Memory retrieval

The hippocampal formation is a crucial region in the encoding and retrieval of memory, thought to be mediated through ensemble formation and recruitment or intrinsic attractor dynamics. Additionally, it has been shown that overall hippocampal population activity reflects environmental novelty. However, a common neural basis supporting these two processes remains unknown. Furthermore, many memories contain overlapping features, and it remains to be established how specific memories are retrieved without interference in the hippocampus. We propose that both engram and attractor models hinge on l

…sequences such as narratives from memory. To understand how compression may arise in human memory, we develop a statistical model of memory retrieval for meaningful material, in which semantic structures are abstracted into a hierarchy of keypoints, each representing a compressed version of the underlying clauses. Our model is motivated by a small set of basic principles, inspired by behavioral and neuroscience experiments on human processing of naturalistic stimuli. Our model predicts com

…cortex (PL) is required for fear memory retrieval across time and is densely interconnected with many subcortical and cortical areas involved in recent and remote memory recall, including the temporal association area (TeA). While the behavioral expression of a memory may remain constant over time, the neural activity mediating memory-guided behavior is dynamic. In PL, different neurons underlie recent and remote memory retrieval and remote memory-encoding neurons have

…related to learning, as well as memory consolidation (DOI: 10.1038/s41583-020-0360-9). Less is known about its role in memory retrieval. In this study, we explored this aspect following training of adult rats over a period of multiple days in an 8-arm radial maze to achieve robust spatial working memory (WM) and reference memory (RM) of the task. We then examined the consequence of patterned electrophysiological activation of the LC on the retrieval of recent (24h after the conclusion of training) or remote

The serotonergic system was previously shown to affect learning and memory processes in humans[1]. Establishing a relation between serotonin-1A receptor (5-HT1AR) distribution with memory processing would allow us to further investigate its potential as a therapeutic target. Here, we aim to investigate the effect of 5-HT1AR spatial distribution on the different memory domains. Positron emission tomography data were collected from 20 healthy volunteers using the radioligand [carbonyl-11C]WAY-100635 [2,3]. Data were quantified using multilinear reference tissue model 2 to obtain non-displaceable

…to relevant cues, thus leading to memory retrieval. Significant evidence exists to support this theory in relation to highly aversive or rewarding experiences, however less evidence exists to support the existence of engrams for day-to-day learning experiences. Here we used TRAP2 mice to characterize expression patterns and plasticity in neurons activat

The dentate gyrus (DG) plays a key role in memory encoding and retrieval, facilitating discrimination of the environmental inputs by separating them into non-overlapping patterns and reducing interference of stored representations. It is highly susceptible to aging-related structural and physiological changes and thought to contribute to age-related cognitive dysfunctions. In this study we examined possible age-related changes in pattern separation function and associated changes in DG cellular engrams using a contextual fear conditioning task. Young adult (3-month-old) and healthy aged (24-mo

This study was undertaken to assess sex differences in the vicarious learning magnitude by exploiting an aversive paradigm in adult mice. Mouse observers were individually subjected to an observational compartment next to the training compartment wherein three demonstrators received 1)a daily 30-min presentation of vanilla odors for 3 consecutive days; or 2)3-days of 30-min vanilla odors contingent on the delivery of 15 pseudo-randomly-arranged footshocks (0.5 mA, 2 s in duration per shock). Vanilla odors-induced freezing response (FR) was used to indicate observers’ vicarious learning magnitu

Numerous machine learning algorithms incorporate memory models that were inspired by episodic memory. However, almost all of them employ pre-defined and rigid mechanisms for the encoding and retrieval of memories. Usually, a pre-determined type of information is stored at each timestep regardless of whether anything interesting has happened. Here, we investigate a model based on a Memory-Augmented Neural Network, which learns autonomously what and when to store into, and retrieve from, an external memory buffer, while solving a navigation task in a simulated maze. The agent learns to navigate

Repetitive cocaine exposure induces the generation of silent synapses in the nucleus accumbens, characterized by the presence of NMDA receptors and absence of AMPA receptors, hindering fast synaptic transmission (Huang et al, 2009). While typically abundant during early postnatal development, cocaine triggers the de novo generation of silent synapses in the adult brain, thereby establishing new synaptic connections within an already refined circuit (Huang et al, 2009; Huang et al, 2015). During withdrawal, some silent synapses undergo unsilencing by incorporating AMPARs, which crucially contri

Remembering events in the past is crucial to intelligent behaviour. Flexible memory retrieval, beyond simple recall, requires a model of how events relate to one another. Two key brain systems are implicated in this process: the hippocampal episodic memory (EM) system and the prefrontal working memory (WM) system. While an understanding of the hippocampal system, from computation to algorithm and representation, is emerging, less is understood about how the prefrontal WM system can give rise to flexible computations beyond simple memory retrieval, and even less is understood about how the two

Inhibitory neurons take on many forms and functions. How this diversity contributes to memory function is not completely known. Previous formal studies indicate inhibition differentiated by local and global connectivity in associative memory networks functions to rescale the level of retrieval of excitatory assemblies. However, such studies lack biological details such as a distinction between types of neurons (excitatory and inhibitory), unrealistic connection schemas, and non-sparse assemblies. In this study, we present a rate-based cortical model where neurons are distinguished (as excitato

…activity, but their role in remote memory is scarcely explored. We manipulated the activity of hippocampal astrocytes during memory acquisition and discovered it impaired remote, but not recent, memory retrieval. We also revealed a massive recruitment of cortical-projecting hippocampal

Autobiographical memories are the ghosts of our past. Through them we visit places long departed, see faces once familiar, and hear voices now silent. These, often decades-old, personal experiences can be recalled on a whim or come unbidden into our everyday consciousness. Autobiographical memories are crucial to cognition because they facilitate almost everything we do, endow us with a sense of self and underwrite our capacity for autonomy. They are often compromised by common neurological and psychiatric pathologies with devastating effects. Despite autobiographical memories being central t