scholarly journals Neurons remap to represent memories in the human entorhinal cortex

2018 ◽  
Author(s):  
Salman Qasim ◽  
Jonathan Miller ◽  
Cory S. Inman ◽  
Robert E. Gross ◽  
Jon T. Willie ◽  
...  
Keyword(s):  
Entorhinal Cortex ◽  
Neuronal Activity ◽  
Memory Retrieval ◽  
Medial Temporal Lobe ◽  
Cell Activity ◽  
Cued Recall ◽  
General Mechanism ◽  
Virtual Reality Environment ◽  
Memory Representations ◽  
Past Experiences

AbstractThe entorhinal cortex (EC) is known to play a key role in both memory and spatial navigation. Despite this overlap in spatial and mnemonic circuits, it is unknown how spatially responsive neurons contribute to our ability to represent and distinguish past experiences. Recording from medial temporal lobe (MTL) neurons in subjects performing cued recall of object–location memories in a virtual-reality environment, we identified “trace cells” in the EC that remap their spatial fields to locations subjects were cued to recall on each trial. In addition to shifting its firing field according to the memory cue, this neuronal activity exhibited a firing rate predictive of the cued memory’s content. Critically, this memory-specific neuronal activity re-emerged when subjects were cued for recall without entering the environment, indicating that trace-cell memory representations generalized beyond navigation. These findings suggest a general mechanism for memory retrieval via trace-cell activity and remapping in the EC.

Lateralization of Prefrontal Activity during Episodic Memory Retrieval: Evidence for the Production-Monitoring Hypothesis

2003 ◽  
Vol 15 (2) ◽  
pp. 249-259 ◽  
Author(s):  
Roberto Cabeza ◽  
Jill K. Locantore ◽  
Nicole D. Anderson
Keyword(s):  
Episodic Memory ◽  
Memory Retrieval ◽  
Medial Temporal Lobe ◽  
Item Recognition ◽  
Cued Recall ◽  
Anterior Cingulate ◽  
Episodic Retrieval ◽  
Context Recognition ◽  
Production Monitoring ◽  
The Right

We propose a new hypothesis concerning the lateralization of prefrontal cortex (PFC) activity during verbal episodic memory retrieval. The hypothesis states that the left PFC is differentially more involved in semantically guided information production than is the right PFC, and that the right PFC is differentially more involved in monitoring and verification than is the left PFC. This “production-monitoring hypothesis” differs from the existing “systematic-heuristic hypothesis,” which proposes that the left PFC is primarily involved in systematic retrieval operations, and the right PFC in heuristic retrieval operations. To compare the two hypotheses, we measured PFC activity using positron emission tomography (PET) during the performance of four episodic retrieval tasks: stem cued recall, associative cued recall, context recognition (source memory), and item recognition. Recall tasks emphasized production processes, whereas recognition tasks emphasized monitoring processes. Stem cued recall and context-recognition tasks underscored systematic operations, whereas associative cued recall and item-recognition tasks underscored heuristic operations. Consistent with the production-monitoring hypothesis, the left PFC was more activated for recall than for recognition tasks and the right PFC was more activated for recognition than for recall tasks. Inconsistent with the systematic-heuristic hypothesis, the left PFC was more activated for heuristic than for systematic tasks and the right PFC showed the converse result. Additionally, the study yielded activation differences outside the PFC. In agreement with a previous recall/recognition PET study, anterior cingulate, cerebellar, and striatal regions were more activated for recall than for recognition tasks, and the converse occurred for posterior parietal regions. A right medial temporal lobe region was more activated for stem cued recall and context recognition than for associative cued recall and item recognition, possibly reflecting perceptual integration. In sum, the results provide evidence for the production-monitoring hypothesis and clarify the role of different brain regions typically activated in PET and functional magnetic resonance imaging (fMRI) studies of episodic retrieval.

scholarly journals Hippocampal–Cortical Encoding Activity Predicts the Precision of Episodic Memory

2021 ◽  
pp. 1-14
Author(s):  
Saana M. Korkki ◽  
Franziska R. Richter ◽  
Jon S. Simons
Keyword(s):  
Memory Retrieval ◽  
Neural Substrates ◽  
Memory Formation ◽  
Continuous Scale ◽  
Neuroimaging Data ◽  
Memory Representations ◽  
Past Experiences ◽  
Object Features ◽  
Memory Precision ◽  
Continuous Measures

