scholarly journals The Prefrontal-Hippocampal Comparator: Volition and Episodic Memory

2021 ◽  
Author(s):  
Robert Numan
Keyword(s):  
Episodic Memory ◽  
Action Plan ◽  
Review Article ◽  
Corollary Discharge ◽  
Error Signal ◽  
Hippocampal Area ◽  
Episodic Memories ◽  
Dependent Tasks ◽  
Hippocampal Theta ◽  
Goal Directed Behavior

This review article supports the following: (1) Hippocampal area CA1 serves as an associative match-mismatch comparator, (2) Voluntary movement strengthens episodic memories for goal-directed behavior, (3) Hippocampal theta power serves as a prediction error signal during hippocampal dependent tasks, (4) The self-referential component of episodic memory in humans is mediated by the corollary discharge (efference copy of the action plan developed by prefrontal cortex), and (5) Impairments in the production or transmission of this corollary discharge may contribute to some of the symptoms of schizophrenia. <br>

scholarly journals The Prefrontal-Hippocampal Comparator: Volition and Episodic Memory

2021 ◽  
Author(s):  
Robert Numan
Keyword(s):  
Episodic Memory ◽  
Action Plan ◽  
Review Article ◽  
Corollary Discharge ◽  
Error Signal ◽  
Hippocampal Area ◽  
Episodic Memories ◽  
Dependent Tasks ◽  
Hippocampal Theta ◽  
Goal Directed Behavior

This review article supports the following: (1) Hippocampal area CA1 serves as an associative match-mismatch comparator, (2) Voluntary movement strengthens episodic memories for goal-directed behavior, (3) Hippocampal theta power serves as a prediction error signal during hippocampal dependent tasks, (4) The self-referential component of episodic memory in humans is mediated by the corollary discharge (efference copy of the action plan developed by prefrontal cortex), and (5) Impairments in the production or transmission of this corollary discharge may contribute to some of the symptoms of schizophrenia. <br>

The Prefrontal-Hippocampal Comparator: Volition and Episodic Memory

2021 ◽  
pp. 003151252110413
Author(s):  
Robert Numan
Keyword(s):  
Episodic Memory ◽  
Action Plan ◽  
Efference Copy ◽  
Corollary Discharge ◽  
Future Research ◽  
Hippocampal Area ◽  
Episodic Memories ◽  
Dependent Tasks ◽  
Hippocampal Theta ◽  
Goal Directed Behavior

This review describes recent research that is relevant to the prefrontal-hippocampal comparator model with the following conclusions: 1. Hippocampal area CA1 serves, at least in part, as an associative match-mismatch comparator. 2. Voluntary movement strengthens episodic memories for goal-directed behavior. 3. Hippocampal theta power serves as a prediction error signal during hippocampal dependent tasks. 4. The self-referential component of episodic memory in humans is mediated by the corollary discharge (the efference copy of the action plan developed by prefrontal cortex and transmitted to hippocampus where it is stored as a working memory; CA1 uses this efference copy to compare the expected consequences of action to the actual consequences of action). 5. Impairments in the production or transmission of this corollary discharge may contribute to some of the symptoms of schizophrenia. Unresolved issues and suggestions for future research are discussed.

scholarly journals Directional coupling of slow and fast hippocampal gamma with neocortical alpha/beta oscillations in human episodic memory

2019 ◽  
Vol 116 (43) ◽  
pp. 21834-21842 ◽  
Author(s):  
Benjamin J. Griffiths ◽  
George Parish ◽  
Frederic Roux ◽  
Sebastian Michelmann ◽  
Mircea van der Plas ◽  
...  
Keyword(s):  
Episodic Memory ◽  
Memory Retrieval ◽  
Memory Formation ◽  
Beta Power ◽  
Wide Range ◽  
Alpha Beta ◽  
Episodic Memories ◽  
Hippocampal Theta ◽  
Multisensory Information ◽  
Flow Of Information

