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 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 Distinct neural mechanisms underlie the success, precision, and vividness of episodic memory

eLife ◽  
2016 ◽  
Vol 5 ◽  
Author(s):  
Franziska R Richter ◽  
Rose A Cooper ◽  
Paul M Bays ◽  
Jon S Simons
Keyword(s):  
Episodic Memory ◽  
Memory Retrieval ◽  
Brain Regions ◽  
Neural Mechanisms ◽  
Angular Gyrus ◽  
Continuous Scale ◽  
Hippocampal Activity ◽  
Object Features ◽  
Continuous Measures ◽  
Made In

A network of brain regions have been linked with episodic memory retrieval, but limited progress has been made in identifying the contributions of distinct parts of the network. Here, we utilized continuous measures of retrieval to dissociate three components of episodic memory: retrieval success, precision, and vividness. In the fMRI scanner, participants encoded objects that varied continuously on three features: color, orientation, and location. Participants’ memory was tested by having them recreate the appearance of the object features using a continuous dial, and continuous vividness judgments were recorded. Retrieval success, precision, and vividness were dissociable both behaviorally and neurally: successful versus unsuccessful retrieval was associated with hippocampal activity, retrieval precision scaled with activity in the angular gyrus, and vividness judgments tracked activity in the precuneus. The ability to dissociate these components of episodic memory reveals the benefit afforded by measuring memory on a continuous scale, allowing functional parcellation of the retrieval network.

scholarly journals Schematic memories develop quickly, but are not expressed unless necessary

2020 ◽  
Vol 10 (1) ◽  
Author(s):  
Alexa Tompary ◽  
WenXi Zhou ◽  
Lila Davachi
Keyword(s):  
Spatial Distribution ◽  
Episodic Memory ◽  
Memory Retrieval ◽  
Fading Memory ◽  
Episodic Retrieval ◽  
Memory Representations ◽  
Over Time

Abstract Episodic memory retrieval is increasingly influenced by schematic information as memories mature, but it is unclear whether this is due to the slow formation of schemas over time, or the slow forgetting of the episodes. To address this, we separately probed memory for newly learned schemas as well as their influence on episodic memory decisions. In this experiment, participants encoded images from two categories, with the location of images in each category drawn from a different spatial distribution. They could thus learn schemas of category locations by encoding specific episodes. We found that images that were more consistent with these distributions were more precisely retrieved, and this schematic influence increased over time. However, memory for the schema distribution, measured using generalization to novel images, also became less precise over time. This incongruity suggests that schemas form rapidly, but their influence on episodic retrieval is dictated by the need to bolster fading memory representations.

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 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 Episodic memory and common sense: how far apart?

2001 ◽  
Vol 356 (1413) ◽  
pp. 1505-1515 ◽  
Author(s):  
Endel Tulving
Keyword(s):  
Episodic Memory ◽  
Common Sense ◽  
Memory Retrieval ◽  
Critical Role ◽  
Human Memory ◽  
Memory Systems ◽  
Perceptual Information ◽  
Subjective Time ◽  
Retrieval Processes ◽  
Past Experiences

Research has revealed facts about human memory in general and episodic memory in particular that deviate from both common sense and previously accepted ideas. This paper discusses some of these deviations in light of the proceedings of The Royal Society's Discussion Meeting on episodic memory. Retrieval processes play a more critical role in memory than commonly assumed; people can remember events that never happened; and conscious thoughts about one's personal past can take two distinct forms—‘autonoetic’ remembering and ‘noetic’ knowing. The serial—dependent—independent (SPI) model of the relations among episodic, semantic and perceptual memory systems accounts for a number of puzzling phenomena, such as some amnesic patients' preserved recognition memory and their ability to learn new semantic facts, and holds that episodic remembering of perceptual information can occur only by virtue of its mediation through semantic memory. Although common sense endows many animals with the ability to remember their past experiences, as yet there is no evidence that humanlike episodic memory—defined in terms of subjective time, self, and autonoetic awareness—is present in any other species.

scholarly journals Total recall: episodic memory retrieval, choice, and memory confidence in the rat

