESULTS Normal-hearing controls reproduced more lists of digits than the CI users, even when the test items were presented visually and the responses were made manually via touchscreen response. CONCLUSIONS Short-term and working memory delays observed in CI users are not due to greater demands from peripheral sensory processes such as audibility or from overt speech-motor planning and response output organization. Instead, CI users are less efficient at encoding and maintaining phonological representations in verbal short-term memory utilizing phonological and linguistic strategies during memory tasks. PMID:26496666

Short-Term and Working Memory Impairments in Early-Implanted, Long-Term Cochlear Implant Users Are Independent of Audibility and Speech Production.

PubMed

AuBuchon, Angela M; Pisoni, David B; Kronenberger, William G

2015-01-01

To determine whether early-implanted, long-term cochlear implant (CI) users display delays in verbal short-term and working memory capacity when processes related to audibility and speech production are eliminated. Twenty-three long-term CI users and 23 normal-hearing controls each completed forward and backward digit span tasks under testing conditions that differed in presentation modality (auditory or visual) and response output (spoken recall or manual pointing). Normal-hearing controls reproduced more lists of digits than the CI users, even when the test items were presented visually and the responses were made manually via touchscreen response. Short-term and working memory delays observed in CI users are not due to greater demands from peripheral sensory processes such as audibility or from overt speech-motor planning and response output organization. Instead, CI users are less efficient at encoding and maintaining phonological representations in verbal short-term memory using phonological and linguistic strategies during memory tasks.

Temporal texture of associative encoding modulates recall processes.

PubMed

Tibon, Roni; Levy, Daniel A

2014-02-01

Binding aspects of an experience that are distributed over time is an important element of episodic memory. In the current study, we examined how the temporal complexity of an experience may govern the processes required for its retrieval. We recorded event-related potentials during episodic cued recall following pair associate learning of concurrently and sequentially presented object-picture pairs. Cued recall success effects over anterior and posterior areas were apparent in several time windows. In anterior locations, these recall success effects were similar for concurrently and sequentially encoded pairs. However, in posterior sites clustered over parietal scalp the effect was larger for the retrieval of sequentially encoded pairs. We suggest that anterior aspects of the mid-latency recall success effects may reflect working-with-memory operations or direct access recall processes, while more posterior aspects reflect recollective processes which are required for retrieval of episodes of greater temporal complexity. Copyright © 2013 Elsevier Inc. All rights reserved.

The Effects of Acute Stress on Episodic Memory: A Meta-Analysis and Integrative Review

PubMed Central

Shields, Grant S.; Sazma, Matthew A.; McCullough, Andrew M.; Yonelinas, Andrew P.

2017-01-01

A growing body of research has indicated that acute stress can critically impact memory. However, there are a number of inconsistencies in the literature, and important questions remain regarding the conditions under which stress effects emerge as well as basic questions about how stress impacts different phases of memory. In this meta-analysis, we examined 113 independent studies in humans with 6,216 participants that explored effects of stress on encoding, post-encoding, retrieval, or post-reactivation phases of episodic memory. The results indicated that when stress occurred prior to or during encoding it impaired memory, unless both the delay between the stressor and encoding was very short and the study materials were directly related to the stressor, in which case stress improved encoding. In contrast, post-encoding stress improved memory unless the stressor occurred in a different physical context than the study materials. When stress occurred just prior to or during retrieval, memory was impaired, and these effects were larger for emotionally valenced materials than neutral materials. Although stress consistently increased cortisol, the magnitude of the cortisol response was not related to the effects of stress on memory. Nonetheless, the effects of stress on memory were generally reduced in magnitude for women taking hormonal contraceptives. These analyses indicate that stress disrupts some episodic memory processes while enhancing others, and that the effects of stress are modulated by a number of critical factors. These results provide important constraints on current theories of stress and memory, and point to new questions for future research. PMID:28368148

Implicit Memory in Music and Language

PubMed Central

Ettlinger, Marc; Margulis, Elizabeth H.; Wong, Patrick C. M.

2011-01-01

Research on music and language in recent decades has focused on their overlapping neurophysiological, perceptual, and cognitive underpinnings, ranging from the mechanism for encoding basic auditory cues to the mechanism for detecting violations in phrase structure. These overlaps have most often been identified in musicians with musical knowledge that was acquired explicitly, through formal training. In this paper, we review independent bodies of work in music and language that suggest an important role for implicitly acquired knowledge, implicit memory, and their associated neural structures in the acquisition of linguistic or musical grammar. These findings motivate potential new work that examines music and language comparatively in the context of the implicit memory system. PMID:21927608

When fear forms memories: threat of shock and brain potentials during encoding and recognition.

PubMed

Weymar, Mathias; Bradley, Margaret M; Hamm, Alfons O; Lang, Peter J

2013-03-01

The anticipation of highly aversive events is associated with measurable defensive activation, and both animal and human research suggests that stress-inducing contexts can facilitate memory. Here, we investigated whether encoding stimuli in the context of anticipating an aversive shock affects recognition memory. Event-related potentials (ERPs) were measured during a recognition test for words that were encoded in a font color that signaled threat or safety. At encoding, cues signaling threat of shock, compared to safety, prompted enhanced P2 and P3 components. Correct recognition of words encoded in the context of threat, compared to safety, was associated with an enhanced old-new ERP difference (500-700 msec; centro-parietal), and this difference was most reliable for emotional words. Moreover, larger old-new ERP differences when recognizing emotional words encoded in a threatening context were associated with better recognition, compared to words encoded in safety. Taken together, the data indicate enhanced memory for stimuli encoded in a context in which an aversive event is merely anticipated, which could assist in understanding effects of anxiety and stress on memory processes. Copyright © 2012 Elsevier Ltd. All rights reserved.

Neural activity in the hippocampus and perirhinal cortex during encoding is associated with the durability of episodic memory.

PubMed

Carr, Valerie A; Viskontas, Indre V; Engel, Stephen A; Knowlton, Barbara J

2010-11-01

Studies examining medial temporal lobe (MTL) involvement in memory formation typically assess memory performance after a single, short delay. Thus, the relationship between MTL encoding activity and memory durability over time remains poorly characterized. To explore this relationship, we scanned participants using high-resolution functional imaging of the MTL as they encoded object pairs; using the remember/know paradigm, we then assessed memory performance for studied items both 10 min and 1 week later. Encoding trials were classified as either subsequently recollected across both delays, transiently recollected (i.e., recollected at 10 min but not after 1 week), consistently familiar, or consistently forgotten. Activity in perirhinal cortex (PRC) and a hippocampal subfield comprising the dentate gyrus and CA fields 2 and 3 reflected successful encoding only when items were recollected consistently across both delays. Furthermore, in PRC, encoding activity for items that later were consistently recollected was significantly greater than that for transiently recollected and consistently familiar items. Parahippocampal cortex, in contrast, showed a subsequent memory effect during encoding of items that were recollected after 10 min, regardless of whether they also were recollected after 1 week. These data suggest that MTL subfields contribute uniquely to the formation of memories that endure over time, and highlight a role for PRC in supporting subsequent durable episodic recollection.

Music improves verbal memory encoding while decreasing prefrontal cortex activity: an fNIRS study.

PubMed

Ferreri, Laura; Aucouturier, Jean-Julien; Muthalib, Makii; Bigand, Emmanuel; Bugaiska, Aurelia

2013-01-01

Listening to music engages the whole brain, thus stimulating cognitive performance in a range of non-purely musical activities such as language and memory tasks. This article addresses an ongoing debate on the link between music and memory for words. While evidence on healthy and clinical populations suggests that music listening can improve verbal memory in a variety of situations, it is still unclear what specific memory process is affected and how. This study was designed to explore the hypothesis that music specifically benefits the encoding part of verbal memory tasks, by providing a richer context for encoding and therefore less demand on the dorsolateral prefrontal cortex (DLPFC). Twenty-two healthy young adults were subjected to functional near-infrared spectroscopy (fNIRS) imaging of their bilateral DLPFC while encoding words in the presence of either a music or a silent background. Behavioral data confirmed the facilitating effect of music background during encoding on subsequent item recognition. fNIRS results revealed significantly greater activation of the left hemisphere during encoding (in line with the HERA model of memory lateralization) and a sustained, bilateral decrease of activity in the DLPFC in the music condition compared to silence. These findings suggest that music modulates the role played by the DLPFC during verbal encoding, and open perspectives for applications to clinical populations with prefrontal impairments, such as elderly adults or Alzheimer's patients.

Posterior Parietal Cortex and Episodic Encoding: Insights from fMRI Subsequent Memory Effects and Dual Attention Theory

PubMed Central

Uncapher, Melina; Wagner, Anthony D.

2010-01-01

The formation of episodic memories –– memories for life events –– is affected by attention during event processing. A leading neurobiological model of attention posits two separate yet interacting systems that depend on distinct regions in lateral posterior parietal cortex (PPC). From this dual-attention perspective, dorsal PPC is thought to support the goal-directed allocation of attention, whereas ventral PPC is thought to support reflexive orienting to information that automatically captures attention. To advance understanding of how parietal mechanisms may impact event encoding, we review functional MRI studies that document the relationship between lateral PPC activation during encoding and subsequent memory performance (e.g., later remembering or forgetting). This review reveals that (a) encoding-related activity is frequently observed in human lateral PPC, (b) increased activation in dorsal PPC is associated with later memory success, and (c) increased activation in ventral PPC predominantly correlates with later memory failure. From a dual-attention perspective, these findings suggest that allocating goal-directed attention during event processing increases the probability that the event will be remembered later, whereas the capture of reflexive attention during event processing may have negative consequences for event encoding. The prevalence of encoding-related activation in parietal cortex suggests that neurobiological models of episodic memory should consider how parietal-mediated attentional mechanisms regulate encoding. PMID:19028591

Music improves verbal memory encoding while decreasing prefrontal cortex activity: an fNIRS study

PubMed Central

Ferreri, Laura; Aucouturier, Jean-Julien; Muthalib, Makii; Bigand, Emmanuel; Bugaiska, Aurelia

2013-01-01

Listening to music engages the whole brain, thus stimulating cognitive performance in a range of non-purely musical activities such as language and memory tasks. This article addresses an ongoing debate on the link between music and memory for words. While evidence on healthy and clinical populations suggests that music listening can improve verbal memory in a variety of situations, it is still unclear what specific memory process is affected and how. This study was designed to explore the hypothesis that music specifically benefits the encoding part of verbal memory tasks, by providing a richer context for encoding and therefore less demand on the dorsolateral prefrontal cortex (DLPFC). Twenty-two healthy young adults were subjected to functional near-infrared spectroscopy (fNIRS) imaging of their bilateral DLPFC while encoding words in the presence of either a music or a silent background. Behavioral data confirmed the facilitating effect of music background during encoding on subsequent item recognition. fNIRS results revealed significantly greater activation of the left hemisphere during encoding (in line with the HERA model of memory lateralization) and a sustained, bilateral decrease of activity in the DLPFC in the music condition compared to silence. These findings suggest that music modulates the role played by the DLPFC during verbal encoding, and open perspectives for applications to clinical populations with prefrontal impairments, such as elderly adults or Alzheimer’s patients. PMID:24339807

Sustaining prospective memory functioning in amnestic mild cognitive impairment: A lifespan approach to the critical role of encoding.

PubMed

Pereira, Antonina; Altgassen, Mareike; Atchison, Lesley; de Mendonça, Alexandre; Ellis, Judi

2018-04-16

Prospective memory (PM), the ability to remember to perform future activities, is a fundamental requirement for independent living. PM tasks pervade our daily lives, and PM failures represent one of the most prominent memory concerns across the entire life span. This study aimed to address this issue by exploring the potential benefits of specific encoding strategies on memory for intentions across healthy adulthood and in the early stages of cognitive impairment. PM performance was explored through an experimental paradigm in 96 participants: 32 amnestic mild cognitively impaired patients aged 64-87 years (M = 6.75, SD = 5.88), 32 healthy older adults aged 62-84 years (M = 76.06, SD = 6.03), and 32 younger adults 18-22 years (M = 19.75, SD = 1.16). The potential benefit of the use of enactment (i.e., physically simulating the intended action) at encoding to support an autonomous performance despite neuronal degeneration was assessed. PM was consistently identified as a sensitive and specific indicator of cognitive impairment. Importantly, enacted encoding was consistently beneficial for PM performance of all the participants, but especially so in the case of healthy and cognitively impaired older adults. These positive results have unveiled the potential of this encoding technique to optimize attentional demands through an adaptive allocation of strategic resources across both healthy and cognitively impaired samples. Theoretical implications of this work are discussed as well as the considerable translational potential to improve social well-being. A better understanding of the strategies that can enhance PM offers the potential for cost-effective and widely applicable tools which may support independent living across the adult life span. (PsycINFO Database Record (c) 2018 APA, all rights reserved).

On the Suitability of Suffix Arrays for Lempel-Ziv Data Compression

NASA Astrophysics Data System (ADS)

Ferreira, Artur J.; Oliveira, Arlindo L.; Figueiredo, Mário A. T.

Lossless compression algorithms of the Lempel-Ziv (LZ) family are widely used nowadays. Regarding time and memory requirements, LZ encoding is much more demanding than decoding. In order to speed up the encoding process, efficient data structures, like suffix trees, have been used. In this paper, we explore the use of suffix arrays to hold the dictionary of the LZ encoder, and propose an algorithm to search over it. We show that the resulting encoder attains roughly the same compression ratios as those based on suffix trees. However, the amount of memory required by the suffix array is fixed, and much lower than the variable amount of memory used by encoders based on suffix trees (which depends on the text to encode). We conclude that suffix arrays, when compared to suffix trees in terms of the trade-off among time, memory, and compression ratio, may be preferable in scenarios (e.g., embedded systems) where memory is at a premium and high speed is not critical.

An overview of the neuro-cognitive processes involved in the encoding, consolidation, and retrieval of true and false memories

PubMed Central

2012-01-01

Perception and memory are imperfect reconstructions of reality. These reconstructions are prone to be influenced by several factors, which may result in false memories. A false memory is the recollection of an event, or details of an episode, that did not actually occur. Memory formation comprises at least three different sub-processes: encoding, consolidation and the retrieval of the learned material. All of these sub-processes are vulnerable for specific errors and consequently may result in false memories. Whereas, processes like imagery, self-referential encoding or spreading activation can lead to the formation of false memories at encoding, semantic generalization during sleep and updating processes due to misleading post event information, in particular, are relevant at the consolidation stage. Finally at the retrieval stage, monitoring processes, which are assumed to be essential to reject false memories, are of specific importance. Different neuro-cognitive processes have been linked to the formation of true and false memories. Most consistently the medial temporal lobe and the medial and lateral prefrontal cortex have been reported with regard to the formation of true and false memories. Despite the fact that all phases entailing memory formation, consolidation of stored information and retrieval processes, are relevant for the forming of false memories, most studies focused on either memory encoding or retrieval. Thus, future studies should try to integrate data from all phases to give a more comprehensive view on systematic memory distortions. An initial outline is developed within this review to connect the different memory stages and research strategies. PMID:22827854

An overview of the neuro-cognitive processes involved in the encoding, consolidation, and retrieval of true and false memories.

PubMed

Straube, Benjamin

2012-07-24

Perception and memory are imperfect reconstructions of reality. These reconstructions are prone to be influenced by several factors, which may result in false memories. A false memory is the recollection of an event, or details of an episode, that did not actually occur. Memory formation comprises at least three different sub-processes: encoding, consolidation and the retrieval of the learned material. All of these sub-processes are vulnerable for specific errors and consequently may result in false memories. Whereas, processes like imagery, self-referential encoding or spreading activation can lead to the formation of false memories at encoding, semantic generalization during sleep and updating processes due to misleading post event information, in particular, are relevant at the consolidation stage. Finally at the retrieval stage, monitoring processes, which are assumed to be essential to reject false memories, are of specific importance. Different neuro-cognitive processes have been linked to the formation of true and false memories. Most consistently the medial temporal lobe and the medial and lateral prefrontal cortex have been reported with regard to the formation of true and false memories. Despite the fact that all phases entailing memory formation, consolidation of stored information and retrieval processes, are relevant for the forming of false memories, most studies focused on either memory encoding or retrieval. Thus, future studies should try to integrate data from all phases to give a more comprehensive view on systematic memory distortions. An initial outline is developed within this review to connect the different memory stages and research strategies.

Neurogenesis-mediated forgetting minimizes proactive interference

PubMed Central

Epp, Jonathan R.; Silva Mera, Rudy; Köhler, Stefan; Josselyn, Sheena A.; Frankland, Paul W.

2016-01-01

Established memories may interfere with the encoding of new memories, particularly when existing and new memories overlap in content. By manipulating levels of hippocampal neurogenesis, here we show that neurogenesis regulates this form of proactive interference. Increasing hippocampal neurogenesis weakens existing memories and, in doing so, facilitates the encoding of new, conflicting (but not non-conflicting) information in mice. Conversely, decreasing neurogenesis stabilizes existing memories, and impedes the encoding of new, conflicting information. These results suggest that reduced proactive interference is an adaptive benefit of neurogenesis-induced forgetting. PMID:26917323

Neural correlates of encoding processes predicting subsequent cued recall and source memory.

PubMed

Angel, Lucie; Isingrini, Michel; Bouazzaoui, Badiâa; Fay, Séverine

2013-03-06

In this experiment, event-related potentials were used to examine whether the neural correlates of encoding processes predicting subsequent successful recall differed from those predicting successful source memory retrieval. During encoding, participants studied lists of words and were instructed to memorize each word and the list in which it occurred. At test, they had to complete stems (the first four letters) with a studied word and then make a judgment of the initial temporal context (i.e. list). Event-related potentials recorded during encoding were segregated according to subsequent memory performance to examine subsequent memory effects (SMEs) reflecting successful cued recall (cued recall SME) and successful source retrieval (source memory SME). Data showed a cued recall SME on parietal electrode sites from 400 to 1200 ms and a late inversed cued recall SME on frontal sites in the 1200-1400 ms period. Moreover, a source memory SME was reported from 400 to 1400 ms on frontal areas. These findings indicate that patterns of encoding-related activity predicting successful recall and source memory are clearly dissociated.

Rest-related consolidation protects the fine detail of new memories.

PubMed

Craig, Michael; Dewar, Michaela

2018-05-01

Newly encoded memories are labile and consolidate over time. The importance of sleep in memory consolidation has been well known for almost a decade. However, recent research has shown that awake quiescence, too, can support consolidation: people remember more new memories if they quietly rest after encoding than if they engage in a task. It is not yet known how exactly this rest-related consolidation benefits new memories, and whether it affects the fine detail of new memories. Using a sensitive picture recognition task, we show that awake quiescence aids the fine detail of new memories. Young adults were significantly better at discriminating recently encoded target pictures from similar lure pictures when the initial encoding of target pictures had been followed immediately by 10 minutes of awake quiescence than an unrelated perceptual task. This novel finding indicates that, in addition to influencing how much we remember, our behavioural state during wakeful consolidation determines, at least in part, the level of fine detail of our new memories. Thus, our results suggest that rest-related consolidation protects the fine detail of new memories, allowing us to retain detailed memories.