Abstract Our recollections of past experiences can vary in both the number of specific event details accessible from memory and the precision with which such details are reconstructed. Prior neuroimaging evidence suggests the success and precision of episodic recollection to rely on distinct neural substrates during memory retrieval. In contrast, the specific encoding mechanisms supporting later memory precision, and whether they differ from those underlying successful memory formation in general, are currently unknown. Here, we combined continuous measures of memory retrieval with model-based analyses of behavioral and neuroimaging data to tease apart the encoding correlates of successful memory formation and mnemonic precision. In the MRI scanner, participants encoded object-scene displays and later reconstructed features of studied objects using a continuous scale. We observed overlapping encoding activity in inferior prefrontal and posterior perceptual regions to predict both which object features were later remembered versus forgotten and the precision with which they were reconstructed from memory. In contrast, hippocampal encoding activity significantly predicted the precision, but not overall success, of subsequent memory retrieval. The current results align with theoretical accounts proposing the hippocampus to be critical for representation of high-fidelity associative information and suggest a contribution of shared cortical encoding mechanisms to the formation of both accessible and precise memory representations.

scholarly journals Imaging recent to very remote object-in-place memories in the medial temporal lobe and prefrontal cortex

2020 ◽  
Author(s):  
Erika Atucha ◽  
Celia Fuerst ◽  
Magdalena Sauvage
Keyword(s):  
Memory Retrieval ◽  
Medial Temporal Lobe ◽  
Brain Regions ◽  
Remote Memory ◽  
General Mechanism ◽  
Cortical Areas ◽  
Prefrontal Cortical ◽  
Place Task ◽  
Cortical Regions ◽  
Over Time

Studies on patient H.M inspired many experiments on the role of the hippocampus and the neocortex in retrieving recent and remote memories. Cortical regions become increasingly engaged for memory retrieval over time, while conflicting results emerge regarding the engagement of the hippocampus, suggested to be ongoing by some or restricted to the retrieval of recent memories by others. In the study of Lux et al, 2016 we tested that this discrepancy might stem from failing to dissociate CA1 from CA3s contribution to memory retrieval over time as CA3 is known to support computations more sensitive to time than CA1. We also reported that parahippocampal cortical areas with tied anatomical connections with the hippocampus were increasingly engaged over time (Lux et al., elife , 2016). This study used a fear conditioning paradigm as emotionally arousing experiences are better remembered than memories devoid of fear content. Here we address whether the differential contribution of brain regions is a general mechanism also subserving memory retrieval devoid of fear content. We succeeded in developing an object-in-place task to investigate remote memory retrieval up to 6 months and the contribution of CA1, CA3, parahippocampal and prefrontal cortical areas to the retrieval of recent versus very remote memories using a high resolution molecular imaging technique based on the detection of the IEG RNA Arc. Preliminary results show that the disengagement of CA3 and persistent engagement of CA1 seem to be a general mechanism in supporting retrieval of remote memory for events.

scholarly journals Lateral entorhinal cortex suppresses drift in cortical memory representations.

2021 ◽  
Author(s):  
Maryna Pilkiw ◽  
Justin Jarovi ◽  
Kaori Takehara-Nishiuchi
Keyword(s):  
Entorhinal Cortex ◽  
Memory Retrieval ◽  
Firing Pattern ◽  
Memory Trace ◽  
Male Rats ◽  
Memory Representations ◽  
Familiar Environment ◽  
Functional Relevance ◽  
The Stability ◽  
Cortical Representations

Memory retrieval is thought to depend on the reinstatement of cortical memory representations guided by pattern completion processes in the hippocampus. The lateral entorhinal cortex (LEC) is one of the intermediary regions supporting hippocampal-cortical interactions and houses neurons that prospectively signal past events in a familiar environment. To investigate the functional relevance of the LEC's activity for cortical reinstatement, we pharmacologically inhibited the LEC and examined its impact on the stability of ensemble firing patterns in one of the LEC's efferent targets, the medial prefrontal cortex (mPFC). When male rats underwent multiple epochs of identical stimulus sequences in the same environment, the mPFC maintained a stable ensemble firing pattern across repetitions, particularly when the sequence included pairings of neutral and aversive stimuli. With LEC inhibition, the mPFC still formed an ensemble pattern that accurately captured stimuli and their associations within each epoch. However, LEC inhibition markedly disrupted its consistency across the epochs by decreasing the proportion of mPFC neurons that stably maintained firing selectivity for stimulus associations. Thus, the LEC stabilizes cortical representations of learned stimulus associations, thereby facilitating the recovery of the original memory trace without generating a new, redundant trace for familiar experiences. Failure of this process might underlie retrieval deficits in conditions associated with degeneration of the LEC, such as normal aging and Alzheimer's disease.

scholarly journals Aging and the encoding of event changes: The role of neural activity pattern reinstatement