2020 ◽  
Author(s):  
Hannah R. Joo ◽  
Hexin Liang ◽  
Jason E Chung ◽  
Charlotte Geaghan-Breiner ◽  
Jiang Lan Fan ◽  
...  
Keyword(s):  
Episodic Memory ◽  
Memory Retrieval ◽  
Memory Task ◽  
Correct Choice ◽  
Decision Variable ◽  
Future Behavior ◽  
Episodic Memories ◽  
Past Experiences ◽  
Memory Confidence ◽  
Modern Machine

Episodic memory enables recollection of past experiences to guide future behavior. Humans know which memories to trust (high confidence) and which to doubt (low confidence). How memory retrieval, memory confidence, and memory-guided decisions are related, however, is not understood. Additionally, whether animals can assess confidence in episodic memories to guide behavior is unknown. We developed a spatial episodic memory task in which rats were incentivized to gamble their time: betting more following a correct choice yielded greater reward. Rat behavior reflected memory confidence, with higher temporal bets following correct choices. We applied modern machine learning to identify a memory decision variable, and built a generative model of memories evolving over time that accurately predicted both choices and confidence reports. Our results reveal in rats an ability thought to exist exclusively in primates, and introduce a unified model of memory dynamics, retrieval, choice, and confidence.

scholarly journals Healthy ageing reduces the precision of episodic memory retrieval

2018 ◽  
Author(s):  
Saana M. Korkki ◽  
Franziska R. Richter ◽  
Priyanga Jeyarathnarajah ◽  
Jon S. Simons
Keyword(s):  
Episodic Memory ◽  
Memory Retrieval ◽  
Contextual Information ◽  
Computational Modelling ◽  
Memory Loss ◽  
Older Age ◽  
Everyday Objects ◽  
Continuous Response ◽  
Age Related ◽  
Memory Representations

AbstractEpisodic memory declines with older age, but it is unresolved whether this decline reflects reduced probability of successfully retrieving information from memory, or decreased precision of the retrieved information. Here, we used continuous measures of episodic memory retrieval in combination with computational modelling of participants’ retrieval errors to distinguish between these two potential accounts of age-related memory deficits. In three experiments, young and older participants encoded stimuli displays consisting of everyday objects varying along different perceptual features (e.g., location, colour and orientation) in a circular space. At test, participants recreated the features of studied objects using a continuous response dial. Across all three experiments, we observed age-related declines in the precision of episodic memory retrieval, whereas age differences in retrieval success were limited to the most challenging task condition. Reductions in mnemonic precision were evident for retrieval of both item-based and contextual information, and persisted after controlling for age-related decreases in the fidelity of perception and working memory. The findings highlight impoverished precision of memory representations as one factor contributing to age-related episodic memory loss, and suggest that the cognitive and neural changes associated with older age can differentially affect distinct aspects of episodic retrieval.

scholarly journals Schematic memories develop quickly, but are not expressed unless necessary

2020 ◽  
Author(s):  
Alexa Tompary ◽  
WenXi Zhou ◽  
Lila Davachi
Keyword(s):  
Spatial Distribution ◽  
Episodic Memory ◽  
Memory Retrieval ◽  
Fading Memory ◽  
Episodic Retrieval ◽  
Slow Decay ◽  
Memory Representations ◽  
Over Time

Episodic memory retrieval is increasingly influenced by schematic information as memories mature, but it is unclear whether this is due to the slow formation of schemas over time, or the slow decay of the episodes. To address this, we separately probed memory for newly learned schemas as well as their influence on episodic memory decisions. In this experiment, participants encoded images from two categories, with the location of images in each category drawn from a different spatial distribution. They could thus learn schemas of category locations by encoding specific episodes. We found that images that were more consistent with these distributions were more precisely retrieved, and this schematic influence increased over time. However, memory for the schema distribution, measured using generalization to novel images, also became less precise over time. This incongruity suggests that schemas form rapidly, but their influence on episodic retrieval is dictated by the need to bolster fading memory representations.

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.

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