Get the gist? The effects of processing depth on false recognition in short-term and long-term memory.

PubMed

Flegal, Kristin E; Reuter-Lorenz, Patricia A

2014-07-01

Gist-based processing has been proposed to account for robust false memories in the converging-associates task. The deep-encoding processes known to enhance verbatim memory also strengthen gist memory and increase distortions of long-term memory (LTM). Recent research has demonstrated that compelling false memory illusions are relatively delay-invariant, also occurring under canonical short-term memory (STM) conditions. To investigate the contributions of gist to false memory at short and long delays, processing depth was manipulated as participants encoded lists of four semantically related words and were probed immediately, following a filled 3- to 4-s retention interval, or approximately 20 min later, in a surprise recognition test. In two experiments, the encoding manipulation dissociated STM and LTM on the frequency, but not the phenomenology, of false memory. Deep encoding at STM increases false recognition rates at LTM, but confidence ratings and remember/know judgments are similar across delays and do not differ as a function of processing depth. These results suggest that some shared and some unique processes underlie false memory illusions at short and long delays.

Interaction between attentional systems and episodic memory encoding: the impact of conflict on binding of information.

PubMed

Sperduti, Marco; Armougum, Allan; Makowski, Dominique; Blondé, Philippe; Piolino, Pascale

2017-12-01

Episodic memory (EM) is defined as a long-term memory system that stores information that can be retrieved along with details of the context of the original events (binding). Several studies have shown that manipulation of attention during encoding can impact subsequent memory performance. An influential model of attention distinguishes between three partially independent attentional networks: the alerting, the orienting and the executive or conflict resolution component. To date, the impact of the engagement of these sub-systems during encoding on item and relational context binding has not been investigated. Here, we developed a new task combining the Attentional Network Test and an incidental episodic memory encoding task to study this issue. We reported that when the alerting network was not solicited, resolving conflict hindered item encoding. Moreover, resolving conflict, independently of the cueing condition, had a negative impact on context binding. These novel findings could have a potential impact in the understanding EM formation, and memory disorders in different populations, including healthy elderly people.

Cingulo-opercular activity affects incidental memory encoding for speech in noise.

PubMed

Vaden, Kenneth I; Teubner-Rhodes, Susan; Ahlstrom, Jayne B; Dubno, Judy R; Eckert, Mark A

2017-08-15

Correctly understood speech in difficult listening conditions is often difficult to remember. A long-standing hypothesis for this observation is that the engagement of cognitive resources to aid speech understanding can limit resources available for memory encoding. This hypothesis is consistent with evidence that speech presented in difficult conditions typically elicits greater activity throughout cingulo-opercular regions of frontal cortex that are proposed to optimize task performance through adaptive control of behavior and tonic attention. However, successful memory encoding of items for delayed recognition memory tasks is consistently associated with increased cingulo-opercular activity when perceptual difficulty is minimized. The current study used a delayed recognition memory task to test competing predictions that memory encoding for words is enhanced or limited by the engagement of cingulo-opercular activity during challenging listening conditions. An fMRI experiment was conducted with twenty healthy adult participants who performed a word identification in noise task that was immediately followed by a delayed recognition memory task. Consistent with previous findings, word identification trials in the poorer signal-to-noise ratio condition were associated with increased cingulo-opercular activity and poorer recognition memory scores on average. However, cingulo-opercular activity decreased for correctly identified words in noise that were not recognized in the delayed memory test. These results suggest that memory encoding in difficult listening conditions is poorer when elevated cingulo-opercular activity is not sustained. Although increased attention to speech when presented in difficult conditions may detract from more active forms of memory maintenance (e.g., sub-vocal rehearsal), we conclude that task performance monitoring and/or elevated tonic attention supports incidental memory encoding in challenging listening conditions. Copyright © 2017 Elsevier Inc. All rights reserved.

Depth, Spread, and Congruence of Encoding in Memory

DTIC Science & Technology

1980-08-01

Alternatively, Craik and Lockhart proposed a more parsimonious frame- work for research based on a levels -of- processing approach. They assumed that the...44. Craik , F. I. M., & Lockhart , R. S. Levels of processing : A framework for memory research. Journal of Verbal Learning and Verbal Behavior, 1972, 11...the basic concepts of the depth-of- processing or domains-of- processing ( Lockhart , Craik , & Jacoby, 1976) framework, suggesting that qualitative

Costs of storing colour and complex shape in visual working memory: Insights from pupil size and slow waves.

PubMed

Kursawe, Michael A; Zimmer, Hubert D

2015-06-01

We investigated the impact of perceptual processing demands on visual working memory of coloured complex random polygons during change detection. Processing load was assessed by pupil size (Exp. 1) and additionally slow wave potentials (Exp. 2). Task difficulty was manipulated by presenting different set sizes (1, 2, 4 items) and by making different features (colour, shape, or both) task-relevant. Memory performance in the colour condition was better than in the shape and both condition which did not differ. Pupil dilation and the posterior N1 increased with set size independent of type of feature. In contrast, slow waves and a posterior P2 component showed set size effects but only if shape was task-relevant. In the colour condition slow waves did not vary with set size. We suggest that pupil size and N1 indicates different states of attentional effort corresponding to the number of presented items. In contrast, slow waves reflect processes related to encoding and maintenance strategies. The observation that their potentials vary with the type of feature (simple colour versus complex shape) indicates that perceptual complexity already influences encoding and storage and not only comparison of targets with memory entries at the moment of testing. Copyright © 2015 Elsevier B.V. All rights reserved.

Left TPJ activity in verbal working memory: implications for storage- and sensory-specific models of short term memory.

PubMed

Ravizza, Susan M; Hazeltine, Eliot; Ruiz, Sandra; Zhu, David C

2011-04-15

Patients with damage to the left temporoparietal junction (TPJ) have a low verbal span without concomitant deficits in speech perception. This pattern of cognitive impairment is taken as evidence for a dedicated phonological buffer that plays little role in perception (storage-specific account). In contrast, other research suggests that items are maintained and perceived in the same regions (sensory-specific account). In an fMRI study, we demonstrate that the left TPJ does not respond in a way predicted of a phonological buffer; that is, activity in this region is not sustained during encoding or maintenance. Instead, a region in the superior temporal gyrus that has been associated with both speech perception and production demonstrated the expected profile of a store: it was more active in the verbal condition than the object condition and was active during both encoding and maintenance. These results support the sensory-specific account of short term memory rather than the storage-specific account. Based on the pattern of activity in the left TPJ, we suggest that the impairment of verbal working memory observed in patients with TPJ damage may be due to diminished attentional processes rather than reduced storage capacity. Copyright © 2010 Elsevier Inc. All rights reserved.

Electrophysiological Evidence for a Sensory Recruitment Model of Somatosensory Working Memory.

PubMed

Katus, Tobias; Grubert, Anna; Eimer, Martin

2015-12-01

Sensory recruitment models of working memory assume that information storage is mediated by the same cortical areas that are responsible for the perceptual processing of sensory signals. To test this assumption, we measured somatosensory event-related brain potentials (ERPs) during a tactile delayed match-to-sample task. Participants memorized a tactile sample set at one task-relevant hand to compare it with a subsequent test set on the same hand. During the retention period, a sustained negativity (tactile contralateral delay activity, tCDA) was elicited over primary somatosensory cortex contralateral to the relevant hand. The amplitude of this component increased with memory load and was sensitive to individual limitations in memory capacity, suggesting that the tCDA reflects the maintenance of tactile information in somatosensory working memory. The tCDA was preceded by a transient negativity (N2cc component) with a similar contralateral scalp distribution, which is likely to reflect selection of task-relevant tactile stimuli at the encoding stage. The temporal sequence of N2cc and tCDA components mirrors previous observations from ERP studies of working memory in vision. The finding that the sustained somatosensory delay period activity varies as a function of memory load supports a sensory recruitment model for spatial working memory in touch. © The Author 2014. Published by Oxford University Press. All rights reserved. For Permissions, please e-mail: journals.permissions@oup.com.

Bidirectional Frontoparietal Oscillatory Systems Support Working Memory.

PubMed

Johnson, Elizabeth L; Dewar, Callum D; Solbakk, Anne-Kristin; Endestad, Tor; Meling, Torstein R; Knight, Robert T

2017-06-19

The ability to represent and select information in working memory provides the neurobiological infrastructure for human cognition. For 80 years, dominant views of working memory have focused on the key role of prefrontal cortex (PFC) [1-8]. However, more recent work has implicated posterior cortical regions [9-12], suggesting that PFC engagement during working memory is dependent on the degree of executive demand. We provide evidence from neurological patients with discrete PFC damage that challenges the dominant models attributing working memory to PFC-dependent systems. We show that neural oscillations, which provide a mechanism for PFC to communicate with posterior cortical regions [13], independently subserve communications both to and from PFC-uncovering parallel oscillatory mechanisms for working memory. Fourteen PFC patients and 20 healthy, age-matched controls performed a working memory task where they encoded, maintained, and actively processed information about pairs of common shapes. In controls, the electroencephalogram (EEG) exhibited oscillatory activity in the low-theta range over PFC and directional connectivity from PFC to parieto-occipital regions commensurate with executive processing demands. Concurrent alpha-beta oscillations were observed over parieto-occipital regions, with directional connectivity from parieto-occipital regions to PFC, regardless of processing demands. Accuracy, PFC low-theta activity, and PFC → parieto-occipital connectivity were attenuated in patients, revealing a PFC-independent, alpha-beta system. The PFC patients still demonstrated task proficiency, which indicates that the posterior alpha-beta system provides sufficient resources for working memory. Taken together, our findings reveal neurologically dissociable PFC and parieto-occipital systems and suggest that parallel, bidirectional oscillatory systems form the basis of working memory. Copyright © 2017 The Authors. Published by Elsevier Ltd.. All rights reserved.

Developmental fMRI study of episodic verbal memory encoding in children.

PubMed

Maril, A; Davis, P E; Koo, J J; Reggev, N; Zuckerman, M; Ehrenfeld, L; Mulkern, R V; Waber, D P; Rivkin, M J

2010-12-07

Understanding the maturation and organization of cognitive function in the brain is a central objective of both child neurology and developmental cognitive neuroscience. This study focuses on episodic memory encoding of verbal information by children, a cognitive domain not previously studied using fMRI. Children from 7 to 19 years of age were scanned at 1.5-T field strength using event-related fMRI while performing a novel verbal memory encoding paradigm in which words were incidentally encoded. A subsequent memory analysis was performed. SPM2 was utilized for whole brain and region-of-interest analyses of data. Both whole-sample intragroup analyses and intergroup analyses of the sample divided into 2 subgroups by age were conducted. Importantly, behavioral memory performance was equal across the age range of children studied. Encoding-related activation in the left hippocampus and bilateral basal ganglia declined as age increased. In addition, while robust blood oxygen level-dependent signal was found in left prefrontal cortex with task performance, no encoding-related age-modulated prefrontal activation was observed in either hemisphere. These data are consistent with a developmental pattern of verbal memory encoding function in which left hippocampal and bilateral basal ganglionic activations are more robust earlier in childhood but then decline with age. No encoding-related activation was found in prefrontal cortex which may relate to this region's recognized delay in biologic maturation in humans. These data represent the first fMRI demonstration of verbal encoding function in children and are relevant developmentally and clinically.

Knowledge cannot explain the developmental growth of working memory capacity.

PubMed

Cowan, Nelson; Ricker, Timothy J; Clark, Katherine M; Hinrichs, Garrett A; Glass, Bret A

2015-01-01

According to some views of cognitive growth, the development of working memory capacity can account for increases in the complexity of cognition. It has been difficult to ascertain, though, that there actually is developmental growth in capacity that cannot be attributed to other developing factors. Here we assess the role of item familiarity. We document developmental increases in working memory for visual arrays of English letters versus unfamiliar characters. Although letter knowledge played a special role in development between the ages of 6 and 8 years, children with adequate letter knowledge showed practically the same developmental growth in normalized functions for letters and unfamiliar characters. The results contribute to a growing body of evidence that the developmental improvement in working memory does not wholly stem from supporting processes such as encoding, mnemonic strategies, and knowledge. A video abstract is available at: https://www.youtube.com/watch?v=LJdqErLR2Hs&feature=youtu.be. © 2014 John Wiley & Sons Ltd.

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.

Attention to Attributes and Objects in Working Memory

PubMed Central

Cowan, Nelson; Blume, Christopher L.; Saults, J. Scott

2013-01-01

It has been debated on the basis of change-detection procedures whether visual working memory is limited by the number of objects, task-relevant attributes within those objects, or bindings between attributes. This debate, however, has been hampered by several limitations, including the use of conditions that vary between studies and the absence of appropriate mathematical models to estimate the number of items in working memory in different stimulus conditions. We re-examined working memory limits in two experiments with a wide array of conditions involving color and shape attributes, relying on a set of new models to fit various stimulus situations. In Experiment 2, a new procedure allowed identical retrieval conditions across different conditions of attention at encoding. The results show that multiple attributes compete for attention, but that retaining the binding between attributes is accomplished only by retaining the attributes themselves. We propose a theoretical account in which a fixed object capacity limit contains within it the possibility of the incomplete retention of object attributes, depending on the direction of attention. PMID:22905929

The Dorsolateral Prefrontal Cortex Plays a Role in Self-Initiated Elaborative Cognitive Processing during Episodic Memory Encoding: rTMS Evidence

PubMed Central

Hawco, Colin; Berlim, Marcelo T.; Lepage, Martin

2013-01-01

During episodic memory encoding, elaborative cognitive processing can improve later recall or recognition. While multiple studies examined the neural correlates of encoding strategies, few studies have explicitly focused on the self-initiation of elaborative encoding. Repetitive transcranial magnetic stimulation (rTMS), a method which can transiently disrupt neural activity, was administered during an associative encoding task. rTMS was either applied to the left dorsolateral prefrontal cortex (DLPFC) or to the vertex (a control region not involved in memory encoding) during presentation of pairs of words. Pairs could be semantically related or not related. Two encoding instructions were given, either cueing participants to analyze semantic relationships (cued condition), or to memorize the pair without any specific strategy cues (the self-initiated condition). Participants filled out a questionnaire regarding their use of memory strategies and performed a cued-recall task. We hypothesized that if the DLPFC plays a role in the self-initiation of elaborative encoding we would observe a reduction in memory performance in the self-initiated condition, particularly for related. We found a significant correlation between the effects of rTMS and strategy use, only in the self-initiated condition with related pairs. High strategy users showed reduced performance following DLPFC stimulation, while low strategy users tended to show increased recall following DLPFC stimulation during encoding. These results suggest the left DLPFC may be involved in the self-initiation of memory strategy use, and individuals may utilize different neural networks depending on their use of encoding strategies. PMID:24040072

Less Effort, Better Results: How Does Music Act on Prefrontal Cortex in Older Adults during Verbal Encoding? An fNIRS Study.

PubMed

Ferreri, Laura; Bigand, Emmanuel; Perrey, Stephane; Muthalib, Makii; Bard, Patrick; Bugaiska, Aurélia

2014-01-01

Several neuroimaging studies of cognitive aging revealed deficits in episodic memory abilities as a result of prefrontal cortex (PFC) limitations. Improving episodic memory performance despite PFC deficits is thus a critical issue in aging research. Listening to music stimulates cognitive performance in several non-purely musical activities (e.g., language and memory). Thus, music could represent a rich and helpful source during verbal encoding and therefore help subsequent retrieval. Furthermore, such benefit could be reflected in less demand of PFC, which is known to be crucial for encoding processes. This study aimed to investigate whether music may improve episodic memory in older adults while decreasing the PFC activity. Sixteen healthy older adults (μ = 64.5 years) encoded lists of words presented with or without a musical background while their dorsolateral prefrontal cortex (DLPFC) activity was monitored using a eight-channel continuous-wave near-infrared spectroscopy (NIRS) system (Oxymon Mk III, Artinis, The Netherlands). Behavioral results indicated a better source-memory performance for words encoded with music compared to words encoded with silence (p < 0.05). Functional NIRS data revealed bilateral decrease of oxyhemoglobin values in the music encoding condition compared to the silence condition (p < 0.05), suggesting that music modulates the activity of the DLPFC during encoding in a less-demanding direction. Taken together, our results indicate that music can help older adults in memory performances by decreasing their PFC activity. These findings open new perspectives about music as tool for episodic memory rehabilitation on special populations with memory deficits due to frontal lobe damage such as Alzheimer's patients.

Less Effort, Better Results: How Does Music Act on Prefrontal Cortex in Older Adults during Verbal Encoding? An fNIRS Study

PubMed Central

Ferreri, Laura; Bigand, Emmanuel; Perrey, Stephane; Muthalib, Makii; Bard, Patrick; Bugaiska, Aurélia

2014-01-01

Several neuroimaging studies of cognitive aging revealed deficits in episodic memory abilities as a result of prefrontal cortex (PFC) limitations. Improving episodic memory performance despite PFC deficits is thus a critical issue in aging research. Listening to music stimulates cognitive performance in several non-purely musical activities (e.g., language and memory). Thus, music could represent a rich and helpful source during verbal encoding and therefore help subsequent retrieval. Furthermore, such benefit could be reflected in less demand of PFC, which is known to be crucial for encoding processes. This study aimed to investigate whether music may improve episodic memory in older adults while decreasing the PFC activity. Sixteen healthy older adults (μ = 64.5 years) encoded lists of words presented with or without a musical background while their dorsolateral prefrontal cortex (DLPFC) activity was monitored using a eight-channel continuous-wave near-infrared spectroscopy (NIRS) system (Oxymon Mk III, Artinis, The Netherlands). Behavioral results indicated a better source-memory performance for words encoded with music compared to words encoded with silence (p < 0.05). Functional NIRS data revealed bilateral decrease of oxyhemoglobin values in the music encoding condition compared to the silence condition (p < 0.05), suggesting that music modulates the activity of the DLPFC during encoding in a less-demanding direction. Taken together, our results indicate that music can help older adults in memory performances by decreasing their PFC activity. These findings open new perspectives about music as tool for episodic memory rehabilitation on special populations with memory deficits due to frontal lobe damage such as Alzheimer’s patients. PMID:24860481

Does working memory load facilitate target detection?

PubMed

Fruchtman-Steinbok, Tom; Kessler, Yoav

2016-02-01

Previous studies demonstrated that increasing working memory (WM) load delays performance of a concurrent task, by distracting attention and thus interfering with encoding and maintenance processes. The present study used a version of the change detection task with a target detection requirement during the retention interval. In contrast to the above prediction, target detection was faster following a larger set-size, specifically when presented shortly after the memory array (up to 400 ms). The effect of set-size on target detection was also evident when no memory retention was required. The set-size effect was also found using different modalities. Moreover, it was only observed when the memory array was presented simultaneously, but not sequentially. These results were explained by increased phasic alertness exerted by the larger visual display. The present study offers new evidence of ongoing attentional processes in the commonly-used change detection paradigm. Copyright © 2015 Elsevier B.V. All rights reserved.