2019 ◽  
Author(s):  
David Stawarczyk ◽  
Christopher N. Wahlheim ◽  
Joset A. Etzel ◽  
Abraham Z. Snyder ◽  
Jeffrey M. Zacks
Keyword(s):  
Older Adults ◽  
Neural Activity ◽  
Activity Pattern ◽  
Medial Temporal Lobe ◽  
Memory Performance ◽  
Original Activity ◽  
Medial Cortex ◽  
Memory Representations ◽  
Past Experiences

AbstractWhen encountering unexpected event changes, memories of relevant past experiences must be updated to form new representations. Current models of memory updating propose that people must first generate memory-based predictions to detect and register that features of the environment have changed, then encode the new event features and integrate them with relevant memories of past experiences to form configural memory representations. Each of these steps may be impaired in older adults. Using functional MRI, we investigated these mechanisms in healthy young and older adults. In the scanner, participants first watched a movie depicting everyday activities in a day of an actor’s life. They next watched a second nearly identical movie in which some scenes ended differently. Crucially, before watching the last part of each activity, the second movie stopped, and participants were asked to mentally replay how the activity previously ended. Three days later, participants were asked to recall the activities. Neural activity pattern reinstatement in medial temporal lobe (MTL) during the replay phase of the second movie was associated with detecting changes and with better memory for the original activity features. Reinstatements in posterior medial cortex (PMC) additionally predicted better memory for changed features. Compared to young adults, older adults showed a reduced ability to detect and remember changes, and weaker associations between reinstatement and memory performance. These findings suggest that PMC and MTL contribute to change processing by reinstating previous event features, and that older adults are less able to use reinstatement to update memory for changed features.

scholarly journals Replay of cortical spiking sequences during human memory retrieval

Science ◽  
2020 ◽  
Vol 367 (6482) ◽  
pp. 1131-1134 ◽  
Author(s):  
Alex P. Vaz ◽  
John H. Wittig ◽  
Sara K. Inati ◽  
Kareem A. Zaghloul
Keyword(s):  
Episodic Memory ◽  
Memory Retrieval ◽  
Medial Temporal Lobe ◽  
Single Unit ◽  
Temporal Order ◽  
Human Memory ◽  
Memory Encoding ◽  
Human Cortex ◽  
Past Experiences ◽  
Specific Sequences

Episodic memory retrieval is thought to rely on the replay of past experiences, yet it remains unknown how human single-unit activity is temporally organized during episodic memory encoding and retrieval. We found that ripple oscillations in the human cortex reflect underlying bursts of single-unit spiking activity that are organized into memory-specific sequences. Spiking sequences occurred repeatedly during memory formation and were replayed during successful memory retrieval, and this replay was associated with ripples in the medial temporal lobe. Together, these data demonstrate that human episodic memory is encoded by specific sequences of neural activity and that memory recall involves reinstating this temporal order of activity.

scholarly journals Hippocampal-cortical encoding activity predicts the precision of episodic memory

2020 ◽  
Author(s):  
Saana M. Korkki ◽  
Franziska R. Richter ◽  
Jon S. Simons
Keyword(s):  
Episodic Memory ◽  
Memory Retrieval ◽  
Neural Substrates ◽  
Memory Formation ◽  
Continuous Scale ◽  
Neuroimaging Data ◽  
Memory Representations ◽  
Past Experiences ◽  
Object Features ◽  
Memory Precision

AbstractOur recollections of past experiences can vary both in the number of specific event details accessible from memory and the precision with which such details are reconstructed. Prior neuroimaging evidence suggests the success and precision of episodic recollection to rely on distinct neural substrates during memory retrieval. In contrast, the specific encoding mechanisms supporting later memory precision, and whether they differ from those underlying successful memory formation in general, are currently unknown. Here, we combined continuous measures of memory retrieval with model-based analyses of behavioural and neuroimaging data to tease apart the encoding correlates of successful memory formation and mnemonic precision. In the MRI scanner, participants encoded object-scene displays, and later reconstructed features of studied objects using a continuous scale. We observed overlapping encoding activity in inferior prefrontal and posterior perceptual regions to predict both which object features were later remembered versus forgotten, and the precision with which they were reconstructed from memory. In contrast, hippocampal encoding activity significantly predicted the precision, but not overall success, of subsequent memory retrieval. The current results identify a hippocampal-cortical encoding basis for episodic memory precision, and suggest a contribution of shared cortical encoding mechanisms to the formation of both accessible and precise memory representations.

scholarly journals Aging and the encoding of changes in events: The role of neural activity pattern reinstatement