Episodic memories hinge upon our ability to process a wide range of multisensory information and bind this information into a coherent, memorable representation. On a neural level, these 2 processes are thought to be supported by neocortical alpha/beta desynchronization and hippocampal theta/gamma synchronization, respectively. Intuitively, these 2 processes should couple to successfully create and retrieve episodic memories, yet this hypothesis has not been tested empirically. We address this by analyzing human intracranial electroencephalogram data recorded during 2 associative memory tasks. We find that neocortical alpha/beta (8 to 20 Hz) power decreases reliably precede and predict hippocampal “fast” gamma (60 to 80 Hz) power increases during episodic memory formation; during episodic memory retrieval, however, hippocampal “slow” gamma (40 to 50 Hz) power increases reliably precede and predict later neocortical alpha/beta power decreases. We speculate that this coupling reflects the flow of information from the neocortex to the hippocampus during memory formation, and hippocampal pattern completion inducing information reinstatement in the neocortex during memory retrieval.

scholarly journals Bi-Temporal Anodal Transcranial Direct Current Stimulation during Slow-Wave Sleep Boosts Slow-Wave Density but Not Memory Consolidation

2021 ◽  
Vol 11 (4) ◽  
pp. 410
Author(s):  
Simon Ruch ◽  
Kristoffer Fehér ◽  
Stephanie Homan ◽  
Yosuke Morishima ◽  
Sarah Maria Mueller ◽  
...  
Keyword(s):  
Episodic Memory ◽  
Slow Wave ◽  
Direct Current ◽  
Memory Consolidation ◽  
Transcranial Direct Current Stimulation ◽  
Slow Wave Sleep ◽  
Memory Performance ◽  
Direct Current Stimulation ◽  
Sleep Parameters ◽  
Episodic Memories

Slow-wave sleep (SWS) has been shown to promote long-term consolidation of episodic memories in hippocampo–neocortical networks. Previous research has aimed to modulate cortical sleep slow-waves and spindles to facilitate episodic memory consolidation. Here, we instead aimed to modulate hippocampal activity during slow-wave sleep using transcranial direct current stimulation in 18 healthy humans. A pair-associate episodic memory task was used to evaluate sleep-dependent memory consolidation with face–occupation stimuli. Pre- and post-nap retrieval was assessed as a measure of memory performance. Anodal stimulation with 2 mA was applied bilaterally over the lateral temporal cortex, motivated by its particularly extensive connections to the hippocampus. The participants slept in a magnetic resonance (MR)-simulator during the recordings to test the feasibility for a future MR-study. We used a sham-controlled, double-blind, counterbalanced randomized, within-subject crossover design. We show that stimulation vs. sham significantly increased slow-wave density and the temporal coupling of fast spindles and slow-waves. While retention of episodic memories across sleep was not affected across the entire sample of participants, it was impaired in participants with below-average pre-sleep memory performance. Hence, bi-temporal anodal direct current stimulation applied during sleep enhanced sleep parameters that are typically involved in memory consolidation, but it failed to improve memory consolidation and even tended to impair consolidation in poor learners. These findings suggest that artificially enhancing memory-related sleep parameters to improve memory consolidation can actually backfire in those participants who are in most need of memory improvement.

scholarly journals Event conjunction: How the hippocampus integrates episodic memories across event boundaries

2019 ◽  
Author(s):  
Benjamin James Griffiths ◽  
Lluís Fuentemilla
Keyword(s):  
Related Event ◽  
Gamma Model ◽  
Apparent Contradiction ◽  
The Past ◽  
Continuous Stream ◽  
Event Model ◽  
Episodic Memories ◽  
Hippocampal Theta ◽  
Conceptual Link ◽  
New Framework

Our lives are a continuous stream of experience. Our episodic memories, however, have a definitive beginning, middle and end. Theories of event segmentation suggest that salient changes in our environment produce event boundaries which partition the past from the present and, as a result, produce discretised memories. However, event boundaries cannot completely discretise two memories; any shared conceptual link will eagerly integrate these memories. Here, we present a new framework inspired by electrophysiological research that resolves this apparent contradiction. At its heart, the framework proposes that hippocampal theta-gamma coupling maintains a highly abstract model of an ongoing event and serves to encode this model as an episodic memory. When a second but related event begins, this theta-gamma model is rapidly reconstructed within the hippocampus where new details of the second event can be appended to the existing event model. The event conjunction framework is the first electrophysiological explanation of how event memories can be formed at, and integrated across, event boundaries.

scholarly journals Theta and gamma hippocampal-neocortical oscillations during the episodic-like memory test: impairment in epileptogenic rats