Examining the causes of memory strength variability: Recollection, attention failure, or encoding variability?

PubMed Central

Koen, Joshua D.; Aly, Mariam; Wang, Wei-Chun; Yonelinas, Andrew P.

2013-01-01

A prominent finding in recognition memory is that studied items are associated with more variability in memory strength than new items. Here, we test three competing theories for why this occurs - the encoding variability, attention failure, and recollection accounts. Distinguishing amongst these theories is critical because each provides a fundamentally different account of the processes underlying recognition memory. The encoding variability and attention failure accounts propose that old item variance will be unaffected by retrieval manipulations because the processes producing this effect are ascribed to encoding. The recollection account predicts that both encoding and retrieval manipulations that preferentially affect recollection will affect memory variability. These contrasting predictions were tested by examining the effect of response speeding (Experiment 1), dividing attention at retrieval (Experiment 2), context reinstatement (Experiment 3), and increased test delay (Experiment 4) on recognition performance. The results of all four experiments confirmed the predictions of the recollection account, and were inconsistent with the encoding variability account. The evidence supporting the attention failure account was mixed, with two of the four experiments confirming the account and two disconfirming the account. These results indicate that encoding variability and attention failure are insufficient accounts of memory variance, and provide support for the recollection account. Several alternative theoretical accounts of the results are also considered. PMID:23834057

Memory strength and specificity revealed by pupillometry

PubMed Central

Papesh, Megan H.; Goldinger, Stephen D.; Hout, Michael C.

2011-01-01

Voice-specificity effects in recognition memory were investigated using both behavioral data and pupillometry. Volunteers initially heard spoken words and nonwords in two voices; they later provided confidence-based old/new classifications to items presented in their original voices, changed (but familiar) voices, or entirely new voices. Recognition was more accurate for old-voice items, replicating prior research. Pupillometry was used to gauge cognitive demand during both encoding and testing: Enlarged pupils revealed that participants devoted greater effort to encoding items that were subsequently recognized. Further, pupil responses were sensitive to the cue match between encoding and retrieval voices, as well as memory strength. Strong memories, and those with the closest encoding-retrieval voice matches, resulted in the highest peak pupil diameters. The results are discussed with respect to episodic memory models and Whittlesea’s (1997) SCAPE framework for recognition memory. PMID:22019480

Level of processing modulates the neural correlates of emotional memory formation

PubMed Central

Ritchey, Maureen; LaBar, Kevin S.; Cabeza, Roberto

2010-01-01

Emotion is known to influence multiple aspects of memory formation, including the initial encoding of the memory trace and its consolidation over time. However, the neural mechanisms whereby emotion impacts memory encoding remain largely unexplored. The present study employed a levels-of-processing manipulation to characterize the impact of emotion on encoding with and without the influence of elaborative processes. Participants viewed emotionally negative, neutral, and positive scenes under two conditions: a shallow condition focused on the perceptual features of the scenes and a deep condition that queried their semantic meaning. Recognition memory was tested 2 days later. Results showed that emotional memory enhancements were greatest in the shallow condition. FMRI analyses revealed that the right amygdala predicted subsequent emotional memory in the shallow more than deep condition, whereas the right ventrolateral prefrontal cortex demonstrated the reverse pattern. Furthermore, the association of these regions with the hippocampus was modulated by valence: the amygdala-hippocampal link was strongest for negative stimuli, whereas the prefrontal-hippocampal link was strongest for positive stimuli. Taken together, these results suggest two distinct activation patterns underlying emotional memory formation: an amygdala component that promotes memory during shallow encoding, especially for negative information, and a prefrontal component that provides extra benefits during deep encoding, especially for positive information. PMID:20350176

Level of processing modulates the neural correlates of emotional memory formation.

PubMed

Ritchey, Maureen; LaBar, Kevin S; Cabeza, Roberto

2011-04-01

Emotion is known to influence multiple aspects of memory formation, including the initial encoding of the memory trace and its consolidation over time. However, the neural mechanisms whereby emotion impacts memory encoding remain largely unexplored. The present study used a levels-of-processing manipulation to characterize the impact of emotion on encoding with and without the influence of elaborative processes. Participants viewed emotionally negative, neutral, and positive scenes under two conditions: a shallow condition focused on the perceptual features of the scenes and a deep condition that queried their semantic meaning. Recognition memory was tested 2 days later. Results showed that emotional memory enhancements were greatest in the shallow condition. fMRI analyses revealed that the right amygdala predicted subsequent emotional memory in the shallow more than deep condition, whereas the right ventrolateral PFC demonstrated the reverse pattern. Furthermore, the association of these regions with the hippocampus was modulated by valence: the amygdala-hippocampal link was strongest for negative stimuli, whereas the prefrontal-hippocampal link was strongest for positive stimuli. Taken together, these results suggest two distinct activation patterns underlying emotional memory formation: an amygdala component that promotes memory during shallow encoding, especially for negative information, and a prefrontal component that provides extra benefits during deep encoding, especially for positive information.

Frontotemporal Functional Connectivity and Executive Functions Contribute to Episodic Memory Performance

PubMed Central

Blankenship, Tashauna L.; O'Neill, Meagan; Deater-Deckard, Kirby; Diana, Rachel A.; Bell, Martha Ann

2016-01-01

The contributions of hemispheric-specific electrophysiology (electroencephalogram or EEG) and independent executive functions (inhibitory control, working memory, cognitive flexibility) to episodic memory performance were examined using abstract paintings. Right hemisphere frontotemporal functional connectivity during encoding and retrieval, measured via EEG alpha coherence, statistically predicted performance on recency but not recognition judgments for the abstract paintings. Theta coherence, however, did not predict performance. Likewise, cognitive flexibility statistically predicted performance on recency judgments, but not recognition. These findings suggest that recognition and recency operate via separate electrophysiological and executive mechanisms. PMID:27388478

Cognitive training of self-initiation of semantic encoding strategies in schizophrenia: A pilot study.

PubMed

Guimond, Synthia; Lepage, Martin

2016-01-01

Available cognitive remediation interventions have a significant but relatively small to moderate impact on episodic memory in schizophrenia. The present study aimed to evaluate the efficacy and feasibility of a brief novel episodic memory training targeting the self-initiation of semantic encoding strategies. To select patients with such deficits, 28 participants with schizophrenia performed our Semantic Encoding Memory Task (SEMT) that provides a measure of self-initiated semantic encoding strategies. This task identified a deficit in 13 participants who were then offered two 60-minute training sessions one week apart. After the training, patients performed an alternate version of the SEMT. The CVLT-II (a standardised measure of semantic encoding strategies) and the BVMT-R (a control spatial memory task) were used to quantify memory pre- and post-training. After the training, participants were significantly better at self-initiating semantic encoding strategies in the SEMT (p = .004) and in the CVLT-II (p = .002). No significant differences were found in the BVMT-R. The current study demonstrates that a brief and specific training in memory strategies can help patients to improve a deficient memory process in schizophrenia. Future studies will need to test this intervention further using a randomised controlled trial, and to explore its functional impact.

The path to memory is guided by strategy: distinct networks are engaged in associative encoding under visual and verbal strategy and influence memory performance in healthy and impaired individuals

PubMed Central

Hales, J. B.; Brewer, J. B.

2018-01-01

Given the diversity of stimuli encountered in daily life, a variety of strategies must be used for learning new information. Relating and encoding visual and verbal stimuli into memory has been probed using various tasks and stimulus-types. Engagement of specific subsequent memory and cortical processing regions depends on the stimulus modality of studied material; however, it remains unclear whether different encoding strategies similarly influence regional activity when stimulus-type is held constant. In this study, subjects encoded object pairs using a visual or verbal associative strategy during functional magnetic resonance imaging (fMRI), and subsequent memory was assessed for pairs encoded under each strategy. Each strategy elicited distinct regional processing and subsequent memory effects: middle / superior frontal, lateral parietal, and lateral occipital for visually-associated pairs and inferior frontal, medial frontal, and medial occipital for verbally-associated pairs. This regional selectivity mimics the effects of stimulus modality, suggesting that cortical involvement in associative encoding is driven by strategy, and not simply by stimulus-type. The clinical relevance of these findings, probed in two patients with recent aphasic strokes, suggest that training with strategies utilizing unaffected cortical regions might improve memory ability in patients with brain damage. PMID:22390467

Effects of Age on Negative Subsequent Memory Effects Associated with the Encoding of Item and Item–Context Information

PubMed Central

Mattson, Julia T.; Wang, Tracy H.; de Chastelaine, Marianne; Rugg, Michael D.

2014-01-01

It has consistently been reported that “negative” subsequent memory effects—lower study activity for later remembered than later forgotten items—are attenuated in older individuals. The present functional magnetic resonance imaging study investigated whether these findings extend to subsequent memory effects associated with successful encoding of item–context information. Older (n = 25) and young (n = 17) subjects were scanned while making 1 of 2 encoding judgments on a series of pictures. Memory was assessed for the study item and, for items judged old, the item's encoding task. Both memory judgments were made using confidence ratings, permitting item and source memory strength to be unconfounded and source confidence to be equated across age groups. Replicating prior findings, negative item effects in regions of the default mode network in young subjects were reversed in older subjects. Negative source effects, however, were invariant with respect to age and, in both age groups, the magnitude of the effects correlated with source memory performance. It is concluded that negative item effects do not reflect processes necessary for the successful encoding of item–context associations in older subjects. Negative source effects, in contrast, appear to reflect the engagement of processes that are equally important for successful episodic encoding in older and younger individuals. PMID:23904464

Episodic Short-Term Recognition Requires Encoding into Visual Working Memory: Evidence from Probe Recognition after Letter Report

PubMed Central

Poth, Christian H.; Schneider, Werner X.

2016-01-01

Human vision is organized in discrete processing episodes (e.g., eye fixations or task-steps). Object information must be transmitted across episodes to enable episodic short-term recognition: recognizing whether a current object has been seen in a previous episode. We ask whether episodic short-term recognition presupposes that objects have been encoded into capacity-limited visual working memory (VWM), which retains visual information for report. Alternatively, it could rely on the activation of visual features or categories that occurs before encoding into VWM. We assessed the dependence of episodic short-term recognition on VWM by a new paradigm combining letter report and probe recognition. Participants viewed displays of 10 letters and reported as many as possible after a retention interval (whole report). Next, participants viewed a probe letter and indicated whether it had been one of the 10 letters (probe recognition). In Experiment 1, probe recognition was more accurate for letters that had been encoded into VWM (reported letters) compared with non-encoded letters (non-reported letters). Interestingly, those letters that participants reported in their whole report had been near to one another within the letter displays. This suggests that the encoding into VWM proceeded in a spatially clustered manner. In Experiment 2, participants reported only one of 10 letters (partial report) and probes either referred to this letter, to letters that had been near to it, or far from it. Probe recognition was more accurate for near than for far letters, although none of these letters had to be reported. These findings indicate that episodic short-term recognition is constrained to a small number of simultaneously presented objects that have been encoded into VWM. PMID:27713722

Episodic Short-Term Recognition Requires Encoding into Visual Working Memory: Evidence from Probe Recognition after Letter Report.

PubMed

Poth, Christian H; Schneider, Werner X

2016-01-01

Human vision is organized in discrete processing episodes (e.g., eye fixations or task-steps). Object information must be transmitted across episodes to enable episodic short-term recognition: recognizing whether a current object has been seen in a previous episode. We ask whether episodic short-term recognition presupposes that objects have been encoded into capacity-limited visual working memory (VWM), which retains visual information for report. Alternatively, it could rely on the activation of visual features or categories that occurs before encoding into VWM. We assessed the dependence of episodic short-term recognition on VWM by a new paradigm combining letter report and probe recognition. Participants viewed displays of 10 letters and reported as many as possible after a retention interval (whole report). Next, participants viewed a probe letter and indicated whether it had been one of the 10 letters (probe recognition). In Experiment 1, probe recognition was more accurate for letters that had been encoded into VWM (reported letters) compared with non-encoded letters (non-reported letters). Interestingly, those letters that participants reported in their whole report had been near to one another within the letter displays. This suggests that the encoding into VWM proceeded in a spatially clustered manner. In Experiment 2, participants reported only one of 10 letters (partial report) and probes either referred to this letter, to letters that had been near to it, or far from it. Probe recognition was more accurate for near than for far letters, although none of these letters had to be reported. These findings indicate that episodic short-term recognition is constrained to a small number of simultaneously presented objects that have been encoded into VWM.

The Role of Anterior Nuclei of the Thalamus: A Subcortical Gate in Memory Processing: An Intracerebral Recording Study.

PubMed

Štillová, Klára; Jurák, Pavel; Chládek, Jan; Chrastina, Jan; Halámek, Josef; Bočková, Martina; Goldemundová, Sabina; Říha, Ivo; Rektor, Ivan

2015-01-01

To study the involvement of the anterior nuclei of the thalamus (ANT) as compared to the involvement of the hippocampus in the processes of encoding and recognition during visual and verbal memory tasks. We studied intracerebral recordings in patients with pharmacoresistent epilepsy who underwent deep brain stimulation (DBS) of the ANT with depth electrodes implanted bilaterally in the ANT and compared the results with epilepsy surgery candidates with depth electrodes implanted bilaterally in the hippocampus. We recorded the event-related potentials (ERPs) elicited by the visual and verbal memory encoding and recognition tasks. P300-like potentials were recorded in the hippocampus by visual and verbal memory encoding and recognition tasks and in the ANT by the visual encoding and visual and verbal recognition tasks. No significant ERPs were recorded during the verbal encoding task in the ANT. In the visual and verbal recognition tasks, the P300-like potentials in the ANT preceded the P300-like potentials in the hippocampus. The ANT is a structure in the memory pathway that processes memory information before the hippocampus. We suggest that the ANT has a specific role in memory processes, especially memory recognition, and that memory disturbance should be considered in patients with ANT-DBS and in patients with ANT lesions. ANT is well positioned to serve as a subcortical gate for memory processing in cortical structures.

The Role of Memory Activation in Creating False Memories of Encoding Context

ERIC Educational Resources Information Center

Arndt, Jason

2010-01-01

Using 3 experiments, I examined false memory for encoding context by presenting Deese-Roediger-McDermott themes (Deese, 1959; Roediger & McDermott, 1995) in usual-looking fonts and by testing related, but unstudied, lure items in a font that was shown during encoding. In 2 of the experiments, testing lure items in the font used to study their…

Differentiation and Response Bias in Episodic Memory: Evidence from Reaction Time Distributions

ERIC Educational Resources Information Center

Criss, Amy H.

2010-01-01

In differentiation models, the processes of encoding and retrieval produce an increase in the distribution of memory strength for targets and a decrease in the distribution of memory strength for foils as the amount of encoding increases. This produces an increase in the hit rate and decrease in the false-alarm rate for a strongly encoded compared…

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.

Motivated encoding selectively promotes memory for future inconsequential semantically-related events.

PubMed

Oyarzún, Javiera P; Packard, Pau A; de Diego-Balaguer, Ruth; Fuentemilla, Lluis

2016-09-01

Neurobiological models of long-term memory explain how memory for inconsequential events fades, unless these happen before or after other relevant (i.e., rewarding or aversive) or novel events. Recently, it has been shown in humans that retrospective and prospective memories are selectively enhanced if semantically related events are paired with aversive stimuli. However, it remains unclear whether motivating stimuli, as opposed to aversive, have the same effect in humans. Here, participants performed a three phase incidental encoding task where one semantic category was rewarded during the second phase. A memory test 24h after, but not immediately after encoding, revealed that memory for inconsequential items was selectively enhanced only if items from the same category had been previously, but not subsequently, paired with rewards. This result suggests that prospective memory enhancement of reward-related information requires, like previously reported for aversive memories, of a period of memory consolidation. The current findings provide the first empirical evidence in humans that the effects of motivated encoding are selectively and prospectively prolonged over time. Copyright © 2016 Elsevier Inc. All rights reserved.

Unconscious relational encoding depends on hippocampus

PubMed Central

Duss, Simone B.; Reber, Thomas P.; Hänggi, Jürgen; Schwab, Simon; Wiest, Roland; Müri, René M.; Brugger, Peter; Gutbrod, Klemens

2014-01-01

Textbooks divide between human memory systems based on consciousness. Hippocampus is thought to support only conscious encoding, while neocortex supports both conscious and unconscious encoding. We tested whether processing modes, not consciousness, divide between memory systems in three neuroimaging experiments with 11 amnesic patients (mean age = 45.55 years, standard deviation = 8.74, range = 23–60) and 11 matched healthy control subjects. Examined processing modes were single item versus relational encoding with only relational encoding hypothesized to depend on hippocampus. Participants encoded and later retrieved either single words or new relations between words. Consciousness of encoding was excluded by subliminal (invisible) word presentation. Amnesic patients and controls performed equally well on the single item task activating prefrontal cortex. But only the controls succeeded on the relational task activating the hippocampus, while amnesic patients failed as a group. Hence, unconscious relational encoding, but not unconscious single item encoding, depended on hippocampus. Yet, three patients performed normally on unconscious relational encoding in spite of amnesia capitalizing on spared hippocampal tissue and connections to language cortex. This pattern of results suggests that processing modes divide between memory systems, while consciousness divides between levels of function within a memory system. PMID:25273998

Common neural substrates for visual working memory and attention.

PubMed

Mayer, Jutta S; Bittner, Robert A; Nikolić, Danko; Bledowski, Christoph; Goebel, Rainer; Linden, David E J

2007-06-01

Humans are severely limited in their ability to memorize visual information over short periods of time. Selective attention has been implicated as a limiting factor. Here we used functional magnetic resonance imaging to test the hypothesis that this limitation is due to common neural resources shared by visual working memory (WM) and selective attention. We combined visual search and delayed discrimination of complex objects and independently modulated the demands on selective attention and WM encoding. Participants were presented with a search array and performed easy or difficult visual search in order to encode one or three complex objects into visual WM. Overlapping activation for attention-demanding visual search and WM encoding was observed in distributed posterior and frontal regions. In the right prefrontal cortex and bilateral insula blood oxygen-level-dependent activation additively increased with increased WM load and attentional demand. Conversely, several visual, parietal and premotor areas showed overlapping activation for the two task components and were severely reduced in their WM load response under the condition with high attentional demand. Regions in the left prefrontal cortex were selectively responsive to WM load. Areas selectively responsive to high attentional demand were found within the right prefrontal and bilateral occipital cortex. These results indicate that encoding into visual WM and visual selective attention require to a high degree access to common neural resources. We propose that competition for resources shared by visual attention and WM encoding can limit processing capabilities in distributed posterior brain regions.

