Tag: Episodic Memory

Mechanisms of critical period in the hippocampus underlie object location learning and memory in infant rats

Mechanisms of critical period in the hippocampus underlie object location learning and memory in infant rats

Published in: Learning & Memory, Volume 25, Issue 4, 176-182

Abstract
“Episodic memories in early childhood are rapidly forgotten, a phenomenon that is associated with “infantile amnesia,” the inability of adults to remember early-life experiences. We recently showed that early aversive contextual memory in infant rats, which is in fact rapidly forgotten, is actually not lost, as reminders presented later in life reinstate a long-lasting and context-specific memory. We also showed that the formation of this infantile memory recruits in the hippocampus mechanisms typical of developmental critical periods. Here, we tested whether similar mechanisms apply to a nonaversive, hippocampal type of learning. We report that novel object location (nOL) learned at postnatal day 17 (PN17) undergoes the typical rapid forgetting of infantile learning. However, a later reminder reinstates memory expression. Furthermore, as for aversive experiences, nOL learning at PN17 engages critical period mechanisms in the dorsal hippocampus: it induces a switch in the GluN2A/2B-NMDA receptor ratio, and brain-derived neurotrophic factor injected bilaterally into the dorsal hippocampus immediately after training results in long-lasting memory expression. We conclude that in infancy the hippocampus plays a necessary role in processing episodic and contextual memories, including nonaversive ones, and matures through a developmental critical period.”

Written by: Alessio Travaglia, Adam B. Steinmetz, Janelle M. Miranda, Cristina M. Alberini
For full text: http://learnmem.cshlp.org/content/25/4/176.full

Evidence for the use of three-way binding structures in associative and source recognition

Evidence for the use of three-way binding structures in associative and source recognition

Published in: Journal of Memory and Language, Volume 100, June 2018, 89-97

Abstract
“Avoiding interference among similar memory traces may be helped by forming complex memory structures that include multiple components of the event. In a laboratory setting, these structures have been studied through list learning paradigms, where the pairs in one list are swapped in another list (i.e., ABABr condition), and one has to form a memory structure that includes items and context together (i.e., three-way binding). However, despite the long history of the theoretical concept, and its importance, three-way bindings have only been examined in recall paradigms. Moreover, not all memory models consider the ability to form three-way binding structures as a default. The current study, therefore, examined the use of three-way binding structures in associative and source recognition. Results indicate that three-way binding structures are used during recognition, thus challenging memory models that are not capable of representing such structures.”

Written by: Hyungwook Yim, Adam F. Osth, Vladimir M. Sloutsky, Simon J. Dennis
For full text: https://doi.org/10.1016/j.jml.2018.02.002

The impact of perceptual changes to studied items on ERP correlates of familiarity and recollection is subject to hemispheric asymmetries

The impact of perceptual changes to studied items on ERP correlates of familiarity and recollection is subject to hemispheric asymmetries

Published in: Brain and Cognition, Volume 122, April 2018, 17-25

Abstract
“It is still unclear which role the right hemisphere (RH) preference for perceptually specific and the left hemisphere (LH) bias towards abstract memory representations play at the level of episodic memory retrieval. When stimulus characteristics hampered the retrieval of abstract memory representations, these hemispheric asymmetries have previously only modulated event-related potential (ERP) correlates of recollection (late positive complex, LPC), but not of familiarity (FN400). In the present experiment, we used stimuli which facilitated the retrieval of abstract memory representations. With the divided visual field technique, new items, identical repetitions and color-modified versions of incidentally studied object pictures were presented in either the right (RVF) or the left visual field (LVF). Participants performed a memory inclusion task, in which they had to categorize both identically repeated and color-modified study items as ‘old’. Only ERP, but not behavioral data showed hemispheric asymmetries: Compared to identical repetitions, FN400 and LPC old/new effects for color-modified items were equivalent with RVF/LH presentation, but reduced with LVF/RH presentation. By promoting the use of abstract stimulus information for memory retrieval, we were thus able to show that hemispheric asymmetries in accessing abstract or specific memory representations can modulate ERP correlates of familiarity as well as recollection processes.”

