Memory engrams

…across regions form distributed memory engrams that have structural and functional connectivity. However, the computational principles underlying the distributed nature of memory remain unclear. Here, we show that distributed engrams enable memory generalization and discrimination in parallel across brain regions. Orthogonal and complementary, generalization and discrimination are computations that must be balanced for adaptive, memory-guided behavior. For instance, while

Neuronal ensembles encoding a specific memory have been shown to be distributed across multiple brain regions. However, the computational principles behind the distributed nature of such memory engrams are unknown. Here we propose that distributed engrams support functional flexibility and versatility. We investigated whether distributed engrams can differentially regulate memory discrimination and generalization, opposing and complementary computations that must be balanced for adaptive memory-guided behavior. For instance, while animals need to discriminate between threat-predictive and neut

…how shifts in the composition of memory-encoding neuronal ensembles influence a memory properties’ evolution over time. Here we leveraged a developmental approach to target distinct subpopulations of principal neurons (“birthdated neurons”), and used calcium imaging, optogenetics, chemogenetics, in association with multiple hippocampus-dependent learning tasks to investigate their contribution to memory engrams over time

…of neuronal ensembles, forming engrams that remain present in the brain in a latent state once forgotten. Recently, it has been shown that alterations in brain development caused by maternal immune activation (MIA) lead to infant memory retention in male o

In mouse models of Down syndrome (DS), cognitive deficits such as memory impairment are believed to be caused by overinhibition. However, recent studies indicate that the overexpression of Grik1, a gene mainly expressed at interneurons in the hippocampus, could be a key driver of memory deficits in individuals with DS due to a bidirectional alteration of synaptic inhibition on CA1 pyramidal cells (Valbuena et al, Nature Comms. 2019, 10:4991). Remarkably, normalizing Grik1 dosage in the Ts2Cje mouse model of DS specifically restores spatial memory and reverses the bidirectional alterations to C

…into already stored activity states or memory engrams, facilitating their categorization or activation of the appropriate memory trace.Here we present set of experiments that question kinetics of fast changes in hippocampal spatial maps upon manipulating se

In the classical views of systems memory consolidation, memories are transferred from the hippocampus to cortex. But with the advance of recording techniques, it appears that many memories are learned and represented in multiple brain regions simultaneously. Moreover, representations change dynamically while the behavior of animals remains stable. Here, we propose a population perspective on memory consolidation that reproduces many features of this “representational drift”. We develop an analytically tractable model for the dynamics of memory engrams that is structurally similar to a recurren

…its effect on social recognition memory — crucial for identifying conspecifics, remains unexplored. To address this, we developed a novel protocol to study the effects of SD on long-term social recognition memory (SRM) in adult male C57BL/6J mice. Our study revealed that 6 hours of SD, following a socialization trial, caused amnesia when SRM was assessed 24 hours later.Next, we investigated whether SD causes permanent loss or suboptimal storage of SRM. We employed mouse mode

Neuronal ensembles that hold specific memories (memory engrams), are defined as enduring physical and/or chemical change in a neural network that is the result of neuronal activation by episodic stimuli [1] Engram cells have been identified in multiple brain regions, including the hippocampus, amygdala, thalamus, and cortex It has been hypothesized that these distributed engrams are functionally connected [2] This neural network can be specifically reactivated, resulting in the recall of the original memory [3]However, how the interaction among multiple regions facilitates the consolidation, o

…and other brain regions involved in memory formation. However, the creation of a brain-wide map for engram formation and stability has proven to be a challenging endeavor that has been only partially solved. Among the methods to label active neurons, the Targeted Recombination in Active Populations v2 (TRAP2) mouse strain sticks out for enabling t

…These neural ensembles constitute memory engrams that are both necessary and sufficient for inducing recall even long after memory acquisition. This suggests that following encoding, engrams are stabilized to support reliable memory retrieval. However, little is known about the temporal evolution of engrams over the course of memory consolidation or how it impacts mnemonic properties. Here we employed computational and experimental approaches to examine how the composition and selectivity of engrams

Memories are thought to be stored in neural ensembles known as engrams that are specifically reactivated during memory recall. According to recent studies, memory engrams of two events that happened close in time tend to overlap in the hippocampus and the amygdala, and this overlap has been shown to support memory linking. It has been hypothesised that these overlaps arise from the mechanisms that regulate memory allocation itself, involving neural excitability, but the exact process remains unclear. Indeed, most theoretical studies focus on synaptic plasticity and little is known about the ro

…the neural substrate that supports the memory, away from rapidly plastic hippocampal networks towards more stable representations in the neocortex. Rehearsal, i.e. repeated activation of the neural circuits that store a memory, is thought to crucially contribute to the formation of neocortical long-term memory representations. This may either be achieved by repeated study during wakefulness or by a covert reactivation of memory traces

…of synaptic connections that form memory engrams. However, recent experimental findings have challenged this idea, revealing that neural population activity in circuits involved in sensory perception, motor planning and spatial memory continually change over time during familiar behavioural tasks. This continual cha