Dehydroepiandrosterone impacts working memory by shaping cortico-hippocampal structural covariance during development.

PubMed

Nguyen, Tuong-Vi; Wu, Mia; Lew, Jimin; Albaugh, Matthew D; Botteron, Kelly N; Hudziak, James J; Fonov, Vladimir S; Collins, D Louis; Campbell, Benjamin C; Booij, Linda; Herba, Catherine; Monnier, Patricia; Ducharme, Simon; McCracken, James T

2017-12-01

Existing studies suggest that dehydroepiandrosterone (DHEA) may be important for human brain development and cognition. For example, molecular studies have hinted at the critical role of DHEA in enhancing brain plasticity. Studies of human brain development also support the notion that DHEA is involved in preserving cortical plasticity. Further, some, though not all, studies show that DHEA administration may lead to improvements in working memory in adults. Yet these findings remain limited by an incomplete understanding of the specific neuroanatomical mechanisms through which DHEA may impact the CNS during development. Here we examined associations between DHEA, cortico-hippocampal structural covariance, and working memory (216 participants [female=123], age range 6-22 years old, mean age: 13.6 +/-3.6 years, each followed for a maximum of 3 visits over the course of 4 years). In addition to administering performance-based, spatial working memory tests to these children, we also collected ecological, parent ratings of working memory in everyday situations. We found that increasingly higher DHEA levels were associated with a shift toward positive insular-hippocampal and occipito-hippocampal structural covariance. In turn, DHEA-related insular-hippocampal covariance was associated with lower spatial working memory but higher overall working memory as measured by the ecological parent ratings. Taken together with previous research, these results support the hypothesis that DHEA may optimize cortical functions related to general attentional and working memory processes, but impair the development of bottom-up, hippocampal-to-cortical connections, resulting in impaired encoding of spatial cues. Copyright © 2017 Elsevier Ltd. All rights reserved.

An age-related deficit in spatial-feature reference memory in homing pigeons (Columba livia).

PubMed

Coppola, Vincent J; Flaim, Mary E; Carney, Samantha N; Bingman, Verner P

2015-03-01

Age-related memory decline in mammals has been well documented. By contrast, very little is known about memory decline in birds as they age. In the current study we trained younger and older homing pigeons on a reference memory task in which a goal location could be encoded by spatial and feature cues. Consistent with a previous working memory study, the results revealed impaired acquisition of combined spatial-feature reference memory in older compared to younger pigeons. Following memory acquisition, we used cue-conflict probe trials to provide an initial assessment of possible age-related differences in cue preference. Both younger and older pigeons displayed a similarly modest preference for feature over spatial cues. Copyright © 2014 Elsevier B.V. All rights reserved.

Effects of distinctive encoding on correct and false memory: a meta-analytic review of costs and benefits and their origins in the DRM paradigm.

PubMed

Huff, Mark J; Bodner, Glen E; Fawcett, Jonathan M

2015-04-01

We review and meta-analyze how distinctive encoding alters encoding and retrieval processes and, thus, affects correct and false recognition in the Deese-Roediger-McDermott (DRM) paradigm. Reductions in false recognition following distinctive encoding (e.g., generation), relative to a nondistinctive read-only control condition, reflected both impoverished relational encoding and use of a retrieval-based distinctiveness heuristic. Additional analyses evaluated the costs and benefits of distinctive encoding in within-subjects designs relative to between-group designs. Correct recognition was design independent, but in a within design, distinctive encoding was less effective at reducing false recognition for distinctively encoded lists but more effective for nondistinctively encoded lists. Thus, distinctive encoding is not entirely "cost free" in a within design. In addition to delineating the conditions that modulate the effects of distinctive encoding on recognition accuracy, we discuss the utility of using signal detection indices of memory information and memory monitoring at test to separate encoding and retrieval processes.

Effects of Post-Encoding Stress on Performance in the DRM False Memory Paradigm

ERIC Educational Resources Information Center

Pardilla-Delgado, Enmanuelle; Alger, Sara E.; Cunningham, Tony J.; Kinealy, Brian; Payne, Jessica D.

2016-01-01

Numerous studies have investigated how stress impacts veridical memory, but how stress influences false memory formation remains poorly understood. In order to target memory consolidation specifically, a psychosocial stress (TSST) or control manipulation was administered following encoding of 15 neutral, semantically related word lists (DRM false…

Alpha Oscillations during Incidental Encoding Predict Subsequent Memory for New "Foil" Information.

PubMed

Vogelsang, David A; Gruber, Matthias; Bergström, Zara M; Ranganath, Charan; Simons, Jon S

2018-05-01

People can employ adaptive strategies to increase the likelihood that previously encoded information will be successfully retrieved. One such strategy is to constrain retrieval toward relevant information by reimplementing the neurocognitive processes that were engaged during encoding. Using EEG, we examined the temporal dynamics with which constraining retrieval toward semantic versus nonsemantic information affects the processing of new "foil" information encountered during a memory test. Time-frequency analysis of EEG data acquired during an initial study phase revealed that semantic compared with nonsemantic processing was associated with alpha decreases in a left frontal electrode cluster from around 600 msec after stimulus onset. Successful encoding of semantic versus nonsemantic foils during a subsequent memory test was related to decreases in alpha oscillatory activity in the same left frontal electrode cluster, which emerged relatively late in the trial at around 1000-1600 msec after stimulus onset. Across participants, left frontal alpha power elicited by semantic processing during the study phase correlated significantly with left frontal alpha power associated with semantic foil encoding during the memory test. Furthermore, larger left frontal alpha power decreases elicited by semantic foil encoding during the memory test predicted better subsequent semantic foil recognition in an additional surprise foil memory test, although this effect did not reach significance. These findings indicate that constraining retrieval toward semantic information involves reimplementing semantic encoding operations that are mediated by alpha oscillations and that such reimplementation occurs at a late stage of memory retrieval, perhaps reflecting additional monitoring processes.

Age differences in medial prefrontal activity for subsequent memory of truth value

PubMed Central

Cassidy, Brittany S.; Hedden, Trey; Yoon, Carolyn; Gutchess, Angela H.

2014-01-01

Much research has demonstrated that aging is marked by decreased source memory relative to young adults, yet a smaller body of work has demonstrated that increasing the socioemotional content of source information may be one way to reduce age-related performance differences. Although dorsomedial prefrontal cortex (dmPFC) activity may support source memory among young and older adults, the extent to which one activates dorsal vs. ventral mPFC may reflect one's personal connection with incoming information. Because truth value may be one salient marker that impacts one's connection with information and allocation of attention toward incoming material, we investigated whether the perceived truth value of information differently impacts differences in mPFC activity associated with encoding source information, particularly with age. Twelve young (18–23 years) and 12 older adults (63–80 years) encoded true and false statements. Behavioral results showed similar memory performance between the age groups. With respect to neural activity associated with subsequent memory, young adults, relative to older adults, exhibited greater activity in dmPFC while older adults displayed enhanced ventromedial prefrontal cortex (vmPFC) and insula engagement relative to young. These results may potentially indicate that young adults focus on a general knowledge acquisition goal, while older adults focus on emotionally relevant aspects of the material. The findings demonstrate that age-related differences in recruitment of mPFC associated with encoding source information may in some circumstances underlie age-equivalent behavioral performance. PMID:24570672

Assessing Spatial Learning and Memory in Rodents

PubMed Central

Vorhees, Charles V.; Williams, Michael T.

2014-01-01

Maneuvering safely through the environment is central to survival of almost all species. The ability to do this depends on learning and remembering locations. This capacity is encoded in the brain by two systems: one using cues outside the organism (distal cues), allocentric navigation, and one using self-movement, internal cues and nearby proximal cues, egocentric navigation. Allocentric navigation involves the hippocampus, entorhinal cortex, and surrounding structures; in humans this system encodes allocentric, semantic, and episodic memory. This form of memory is assessed in laboratory animals in many ways, but the dominant form of assessment is the Morris water maze (MWM). Egocentric navigation involves the dorsal striatum and connected structures; in humans this system encodes routes and integrated paths and, when overlearned, becomes procedural memory. In this article, several allocentric assessment methods for rodents are reviewed and compared with the MWM. MWM advantages (little training required, no food deprivation, ease of testing, rapid and reliable learning, insensitivity to differences in body weight and appetite, absence of nonperformers, control methods for proximal cue learning, and performance effects) and disadvantages (concern about stress, perhaps not as sensitive for working memory) are discussed. Evidence-based design improvements and testing methods are reviewed for both rats and mice. Experimental factors that apply generally to spatial navigation and to MWM specifically are considered. It is concluded that, on balance, the MWM has more advantages than disadvantages and compares favorably with other allocentric navigation tasks. PMID:25225309

A functional magnetic resonance imaging study mapping the episodic memory encoding network in temporal lobe epilepsy

PubMed Central

Sidhu, Meneka K.; Stretton, Jason; Winston, Gavin P.; Bonelli, Silvia; Centeno, Maria; Vollmar, Christian; Symms, Mark; Thompson, Pamela J.; Koepp, Matthias J.

2013-01-01

Functional magnetic resonance imaging has demonstrated reorganization of memory encoding networks within the temporal lobe in temporal lobe epilepsy, but little is known of the extra-temporal networks in these patients. We investigated the temporal and extra-temporal reorganization of memory encoding networks in refractory temporal lobe epilepsy and the neural correlates of successful subsequent memory formation. We studied 44 patients with unilateral temporal lobe epilepsy and hippocampal sclerosis (24 left) and 26 healthy control subjects. All participants performed a functional magnetic resonance imaging memory encoding paradigm of faces and words with subsequent out-of-scanner recognition assessments. A blocked analysis was used to investigate activations during encoding and neural correlates of subsequent memory were investigated using an event-related analysis. Event-related activations were then correlated with out-of-scanner verbal and visual memory scores. During word encoding, control subjects activated the left prefrontal cortex and left hippocampus whereas patients with left hippocampal sclerosis showed significant additional right temporal and extra-temporal activations. Control subjects displayed subsequent verbal memory effects within left parahippocampal gyrus, left orbitofrontal cortex and fusiform gyrus whereas patients with left hippocampal sclerosis activated only right posterior hippocampus, parahippocampus and fusiform gyrus. Correlational analysis showed that patients with left hippocampal sclerosis with better verbal memory additionally activated left orbitofrontal cortex, anterior cingulate cortex and left posterior hippocampus. During face encoding, control subjects showed right lateralized prefrontal cortex and bilateral hippocampal activations. Patients with right hippocampal sclerosis showed increased temporal activations within the superior temporal gyri bilaterally and no increased extra-temporal areas of activation compared with control subjects. Control subjects showed subsequent visual memory effects within right amygdala, hippocampus, fusiform gyrus and orbitofrontal cortex. Patients with right hippocampal sclerosis showed subsequent visual memory effects within right posterior hippocampus, parahippocampal and fusiform gyri, and predominantly left hemisphere extra-temporal activations within the insula and orbitofrontal cortex. Correlational analysis showed that patients with right hippocampal sclerosis with better visual memory activated the amygdala bilaterally, right anterior parahippocampal gyrus and left insula. Right sided extra-temporal areas of reorganization observed in patients with left hippocampal sclerosis during word encoding and bilateral lateral temporal reorganization in patients with right hippocampal sclerosis during face encoding were not associated with subsequent memory formation. Reorganization within the medial temporal lobe, however, is an efficient process. The orbitofrontal cortex is critical to subsequent memory formation in control subjects and patients. Activations within anterior cingulum and insula correlated with better verbal and visual subsequent memory in patients with left and right hippocampal sclerosis, respectively, representing effective extra-temporal recruitment. PMID:23674488

fMRI characterization of visual working memory recognition.

PubMed

Rahm, Benjamin; Kaiser, Jochen; Unterrainer, Josef M; Simon, Juliane; Bledowski, Christoph

2014-04-15

Encoding and maintenance of information in visual working memory have been extensively studied, highlighting the crucial and capacity-limiting role of fronto-parietal regions. In contrast, the neural basis of recognition in visual working memory has remained largely unspecified. Cognitive models suggest that recognition relies on a matching process that compares sensory information with the mental representations held in memory. To characterize the neural basis of recognition we varied both the need for recognition and the degree of similarity between the probe item and the memory contents, while independently manipulating memory load to produce load-related fronto-parietal activations. fMRI revealed a fractionation of working memory functions across four distributed networks. First, fronto-parietal regions were activated independent of the need for recognition. Second, anterior parts of load-related parietal regions contributed to recognition but their activations were independent of the difficulty of matching in terms of sample-probe similarity. These results argue against a key role of the fronto-parietal attention network in recognition. Rather the third group of regions including bilateral temporo-parietal junction, posterior cingulate cortex and superior frontal sulcus reflected demands on matching both in terms of sample-probe-similarity and the number of items to be compared. Also, fourth, bilateral motor regions and right superior parietal cortex showed higher activation when matching provided clear evidence for a decision. Together, the segregation between the well-known fronto-parietal activations attributed to attentional operations in working memory from those regions involved in matching supports the theoretical view of separable attentional and mnemonic contributions to working memory. Yet, the close theoretical and empirical correspondence to perceptual decision making may call for an explicit consideration of decision making mechanisms in conceptions of working memory. Copyright © 2013 Elsevier Inc. All rights reserved.

Visual Working Memory Is Independent of the Cortical Spacing Between Memoranda.

PubMed

Harrison, William J; Bays, Paul M

2018-03-21

The sensory recruitment hypothesis states that visual short-term memory is maintained in the same visual cortical areas that initially encode a stimulus' features. Although it is well established that the distance between features in visual cortex determines their visibility, a limitation known as crowding, it is unknown whether short-term memory is similarly constrained by the cortical spacing of memory items. Here, we investigated whether the cortical spacing between sequentially presented memoranda affects the fidelity of memory in humans (of both sexes). In a first experiment, we varied cortical spacing by taking advantage of the log-scaling of visual cortex with eccentricity, presenting memoranda in peripheral vision sequentially along either the radial or tangential visual axis with respect to the fovea. In a second experiment, we presented memoranda sequentially either within or beyond the critical spacing of visual crowding, a distance within which visual features cannot be perceptually distinguished due to their nearby cortical representations. In both experiments and across multiple measures, we found strong evidence that the ability to maintain visual features in memory is unaffected by cortical spacing. These results indicate that the neural architecture underpinning working memory has properties inconsistent with the known behavior of sensory neurons in visual cortex. Instead, the dissociation between perceptual and memory representations supports a role of higher cortical areas such as posterior parietal or prefrontal regions or may involve an as yet unspecified mechanism in visual cortex in which stimulus features are bound to their temporal order. SIGNIFICANCE STATEMENT Although much is known about the resolution with which we can remember visual objects, the cortical representation of items held in short-term memory remains contentious. A popular hypothesis suggests that memory of visual features is maintained via the recruitment of the same neural architecture in sensory cortex that encodes stimuli. We investigated this claim by manipulating the spacing in visual cortex between sequentially presented memoranda such that some items shared cortical representations more than others while preventing perceptual interference between stimuli. We found clear evidence that short-term memory is independent of the intracortical spacing of memoranda, revealing a dissociation between perceptual and memory representations. Our data indicate that working memory relies on different neural mechanisms from sensory perception. Copyright © 2018 Harrison and Bays.

Dissociation of long-term verbal memory and fronto-executive impairment in first-episode psychosis

PubMed Central

Leeson, V. C.; Robbins, T. W.; Franklin, C.; Harrison, M.; Harrison, I.; Ron, M. A.; Barnes, T. R. E.; Joyce, E. M.

2009-01-01

Background Verbal memory is frequently and severely affected in schizophrenia and has been implicated as a mediator of poor clinical outcome. Whereas encoding deficits are well demonstrated, it is unclear whether retention is impaired. This distinction is important because accelerated forgetting implies impaired consolidation attributable to medial temporal lobe (MTL) dysfunction whereas impaired encoding and retrieval implicates involvement of prefrontal cortex. Method We assessed a group of healthy volunteers (n=97) and pre-morbid IQ- and sex-matched first-episode psychosis patients (n=97), the majority of whom developed schizophrenia. We compared performance of verbal learning and recall with measures of visuospatial working memory, planning and attentional set-shifting, and also current IQ. Results All measures of performance, including verbal memory retention, a memory savings score that accounted for learning impairments, were significantly impaired in the schizophrenia group. The difference between groups for delayed recall remained even after the influence of learning and recall was accounted for. Factor analyses showed that, in patients, all variables except verbal memory retention loaded on a single factor, whereas in controls verbal memory and fronto-executive measures were separable. Conclusions The results suggest that IQ, executive function and verbal learning deficits in schizophrenia may reflect a common abnormality of information processing in prefrontal cortex rather than specific impairments in different cognitive domains. Verbal memory retention impairments, however, may have a different aetiology. PMID:19419594

Encoding specificity manipulations do affect retrieval from memory.

PubMed

Zeelenberg, René

2005-05-01

In a recent article, P.A. Higham (2002) [Strong cues are not necessarily weak: Thomson and Tulving (1970) and the encoding specificity principle revisited. Memory &Cognition, 30, 67-80] proposed a new way to analyze cued recall performance in terms of three separable aspects of memory (retrieval, monitoring, and report bias) by comparing performance under both free-report and forced-report instructions. He used this method to derive estimates of these aspects of memory in an encoding specificity experiment similar to that reported by D.M. Thomson and E. Tulving (1970) [Associative encoding and retrieval: weak and strong cues. Journal of Experimental Psychology, 86, 255-262]. Under forced-report instructions, the encoding specificity manipulation did not affect performance. Higham concluded that the manipulation affected monitoring and report bias, but not retrieval. I argue that this interpretation of the results is problematic because the Thomson and Tulving paradigm is confounded, and show in three experiments using a more appropriate design that encoding specificity manipulations do affect performance in forced-report cued recall. Because in Higham's framework forced-report performance provides a measure of retrieval that is uncontaminated by monitoring and report bias it is concluded that encoding specificity manipulations do affect retrieval from memory.

Dopamine modulates episodic memory persistence in old age

PubMed Central

Chowdhury, Rumana; Guitart-Masip, Marc; Bunzeck, Nico; Dolan, Raymond J; Düzel, Emrah

2013-01-01

Activation of the hippocampus is required in order to encode memories for new events (or episodes). Observations from animal studies suggest that for these memories to persist beyond 4 to 6 hours, a release of dopamine generated by strong hippocampal activation is needed. This predicts that dopaminergic enhancement should improve human episodic memory persistence also for events encoded with weak hippocampal activation. Here, using pharmacological fMRI in an elderly population where there is a loss of dopamine neurons as part of normal aging, we show this very effect. The dopamine precursor levodopa led to a dose-dependent (inverted U-shape) persistent episodic memory benefit for images of scenes when tested after 6 hours, independent of whether encoding-related hippocampal fMRI activity was weak or strong (U-shaped dose-response relationship). This lasting improvement even for weakly encoded events supports a role for dopamine in human episodic memory consolidation albeit operating within a narrow dose range. PMID:23055489

An Electrophysiological Signature of Unconscious Recognition Memory

PubMed Central

Voss, Joel L.; Paller, Ken A.

