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 Controlling Conflict from Interfering Long-term Memory Representations

2012 ◽  
Vol 24 (5) ◽  
pp. 1173-1190 ◽  
Author(s):  
Kerstin Jost ◽  
Patrick H. Khader ◽  
Peter Düsel ◽  
Franziska R. Richter ◽  
Kristina B. Rohde ◽  
...  
Keyword(s):  
Memory Retrieval ◽  
Memory Trace ◽  
Long Term Memory ◽  
Retrieval Cues ◽  
Domain Specific ◽  
Specific Memory ◽  
Memory Representations ◽  
Retrieval Interference ◽  
Relevant Material

Remembering is more than an activation of a memory trace. As retrieval cues are often not uniquely related to one specific memory, cognitive control should come into play to guide selective memory retrieval by focusing on relevant while ignoring irrelevant information. Here, we investigated, by means of EEG and fMRI, how the memory system deals with retrieval interference arising when retrieval cues are associated with two material types (faces and spatial positions), but only one is task-relevant. The topography of slow EEG potentials and the fMRI BOLD signal in posterior storage areas indicated that in such situations not only the relevant but also the irrelevant material becomes activated. This results in retrieval interference that triggers control processes mediated by the medial and lateral PFC, which are presumably involved in biasing target representations by boosting the task-relevant material. Moreover, memory-based conflict was found to be dissociable from response conflict that arises when the relevant and irrelevant materials imply different responses. The two types of conflict show different activations in the medial frontal cortex, supporting the claim of domain-specific prefrontal control systems.

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.

scholarly journals Electroconvulsive Shock Does Not Impair the Reconsolidation of Cued and Contextual Pavlovian Threat Memory

2020 ◽  
Vol 21 (19) ◽  
pp. 7072
Author(s):  
Hajira Elahi ◽  
Veronica Hong ◽  
Jonathan E. Ploski
Keyword(s):  
Electroconvulsive Shock ◽  
Post Traumatic Stress Disorder ◽  
Traumatic Stress ◽  
Memory Retrieval ◽  
Memory Trace ◽  
Stress Disorder ◽  
Fear Memory ◽  
Post Traumatic Stress ◽  
Post Traumatic ◽  
Electroconvulsive Seizure

Existing memories, when retrieved under certain circumstances, can undergo modification through the protein synthesis-dependent process of reconsolidation. Disruption of this process can lead to the weakening of a memory trace, an approach which is being examined as a potential treatment for disorders characterized by pathological memories, such as Post-Traumatic Stress Disorder. The success of this approach relies upon the ability to robustly attenuate reconsolidation; however, the available literature brings into question the reliability of the various drugs used to achieve such a blockade. The identification of a drug or intervention that can reliably disrupt reconsolidation without requiring intracranial access for administration would be extremely useful. Electroconvulsive shock (ECS) delivered after memory retrieval has been demonstrated in some studies to disrupt memory reconsolidation; however, there exists a paucity of literature characterizing its effects on Pavlovian fear memory. Considering this, we chose to examine ECS as an inexpensive and facile means to impair reconsolidation in rats. Here we show that electroconvulsive seizure induction, when administered after memory retrieval, (immediately, after 30 min, or after 1 h), does not impair the reconsolidation of cued or contextual Pavlovian fear memories. On the contrary, ECS administration immediately after extinction training may modestly impair the consolidation of fear extinction memory.

scholarly journals Cortical Representations Are Reinstated by the Hippocampus during Memory Retrieval

Neuron ◽  
2014 ◽  
Vol 84 (2) ◽  
pp. 347-354 ◽  
Author(s):  
Kazumasa Z. Tanaka ◽  
Aleksandr Pevzner ◽  
Anahita B. Hamidi ◽  
Yuki Nakazawa ◽  
Jalina Graham ◽  
...  
Keyword(s):  
Memory Retrieval ◽  
Cortical Representations

Regulated hypothermia in the hypothyroid rat induced by administration of propylthiouracil

1997 ◽  
Vol 272 (5) ◽  
pp. R1390-R1395 ◽  
Author(s):  
Y. Yang ◽  
C. J. Gordon
Keyword(s):  
Drinking Water ◽  
Heat Stress ◽  
Temperature Gradient ◽  
Serum Levels ◽  
Male Rats ◽  
Light Phase ◽  
Grooming Behavior ◽  
Ambient Temperatures ◽  
Wide Range ◽  
The Stability

Propylthiouracil (PTU), an antithyroidal drug that reduces serum L-thyroxine (T4) and 3,5,3'-triiodothyronine (T3), is presumed to lower core temperature (T0) by impairing metabolic thermogenesis. However, it is not understood why PTU-treated animals cannot use behavioral and other thermoeffectors to maintain normal Tc. Male rats were administered PTU in drinking water (0.05 mg/ml) while the following parameters were measured: 1) Tc and motor activity (MA) recorded by radiotelemetry for 24 h at ambient temperatures (Ta) of 10-30 degrees C; 2) selected Ta, MA, and Tc in a temperature gradient; and 3) Tc, MA, and grooming behavior during exposure to heat stress (TH = 34.5 degrees C) for 2 h. PTU reduced serum levels of T4, and T3 by 95 and 60%, respectively. Tc decreased after 3 days of PTU treatment; a 0.5 degree C decrease in Tc persisted throughout the PTU treatment. PTU rats exposed to Ta of 10-30 degrees C maintained a consistent hypothermic Tc during the light phase; however, a deficit in the stability of Tc at night was noted during exposure to 10 degrees C. In the temperature gradient, PTU rats selected warmer Ta, but their Tc was maintained at the same hypothermic levels as observed at fixed Ta values of 15-30 degrees C. Heat stress caused Tc of control rats to increase to 39 degrees C, whereas Tc of the PTU rats was maintained below 38 degrees C. The regulation of Tc at hypothermic levels over a wide range of Ta values and when rats were housed in a temperature gradient indicates that chronic PTU induces a state of regulated hypothermia.