2020 ◽  
Vol 117 (47) ◽  
pp. 29346-29353 ◽  
Author(s):  
David Stawarczyk ◽  
Christopher N. Wahlheim ◽  
Joset A. Etzel ◽  
Abraham Z. Snyder ◽  
Jeffrey M. Zacks
Keyword(s):  
Older Adults ◽  
Neural Activity ◽  
Activity Pattern ◽  
Medial Temporal Lobe ◽  
Memory Performance ◽  
Original Activity ◽  
Medial Cortex ◽  
Memory Representations ◽  
Past Experiences

When encountering unexpected event changes, memories of relevant past experiences must be updated to form new representations. Current models of memory updating propose that people must first generate memory-based predictions to detect and register that features of the environment have changed, then encode the new event features and integrate them with relevant memories of past experiences to form configural memory representations. Each of these steps may be impaired in older adults. Using functional MRI, we investigated these mechanisms in healthy young and older adults. In the scanner, participants first watched a movie depicting everyday activities in a day of an actor’s life. They next watched a second nearly identical movie in which some scenes ended differently. Crucially, before watching the last part of each activity, the second movie stopped, and participants were asked to mentally replay how the activity previously ended. Three days later, participants were asked to recall the activities. Neural activity pattern reinstatement in medial temporal lobe (MTL) during the replay phase of the second movie was associated with detecting changes and with better memory for the original activity features. Reinstatements in posterior medial cortex (PMC) additionally predicted better memory for changed features. Compared to young adults, older adults showed a reduced ability to detect and remember changes and weaker associations between reinstatement and memory performance. These findings suggest that PMC and MTL contribute to change processing by reinstating previous event features, and that older adults are less able to use reinstatement to update memory for changed features.

scholarly journals The Potentiation of Associative Memory by Emotions: An Event-Related FMRI Study

2014 ◽  
Vol 2014 ◽  
pp. 1-9 ◽  
Author(s):  
David Luck ◽  
Marie-Eve Leclerc ◽  
Martin Lepage
Keyword(s):  
Performance Improvement ◽  
Entorhinal Cortex ◽  
Associative Memory ◽  
Temporal Lobe ◽  
Memory Retrieval ◽  
Medial Temporal Lobe ◽  
Emotional Valence ◽  
Neural Correlates ◽  
Fmri Study ◽  
The Right

Establishing associations between pieces of information is related to the medial temporal lobe (MTL). However, it remains unclear how emotions affect memory for associations and, consequently, MTL activity. Thus, this event-related fMRI study attempted to identify neural correlates of the influence of positive and negative emotions on associative memory. Twenty-five participants were instructed to memorize 90 pairs of standardized pictures during a scanned encoding phase. Each pair was composed of a scene and an unrelated object. Trials were neutral, positive, or negative as a function of the emotional valence of the scene. At the behavioral level, participants exhibited better memory retrieval for both emotional conditions relative to neutral trials. Within the right MTL, a functional dissociation was observed, with entorhinal activation elicited by emotional associations, posterior parahippocampal activation elicited by neutral associations, and hippocampal activation elicited by both emotional and neutral associations. In addition, emotional associations induced greater activation than neutral trials in the right amygdala. This fMRI study shows that emotions are associated with the performance improvement of associative memory, by enhancing activity in the right amygdala and the right entorhinal cortex. It also provides evidence for a rostrocaudal specialization within the MTL regarding the emotional valence of associations.

scholarly journals Mouse entorhinal cortex encodes a diverse repertoire of self-motion signals

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Caitlin S. Mallory ◽  
Kiah Hardcastle ◽  
Malcolm G. Campbell ◽  
Alexander Attinger ◽  
Isabel I. C. Low ◽  
...  
Keyword(s):  
Entorhinal Cortex ◽  
Medial Temporal Lobe ◽  
Visual Cues ◽  
Neural Circuits ◽  
Sensory Cues ◽  
Medial Entorhinal Cortex ◽  
Representation Of Space ◽  
Self Motion ◽  
Information Streams ◽  
Representations Of Space

AbstractNeural circuits generate representations of the external world from multiple information streams. The navigation system provides an exceptional lens through which we may gain insights about how such computations are implemented. Neural circuits in the medial temporal lobe construct a map-like representation of space that supports navigation. This computation integrates multiple sensory cues, and, in addition, is thought to require cues related to the individual’s movement through the environment. Here, we identify multiple self-motion signals, related to the position and velocity of the head and eyes, encoded by neurons in a key node of the navigation circuitry of mice, the medial entorhinal cortex (MEC). The representation of these signals is highly integrated with other cues in individual neurons. Such information could be used to compute the allocentric location of landmarks from visual cues and to generate internal representations of space.

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