2009-01-01

Contradicting the common assumption that accurate recognition reflects explicit-memory processing, we describe evidence for recognition lacking two hallmark explicit-memory features: awareness of memory retrieval and facilitation by attentive encoding. Kaleidoscope images were encoded in conjunction with an attentional diversion and subsequently recognized more accurately than those encoded without diversion. Confidence in recognition was superior following attentive encoding, though recognition was remarkably accurate when people claimed to be unaware of memory retrieval. This “implicit recognition” was associated with frontal-occipital negative brain potentials at 200-400 ms post-stimulus-onset, which were spatially and temporally distinct from positive brain potentials corresponding to explicit recollection and familiarity. This dissociation between behavioral and electrophysiological characteristics of “implicit recognition” versus explicit recognition indicates that a neurocognitive mechanism with properties similar to those that produce implicit memory can be operative in standard recognition tests. People can accurately discriminate repeat stimuli from new stimuli without necessarily knowing it. PMID:19198606

Inhibition-Induced Forgetting Results from Resource Competition between Response Inhibition and Memory Encoding Processes.

PubMed

Chiu, Yu-Chin; Egner, Tobias

2015-08-26

Response inhibition is a key component of executive control, but its relation to other cognitive processes is not well understood. We recently documented the "inhibition-induced forgetting effect": no-go cues are remembered more poorly than go cues. We attributed this effect to central-resource competition, whereby response inhibition saps attention away from memory encoding. However, this proposal is difficult to test with behavioral means alone. We therefore used fMRI in humans to test two neural predictions of the "common resource hypothesis": (1) brain regions associated with response inhibition should exhibit greater resource demands during encoding of subsequently forgotten than remembered no-go cues; and (2) this higher inhibitory resource demand should lead to memory encoding regions having less resources available during encoding of subsequently forgotten no-go cues. Participants categorized face stimuli by gender in a go/no-go task and, following a delay, performed a surprise recognition memory test for those faces. Replicating previous findings, memory was worse for no-go than for go stimuli. Crucially, forgetting of no-go cues was predicted by high inhibitory resource demand, as quantified by the trial-by-trial ratio of activity in neural "no-go" versus "go" networks. Moreover, this index of inhibitory demand exhibited an inverse trial-by-trial relationship with activity in brain regions responsible for the encoding of no-go cues into memory, notably the ventrolateral prefrontal cortex. This seesaw pattern between the neural resource demand of response inhibition and activity related to memory encoding directly supports the hypothesis that response inhibition temporarily saps attentional resources away from stimulus processing. Recent behavioral experiments showed that inhibiting a motor response to a stimulus (a "no-go cue") impairs subsequent memory for that cue. Here, we used fMRI to test whether this "inhibition-induced forgetting effect" is caused by competition for neural resources between the processes of response inhibition and memory encoding. We found that trial-by-trial variations in neural inhibitory resource demand predicted subsequent forgetting of no-go cues and that higher inhibitory demand was furthermore associated with lower concurrent activation in brain regions responsible for successful memory encoding of no-go cues. Thus, motor inhibition and stimulus encoding appear to compete with each other: when more resources have to be devoted to inhibiting action, less are available for encoding sensory stimuli. Copyright © 2015 the authors 0270-6474/15/3511936-10$15.00/0.

Emotion regulation modulates anticipatory brain activity that predicts emotional memory encoding in women.

PubMed

Galli, Giulia; Griffiths, Victoria A; Otten, Leun J

2014-03-01

It has been shown that the effectiveness with which unpleasant events are encoded into memory is related to brain activity set in train before the events. Here, we assessed whether encoding-related activity before an aversive event can be modulated by emotion regulation. Electrical brain activity was recorded from the scalps of healthy women while they performed an incidental encoding task on randomly intermixed unpleasant and neutral visual scenes. A cue presented 1.5 s before each picture indicated the upcoming valence. In half of the blocks of trials, the instructions emphasized to let emotions arise in a natural way. In the other half, participants were asked to decrease their emotional response by adopting the perspective of a detached observer. Memory for the scenes was probed 1 day later with a recognition memory test. Brain activity before unpleasant scenes predicted later memory of the scenes, but only when participants felt their emotions and did not detach from them. The findings indicate that emotion regulation can eliminate the influence of anticipatory brain activity on memory encoding. This may be relevant for the understanding and treatment of psychiatric diseases with a memory component.

Depth of processing effects on neural correlates of memory encoding: relationship between findings from across- and within-task comparisons.

PubMed

Otten, L J; Henson, R N; Rugg, M D

2001-02-01

Neuroimaging studies have implicated the prefrontal cortex and medial temporal areas in the successful encoding of verbal material into episodic memory. The present study used event-related functional MRI to investigate whether the brain areas associated with successful episodic encoding of words in a semantic study task are a subset of those demonstrating depth of processing effects. In addition, we tested whether the brain areas associated with successful episodic encoding differ depending on the nature of the study task. At study, 15 volunteers were cued to make either animacy or alphabetical decisions about words. A recognition memory test including confidence judgements followed after a delay of 15 min. Prefrontal and medial temporal regions showed greater functional MRI activations for semantically encoded words relative to alphabetically encoded words. Two of these regions (left anterior hippocampus and left ventral inferior frontal gyrus) showed greater activation for semantically encoded words that were subsequently recognized confidently. However, other regions (left posterior hippocampus and right inferior frontal cortex) demonstrated subsequent memory effects, but not effects of depth of processing. Successful memory for alphabetically encoded words was also associated with greater activation in the left anterior hippocampus and left ventral inferior frontal gyrus. The findings suggest that episodic encoding for words in a semantic study task involves a subset of the regions activated by deep relative to shallow processing. The data provide little evidence that successful episodic encoding during a shallow study task depends upon regions different from those that support the encoding of deeply studied words. Instead, the findings suggest that successful episodic encoding during a shallow study task relies on a subset of the regions engaged during successful encoding in a deep task.

Successful physiological aging and episodic memory: a brain stimulation study.

PubMed

Manenti, Rosa; Cotelli, Maria; Miniussi, Carlo

2011-01-01

Functional neuroimaging studies have shown that younger adults tend to asymmetrically recruit specific regions of an hemisphere in an episodic memory task (Hemispheric Encoding Retrieval Asymmetry-HERA model). In older adults, this hemispheric asymmetry is generally reduced as suggested by the Hemispheric Asymmetry Reduction for OLDer Adults-HAROLD-model. Recent works suggest that while low-performing older adults do not show this reduced asymmetry, high-performing older adults counteract age-related neural decline through a plastic reorganization of cerebral networks that results in reduced functional asymmetry. However, the issue of whether high- and low-performing older adults show different degrees of asymmetry and the relevance of this process for counteracting aging have not been clarified. We used transcranial magnetic stimulation (TMS) to transiently interfere with the function of the dorsolateral prefrontal cortex (DLPFC) during encoding or retrieval of associated and non-associated word pairs. A group of healthy older adults was studied during encoding and retrieval of word pairs. The subjects were divided in two subgroups according to their experimental performance (i.e., high- and low-performing). TMS effects on retrieval differed according to the subject's subgroup. In particular, the predominance of left vs. right DLPFC effects during encoding, predicted by the HERA model, was observed only in low-performing older adults, while the asymmetry reduction predicted by the HAROLD model was selectively shown for the high-performing group. The present data confirm that older adults with higher memory performance show less prefrontal asymmetry as an efficient strategy to counteract age-related memory decline. Copyright © 2010 Elsevier B.V. All rights reserved.

Memory for environmental sounds in sighted, congenitally blind and late blind adults: evidence for cross-modal compensation.

PubMed

Röder, Brigitte; Rösler, Frank

2003-10-01

Several recent reports suggest compensatory performance changes in blind individuals. It has, however, been argued that the lack of visual input leads to impoverished semantic networks resulting in the use of data-driven rather than conceptual encoding strategies on memory tasks. To test this hypothesis, congenitally blind and sighted participants encoded environmental sounds either physically or semantically. In the recognition phase, both conceptually as well as physically distinct and physically distinct but conceptually highly related lures were intermixed with the environmental sounds encountered during study. Participants indicated whether or not they had heard a sound in the study phase. Congenitally blind adults showed elevated memory both after physical and semantic encoding. After physical encoding blind participants had lower false memory rates than sighted participants, whereas the false memory rates of sighted and blind participants did not differ after semantic encoding. In order to address the question if compensatory changes in memory skills are restricted to critical periods during early childhood, late blind adults were tested with the same paradigm. When matched for age, they showed similarly high memory scores as the congenitally blind. These results demonstrate compensatory performance changes in long-term memory functions due to the loss of a sensory system and provide evidence for high adaptive capabilities of the human cognitive system.

Evidence for a differential contribution of early perceptual and late cognitive processes during encoding to episodic memory impairment in schizophrenia.

PubMed

Green, Amity E; Fitzgerald, Paul B; Johnston, Patrick J; Nathan, Pradeep J; Kulkarni, Jayashri; Croft, Rodney J

2017-08-01

Schizophrenia is characterised by significant episodic memory impairment that is thought to be related to problems with encoding, however the neuro-functional mechanisms underlying these deficits are not well understood. The present study used a subsequent recognition memory paradigm and event-related potentials (ERPs) to investigate temporal aspects of episodic memory encoding deficits in schizophrenia. Electroencephalographic data was recorded in 24 patients and 19 healthy controls whilst participants categorised single words as pleasant/unpleasant. ERPs were generated to subsequently recognised versus unrecognised words on the basis of a forced-choice recognition memory task. Subsequent memory effects were examined with the late positive component (LPP). Group differences in N1, P2, N400 and LPP were examined for words correctly recognised. Patients performed more poorly than controls on the recognition task. During encoding patients had significantly reduced N400 and LPP amplitudes than controls. LPP amplitude correlated with task performance however amplitudes did not differ between patients and controls as a function of subsequent memory. No significant differences in N1 or P2 amplitude or latency were observed. The present results indicate that early sensory processes are intact and dysfunctional higher order cognitive processes during encoding are contributing to episodic memory impairments in schizophrenia.

Retrospective Attention Interacts with Stimulus Strength to Shape Working Memory Performance.

PubMed

Wildegger, Theresa; Humphreys, Glyn; Nobre, Anna C

2016-01-01

Orienting attention retrospectively to selective contents in working memory (WM) influences performance. A separate line of research has shown that stimulus strength shapes perceptual representations. There is little research on how stimulus strength during encoding shapes WM performance, and how effects of retrospective orienting might vary with changes in stimulus strength. We explore these questions in three experiments using a continuous-recall WM task. In Experiment 1 we show that benefits of cueing spatial attention retrospectively during WM maintenance (retrocueing) varies according to stimulus contrast during encoding. Retrocueing effects emerge for supraliminal but not sub-threshold stimuli. However, once stimuli are supraliminal, performance is no longer influenced by stimulus contrast. In Experiments 2 and 3 we used a mixture-model approach to examine how different sources of error in WM are affected by contrast and retrocueing. For high-contrast stimuli (Experiment 2), retrocues increased the precision of successfully remembered items. For low-contrast stimuli (Experiment 3), retrocues decreased the probability of mistaking a target with distracters. These results suggest that the processes by which retrospective attentional orienting shape WM performance are dependent on the quality of WM representations, which in turn depends on stimulus strength during encoding.

The Effects of Valence and Arousal on Associative Working Memory and Long-Term Memory

PubMed Central

Bergmann, Heiko C.; Rijpkema, Mark; Fernández, Guillén; Kessels, Roy P. C.

2012-01-01

Background Emotion can either facilitate or impair memory, depending on what, when and how memory is tested and whether the paradigm at hand is administered as a working memory (WM) or a long-term memory (LTM) task. Whereas emotionally arousing single stimuli are more likely to be remembered, memory for the relationship between two or more component parts (i.e., relational memory) appears to be worse in the presence of emotional stimuli, at least in some relational memory tasks. The current study investigated the effects of both valence (neutral vs. positive vs. negative) and arousal (low vs. high) in an inter-item WM binding and LTM task. Methodology/Principal Findings A five-pair delayed-match-to-sample (WM) task was administered. In each trial, study pairs consisted of one neutral picture and a second picture of which the emotional qualities (valence and arousal levels) were manipulated. These pairs had to be remembered across a delay interval of 10 seconds. This was followed by a probe phase in which five pairs were tested. After completion of this task, an unexpected single item LTM task as well as an LTM task for the pairs was assessed. As expected, emotional arousal impaired WM processing. This was reflected in lower accuracy for pairs consisting of high-arousal pictures compared to pairs with low-arousal pictures. A similar effect was found for the associative LTM task. However, the arousal effect was modulated by affective valence for the WM but not the LTM task; pairs with low-arousal negative pictures were not processed as well in the WM task. No significant differences were found for the single-item LTM task. Conclusions/Significance The present study provides additional evidence that processes during initial perception/encoding and post-encoding processes, the time interval between study and test and the interaction between valence and arousal might modulate the effects of “emotion” on associative memory. PMID:23300724

Which way and how far? Tracking of translation and rotation information for human path integration.

PubMed

Chrastil, Elizabeth R; Sherrill, Katherine R; Hasselmo, Michael E; Stern, Chantal E

2016-10-01

Path integration, the constant updating of the navigator's knowledge of position and orientation during movement, requires both visuospatial knowledge and memory. This study aimed to develop a systems-level understanding of human path integration by examining the basic building blocks of path integration in humans. To achieve this goal, we used functional imaging to examine the neural mechanisms that support the tracking and memory of translational and rotational components of human path integration. Critically, and in contrast to previous studies, we examined movement in translation and rotation tasks with no defined end-point or goal. Navigators accumulated translational and rotational information during virtual self-motion. Activity in hippocampus, retrosplenial cortex (RSC), and parahippocampal cortex (PHC) increased during both translation and rotation encoding, suggesting that these regions track self-motion information during path integration. These results address current questions regarding distance coding in the human brain. By implementing a modified delayed match to sample paradigm, we also examined the encoding and maintenance of path integration signals in working memory. Hippocampus, PHC, and RSC were recruited during successful encoding and maintenance of path integration information, with RSC selective for tasks that required processing heading rotation changes. These data indicate distinct working memory mechanisms for translation and rotation, which are essential for updating neural representations of current location. The results provide evidence that hippocampus, PHC, and RSC flexibly track task-relevant translation and rotation signals for path integration and could form the hub of a more distributed network supporting spatial navigation. Hum Brain Mapp 37:3636-3655, 2016. © 2016 Wiley Periodicals, Inc. © 2016 Wiley Periodicals, Inc.

Differential contributions of dorso-ventral and rostro-caudal prefrontal white matter tracts to cognitive control in healthy older adults.

PubMed

Strenziok, Maren; Greenwood, Pamela M; Santa Cruz, Sophia A; Thompson, James C; Parasuraman, Raja

2013-01-01

Prefrontal cortex mediates cognitive control by means of circuitry organized along dorso-ventral and rostro-caudal axes. Along the dorso-ventral axis, ventrolateral PFC controls semantic information, whereas dorsolateral PFC encodes task rules. Along the rostro-caudal axis, anterior prefrontal cortex encodes complex rules and relationships between stimuli, whereas posterior prefrontal cortex encodes simple relationships between stimuli and behavior. Evidence of these gradients of prefrontal cortex organization has been well documented in fMRI studies, but their functional correlates have not been examined with regard to integrity of underlying white matter tracts. We hypothesized that (a) the integrity of specific white matter tracts is related to cognitive functioning in a manner consistent with the dorso-ventral and rostro-caudal organization of the prefrontal cortex, and (b) this would be particularly evident in healthy older adults. We assessed three cognitive processes that recruit the prefrontal cortex and can distinguish white matter tracts along the dorso-ventral and rostro-caudal dimensions -episodic memory, working memory, and reasoning. Correlations between cognition and fractional anisotropy as well as fiber tractography revealed: (a) Episodic memory was related to ventral prefrontal cortex-thalamo-hippocampal fiber integrity; (b) Working memory was related to integrity of corpus callosum body fibers subserving dorsolateral prefrontal cortex; and (c) Reasoning was related to integrity of corpus callosum body fibers subserving rostral and caudal dorsolateral prefrontal cortex. These findings confirm the ventrolateral prefrontal cortex's role in semantic control and the dorsolateral prefrontal cortex's role in rule-based processing, in accordance with the dorso-ventral prefrontal cortex gradient. Reasoning-related rostral and caudal superior frontal white matter may facilitate different levels of task rule complexity. This study is the first to demonstrate dorso-ventral and rostro-caudal prefrontal cortex processing gradients in white matter integrity.

Effortful Retrieval Reduces Hippocampal Activity and Impairs Incidental Encoding

PubMed Central

Reas, Emilie T.; Brewer, James B.

2014-01-01

Functional imaging studies frequently report that the hippocampus is engaged by successful episodic memory retrieval. However, considering that concurrent encoding of the background environment occurs during retrieval and influences medial temporal lobe activity, it is plausible that hippocampal encoding functions are reduced with increased attentional engagement during effortful retrieval. Expanding upon evidence that retrieval efforts suppress activity in hippocampal regions implicated in encoding, this study examines the influence of retrieval effort on encoding performance and the interactive effects of encoding and retrieval on hippocampal and neocortical activity. Functional magnetic resonance imaging was conducted while subjects performed a word recognition task with incidental picture encoding. Both lower memory strength and increased search duration were associated with encoding failure and reduced hippocampal and default network activity. Activity in the anterior hippocampus tracked encoding, which was more strongly deactivated when incidental encoding was unsuccessful. These findings highlight potential contributions from background encoding processes to hippocampal activations during neuroimaging studies of episodic memory retrieval. PMID:23378272

Thought probes during prospective memory encoding: Evidence for perfunctory processes

PubMed Central

McDaniel, Mark A.; Dasse, Michelle N.; Lee, Ji hae; Kurinec, Courtney A.; Tami, Claudina; Krueger, Madison L.

2018-01-01

For nearly 50 years, psychologists have studied prospective memory, or the ability to execute delayed intentions. Yet, there remains a gap in understanding as to whether initial encoding of the intention must be elaborative and strategic, or whether some components of successful encoding can occur in a perfunctory, transient manner. In eight studies (N = 680), we instructed participants to remember to press the Q key if they saw words representing fruits (cue) during an ongoing lexical decision task. They then typed what they were thinking and responded whether they encoded fruits as a general category, as specific exemplars, or hardly thought about it at all. Consistent with the perfunctory view, participants often reported mind wandering (42.9%) and hardly thinking about the prospective memory task (22.5%). Even though participants were given a general category cue, many participants generated specific category exemplars (34.5%). Bayesian analyses of encoding durations indicated that specific exemplars came to mind in a perfunctory manner rather than via strategic, elaborative mechanisms. Few participants correctly guessed the research hypotheses and changing from fruit category cues to initial-letter cues eliminated reports of specific exemplar generation, thereby arguing against demand characteristics in the thought probe procedure. In a final experiment, encoding duration was unrelated to prospective memory performance; however, specific-exemplar encoders outperformed general-category encoders with no ongoing task monitoring costs. Our findings reveal substantial variability in intention encoding, and demonstrate that some components of prospective memory encoding can be done “in passing.” PMID:29874277

Thought probes during prospective memory encoding: Evidence for perfunctory processes.