2021 ◽  
Author(s):  
Anton E Malkov ◽  
Ludmila Shevkova ◽  
Alexandra Latyshkova ◽  
Valentina Kitchigina
Keyword(s):  
Episodic Memory ◽  
Memory Task ◽  
Gamma Oscillations ◽  
High Amplitude ◽  
Memory Test ◽  
Interictal Spikes ◽  
Paroxysmal Activity ◽  
Cortical Oscillations ◽  
Gamma Rhythms ◽  
Hippocampal Theta

Cortical oscillations in different frequency bands have been shown to be intimately involved in exploration of environment and cognition. Here, the local field potentials in the hippocampus, the medial prefrontal cortex (mPFC), and the medial entorhinal cortex (mEC) were recorded simultaneously in rats during the execution of the episodic-like memory task. The power of hippocampal theta (~4-10 Hz), slow gamma (~25-50 Hz), and fast gamma oscillations (~55-100 Hz) was analyzed in all structures examined. Particular attention was paid to the theta coherence between three mentioned structures. The modulation of the power of gamma rhythms by the phase of theta cycle during the execution of the episodic-like memory test by rats was also closely studied. Healthy rats and rats one month after kainate-induced status epilepticus (SE) were examined. Paroxysmal activity in the hippocampus (high amplitude interictal spikes), excessive excitability of animals, and the death of hippocampal and dentate granular cells in rats with kainate-evoked SE were observed, which indicated the development of seizure focus in the hippocampus (epileptogenesis). One month after SE, the rats exhibited a specific impairment of episodic memory for the what-where-when triad: unlike healthy rats, epileptogenic SE animals did not identify the objects during the test. This impairment was associated with the changes in the characteristics of theta and gamma rhythms and specific violation of theta coherence and theta/gamma coupling in these structures in comparison with the healthy animals. We believe that these disturbances in the cortical areas play a role in episodic memory dysfunction in kainate-treated animals. These findings can shed light on the mechanisms of cognitive deficit during epileptogenesis.

scholarly journals Autobiographically Significant Concepts: More Episodic than Semantic in Nature? An Electrophysiological Investigation of Overlapping Types of Memory

2015 ◽  
Vol 27 (1) ◽  
pp. 57-72 ◽  
Author(s):  
Louis Renoult ◽  
Patrick S. R. Davidson ◽  
Erika Schmitz ◽  
Lillian Park ◽  
Kenneth Campbell ◽  
...  
Keyword(s):  
Episodic Memory ◽  
Semantic Memory ◽  
Recognition Task ◽  
Positive Component ◽  
Late Positive Component ◽  
Episodic Information ◽  
Semantic Concepts ◽  
N400 Component ◽  
Episodic Memories ◽  
Highly Correlated

A common assertion is that semantic memory emerges from episodic memory, shedding the distinctive contexts associated with episodes over time and/or repeated instances. Some semantic concepts, however, may retain their episodic origins or acquire episodic information during life experiences. The current study examined this hypothesis by investigating the ERP correlates of autobiographically significant (AS) concepts, that is, semantic concepts that are associated with vivid episodic memories. We inferred the contribution of semantic and episodic memory to AS concepts using the amplitudes of the N400 and late positive component, respectively. We compared famous names that easily brought to mind episodic memories (high AS names) against equally famous names that did not bring such recollections to mind (low AS names) on a semantic task (fame judgment) and an episodic task (recognition memory). Compared with low AS names, high AS names were associated with increased amplitude of the late positive component in both tasks. Moreover, in the recognition task, this effect of AS was highly correlated with recognition confidence. In contrast, the N400 component did not differentiate the high versus low AS names but, instead, was related to the amount of general knowledge participants had regarding each name. These results suggest that semantic concepts high in AS, such as famous names, have an episodic component and are associated with similar brain processes to those that are engaged by episodic memory. Studying AS concepts may provide unique insights into how episodic and semantic memory interact.

scholarly journals Parvalbumin-expressing interneurons coordinate hippocampal network dynamics required for memory consolidation

2017 ◽  
Vol 8 (1) ◽  
Author(s):  
Nicolette Ognjanovski ◽  
Samantha Schaeffer ◽  
Jiaxing Wu ◽  
Sima Mofakham ◽  
Daniel Maruyama ◽  
...  
Keyword(s):  
Memory Consolidation ◽  
Activity Patterns ◽  
Memory Formation ◽  
Contextual Fear Conditioning ◽  
Long Term Memory ◽  
Ca1 Neurons ◽  
Functional Connections ◽  
The Hours ◽  
Hippocampal Area ◽  
Episodic Memories