Written by: Kristina Kuper, Hubert D. Zimmer
For full text: https://doi.org/10.1016/j.bandc.2018.01.006

Free recall dynamics in value-directed remembering

Free recall dynamics in value-directed remembering

Published in: Journal of Memory and Language, Volume 100, June 2018, 18-31

Abstract
“An emerging literature on value-directed remembering has shown that people are able to encode and remember information that is more important. Researchers operationalize importance by differentially assigning value to the memoranda that participants are asked to encode and remember. In the present investigation, a slightly altered value-directed-remembering paradigm was used to investigate how value modifies the dynamics of memory organization and search in free recall. In Experiment 1, free recall dynamics were compared between a control and a value condition. In Experiment 2, we manipulated the order of presentation of the values by adding an ascending and a descending condition where values were presented congruently or incongruently with the evolution of temporal context. Experiments 3 and 4 paralleled Experiments 1 and 2 respectively, with the addition of overt rehearsal and an unexpected memory test for the numbers/values. Overall, the results indicated that value-directed encoding has an influence on measures of delayed free recall encoding, organization, and search processes.”

Written by: Aikaterini Stefanidi, Derek M. Ellis, Gene A. Brewer
For full text: https://doi.org/10.1016/j.jml.2017.11.004

The ERP correlates of self-knowledge: Are assessments of one’s past, present, and future traits closer to semantic or episodic memory?

The ERP correlates of self-knowledge: Are assessments of one’s past, present, and future traits closer to semantic or episodic memory?

Published in: Neuropsychologia, Volume 110, February 2018, 65-83

Abstract
“Self-knowledge concerns one’s own preferences and personality. It pertains to the self (similar to episodic memory), yet does not concern events. It is factual (like semantic memory), but also idiosyncratic. For these reasons, it is unclear where self-knowledge might fall on a continuum in relation to semantic and episodic memory. In this study, we aimed to compare the event-related potential(ERP) correlates of self-knowledge to those of semantic and episodic memory, using N400 and Late Positive Component (LPC) as proxies for semantic and episodic processing, respectively. We considered an additional factor: time perspective. Temporally distant selves have been suggested to be more semantic compared to the present self, but thinking about one’s past and future selves may also engage episodic memory. Twenty-eight adults answered whether traits (e.g., persistent) were true of most people holding an occupation (e.g., soldiers; semantic memory condition), or true of themselves 5 years ago, in the present, or 5 years from now (past, present, and future self-knowledge conditions). The study ended with an episodic recognition memory task for previously seen traits. Present self-knowledge produced mean LPC amplitudes at posterior parietal sites that fell between semantic and episodic memory. Mean LPC amplitudes for past and future self-knowledge were greater than for semantic memory, and not significantly different from episodic memory. Mean N400 amplitudes for the self-knowledge conditions were smaller than for semantic memory at sagittal sites. However, this N400 effect was not separable from a preceding P200 effect at these same electrode sites. This P200 effect can be interpreted as reflecting the greater emotional salience of self as compared to general knowledge, which may have facilitated semantic processing. Overall, our findings are consistent with a distinction between knowledge of others and self-knowledge, but the closeness of self-knowledge’s neural correlates to either semantic or episodic memory appears to depend to some extent on time perspective.”

Written by: Annick N. Tanguay, Lauren Benton, Lorenza Romio, Carolin Sievers, Patrick S. R. Davidson, Louis Renoult
For full text: https://doi.org/10.1016/j.neuropsychologia.2017.10.024

Dynamic changes in large-scale functional network organization during autobiographical memory retrieval

Dynamic changes in large-scale functional network organization during autobiographical memory retrieval