PubMed

Scullin, Michael K; McDaniel, Mark A; Dasse, Michelle N; Lee, Ji Hae; Kurinec, Courtney A; Tami, Claudina; Krueger, Madison L

2018-01-01

For nearly 50 years, psychologists have studied prospective memory, or the ability to execute delayed intentions. Yet, there remains a gap in understanding as to whether initial encoding of the intention must be elaborative and strategic, or whether some components of successful encoding can occur in a perfunctory, transient manner. In eight studies (N = 680), we instructed participants to remember to press the Q key if they saw words representing fruits (cue) during an ongoing lexical decision task. They then typed what they were thinking and responded whether they encoded fruits as a general category, as specific exemplars, or hardly thought about it at all. Consistent with the perfunctory view, participants often reported mind wandering (42.9%) and hardly thinking about the prospective memory task (22.5%). Even though participants were given a general category cue, many participants generated specific category exemplars (34.5%). Bayesian analyses of encoding durations indicated that specific exemplars came to mind in a perfunctory manner rather than via strategic, elaborative mechanisms. Few participants correctly guessed the research hypotheses and changing from fruit category cues to initial-letter cues eliminated reports of specific exemplar generation, thereby arguing against demand characteristics in the thought probe procedure. In a final experiment, encoding duration was unrelated to prospective memory performance; however, specific-exemplar encoders outperformed general-category encoders with no ongoing task monitoring costs. Our findings reveal substantial variability in intention encoding, and demonstrate that some components of prospective memory encoding can be done "in passing."

Different effects of color-based and location-based selection on visual working memory.

PubMed

Li, Qi; Saiki, Jun

2015-02-01

In the present study, we investigated how feature- and location-based selection influences visual working memory (VWM) encoding and maintenance. In Experiment 1, cue type (color, location) and cue timing (precue, retro-cue) were manipulated in a change detection task. The stimuli were color-location conjunction objects, and binding memory was tested. We found a significantly greater effect for color precues than for either color retro-cues or location precues, but no difference between location pre- and retro-cues, consistent with previous studies (e.g., Griffin & Nobre in Journal of Cognitive Neuroscience, 15, 1176-1194, 2003). We also found no difference between location and color retro-cues. Experiment 2 replicated the color precue advantage with more complex color-shape-location conjunction objects. Only one retro-cue effect was different from that in Experiment 1: Color retro-cues were significantly less effective than location retro-cues in Experiment 2, which may relate to a structural property of multidimensional VWM representations. In Experiment 3, a visual search task was used, and the result of a greater location than color precue effect suggests that the color precue advantage in a memory task is related to the modulation of VWM encoding rather than of sensation and perception. Experiment 4, using a task that required only memory for individual features but not for feature bindings, further confirmed that the color precue advantage is specific to binding memory. Together, these findings reveal new aspects of the interaction between attention and VWM and provide potentially important implications for the structural properties of VWM representations.

Aging and Memory as Discrimination: Influences of Encoding Specificity, Cue Overload, and Prior Knowledge

PubMed Central

2016-01-01

From the perspective of memory-as-discrimination, whether a cue leads to correct retrieval simultaneously depends on the cue’s relationship to (a) the memory target and (b) the other retrieval candidates. A corollary of the view is that increasing encoding-retrieval match may only help memory if it improves the cue’s capacity to discriminate the target from competitors. Here, age differences in this discrimination process were assessed by manipulating the overlap between cues present at encoding and retrieval orthogonally with cue–target distinctiveness. In Experiment 1, associative memory differences for cue–target sets between young and older adults were minimized through training and retrieval efficiency was assessed through response time. In Experiment 2, age-group differences in associative memory were left to vary and retrieval efficiency was assessed through accuracy. Both experiments showed age-invariance in memory-as-discrimination: cues increasing encoding-retrieval match did not benefit memory unless they also improved discrimination between the target and competitors. Predictions based on the age-related associative deficit were also supported: prior knowledge alleviated age-related associative deficits (Experiment 1), and increasing encoding-retrieval match benefited older more than young adults (Experiment 2). We suggest that the latter occurred because older adults’ associative memory deficits reduced the impact of competing retrieval candidates—hence the age-related benefit was not attributable to encoding-retrieval match per se, but rather it was a joint function of an increased probability of the cue connecting to the target combined with a decrease in competing retrieval candidates. PMID:27831714

Effects of Δ9-tetrahydrocannabinol administration on human encoding and recall memory function: a pharmacological FMRI study.

PubMed

Bossong, Matthijs G; Jager, Gerry; van Hell, Hendrika H; Zuurman, Lineke; Jansma, J Martijn; Mehta, Mitul A; van Gerven, Joop M A; Kahn, René S; Ramsey, Nick F

2012-03-01

Deficits in memory function are an incapacitating aspect of various psychiatric and neurological disorders. Animal studies have recently provided strong evidence for involvement of the endocannabinoid (eCB) system in memory function. Neuropsychological studies in humans have shown less convincing evidence but suggest that administration of cannabinoid substances affects encoding rather than recall of information. In this study, we examined the effects of perturbation of the eCB system on memory function during both encoding and recall. We performed a pharmacological MRI study with a placebo-controlled, crossover design, investigating the effects of Δ9-tetrahydrocannabinol (THC) inhalation on associative memory-related brain function in 13 healthy volunteers. Performance and brain activation during associative memory were assessed using a pictorial memory task, consisting of separate encoding and recall conditions. Administration of THC caused reductions in activity during encoding in the right insula, the right inferior frontal gyrus, and the left middle occipital gyrus and a network-wide increase in activity during recall, which was most prominent in bilateral cuneus and precuneus. THC administration did not affect task performance, but while during placebo recall activity significantly explained variance in performance, this effect disappeared after THC. These findings suggest eCB involvement in encoding of pictorial information. Increased precuneus activity could reflect impaired recall function, but the absence of THC effects on task performance suggests a compensatory mechanism. These results further emphasize the eCB system as a potential novel target for treatment of memory disorders and a promising target for development of new therapies to reduce memory deficits in humans.

Aging and memory as discrimination: Influences of encoding specificity, cue overload, and prior knowledge.

PubMed

Badham, Stephen P; Poirier, Marie; Gandhi, Navina; Hadjivassiliou, Anna; Maylor, Elizabeth A

2016-11-01

From the perspective of memory-as-discrimination, whether a cue leads to correct retrieval simultaneously depends on the cue's relationship to (a) the memory target and (b) the other retrieval candidates. A corollary of the view is that increasing encoding-retrieval match may only help memory if it improves the cue's capacity to discriminate the target from competitors. Here, age differences in this discrimination process were assessed by manipulating the overlap between cues present at encoding and retrieval orthogonally with cue-target distinctiveness. In Experiment 1, associative memory differences for cue-target sets between young and older adults were minimized through training and retrieval efficiency was assessed through response time. In Experiment 2, age-group differences in associative memory were left to vary and retrieval efficiency was assessed through accuracy. Both experiments showed age-invariance in memory-as-discrimination: cues increasing encoding-retrieval match did not benefit memory unless they also improved discrimination between the target and competitors. Predictions based on the age-related associative deficit were also supported: prior knowledge alleviated age-related associative deficits (Experiment 1), and increasing encoding-retrieval match benefited older more than young adults (Experiment 2). We suggest that the latter occurred because older adults' associative memory deficits reduced the impact of competing retrieval candidates-hence the age-related benefit was not attributable to encoding-retrieval match per se, but rather it was a joint function of an increased probability of the cue connecting to the target combined with a decrease in competing retrieval candidates. (PsycINFO Database Record (c) 2016 APA, all rights reserved).

Reinstatement of Individual Past Events Revealed by the Similarity of Distributed Activation Patterns during Encoding and Retrieval

PubMed Central

Wing, Erik A.; Ritchey, Maureen; Cabeza, Roberto

2015-01-01

Neurobiological memory models assume memory traces are stored in neocortex, with pointers in the hippocampus, and are then reactivated during retrieval, yielding the experience of remembering. Whereas most prior neuroimaging studies on reactivation have focused on the reactivation of sets or categories of items, the current study sought to identify cortical patterns pertaining to memory for individual scenes. During encoding, participants viewed pictures of scenes paired with matching labels (e.g., “barn,” “tunnel”), and, during retrieval, they recalled the scenes in response to the labels and rated the quality of their visual memories. Using representational similarity analyses, we interrogated the similarity between activation patterns during encoding and retrieval both at the item level (individual scenes) and the set level (all scenes). The study yielded four main findings. First, in occipitotemporal cortex, memory success increased with encoding-retrieval similarity (ERS) at the item level but not at the set level, indicating the reactivation of individual scenes. Second, in ventrolateral pFC, memory increased with ERS for both item and set levels, indicating the recapitulation of memory processes that benefit encoding and retrieval of all scenes. Third, in retrosplenial/posterior cingulate cortex, ERS was sensitive to individual scene information irrespective of memory success, suggesting automatic activation of scene contexts. Finally, consistent with neurobiological models, hippocampal activity during encoding predicted the subsequent reactivation of individual items. These findings show the promise of studying memory with greater specificity by isolating individual mnemonic representations and determining their relationship to factors like the detail with which past events are remembered. PMID:25313659

Visual mental image generation does not overlap with visual short-term memory: a dual-task interference study.

PubMed

Borst, Gregoire; Niven, Elaine; Logie, Robert H

2012-04-01

Visual mental imagery and working memory are often assumed to play similar roles in high-order functions, but little is known of their functional relationship. In this study, we investigated whether similar cognitive processes are involved in the generation of visual mental images, in short-term retention of those mental images, and in short-term retention of visual information. Participants encoded and recalled visually or aurally presented sequences of letters under two interference conditions: spatial tapping or irrelevant visual input (IVI). In Experiment 1, spatial tapping selectively interfered with the retention of sequences of letters when participants generated visual mental images from aural presentation of the letter names and when the letters were presented visually. In Experiment 2, encoding of the sequences was disrupted by both interference tasks. However, in Experiment 3, IVI interfered with the generation of the mental images, but not with their retention, whereas spatial tapping was more disruptive during retention than during encoding. Results suggest that the temporary retention of visual mental images and of visual information may be supported by the same visual short-term memory store but that this store is not involved in image generation.

78. Augmenting NMDA Receptor Signaling Enhances Working Memory and Alters Gamma Oscillations in Patients With Schizophrenia

PubMed Central

Forsyth, Jennifer; Bachman, Peter; Asarnow, Robert

2017-01-01

Abstract Background: Gamma band oscillations (30–80 Hz) are associated with numerous sensory and higher cognitive functions and are abnormal in patients with schizophrenia. Glutamate signaling at the N-methyl-D-aspartate receptor (NMDAR) is theorized to play a key role in the pathophysiology of schizophrenia and NMDAR antagonists disrupt working memory and gamma oscillations in healthy individuals. It has therefore been suggested that NMDAR dysfunction may contribute to abnormalities in gamma oscillations and working memory in schizophrenia. In the current study, we examined the effects of acutely augmenting NMDAR signaling using the NMDAR agonist, d-cycloserine (DCS), on working memory and gamma power in patients with schizophrenia. Methods: In a double-blind design, patients with schizophrenia were randomized to receive a single dose of 100 mg DCS (SZ-DCS; n = 24) or Placebo (SZ-PLC; n = 21). Patients completed a spatial n-back task involving a 0-back control condition and 1-back and 2-back working memory loads while undergoing EEG recording. Gamma power (30–80 Hz) during the 0-back condition assessed gamma power associated with basic perceptual, motor, and attentive processes. Change in gamma power for correct working memory trials relative to the 0-back condition assessed gamma power associated with working memory function. Results: Among patients who performed above chance (SZ-DCS = 17, SZ-PLC = 16), patients who received DCS showed superior working memory performance compared to patients who received Placebo. Gamma power during the 0-back control condition was similar between SZ-DCS and SZ-PLC who performed above chance. However, gamma power associated with working memory function was significantly suppressed in SZ-DCS compared to SZ-PLC, particularly over frontal right channels. In addition, whereas higher working memory gamma power over frontal right channels was associated with better working memory performance in SZ-PLC, this relationship was not evident in SZ-DCS. Conclusion: Results suggest that augmenting NMDAR signaling enhanced working memory performance and suppressed gamma activity associated with working memory function in patients with schizophrenia. Given prior reports that schizophrenia patients may utilize excessive gamma power for successful working memory performance, these findings suggest that augmenting NMDAR signaling may improve the efficiency of neural encoding for successful working memory function in schizophrenia.

Examining the causes of memory strength variability: recollection, attention failure, or encoding variability?

PubMed

Koen, Joshua D; Aly, Mariam; Wang, Wei-Chun; Yonelinas, Andrew P

2013-11-01

A prominent finding in recognition memory is that studied items are associated with more variability in memory strength than new items. Here, we test 3 competing theories for why this occurs-the encoding variability, attention failure, and recollection accounts. Distinguishing among these theories is critical because each provides a fundamentally different account of the processes underlying recognition memory. The encoding variability and attention failure accounts propose that old item variance will be unaffected by retrieval manipulations because the processes producing this effect are ascribed to encoding. The recollection account predicts that both encoding and retrieval manipulations that preferentially affect recollection will affect memory variability. These contrasting predictions were tested by examining the effect of response speeding (Experiment 1), dividing attention at retrieval (Experiment 2), context reinstatement (Experiment 3), and increased test delay (Experiment 4) on recognition performance. The results of all 4 experiments confirm the predictions of the recollection account and are inconsistent with the encoding variability account. The evidence supporting the attention failure account is mixed, with 2 of the 4 experiments confirming the account and 2 disconfirming the account. These results indicate that encoding variability and attention failure are insufficient accounts of memory variance and provide support for the recollection account. Several alternative theoretical accounts of the results are also considered. PsycINFO Database Record (c) 2013 APA, all rights reserved.

Encoding-related brain activity and accelerated forgetting in transient epileptic amnesia.

PubMed

Atherton, Kathryn E; Filippini, Nicola; Zeman, Adam Z J; Nobre, Anna C; Butler, Christopher R

2018-05-17

The accelerated forgetting of newly learned information is common amongst patients with epilepsy and, in particular, in the syndrome of transient epileptic amnesia (TEA). However, the neural mechanisms underlying accelerated forgetting are poorly understood. It has been hypothesised that interictal epileptiform activity during longer retention intervals disrupts normally established memory traces. Here, we tested a distinct hypothesis-that accelerated forgetting relates to the abnormal encoding of memories. We studied a group of 15 patients with TEA together with matched, healthy control subjects. Despite normal performance on standard anterograde memory tasks, patients showed accelerated forgetting of a word list over one week. We used a subsequent memory paradigm to compare encoding-related brain activity in patients and controls. Participants studied a series of visually presented scenes whilst undergoing functional MRI scanning. Recognition memory for these scenes was then probed outside the scanner after delays of 45 min and of 4 days. Patients showed poorer memory for the scenes compared with controls. In the patients but not the controls, subsequently forgotten stimuli were associated with reduced hippocampal activation at encoding. Furthermore, patients demonstrated reduced deactivation of posteromedial cortex regions upon viewing subsequently remembered stimuli as compared to subsequently forgotten ones. These data suggest that abnormal encoding-related activity in key memory areas of the brain contributes to accelerated forgetting in TEA. We propose that abnormally encoded memory traces may be particularly vulnerable to interference from subsequently encountered material and hence be forgotten more rapidly. Our results shed light on the mechanisms underlying memory impairment in epilepsy, and offer support to the proposal that accelerated forgetting may be a useful marker of subtle dysfunction in memory-related brain systems. Copyright © 2018 The Authors. Published by Elsevier Ltd.. All rights reserved.

Spontaneously hypertensive rat (SHR) as an animal model for ADHD: a short overview.

PubMed

Meneses, Alfredo; Perez-Garcia, Georgina; Ponce-Lopez, Teresa; Tellez, Ruth; Gallegos-Cari, Andrea; Castillo, Carlos

2011-01-01

Diverse studies indicate that attention-deficit hyperactivity disorder (ADHD) is associated with alterations in encoding processes, including working or short-term memory. Some ADHD dysfunctional domains are reflected in the spontaneously hypertensive rat (SHR). Because ADHD, drugs and animal models are eliciting a growing interest, hence the aim of this work is to present a brief overview with a focus on the SHR as an animal model for ADHD and memory deficits. Thus, this paper reviews the concept of SHR as a model system for ADHD, comparing SHR, Wistar-Kyoto and Sprague-Dawley rats with a focus on the hypertension level and working, short-term memory and attention in different behavioral tasks, such as open field, five choice serial reaction time, water maze, passive avoidance, and autoshaping. In addition, drug treatments (d-amphetamine and methylphenidate) are evaluated.

Benefits and Costs of Context Reinstatement in Episodic Memory: An ERP Study.

PubMed

Bramão, Inês; Johansson, Mikael

2017-01-01

This study investigated context-dependent episodic memory retrieval. An influential idea in the memory literature is that performance benefits when the retrieval context overlaps with the original encoding context. However, such memory facilitation may not be driven by the encoding-retrieval overlap per se but by the presence of diagnostic features in the reinstated context that discriminate the target episode from competing episodes. To test this prediction, the encoding-retrieval overlap and the diagnostic value of the context were manipulated in a novel associative recognition memory task. Participants were asked to memorize word pairs presented together with diagnostic (unique) and nondiagnostic (shared) background scenes. At test, participants recognized the word pairs in the presence and absence of the previously encoded contexts. Behavioral data show facilitated memory performance in the presence of the original context but, importantly, only when the context was diagnostic of the target episode. The electrophysiological data reveal an early anterior ERP encoding-retrieval overlap effect that tracks the cost associated with having nondiagnostic contexts present at retrieval, that is, shared by multiple previous episodes, and a later posterior encoding-retrieval overlap effect that reflects facilitated access to the target episode during retrieval in diagnostic contexts. Taken together, our results underscore the importance of the diagnostic value of the context and suggest that context-dependent episodic memory effects are multiple determined.

Facilitation of memory encoding in primate hippocampus by a neuroprosthesis that promotes task-specific neural firing

NASA Astrophysics Data System (ADS)

Hampson, Robert E.; Song, Dong; Opris, Ioan; Santos, Lucas M.; Shin, Dae C.; Gerhardt, Greg A.; Marmarelis, Vasilis Z.; Berger, Theodore W.; Deadwyler, Sam A.

