-
Nature Neuroscience Oct 2019Memory retrieval involves the interaction between external sensory or internally generated cues and stored memory traces (or engrams) in a process termed 'ecphory'.... (Review)
Review
Memory retrieval involves the interaction between external sensory or internally generated cues and stored memory traces (or engrams) in a process termed 'ecphory'. While ecphory has been examined in human cognitive neuroscience research, its neurobiological foundation is less understood. To the extent that ecphory involves 'reawakening' of engrams, leveraging recently developed technologies that can identify and manipulate engrams in rodents provides a fertile avenue for examining retrieval at the level of neuronal ensembles. Here we evaluate emerging neuroscientific research of this type, using cognitive theory as a guiding principle to organize and interpret initial findings. Our Review highlights the critical interaction between engrams and retrieval cues (environmental or artificial) for memory accessibility and retrieval success. These findings also highlight the intimate relationship between the mechanisms important in forming engrams and those important in their recovery, as captured in the cognitive notion of 'encoding specificity'. Finally, we identify several questions that currently remain unanswered.
Topics: Animals; Cognitive Science; Humans; Memory; Mental Recall; Neurobiology
PubMed: 31551594
DOI: 10.1038/s41593-019-0493-1 -
Nature Reviews. Neuroscience Mar 2020The dentate gyrus (DG) has a key role in hippocampal memory formation. Intriguingly, DG lesions impair many, but not all, hippocampus-dependent mnemonic functions,... (Review)
Review
The dentate gyrus (DG) has a key role in hippocampal memory formation. Intriguingly, DG lesions impair many, but not all, hippocampus-dependent mnemonic functions, indicating that the rest of the hippocampus (CA1-CA3) can operate autonomously under certain conditions. An extensive body of theoretical work has proposed how the architectural elements and various cell types of the DG may underlie its function in cognition. Recent studies recorded and manipulated the activity of different neuron types in the DG during memory tasks and have provided exciting new insights into the mechanisms of DG computational processes, particularly for the encoding, retrieval and discrimination of similar memories. Here, we review these DG-dependent mnemonic functions in light of the new findings and explore mechanistic links between the cellular and network properties of, and the computations performed by, the DG.
Topics: Animals; Dentate Gyrus; Discrimination Learning; Entorhinal Cortex; Humans; Memory Consolidation; Memory, Episodic; Mental Recall; Models, Neurological; Neurons
PubMed: 32042144
DOI: 10.1038/s41583-019-0260-z -
Science (New York, N.Y.) Nov 2023The hippocampus is critical for recollecting and imagining experiences. This is believed to involve voluntarily drawing from hippocampal memory representations of...
The hippocampus is critical for recollecting and imagining experiences. This is believed to involve voluntarily drawing from hippocampal memory representations of people, events, and places, including maplike representations of familiar environments. However, whether representations in such "cognitive maps" can be volitionally accessed is unknown. We developed a brain-machine interface to test whether rats can do so by controlling their hippocampal activity in a flexible, goal-directed, and model-based manner. We found that rats can efficiently navigate or direct objects to arbitrary goal locations within a virtual reality arena solely by activating and sustaining appropriate hippocampal representations of remote places. This provides insight into the mechanisms underlying episodic memory recall, mental simulation and planning, and imagination and opens up possibilities for high-level neural prosthetics that use hippocampal representations.
Topics: Animals; Rats; Brain-Computer Interfaces; Hippocampus; Imagination; Memory, Episodic; Mental Recall; Volition; Spatial Navigation; Brain Mapping
PubMed: 37917713
DOI: 10.1126/science.adh5206 -
ELife Jun 2020Deep inside the temporal lobe of the brain, the hippocampus has a central role in our ability to remember, imagine and dream.
Deep inside the temporal lobe of the brain, the hippocampus has a central role in our ability to remember, imagine and dream.
Topics: Brain; Dreams; Hippocampus; Mental Recall
PubMed: 32508304
DOI: 10.7554/eLife.58874 -
Annual Review of Psychology Jan 2022By linking the past with the future, our memories define our sense of identity. Because human memory engages the conscious realm, its examination has historically been...
By linking the past with the future, our memories define our sense of identity. Because human memory engages the conscious realm, its examination has historically been approached from language and introspection and proceeded largely along separate parallel paths in humans and other animals. Here, we first highlight the achievements and limitations of this mind-based approach and make the case for a new brain-based understanding of declarative memory with a focus on hippocampal physiology. Next, we discuss the interleaved nature and common physiological mechanisms of navigation in real and mental spacetime. We suggest that a distinguishing feature of memory types is whether they subserve actions for single or multiple uses. Finally, in contrast to the persisting view of the mind as a highly plastic blank slate ready for the world to make its imprint, we hypothesize that neuronal networks are endowed with a reservoir of neural trajectories, and the challenge faced by the brain is how to select and match preexisting neuronal trajectories with events in the world.