Published in: Neuropsychologia, Volume 110, February 2018, 208-224

Abstract
“Autobiographical memory (AM), episodic memory for life events, involves the orchestration of multiple dynamic cognitive processes, including memory access and subsequent elaboration. Previous neuroimaging studies have contrasted memory access and elaboration processes in terms of regional brain activation and connectivity within large, multi-region networks. Although interactions between key memory-related regions such as the hippocampus and prefrontal cortex (PFC) have been shown to play an important role in AM retrieval, it remains unclear how such connectivity between specific, individual regions involved in AM retrieval changes dynamically across the retrieval process and how these changes relate to broader memory networks throughout the whole brain. The present functional magnetic resonance imaging (fMRI) study sought to assess the specific changes in interregional connectivity patterns across the AM retrieval processes to understand network level mechanisms of AM retrieval and further test current theoretical accounts of dynamic AM retrieval processes. We predicted that dynamic connections would reflect two hypothesized memory processes, with initial processes reflecting memory-access related connections between regions such as the anterior hippocampal and ventrolateral PFC regions, and later processes reflecting elaboration-related connections between dorsolateral frontal working memory regions and parietal-occipital visual imagery regions. One week prior to fMRI scanning, fifteen healthy adult participants generated AMs using personally selected cue words. During scanning, participants were cued to retrieve the AMs. We used a moving-window functional connectivity analysis and graph theoretic measures to examine dynamic changes in the strength and centrality of connectivity among regions involved in AM retrieval. Consistent with predictions, early, access-related processing primarily involved a ventral frontal to temporal-parietal network associated with strategic search and initial reactivation of specific episodic memory traces. In addition, neural network connectivity during later retrieval processes was associated with strong connections between occipital-parietal regions and dorsal fronto-parietal regions associated with mental imagery, reliving, and working memory processes. Taken together, these current findings help refine and extend dynamic neural processing models of AM retrieval by providing evidence of the specific connections throughout the brain that change in their synchrony with one another as processing progresses from access of specific event memories to elaborative reliving of the past event.”

Written by: Cory S. Inman, G. Andrew James, Katherine Vytal, Stephan Hamann
For full text: https://doi.org/10.1016/j.neuropsychologia.2017.09.020

Best not to bet on the horserace: A comment on Forrin and MacLeod (2017) and a relevant stimulus-response compatibility view of colour-word contingency learning asymmetries

Best not to bet on the horserace: A comment on Forrin and MacLeod (2017) and a relevant stimulus-response compatibility view of colour-word contingency learning asymmetries

Published in: Memory & Cognition, Volume 46, Issue 2, 326-335

Abstract
“One powerfully robust method for the study of human contingency learning is the colour-word contingency learning paradigm. In this task, participants respond to the print colour of neutral words, each of which is presented most often in one colour. The contingencies between words and colours are learned, as indicated by faster and more accurate responses when words are presented in their expected colour relative to an unexpected colour. In a recent report, Forrin and MacLeod (2017bMemory & Cognition) asked to what extent this performance (i.e., response time) measure of learning might depend on the relative speed of processing of the word and the colour. With keypress responses, learning effects were comparable when responding to the word and to the colour (contrary to predictions). However, an asymmetry appeared in a second experiment with vocal responses, with a contingency effect only present for colour identification. In a third experiment, the colour was preexposed, and contingency effects were again roughly symmetrical. In their report, they suggested that a simple speed-of-processing (or “horserace”) model might explain when contingency effects are observed in colour and word identification. In the present report, an alternative view is presented. In particular, it is argued that the results are best explained by appealing to the notion of relevant stimulus–response compatibility, which also resolves discrepancies between horserace model predictions and participant results. The article presents simulations with the Parallel Episodic Processing model to demonstrate this case.”

Written by: James R. Schmidt
For full text: https://doi.org/10.3758/s13421-017-0755-7

Gamma phase-synchrony in autobiographical memory: Evidence from magnetoencephalography and severely deficient autobiographical memory

Gamma phase-synchrony in autobiographical memory: Evidence from magnetoencephalography and severely deficient autobiographical memory

Published in: Neuropsychologia, Volume 110, February 2018, 7-13

Abstract
“The subjective sense of recollecting events from one’s past is an essential feature of episodic memory, but the neural mechanisms supporting this capacity are poorly understood. We examined the role of large-scale patterns of neural synchrony using whole-head MEG recordings in healthy adults and S.M., who has severely deficient autobiographical memory (SDAM; Palombo et al., 2015), a syndrome in which autobiographical recollection is absent but other functions (including other mnemonic functions), are normal. MEG was conducted while participants listened to prospectively collected recordings documenting unique personal episodes (PE) that normally evoke rich recollection, as well as a condition including general semantic information that is non-specific in place or time (GS; Levine et al., 2004). We predicted that PE (and not GS) would be associated with changes in patterns of large-scale neural synchrony in comparison subjects. We found large-scale neural synchrony, specifically in the gamma frequency ranges (i.e., 27–45 Hz), specific to PE and not GS. These synchrony differences between PE and GS were not apparent in S.M. Our findings provide empirical evidence for the supporting role of large-scale gamma neural synchrony underlying autobiographical recollection.”