2013-12-01

Objective. Memory accuracy is a major problem in human disease and is the primary factor that defines Alzheimer’s, ageing and dementia resulting from impaired hippocampal function in the medial temporal lobe. Development of a hippocampal memory neuroprosthesis that facilitates normal memory encoding in nonhuman primates (NHPs) could provide the basis for improving memory in human disease states. Approach. NHPs trained to perform a short-term delayed match-to-sample (DMS) memory task were examined with multi-neuron recordings from synaptically connected hippocampal cell fields, CA1 and CA3. Recordings were analyzed utilizing a previously developed nonlinear multi-input multi-output (MIMO) neuroprosthetic model, capable of extracting CA3-to-CA1 spatiotemporal firing patterns during DMS performance. Main results. The MIMO model verified that specific CA3-to-CA1 firing patterns were critical for the successful encoding of sample phase information on more difficult DMS trials. This was validated by the delivery of successful MIMO-derived encoding patterns via electrical stimulation to the same CA1 recording locations during the sample phase which facilitated task performance in the subsequent, delayed match phase, on difficult trials that required more precise encoding of sample information. Significance. These findings provide the first successful application of a neuroprosthesis designed to enhance and/or repair memory encoding in primate brain.

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

Facilitation of Memory Encoding in Primate Hippocampus by a Neuroprosthesis that Promotes Task Specific Neural Firing

PubMed Central

Hampson, Robert E.; Song, Dong; Opris, Ioan; Santos, Lucas M.; Shin, Dae C.; Gerhardt, Greg A.; Marmarelis, Vasilis Z.; Berger, Theodore W.; Deadwyler, Sam A.

2014-01-01

Objective Memory accuracy is a major problem in human disease and is the primary factor that defines Alzheimer’s’, aging and dementia resulting from impaired hippocampal function in medial temporal lobe. Development of a hippocampal memory neuroprosthesis that facilitates normal memory encoding in nonhuman primates (NHPs) could provide the basis for improving memory in human disease states. Approach NHPs trained to perform a short-term delayed match to sample (DMS) memory task were examined with multi-neuron recordings from synaptically connected hippocampal cell fields, CA1 and CA3. Recordings were analyzed utilizing a previously developed nonlinear multi-input multi-output (MIMO) neuroprosthetic model, capable of extracting CA3-to-CA1 spatiotemporal firing patterns during DMS performance. Main Results The MIMO model verified that specific CA3-to-CA1 firing patterns were critical for successful encoding of Sample phase information on more difficult DMS trials. This was validated by delivery of successful MIMO-derived encoding patterns via electrical stimulation to the same CA1 recording locations during the Sample phase which facilitated task performance in the subsequent delayed Match phase on difficult trials that required more precise encoding of Sample information. Significance These findings provide the first successful application of a neuroprosthesis designed to enhance and/or repair memory encoding in primate brain. PMID:24216292

Effects of age on negative subsequent memory effects associated with the encoding of item and item-context information.

PubMed

Mattson, Julia T; Wang, Tracy H; de Chastelaine, Marianne; Rugg, Michael D

2014-12-01

It has consistently been reported that "negative" subsequent memory effects--lower study activity for later remembered than later forgotten items--are attenuated in older individuals. The present functional magnetic resonance imaging study investigated whether these findings extend to subsequent memory effects associated with successful encoding of item-context information. Older (n = 25) and young (n = 17) subjects were scanned while making 1 of 2 encoding judgments on a series of pictures. Memory was assessed for the study item and, for items judged old, the item's encoding task. Both memory judgments were made using confidence ratings, permitting item and source memory strength to be unconfounded and source confidence to be equated across age groups. Replicating prior findings, negative item effects in regions of the default mode network in young subjects were reversed in older subjects. Negative source effects, however, were invariant with respect to age and, in both age groups, the magnitude of the effects correlated with source memory performance. It is concluded that negative item effects do not reflect processes necessary for the successful encoding of item-context associations in older subjects. Negative source effects, in contrast, appear to reflect the engagement of processes that are equally important for successful episodic encoding in older and younger individuals. © The Author 2013. Published by Oxford University Press. All rights reserved. For Permissions, please e-mail: journals.permissions@oup.com.

Sparse distributed memory overview

NASA Technical Reports Server (NTRS)

Raugh, Mike

1990-01-01

The Sparse Distributed Memory (SDM) project is investigating the theory and applications of massively parallel computing architecture, called sparse distributed memory, that will support the storage and retrieval of sensory and motor patterns characteristic of autonomous systems. The immediate objectives of the project are centered in studies of the memory itself and in the use of the memory to solve problems in speech, vision, and robotics. Investigation of methods for encoding sensory data is an important part of the research. Examples of NASA missions that may benefit from this work are Space Station, planetary rovers, and solar exploration. Sparse distributed memory offers promising technology for systems that must learn through experience and be capable of adapting to new circumstances, and for operating any large complex system requiring automatic monitoring and control. Sparse distributed memory is a massively parallel architecture motivated by efforts to understand how the human brain works. Sparse distributed memory is an associative memory, able to retrieve information from cues that only partially match patterns stored in the memory. It is able to store long temporal sequences derived from the behavior of a complex system, such as progressive records of the system's sensory data and correlated records of the system's motor controls.

Level of Processing Modulates the Neural Correlates of Emotional Memory Formation

ERIC Educational Resources Information Center

Ritchey, Maureen; LaBar, Kevin S.; Cabeza, Roberto

2011-01-01

Emotion is known to influence multiple aspects of memory formation, including the initial encoding of the memory trace and its consolidation over time. However, the neural mechanisms whereby emotion impacts memory encoding remain largely unexplored. The present study used a levels-of-processing manipulation to characterize the impact of emotion on…

Opposite Effects of Cortisol on Consolidation of Temporal Sequence Memory during Waking and Sleep

ERIC Educational Resources Information Center

Wilhelm, Ines; Wagner, Ullrich; Born, Jan

2011-01-01

Memory functions involve three stages: encoding, consolidation, and retrieval. Modulating effects of glucocorticoids (GCs) have been consistently observed for declarative memory with GCs enhancing encoding and impairing retrieval, but surprisingly, little is known on how GCs affect memory consolidation. Studies in rats suggest a beneficial effect…

Binding and strategic selection in working memory: a lifespan dissociation.

PubMed

Sander, Myriam C; Werkle-Bergner, Markus; Lindenberger, Ulman

2011-09-01

Working memory (WM) shows a gradual increase during childhood, followed by accelerating decline from adulthood to old age. To examine these lifespan differences more closely, we asked 34 children (10-12 years), 40 younger adults (20-25 years), and 39 older adults (70-75 years) to perform a color change detection task. Load levels and encoding durations were varied for displays including targets only (Experiment 1) or targets plus distracters (Experiment 2, investigating a subsample of Experiment 1). WM performance was lower in older adults and children than in younger adults. Longer presentation times were associated with better performance in all age groups, presumably reflecting increasing effects of strategic selection mechanisms on WM performance. Children outperformed older adults when encoding times were short, and distracter effects were larger in children and older adults than in younger adults. We conclude that strategic selection in WM develops more slowly during childhood than basic binding operations, presumably reflecting the delay in maturation of frontal versus medio-temporal brain networks. In old age, both sets of mechanisms decline, reflecting senescent change in both networks. We discuss similarities to episodic memory development and address open questions for future research.

The Role of Anterior Nuclei of the Thalamus: A Subcortical Gate in Memory Processing: An Intracerebral Recording Study

PubMed Central

Štillová, Klára; Jurák, Pavel; Chládek, Jan; Chrastina, Jan; Halámek, Josef; Bočková, Martina; Goldemundová, Sabina; Říha, Ivo; Rektor, Ivan

2015-01-01

Objective To study the involvement of the anterior nuclei of the thalamus (ANT) as compared to the involvement of the hippocampus in the processes of encoding and recognition during visual and verbal memory tasks. Methods We studied intracerebral recordings in patients with pharmacoresistent epilepsy who underwent deep brain stimulation (DBS) of the ANT with depth electrodes implanted bilaterally in the ANT and compared the results with epilepsy surgery candidates with depth electrodes implanted bilaterally in the hippocampus. We recorded the event-related potentials (ERPs) elicited by the visual and verbal memory encoding and recognition tasks. Results P300-like potentials were recorded in the hippocampus by visual and verbal memory encoding and recognition tasks and in the ANT by the visual encoding and visual and verbal recognition tasks. No significant ERPs were recorded during the verbal encoding task in the ANT. In the visual and verbal recognition tasks, the P300-like potentials in the ANT preceded the P300-like potentials in the hippocampus. Conclusions The ANT is a structure in the memory pathway that processes memory information before the hippocampus. We suggest that the ANT has a specific role in memory processes, especially memory recognition, and that memory disturbance should be considered in patients with ANT-DBS and in patients with ANT lesions. ANT is well positioned to serve as a subcortical gate for memory processing in cortical structures. PMID:26529407

Reader set encoding for directory of shared cache memory in multiprocessor system

DOEpatents

Ahn, Dnaiel; Ceze, Luis H.; Gara, Alan; Ohmacht, Martin; Xiaotong, Zhuang

2014-06-10

In a parallel processing system with speculative execution, conflict checking occurs in a directory lookup of a cache memory that is shared by all processors. In each case, the same physical memory address will map to the same set of that cache, no matter which processor originated that access. The directory includes a dynamic reader set encoding, indicating what speculative threads have read a particular line. This reader set encoding is used in conflict checking. A bitset encoding is used to specify particular threads that have read the line.

Using warnings to reduce categorical false memories in younger and older adults.

PubMed

Carmichael, Anna M; Gutchess, Angela H

2016-07-01

Warnings about memory errors can reduce their incidence, although past work has largely focused on associative memory errors. The current study sought to explore whether warnings could be tailored to specifically reduce false recall of categorical information in both younger and older populations. Before encoding word pairs designed to induce categorical false memories, half of the younger and older participants were warned to avoid committing these types of memory errors. Older adults who received a warning committed fewer categorical memory errors, as well as other types of semantic memory errors, than those who did not receive a warning. In contrast, young adults' memory errors did not differ for the warning versus no-warning groups. Our findings provide evidence for the effectiveness of warnings at reducing categorical memory errors in older adults, perhaps by supporting source monitoring, reduction in reliance on gist traces, or through effective metacognitive strategies.

Memory for emotional words: The role of semantic relatedness, encoding task and affective valence.

PubMed

Ferré, Pilar; Fraga, Isabel; Comesaña, Montserrat; Sánchez-Casas, Rosa

2015-01-01

Emotional stimuli have been repeatedly demonstrated to be better remembered than neutral ones. The aim of the present study was to test whether this advantage in memory is mainly produced by the affective content of the stimuli or it can be rather accounted for by factors such as semantic relatedness or type of encoding task. The valence of the stimuli (positive, negative and neutral words that could be either semantically related or unrelated) as well as the type of encoding task (focused on either familiarity or emotionality) was manipulated. The results revealed an advantage in memory for emotional words (either positive or negative) regardless of semantic relatedness. Importantly, this advantage was modulated by the encoding task, as it was reliable only in the task which focused on emotionality. These findings suggest that congruity with the dimension attended at encoding might contribute to the superiority in memory for emotional words, thus offering us a more complex picture of the underlying mechanisms behind the advantage for emotional information in memory.

The neural correlates of age effects on verbal-spatial binding in working memory.

PubMed

Meier, Timothy B; Nair, Veena A; Meyerand, Mary E; Birn, Rasmus M; Prabhakaran, Vivek

2014-06-01

In this study, we investigated the neural correlates of age-related differences in the binding of verbal and spatial information utilizing event-related working memory tasks. Twenty-one right handed younger adults and twenty-one right handed older adults performed two versions of a dual task of verbal and spatial working memory. In the unbound dual task version letters and locations were presented simultaneously in separate locations, while in the bound dual task version each letter was paired with a specific location. In order to identify binding-specific differences, mixed-effects ANOVAs were run with the interaction of age and task as the effect of interest. Although older adults performed worse in the bound task than younger adults, there was no significant interaction between task and age on working memory performance. However, interactions of age and task were observed in brain activity analyses. Older adults did not display the greater unbound than bound task activity that younger adults did at the encoding phase in bilateral inferior parietal lobule, right putamen, and globus pallidus as well as at the maintenance phase in the cerebellum. We conclude that the binding of letters and locations in working memory is not as efficient in older adults as it is in younger adults, possibly due to the decline of cognitive control processes that are specific to working memory binding. Copyright © 2014 Elsevier B.V. All rights reserved.

Neural Similarity Between Encoding and Retrieval is Related to Memory Via Hippocampal Interactions

PubMed Central

Ritchey, Maureen; Wing, Erik A.; LaBar, Kevin S.; Cabeza, Roberto

2013-01-01

A fundamental principle in memory research is that memory is a function of the similarity between encoding and retrieval operations. Consistent with this principle, many neurobiological models of declarative memory assume that memory traces are stored in cortical regions, and the hippocampus facilitates the reactivation of these traces during retrieval. The present investigation tested the novel prediction that encoding–retrieval similarity can be observed and related to memory at the level of individual items. Multivariate representational similarity analysis was applied to functional magnetic resonance imaging data collected during encoding and retrieval of emotional and neutral scenes. Memory success tracked fluctuations in encoding–retrieval similarity across frontal and posterior cortices. Importantly, memory effects in posterior regions reflected increased similarity between item-specific representations during successful recognition. Mediation analyses revealed that the hippocampus mediated the link between cortical similarity and memory success, providing crucial evidence for hippocampal–cortical interactions during retrieval. Finally, because emotional arousal is known to modulate both perceptual and memory processes, similarity effects were compared for emotional and neutral scenes. Emotional arousal was associated with enhanced similarity between encoding and retrieval patterns. These findings speak to the promise of pattern similarity measures for evaluating memory representations and hippocampal–cortical interactions. PMID:22967731

Ignoring versus updating in working memory reveal differential roles of attention and feature binding.

PubMed

Fallon, Sean J; Mattiesing, Rozemarijn M; Dolfen, Nina; Manohar, Sanjay G; Husain, Masud

2018-01-05

Ignoring distracting information and updating current contents are essential components of working memory (WM). Yet, although both require controlling irrelevant information, it is unclear whether they have the same effects on recall and produce the same level of misbinding errors (incorrectly joining the features of different memoranda). Moreover, the likelihood of misbinding may be affected by the feature similarity between the items already encoded into memory and the information that has to be filtered out (ignored) or updated into memory. Here, we investigate these questions. Participants were sequentially presented with two pairs of arrows. The first pair of arrows always had to be encoded into memory, but the second pair either had to be ignored (ignore condition) or allowed to displace the previously encoded items (update condition). To investigate the effect of similarity on recall, we also varied, in a factorial manner, whether the items that had to be ignored or updated were presented in the same or different colours and/or same or different spatial locations to the original memoranda. By applying a computational model, we were able to quantify the levels of misbinding. Ignoring, but not updating, increased overall recall error as well as misbinding rates, even when accounting for the retention period. This indicates that not all manipulations of attention in WM are equal in terms of their effects on recall and misbinding. Misbinding rates in the ignore condition were affected by the colour and spatial congruence of relevant and irrelevant information to a greater extent than in the update condition. This finding suggests that attentional templates are used to evaluate relevant and irrelevant information in different ways during ignoring and updating. Together, the results suggest that differences between the two functions might occur due to higher levels of attentional compartmentalisation - or protection - during updating compared to ignoring. Copyright © 2018 The Authors. Published by Elsevier Ltd.. All rights reserved.

The dissociable effects of stereotype threat on older adults’ memory encoding and retrieval

PubMed Central

Krendl, Anne C.; Ambady, Nalini; Kensinger, Elizabeth A.

2015-01-01

The present study asks how subliminal exposure to negative stereotypes about age-related memory deficits affects older adults’ memory performance. Whereas prior research has focused on the effect of “stereotype threat” on older adults’ memory for neutral material, the present study additionally examines the effect on memory for positive and negative words, as well as whether the subliminal “threat” has a larger impact on memory performance when it occurs prior to encoding or prior to retrieval (as compared to a control condition). Results revealed that older adults’ memory impairments were most pronounced when the threat was placed prior to retrieval as compared to when the threat was placed prior to encoding or no threat occurred. Moreover, the threat specifically increased false memory rates, particularly for neutral items compared to positive and negative ones. These results emphasize that stereotype threat effects vary depending upon the phase of memory it impacts. PMID:26029498

Memory processing in great apes: the effect of time and sleep

PubMed Central

Martin-Ordas, Gema; Call, Josep

2011-01-01

Following encoding, memory remains temporarily vulnerable to disruption. Consolidation refers to offline time-dependent processes that continue after encoding and stabilize, transform or enhance the memory trace. Memory consolidation resulting from sleep has been reported for declarative and non-declarative memories in humans. We first investigated the temporal course of memory retrieval in chimpanzees, bonobos and orangutans. We found that the amount of retrieved information was time dependent: apes' performance degraded after 1 and 2 h, stabilized after 4 h, started to increase after 8 and 12 h and fully recovered after 24 h. Second, we show that although memories during wakefulness were highly vulnerable to interference from events similar to those witnessed during the original encoding event, an intervening period of sleep not only stabilized apes' memories into more permanent ones but also protected them against interference. PMID:21632621

Memory processing in great apes: the effect of time and sleep.

PubMed

Martin-Ordas, Gema; Call, Josep

2011-12-23

Following encoding, memory remains temporarily vulnerable to disruption. Consolidation refers to offline time-dependent processes that continue after encoding and stabilize, transform or enhance the memory trace. Memory consolidation resulting from sleep has been reported for declarative and non-declarative memories in humans. We first investigated the temporal course of memory retrieval in chimpanzees, bonobos and orangutans. We found that the amount of retrieved information was time dependent: apes' performance degraded after 1 and 2 h, stabilized after 4 h, started to increase after 8 and 12 h and fully recovered after 24 h. Second, we show that although memories during wakefulness were highly vulnerable to interference from events similar to those witnessed during the original encoding event, an intervening period of sleep not only stabilized apes' memories into more permanent ones but also protected them against interference.

Cortical Activation Patterns during Long-Term Memory Retrieval of Visually or Haptically Encoded Objects and Locations

ERIC Educational Resources Information Center

Stock, Oliver; Roder, Brigitte; Burke, Michael; Bien, Siegfried; Rosler, Frank

2009-01-01

The present study used functional magnetic resonance imaging to delineate cortical networks that are activated when objects or spatial locations encoded either visually (visual encoding group, n = 10) or haptically (haptic encoding group, n = 10) had to be retrieved from long-term memory. Participants learned associations between auditorily…

Effects of Pre-Encoding Stress on Brain Correlates Associated with the Long-Term Memory for Emotional Scenes

PubMed Central

Wirkner, Janine; Weymar, Mathias; Löw, Andreas; Hamm, Alfons O.