Abstract Activity in hippocampal area CA1 is essential for consolidating episodic memories, but it is unclear how CA1 activity patterns drive memory formation. We find that in the hours following single-trial contextual fear conditioning (CFC), fast-spiking interneurons (which typically express parvalbumin (PV)) show greater firing coherence with CA1 network oscillations. Post-CFC inhibition of PV+ interneurons blocks fear memory consolidation. This effect is associated with loss of two network changes associated with normal consolidation: (1) augmented sleep-associated delta (0.5–4 Hz), theta (4–12 Hz) and ripple (150–250 Hz) oscillations; and (2) stabilization of CA1 neurons’ functional connectivity patterns. Rhythmic activation of PV+ interneurons increases CA1 network coherence and leads to a sustained increase in the strength and stability of functional connections between neurons. Our results suggest that immediately following learning, PV+ interneurons drive CA1 oscillations and reactivation of CA1 ensembles, which directly promotes network plasticity and long-term memory formation.

scholarly journals Corticoinsular circuits encode subjective value expectation and violation for effortful goal-directed behavior

2018 ◽  
Vol 115 (22) ◽  
pp. E5233-E5242 ◽  
Author(s):  
Amanda R. Arulpragasam ◽  
Jessica A. Cooper ◽  
Makiah R. Nuutinen ◽  
Michael T. Treadway
Keyword(s):  
Decision Making ◽  
Relevant Information ◽  
Neural Mechanisms ◽  
Anterior Cingulate ◽  
Error Signal ◽  
Value Prediction ◽  
Subjective Value ◽  
Effort Discounting ◽  
Trial History ◽  
Goal Directed Behavior

We are presented with choices each day about how to invest our effort to achieve our goals. Critically, these decisions must frequently be made under conditions of incomplete information, where either the effort required or possible reward to be gained is uncertain. Such choices therefore require the development of potential value estimates to guide effortful goal-directed behavior. To date, however, the neural mechanisms for this expectation process are unknown. Here, we used computational fMRI during an effort-based decision-making task where trial-wise information about effort costs and reward magnitudes was presented separately over time, thereby allowing us to model distinct effort/reward computations as choice-relevant information unfolded. We found that ventromedial prefrontal cortex (vmPFC) encoded expected subjective value. Further, activity in dorsal anterior cingulate (dACC) and anterior insula (aI) reflected both effort discounting as well as a subjective value prediction error signal derived from trial history. While prior studies have identified these regions as being involved in effort-based decision making, these data demonstrate their specific role in the formation and maintenance of subjective value estimates as relevant information becomes available.

scholarly journals Coding of episodic memory in the human hippocampus

2018 ◽  
Vol 115 (5) ◽  
pp. 1093-1098 ◽  
Author(s):  
John T. Wixted ◽  
Stephen D. Goldinger ◽  
Larry R. Squire ◽  
Joel R. Kuhn ◽  
Megan H. Papesh ◽  
...  
Keyword(s):  
Episodic Memory ◽  
Single Neuron ◽  
Large Fraction ◽  
Memory Task ◽  
Neuron Activity ◽  
Distributed Coding ◽  
Repeated Word ◽  
Human Hippocampus ◽  
Left Hippocampus ◽  
Episodic Memories

Neurocomputational models have long posited that episodic memories in the human hippocampus are represented by sparse, stimulus-specific neural codes. A concomitant proposal is that when sparse-distributed neural assemblies become active, they suppress the activity of competing neurons (neural sharpening). We investigated episodic memory coding in the hippocampus and amygdala by measuring single-neuron responses from 20 epilepsy patients (12 female) undergoing intracranial monitoring while they completed a continuous recognition memory task. In the left hippocampus, the distribution of single-neuron activity indicated that only a small fraction of neurons exhibited strong responding to a given repeated word and that each repeated word elicited strong responding in a different small fraction of neurons. This finding reflects sparse distributed coding. The remaining large fraction of neurons exhibited a concurrent reduction in firing rates relative to novel words. The observed pattern accords with longstanding predictions that have previously received scant support from single-cell recordings from human hippocampus.

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