Written by: Lluís Fuentemilla, Daniela J. Palombo, Brian Levine
For full text: https://doi.org/10.1016/j.neuropsychologia.2017.08.020

Narrative construction is intact in episodic amnesia

Narrative construction is intact in episodic amnesia

Published in: Neuropsychologia, Volume 110, February 2018, 104-112

Abstract
“Autobiographical remembering and future imagining overlap in their underlying psychological and neurological mechanisms. The hippocampus and surrounding regions within the medial temporal lobes (MTL), known for their role in forming and maintaining autobiographical episodic memories, are also thought to play an essential role in fictitious and future constructions. Amnesic individuals with bilateral hippocampal damage cannot reconstruct their past personal experiences and also have severe deficits in the ability to construct coherent fictitious or future narratives. However, it is not known whether this impairment reflects a failure to generate details from autobiographical episodic memory to populate personal narratives or an inability to bind such details into coherent narratives. We show that four individuals with hippocampal damage and episodic amnesia can construct narratives when the relevant details of the story are provided in a picture book and that their narratives maintain overall coherence on several measures. These findings indicate that individuals with hippocampal damage can bind details into coherent narratives when details are available to them. We conclude that the hippocampal system instead likely plays a role in the generation of details from which narratives are constructed.”

Written by: Nazim Keven, Jake Kurczek, R. Shayna Rosenbaum, Carl F. Craver
For full text: https://doi.org/10.1016/j.neuropsychologia.2017.07.028

Search and recovery of autobiographical and laboratory memories: Shared and distinct neural components

Search and recovery of autobiographical and laboratory memories: Shared and distinct neural components

Published in: Neuropsychologia, Volume 110, February 2018, 44-54

Abstract
“Functional neuroimaging evidence suggests that there are differences in the neural correlates of episodic memory for laboratory stimuli (laboratory memory) and for events from one’s own life (autobiographical memory). However, this evidence is scarce and often confounded with differences in memory testing procedures. Here, we directly compared the neural mechanisms underlying the search and recovery of autobiographical and laboratory memories while minimizing testing differences. Before scanning, participants completed a laboratory memory encoding task in which they studied four-word “chains” spread across three word pairs. During scanning, participants completed a laboratory memory retrieval task, in which they recalled the word chains, and an autobiographical memory retrieval task, in which they recalled specific personal events associated with word cues. Importantly, response times were similar in the two tasks, allowing for a direct comparison of the activation time courses. We found that during memory search (searching for the memory target), similar brain regions were activated during both the autobiographical and laboratory tasks, whereas during memory recovery (accessing the memory traces; i.e., ecphory), clear differences emerged: regions of the default mode network (DMN) were activated greater during autobiographical than laboratory memory, whereas the bilateral superior parietal lobules were activated greater during laboratory than autobiographical memory. Also, multivariate functional connectivity analyses revealed that regardless of memory stage, the DMN and ventral attention network exhibited a more integrated topology in the functional network underlying autobiographical (vs. laboratory) memory retrieval, whereas the fronto-parietal task control network exhibited a more integrated topology in the functional network underlying laboratory (vs. autobiographical) memory retrieval. These findings further characterize the shared and distinct neural components underlying autobiographical and laboratory memories, and suggest that differences in autobiographical vs. laboratory memory brain activation previously reported in the literature reflect memory recovery rather than search differences.”

Written by: Zachary A. Monge, Erik A. Wing, Jared Stokes, Roberto Cabeza
For full text: https://doi.org/10.1016/j.neuropsychologia.2017.07.030

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