2013-01-01

Recent animal and human research indicates that stress around the time of encoding enhances long-term memory for emotionally arousing events but neural evidence remains unclear. In the present study we used the ERP old/new effect to investigate brain dynamics underlying the long-term effects of acute pre-encoding stress on memory for emotional and neutral scenes. Participants were exposed either to the Socially Evaluated Cold Pressure Test (SECPT) or a warm water control procedure before viewing 30 unpleasant, 30 neutral and 30 pleasant pictures. Two weeks after encoding, recognition memory was tested using 90 old and 90 new pictures. Emotional pictures were better recognized than neutral pictures in both groups and related to an enhanced centro-parietal ERP old/new difference (400–800 ms) during recognition, which suggests better recollection. Most interestingly, pre-encoding stress exposure specifically increased the ERP old/new-effect for emotional (unpleasant) pictures, but not for neutral pictures. These enhanced ERP/old new differences for emotional (unpleasant) scenes were particularly pronounced for those participants who reported high levels of stress during the SECPT. The results suggest that acute pre-encoding stress specifically strengthens brain signals of emotional memories, substantiating a facilitating role of stress on memory for emotional scenes. PMID:24039697

Source memory that encoding was self-referential: the influence of stimulus characteristics.

PubMed

Durbin, Kelly A; Mitchell, Karen J; Johnson, Marcia K

2017-10-01

Decades of research suggest that encoding information with respect to the self improves memory (self-reference effect, SRE) for items (item SRE). The current study focused on how processing information in reference to the self affects source memory for whether an item was self-referentially processed (a source SRE). Participants self-referentially or non-self-referentially encoded words (Experiment 1) or pictures (Experiment 2) that varied in valence (positive, negative, neutral). Relative to non-self-referential processing, self-referential processing enhanced item recognition for all stimulus types (an item SRE), but it only enhanced source memory for positive words (a source SRE). In fact, source memory for negative and neutral pictures was worse for items processed self-referentially than non-self-referentially. Together, the results suggest that item SRE and source SRE (e.g., remembering an item was encoded self-referentially) are not necessarily the same across stimulus types (e.g., words, pictures; positive, negative). While an item SRE may depend on the overall likelihood the item generates any association, the enhancing effects of self-referential processing on source memory for self-referential encoding may depend on how embedded a stimulus becomes in one's self-schema, and that depends, in part, on the stimulus' valence and format. Self-relevance ratings during encoding provide converging evidence for this interpretation.

Continuous-variable quantum computing in optical time-frequency modes using quantum memories.

PubMed

Humphreys, Peter C; Kolthammer, W Steven; Nunn, Joshua; Barbieri, Marco; Datta, Animesh; Walmsley, Ian A

2014-09-26

We develop a scheme for time-frequency encoded continuous-variable cluster-state quantum computing using quantum memories. In particular, we propose a method to produce, manipulate, and measure two-dimensional cluster states in a single spatial mode by exploiting the intrinsic time-frequency selectivity of Raman quantum memories. Time-frequency encoding enables the scheme to be extremely compact, requiring a number of memories that are a linear function of only the number of different frequencies in which the computational state is encoded, independent of its temporal duration. We therefore show that quantum memories can be a powerful component for scalable photonic quantum information processing architectures.

Audiovisual semantic congruency during encoding enhances memory performance.

PubMed

Heikkilä, Jenni; Alho, Kimmo; Hyvönen, Heidi; Tiippana, Kaisa

2015-01-01

Studies of memory and learning have usually focused on a single sensory modality, although human perception is multisensory in nature. In the present study, we investigated the effects of audiovisual encoding on later unisensory recognition memory performance. The participants were to memorize auditory or visual stimuli (sounds, pictures, spoken words, or written words), each of which co-occurred with either a semantically congruent stimulus, incongruent stimulus, or a neutral (non-semantic noise) stimulus in the other modality during encoding. Subsequent memory performance was overall better when the stimulus to be memorized was initially accompanied by a semantically congruent stimulus in the other modality than when it was accompanied by a neutral stimulus. These results suggest that semantically congruent multisensory experiences enhance encoding of both nonverbal and verbal materials, resulting in an improvement in their later recognition memory.

Prefrontal activity and impaired memory encoding strategies in schizophrenia.

PubMed

Guimond, Synthia; Hawco, Colin; Lepage, Martin

2017-08-01

Schizophrenia patients have significant memory difficulties that have far-reaching implications in their daily life. These impairments are partly attributed to an inability to self-initiate effective memory encoding strategies, but its core neurobiological correlates remain unknown. The current study addresses this critical gap in our knowledge of episodic memory impairments in schizophrenia. Schizophrenia patients (n = 35) and healthy controls (n = 23) underwent a Semantic Encoding Memory Task (SEMT) during an fMRI scan. Brain activity was examined for conditions where participants were a) prompted to use semantic encoding strategies, or b) not prompted but required to self-initiate such strategies. When prompted to use semantic encoding strategies, schizophrenia patients exhibited similar recognition performance and brain activity as healthy controls. However, when required to self-initiate these strategies, patients had significant reduced recognition performance and brain activity in the left dorsolateral prefrontal cortex, as well as in the left temporal gyrus, left superior parietal lobule, and cerebellum. When patients were divided based on performance on the SEMT, the subgroup with more severe deficits in self-initiation also showed greater reduction in left dorsolateral prefrontal activity. These results suggest that impaired self-initiation of elaborative encoding strategies is a driving feature of memory deficits in schizophrenia. We also identified the neural correlates of impaired self-initiation of semantic encoding strategies, in which a failure to activate the left dorsolateral prefrontal cortex plays a key role. These findings provide important new targets in the development of novel treatments aiming to improve memory and ultimately patients' outcome. Copyright © 2017. Published by Elsevier Ltd.

Staying Cool when Things Get Hot: Emotion Regulation Modulates Neural Mechanisms of Memory Encoding

PubMed Central

Hayes, Jasmeet Pannu; Morey, Rajendra A.; Petty, Christopher M.; Seth, Srishti; Smoski, Moria J.; McCarthy, Gregory; LaBar, Kevin S.

2010-01-01

During times of emotional stress, individuals often engage in emotion regulation to reduce the experiential and physiological impact of negative emotions. Interestingly, emotion regulation strategies also influence memory encoding of the event. Cognitive reappraisal is associated with enhanced memory while expressive suppression is associated with impaired explicit memory of the emotional event. However, the mechanism by which these emotion regulation strategies affect memory is unclear. We used event-related fMRI to investigate the neural mechanisms that give rise to memory formation during emotion regulation. Twenty-five participants viewed negative pictures while alternately engaging in cognitive reappraisal, expressive suppression, or passive viewing. As part of the subsequent memory design, participants returned to the laboratory two weeks later for a surprise memory test. Behavioral results showed a reduction in negative affect and a retention advantage for reappraised stimuli relative to the other conditions. Imaging results showed that successful encoding during reappraisal was uniquely associated with greater co-activation of the left inferior frontal gyrus, amygdala, and hippocampus, suggesting a possible role for elaborative encoding of negative memories. This study provides neurobehavioral evidence that engaging in cognitive reappraisal is advantageous to both affective and mnemonic processes. PMID:21212840

The Effects of Age, Memory Performance, and Callosal Integrity on the Neural Correlates of Successful Associative Encoding

PubMed Central

Wang, Tracy H.; Minton, Brian; Muftuler, L. Tugan; Rugg, Michael D.

2011-01-01

This functional magnetic resonance imaging study investigated the relationship between the neural correlates of associative memory encoding, callosal integrity, and memory performance in older adults. Thirty-six older and 18 young subjects were scanned while making relational judgments on word pairs. Neural correlates of successful encoding (subsequent memory effects) were identified by contrasting the activity elicited by study pairs that were correctly identified as having been studied together with the activity elicited by pairs wrongly judged to have come from different study trials. Subsequent memory effects common to the 2 age groups were identified in several regions, including left inferior frontal gyrus and bilateral hippocampus. Negative effects (greater activity for forgotten than for remembered items) in default network regions in young subjects were reversed in the older group, and the amount of reversal correlated negatively with memory performance. Additionally, older subjects' subsequent memory effects in right frontal cortex correlated positively with anterior callosal integrity and negatively with memory performance. It is suggested that recruitment of right frontal cortex during verbal memory encoding may reflect the engagement of processes that compensate only partially for age-related neural degradation. PMID:21282317

Dopaminergic influences on formation of a motor memory.

PubMed

Flöel, Agnes; Breitenstein, Caterina; Hummel, Friedhelm; Celnik, Pablo; Gingert, Christian; Sawaki, Lumy; Knecht, Stefan; Cohen, Leonardo G

2005-07-01

The ability of the central nervous system to form motor memories, a process contributing to motor learning and skill acquisition, decreases with age. Dopaminergic activity, one of the mechanisms implicated in memory formation, experiences a similar decline with aging. It is possible that restoring dopaminergic function in elderly adults could lead to improved formation of motor memories with training. We studied the influence of a single oral dose of levodopa (100mg) administered preceding training on the ability to encode an elementary motor memory in the primary motor cortex of elderly and young healthy volunteers in a randomized, double-blind, placebo-controlled design. Attention to the task and motor training kinematics were comparable across age groups and sessions. In young subjects, encoding a motor memory under placebo was more prominent than in older subjects, and the encoding process was accelerated by intake of levodopa. In the elderly group, diminished motor memory encoding under placebo was enhanced by intake of levodopa to levels present in younger subjects. Therefore, upregulation of dopaminergic activity accelerated memory formation in young subjects and restored the ability to form a motor memory in elderly subjects; possible mechanisms underlying the beneficial effects of dopaminergic agents on motor learning in neurorehabilitation.

Cognitive control, attention, and the other race effect in memory.

PubMed

Brown, Thackery I; Uncapher, Melina R; Chow, Tiffany E; Eberhardt, Jennifer L; Wagner, Anthony D

2017-01-01

People are better at remembering faces from their own race than other races-a phenomenon with significant societal implications. This Other Race Effect (ORE) in memory could arise from different attentional allocation to, and cognitive control over, same- and other-race faces during encoding. Deeper or more differentiated processing of same-race faces could yield more robust representations of same- vs. other-race faces that could support better recognition memory. Conversely, to the extent that other-race faces may be characterized by lower perceptual expertise, attention and cognitive control may be more important for successful encoding of robust, distinct representations of these stimuli. We tested a mechanistic model in which successful encoding of same- and other-race faces, indexed by subsequent memory performance, is differentially predicted by (a) engagement of frontoparietal networks subserving top-down attention and cognitive control, and (b) interactions between frontoparietal networks and fusiform cortex face processing. European American (EA) and African American (AA) participants underwent fMRI while intentionally encoding EA and AA faces, and ~24 hrs later performed an "old/new" recognition memory task. Univariate analyses revealed greater engagement of frontoparietal top-down attention and cognitive control networks during encoding for same- vs. other-race faces, stemming particularly from a failure to engage the cognitive control network during processing of other-race faces that were subsequently forgotten. Psychophysiological interaction (PPI) analyses further revealed that OREs were characterized by greater functional interaction between medial intraparietal sulcus, a component of the top-down attention network, and fusiform cortex during same- than other-race face encoding. Together, these results suggest that group-based face memory biases at least partially stem from differential allocation of cognitive control and top-down attention during encoding, such that same-race memory benefits from elevated top-down attentional engagement with face processing regions; conversely, reduced recruitment of cognitive control circuitry appears more predictive of memory failure when encoding out-group faces.

Cognitive control, attention, and the other race effect in memory

PubMed Central

Uncapher, Melina R.; Chow, Tiffany E.; Eberhardt, Jennifer L.; Wagner, Anthony D.

2017-01-01

People are better at remembering faces from their own race than other races–a phenomenon with significant societal implications. This Other Race Effect (ORE) in memory could arise from different attentional allocation to, and cognitive control over, same- and other-race faces during encoding. Deeper or more differentiated processing of same-race faces could yield more robust representations of same- vs. other-race faces that could support better recognition memory. Conversely, to the extent that other-race faces may be characterized by lower perceptual expertise, attention and cognitive control may be more important for successful encoding of robust, distinct representations of these stimuli. We tested a mechanistic model in which successful encoding of same- and other-race faces, indexed by subsequent memory performance, is differentially predicted by (a) engagement of frontoparietal networks subserving top-down attention and cognitive control, and (b) interactions between frontoparietal networks and fusiform cortex face processing. European American (EA) and African American (AA) participants underwent fMRI while intentionally encoding EA and AA faces, and ~24 hrs later performed an “old/new” recognition memory task. Univariate analyses revealed greater engagement of frontoparietal top-down attention and cognitive control networks during encoding for same- vs. other-race faces, stemming particularly from a failure to engage the cognitive control network during processing of other-race faces that were subsequently forgotten. Psychophysiological interaction (PPI) analyses further revealed that OREs were characterized by greater functional interaction between medial intraparietal sulcus, a component of the top-down attention network, and fusiform cortex during same- than other-race face encoding. Together, these results suggest that group-based face memory biases at least partially stem from differential allocation of cognitive control and top-down attention during encoding, such that same-race memory benefits from elevated top-down attentional engagement with face processing regions; conversely, reduced recruitment of cognitive control circuitry appears more predictive of memory failure when encoding out-group faces. PMID:28282414

Visuospatial bootstrapping: Binding useful visuospatial information during verbal working memory encoding does not require set-shifting executive resources.

PubMed

Calia, Clara; Darling, Stephen; Havelka, Jelena; Allen, Richard J

2018-05-01

Immediate serial recall of digits is better when the digits are shown by highlighting them in a familiar array, such as a phone keypad, compared with presenting them serially in a single location, a pattern referred to as "visuospatial bootstrapping." This pattern implies the establishment of temporary links between verbal and spatial working memory, alongside access to information in long-term memory. However, the role of working memory control processes like those implied by the "Central Executive" in bootstrapping has not been directly investigated. Here, we report a study addressing this issue, focusing on executive processes of attentional shifting. Tasks in which information has to be sequenced are thought to be heavily dependent on shifting. Memory for digits presented in keypads versus single locations was assessed under two secondary task load conditions, one with and one without a sequencing requirement, and hence differing in the degree to which they invoke shifting. Results provided clear evidence that multimodal binding (visuospatial bootstrapping) can operate independently of this form of executive control process.

Subjective memory complaints are associated with brain activation supporting successful memory encoding.

PubMed

Hayes, Jessica M; Tang, Lingfei; Viviano, Raymond P; van Rooden, Sanneke; Ofen, Noa; Damoiseaux, Jessica S

2017-12-01

Subjective memory complaints, the perceived decline in cognitive abilities in the absence of clinical deficits, may precede Alzheimer's disease. Individuals with subjective memory complaints show differential brain activation during memory encoding; however, whether such differences contribute to successful memory formation remains unclear. Here, we investigated how subsequent memory effects, activation which is greater for hits than misses during an encoding task, differed between healthy older adults aged 50 to 85 years with (n = 23) and without (n = 41) memory complaints. Older adults with memory complaints, compared to those without, showed lower subsequent memory effects in the occipital lobe, superior parietal lobe, and posterior cingulate cortex. In addition, older adults with more memory complaints showed a more negative subsequent memory effects in areas of the default mode network, including the posterior cingulate cortex, precuneus, and ventromedial prefrontal cortex. Our findings suggest that for successful memory formation, older adults with subjective memory complaints rely on distinct neural mechanisms which may reflect an overall decreased task-directed attention. Copyright © 2017 Elsevier Inc. All rights reserved.

High Neuromagnetic Activation in the Left Prefrontal and Frontal Cortices Correlates with Better Memory Performance for Abstract Words

ERIC Educational Resources Information Center

Chen, Tzu-Ching; Lin, Yung-Yang

2012-01-01

The present study aimed to clarify the spatiotemporal characteristics of memory processing for abstract and concrete words. Neuromagnetic responses to memory encoding and recognition tasks of abstract and concrete nouns were obtained in 18 healthy adults using a whole-head neuromagnetometer. During memory encoding, abstract words elicited larger…

Can the hippocampus tell time? The temporo-septal engram shift model.

PubMed

Lytton, W W; Lipton, P

1999-08-02

An essential feature of episodic memory, the type of memory dependent on hippocampus, is that individual memories belong to particular moments in time. Recent PET studies suggest that memory encoding and recall occur at different locations in human hippocampus. Coupled with other attributes of hippocampus, this suggested to us that the septo-temporal hippocampal axis may play an important role in time perception. We propose a temporo-septal engram shift model of hippocampal memory. The model posits that memories gradually move along the hippocampus from a temporal encoding site to ever more septal sites from which they are recalled. We propose that the sense of time is encoded by the location of the engram along the temporo-septal axis.

Working memory still needs verbal rehearsal.

PubMed

Lucidi, Annalisa; Langerock, Naomi; Hoareau, Violette; Lemaire, Benoît; Camos, Valérie; Barrouillet, Pierre

2016-02-01

The causal role of verbal rehearsal in working memory has recently been called into question. For example, the SOB-CS (Serial Order in a Box-Complex Span) model assumes that there is no maintenance process for the strengthening of items in working memory, but instead a process of removal of distractors that are involuntarily encoded and create interference with memory items. In the present study, we tested the idea that verbal working memory performance can be accounted for without assuming a causal role of the verbal rehearsal process. We demonstrate in two experiments using a complex span task and a Brown-Peterson paradigm that increasing the number of repetitions of the same distractor (the syllable ba that was read aloud at each of its occurrences on screen) has a detrimental effect on the concurrent maintenance of consonants whereas the maintenance of spatial locations remains unaffected. A detailed analysis of the tasks demonstrates that accounting for this effect within the SOB-CS model requires a series of unwarranted assumptions leading to undesirable further predictions contradicted by available experimental evidence. We argue that the hypothesis of a maintenance mechanism based on verbal rehearsal that is impeded by concurrent articulation still provides the simplest and most compelling account of our results.

Phonological working memory impairments in children with specific language impairment: where does the problem lie?

PubMed

Alt, Mary

2011-01-01

The purpose of this study was to determine which factors contribute to the lexical learning deficits of children with specific language impairment (SLI). Participants included 40 7-8-year old participants, half of whom were diagnosed with SLI and half of whom had normal language skills. We tested hypotheses about the contributions to word learning of the initial encoding of phonological information and the link to long-term memory. Children took part in a computer-based fast-mapping task which manipulated word length and phonotactic probability to address the hypotheses. The task had a recognition and a production component. Data were analyzed using mixed ANOVAs with post-hoc testing. Results indicate that the main problem for children with SLI is with initial encoding, with implications for limited capacity. There was not strong evidence for specific deficits in the link to long-term memory. We were able to ascertain which aspects of lexical learning are most problematic for children with SLI in terms of fast-mapping. These findings may allow clinicians to focus intervention on known areas of weakness. Future directions include extending these findings to slow mapping scenarios. The reader will understand how different components of phonological working memory contribute to the word learning problems of children with specific language impairment. Copyright © 2010 Elsevier Inc. All rights reserved.