Topics: Animals; Brain; Hippocampus; Humans; Mental Recall
PubMed: 34535061
DOI: 10.1146/annurev-psych-021721-110002 -
Nature Reviews. Neuroscience Feb 2022Memory recollections and voluntary actions are often perceived as spontaneously generated irrespective of external stimuli. Although products of our neurons, they are... (Review)
Review
Memory recollections and voluntary actions are often perceived as spontaneously generated irrespective of external stimuli. Although products of our neurons, they are only rarely accessible in humans at the neuronal level. Here I review insights gleaned from unique neurosurgical opportunities to record and stimulate single-neuron activity in people who can declare their thoughts, memories and wishes. I discuss evidence that the subjective experience of human recollection and that of voluntary action arise from the activity of two internal neuronal generators, the former from medial temporal lobe reactivation and the latter from frontoparietal preactivation. I characterize properties of these generators and their interaction, enabling flexible recruitment of memory-based choices for action as well as recruitment of action-based plans for the representation of conceptual knowledge in memories. Both internal generators operate on surprisingly explicit but different neuronal codes, which appear to arise with distinct single-neuron activity, often observed before participants' reports of conscious awareness. I discuss prediction of behaviour based on these codes, and the potential for their modulation. The prospects of editing human memories and volitions by enhancement, inception or deletion of specific, selected content raise therapeutic possibilities and ethical concerns.
Topics: Animals; Humans; Memory; Memory, Episodic; Mental Recall; Neurons; Volition
PubMed: 34931068
DOI: 10.1038/s41583-021-00543-8 -
ELife May 2024Our ability to recall details from a remembered image depends on a single mechanism that is engaged from the very moment the image disappears from view.
Our ability to recall details from a remembered image depends on a single mechanism that is engaged from the very moment the image disappears from view.
Topics: Humans; Mental Recall
PubMed: 38700912
DOI: 10.7554/eLife.98274 -
NeuroImage Feb 2022Brain activity in the moments leading up to spontaneous verbal recall provide a window into the cognitive processes underlying memory retrieval. But these same...
Brain activity in the moments leading up to spontaneous verbal recall provide a window into the cognitive processes underlying memory retrieval. But these same recordings also subsume neural signals unrelated to mnemonic retrieval, such as response-related motor activity. Here we examined spectral EEG biomarkers of memory retrieval under an extreme manipulation of mnemonic demands: subjects either recalled items after a few seconds or after several days. This manipulation helped to isolate EEG components specifically related to long-term memory retrieval. In the moments immediately preceding recall we observed increased theta (4-8 Hz) power (+T), decreased alpha (8-20 Hz) power (-A), and increased gamma (40-128 Hz) power (+G), with this spectral pattern (+T-A + G) distinguishing the long-delay and immediate recall conditions. As subjects vocalized the same set of studied words in both conditions, we interpret the spectral +T-A + G as a biomarker of episodic memory retrieval.
Topics: Adolescent; Adult; Biomarkers; Brain Waves; Electroencephalography; Female; Humans; Male; Memory, Episodic; Mental Recall; Young Adult
PubMed: 34863960
DOI: 10.1016/j.neuroimage.2021.118748 -
Cognition Sep 2021We investigated visual working memory (VWM) with a whole-report task, where participants were asked to sequentially recall all the items in an order either chosen by...
We investigated visual working memory (VWM) with a whole-report task, where participants were asked to sequentially recall all the items in an order either chosen by themselves (free recall) or randomly chosen by the computer (forced recall). Comparisons between free and forced recalls helped us understand important but largely neglected aspects of VWM, such as inhomogeneity (different levels of precision) and between-item interference. One unique part of our task was the introduction of a separate item-selection stage before each recall, during which participants located the next item to recall. Their mouse trajectory was recorded and served as a dynamic measure of between-item interference over time. We found a free-recall benefit: the overall precision of all items is higher in free recall than in forced recall. Meanwhile, during item-selection, free recall is associated with faster localization of the target and less interference from the other items in memory. We also found evidence for inhomogeneity and discuss the connection of inhomogeneity and between-item interference to the free-recall benefit.
Topics: Cues; Humans; Memory, Short-Term; Mental Recall
PubMed: 33901834
DOI: 10.1016/j.cognition.2021.104739 -
Trends in Cognitive Sciences Dec 2019Episodic memory allows us to mentally travel through time. How does the brain convert a simple reminder cue into a full-blown memory of past events and experiences? In... (Review)
Review
Episodic memory allows us to mentally travel through time. How does the brain convert a simple reminder cue into a full-blown memory of past events and experiences? In this review, we integrate recent developments in the cognitive neuroscience of human memory retrieval, pinpointing the neural chronometry underlying successful recall. Electrophysiological recordings suggest that sensory cues proceed into the medial temporal lobe within the first 500 ms. At this point, a hippocampal process sets in, geared toward internal pattern completion and coordination of cortical memory reinstatement between 500 and 1500 ms. We further highlight the dynamic principles governing the recall process, which include a reversal of perceptual information flows, temporal compression, and theta clocking.
Topics: Animals; Brain; Humans; Mental Recall; Time Factors
PubMed: 31672429
DOI: 10.1016/j.tics.2019.09.011