scholarly journals Functional Dissociation within the Entorhinal Cortex for Memory Retrieval of an Association between Temporally Discontiguous Stimuli

2012 ◽  
Vol 32 (16) ◽  
pp. 5356-5361 ◽  
Author(s):  
M. D. Morrissey ◽  
G. Maal-Bared ◽  
S. Brady ◽  
K. Takehara-Nishiuchi
Keyword(s):  
Entorhinal Cortex ◽  
Memory Retrieval

scholarly journals The Neurocognitive Cost of Enhancing Cognition with Methylphenidate: Improved Distractor Resistance but Impaired Updating

2017 ◽  
Vol 29 (4) ◽  
pp. 652-663 ◽  
Author(s):  
Sean James Fallon ◽  
Marieke E. van der Schaaf ◽  
Niels ter Huurne ◽  
Roshan Cools
Keyword(s):  
Working Memory ◽  
Cognitive Flexibility ◽  
Dependent Manner ◽  
Neural Signal ◽  
Specific Effects ◽  
Cognitive Stability ◽  
Paradoxical Effects ◽  
Memory Representations ◽  
The Stability ◽  
And Task

A balance has to be struck between supporting distractor-resistant representations in working memory and allowing those representations to be updated. Catecholamine, particularly dopamine, transmission has been proposed to modulate the balance between the stability and flexibility of working memory representations. However, it is unclear whether drugs that increase catecholamine transmission, such as methylphenidate, optimize this balance in a task-dependent manner or bias the system toward stability at the expense of flexibility (or vice versa). Here we demonstrate, using pharmacological fMRI, that methylphenidate improves the ability to resist distraction (cognitive stability) but impairs the ability to flexibly update items currently held in working memory (cognitive flexibility). These behavioral effects were accompanied by task-general effects in the striatum and opposite and task-specific effects on neural signal in the pFC. This suggests that methylphenidate exerts its cognitive enhancing and impairing effects through acting on the pFC, an effect likely associated with methylphenidate's action on the striatum. These findings highlight that methylphenidate acts as a double-edged sword, improving one cognitive function at the expense of another, while also elucidating the neurocognitive mechanisms underlying these paradoxical effects.

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 Mnemonic prediction errors promote detailed memories

2021 ◽  
Vol 28 (11) ◽  
pp. 422-434
Author(s):  
Oded Bein ◽  
Natalie A. Plotkin ◽  
Lila Davachi
Keyword(s):  
Memory Trace ◽  
Theoretical Models ◽  
Item Memory ◽  
Prediction Errors ◽  
Memory Enhancement ◽  
Object A ◽  
Memory Traces ◽  
Memory Representations ◽  
Memory Advantage ◽  
Violated Expectations

When our experience violates our predictions, it is adaptive to update our knowledge to promote a more accurate representation of the world and facilitate future predictions. Theoretical models propose that these mnemonic prediction errors should be encoded into a distinct memory trace to prevent interference with previous, conflicting memories. We investigated this proposal by repeatedly exposing participants to pairs of sequentially presented objects (A → B), thus evoking expectations. Then, we violated participants’ expectations by replacing the second object in the pairs with a novel object (A → C). The following item memory test required participants to discriminate between identical old items and similar lures, thus testing detailed and distinctive item memory representations. In two experiments, mnemonic prediction errors enhanced item memory: Participants correctly identified more old items as old when those items violated expectations during learning, compared with items that did not violate expectations. This memory enhancement for C items was only observed when participants later showed intact memory for the related A → B pairs, suggesting that strong predictions are required to facilitate memory for violations. Following up on this, a third experiment reduced prediction strength prior to violation and subsequently eliminated the memory advantage of violations. Interestingly, mnemonic prediction errors did not increase gist-based mistakes of identifying old items as similar lures or identifying similar lures as old. Enhanced item memory in the absence of gist-based mistakes suggests that violations enhanced memory for items’ details, which could be mediated via distinct memory traces. Together, these results advance our knowledge of how mnemonic prediction errors promote memory formation.

scholarly journals Tracking induced forgetting across both strong and weak memory representations to test competing theories of forgetting

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Ashleigh M. Maxcey ◽  
Zara Joykutty ◽  
Emma Megla
Keyword(s):  
Memory Trace ◽  
Memory Representation ◽  
The Novel ◽  
Moderate Amount ◽  
Future Directions ◽  
Inhibitory Mechanisms ◽  
Memory Probe ◽  
Global Matching ◽  
Memory Representations ◽  
Induced Forgetting

AbstractHere we employ a novel analysis to address the question: what causes induced forgetting of pictures? We use baseline memorability as a measure of initial memory strength to ask whether induced forgetting is due to (1) recognition practice damaging the association between the memory representation and the category cue used to activate the representation, (2) the updating of a memory trace by incorporating information about a memory probe presented during recognition practice to the stored trace, (3) inhibitory mechanisms used to resolve the conflict created when correctly selecting the practiced item activates competing exemplars, (4) a global matching model in which repeating some items will hurt memory for other items, or (5) falling into the zone of destruction, where a moderate amount of activation leads to the highest degree of forgetting. None of the accounts of forgetting tested here can comprehensively account for both the novel analyses reported here and previous data using the induced forgetting paradigm. We discuss aspects of forgetting theories that are consistent with the novel analyses and existing data, a potential solution for existing models, proposals for future directions, and considerations when incorporating memorability into models of memory.

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