The quest to understand the memory engram has intrigued humans for centuries. Recent technological advances, including genetic labelling, imaging, optogenetic and chemogenetic techniques, have propelled the field of memory research forward. These tools have enabled researchers to create and erase memory components. While these innovative techniques have yielded invaluable insights, they often focus on specific elements of the memory trace. Genetic labelling may rely on a particular immediate early gene as a marker of activity, optogenetics may activate or inhibit one specific type of neuron, and imaging may capture activity snapshots in a given brain region at specific times. Yet, memories are multifaceted, involving diverse arrays of neuronal subpopulations, circuits, and regions that work in concert to create, store, and retrieve information. Consideration of contributions of both excitatory and inhibitory neurons, micro and macro circuits across brain regions, the dynamic nature of active ensembles, and representational drift is crucial for a comprehensive understanding of the complex nature of memory.
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http://dx.doi.org/10.1016/j.neubiorev.2024.105574 | DOI Listing |
Subcell Biochem
January 2025
Faculty of Medicine and Faculty of Life Sciences, Institute of Biomedical Sciences (ICB), Universidad Andres Bello, Santiago, Chile.
In animals, memory formation and recall are essential for their survival and for adaptations to a complex and often dynamically changing environment. During memory formation, experiences prompt the activation of a selected and sparse population of cells (engram cells) that undergo persistent physical and/or chemical changes allowing long-term memory formation, which can last for decades. Over the past few decades, important progress has been made on elucidating signaling mechanisms by which synaptic transmission leads to the induction of activity-dependent gene regulation programs during the different phases of learning (acquisition, consolidation, and recall).
View Article and Find Full Text PDFExp Neurobiol
December 2024
Center for Cognition and Sociality, Institute for Basic Science, Daejeon 34126, Korea.
Behav Brain Res
January 2025
Department of Neurology, Changzhi People's Hospital, Changzhi, Shanxi Province 046000, China. Electronic address:
Memory is the ability to acquire and store information following an experience, which can be retrieved by related context exposure. Pioneering studies have demonstrated that sparsely distributed neuronal ensembles or engram cells can serve as neural substrates for storing and recalling memory traces. Many studies of neuronal ensembles have focused on the hippocampus, and increasing evidence has indicated that the neuronal oscillation is closely associated with hippocampal memory functions, including both encoding and retrieval processes.
View Article and Find Full Text PDFFront Behav Neurosci
December 2024
Department of Psychology, University of California, Davis, Davis, CA, United States.
Molecular and genetic techniques now allow selective tagging and manipulation of the population of neurons, often referred to as "engram cells," that were active during a specific experience. One common approach to labeling these cells is to use the transgenic mouse (TetTag). In addition to tagging cells active during learning, it is common to examine the reactivation of these cells using immediate early gene (IEG) expression as an index of neural activity.
View Article and Find Full Text PDFCortex
December 2024
Brain Research and Cognition Center (CerCo), CNRS, UMR5549, France; University of Toulouse, Faculty of Health, France.
The precise and fleeting moment of rich recollection triggered by an environmental cue is difficult to reproduce in the lab. However, epilepsy patients can experience sudden reminiscences after intracranial electrical brain stimulation (EBS). In these cases, the transient brain state related to the activation of the engram and its conscious perception can be recorded using intracerebral EEG (iEEG).
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