Topic: episodic memories

Memory reconsolidation is the mechanism by which consolidated memories are updated in strength and/or content. Thus, memory reactivation can enhance the retention of reactivated items at long delays. An underlying hypothesis to these findings suggests that reconsolidation would be “reactivation specific”, implying that only the reactivated elements after consolidation would be susceptible to modifications. However, episodic memories are intrinsically associative, which implies that they are integrated into interconnected- networks between its elements and the acquisition context. Reactivation

Episodic memories are encoded by sparse populations of neurons activated during an experience. 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

Throughout each day the brain captures snapshots of distinct experiences, forming episodic memories that often last a lifetime. This function depends on the hippocampus – a brain region that is evolutionarily conserved across vertebrates. My lab studies the relationship between hippocampal activity and episodic memory using a unique model organism – the black-capped chickadee. Chickadees are specialist food-caching birds that store thousands of food items at concealed locations in their environment and use memory later in time to retrieve their caches. I will describe our effort in designing b

The canonical model of the dentate gyrus (DG) of the hippocampus suggests the DG performs pattern separation, orthogonalizing similar input patterns [1, 2] aided by an approximate 5-fold expansion of the cell population relative to its entorhinal cortex inputs [3]. However, more recent experimental results challenge this standard model, suggesting the DG also supports the precise binding of objects and events to space and the integration of information across episodes [4]. Very recent studies attribute pattern separation and pattern integration to anatomically distinct parts of the DG, the sup

We can draw on both episodic memories and semantic knowledge to guide behavior in novel situations. Despite growing interest, key questions remain on the interplay between these systems. How do semantic representations guide the retrieval of episodic memories? How are low-level semantic relationships abstracted from everyday observations (episodes)? How are these low-level relationships transformed to higher-order knowledge structures? By bridging insights from memory-neuroscience with findings in memory-based decision-making, we propose that the sequential sampling of related episodic memorie

A growing body of evidence indicates a functional dichotomy between the dorsal (dHC) and ventral poles of the hippocampus (vHC). Specifically, the dorsal region is implicated in encoding spatial information and episodic memories, whereas the ventral region is recognized for its role in processing the emotional aspects associated with those memories. The medial septum/diagonal band of Broca complex (MSDB) plays pivotal role in both cognitive and emotional functions, implying anatomically distinct pathways of MSDB efferents conducting information to dHC and vHC, respectively. To test this, we tr

The entorhinal cortex is an area known to be involved in spatial navigation and episodic memories. While the spatial aspects of episodic memories have been studied in great detail, questions still remain regarding the processing of social information in the brain.Emerging evidence points towards a complex network of brain areas involved in social memory processing. In particular, the hippocampal regions CA2 and ventral CA1 play an important role, but the role of computations within the hippocampus compared to the input regions remains unresolved. With entorhinal cortex being the main input reg

Episodic memories become gradually independent from the hippocampus and progressively consolidate in the neocortex. During sleep and rest periods, neuronal traces are reactivated at the time of hippocampal sharp-wave ripples (SWRs) thought to mediate memory consolidation. Though SWRs have been widely studied within the hippocampus, the ongoing activity within the rest of the brain remains elusive, because technically challenging: electrophysiology cannot easily resolve the whole brain and optical recording techniques have limited access to deep tissue. In a 2012 study, Logothetis and colleague

Animals and humans acquire knowledge through experience allowing them to flexibly generalize to novel situations. Several findings suggest that the Hippocampus (HC) is involved in the development of this conceptual learning not only for navigational but for other non-spatial variables if relevant to a task. However, how concepts arise with learning and how the hippocampus is involved in building these from the statistical structure of episodic memories still remains unknown. To study this, we trained mice on a binary categorization task consisting of a category split between low and high tone

Both the formation and retrieval of episodic memories are closely associated with the activation of the hippocampal complex and medial temporal lobe (MTL) areas. These areas however are not sufficient by themselves to support most episodic memory functions. Instead, MTL areas are embedded as a central hub into a more distributed cortical network that supports both the storing, consolidation and subsequent reactivation of memories. Recently emerging evidence however indicates that cortical areas like posterior parietal regions and prefrontal areas contribute more to the processes than previousl

The hippocampus plays a pivotal role in the formation of episodic memories, facilitating spatial navigation and detection of novel stimuli. Within this structure, the dentate gyrus (DG) is crucial for discriminating novel from familiar content. Despite GABAergic inhibitory interneurons (INs) being increasingly recognized to participate to the hippocampal computation by controlling the activity of principal cells, the specific mechanisms by which they contribute to the encoding of episodic memories remain elusive. This study explores how interneurons (INs) representations of spatial context are

Children are able to form episodic memories from an early age, which are consolidated during sleep. However, the emergence of the ability to form more abstract, semantic memories and the role of sleep in this process remain uncertain. In the present study, we investigated how sleep influences the formation of abstract spatial context representations in toddlers aged 2-3 years. Utilizing a within-subject naturalistic design, participants (N = 35) were familiarized with two different spatial contexts. After familiarization, the toddlers either took a nap (approximately 90 minutes) or stayed awak

Fact knowledge – known as semantic memories – is proposed to be derived from individual memories of events during a memory consolidation period after learning. But so far, this has never been shown. Here, we tracked gene expression in a 2-week semantic-like memory paradigm in mice across the whole-brain spatial memory network. Absolute gene expression was driven by first experiences and later learning led to smaller changes, highlighting that multiple episodic memories are not encoded and then consolidated to create semantic-memories, instead already by the second experience semantic-memories

Memories associating personal experiences and places can be recalled after extended periods of life-time. Despite the current prevailing view that episodic memories are fully allocated to cortical areas after an initial encoding phase within the hippocampus, lesion studies suggest that memories might be partially retained within the hippocampus. We hypothesize that sparsely active and spatially tuned dentate gyrus granule cell (GC) assemblies efficiently store and retrieve episodic memories over extended live spans.We employed two-photon in vivo calcium-imaging of somata and mossy-fiber bouton

The hippocampal formation is important for encoding, consolidation and retrieval of episodic memories. While integration of spatial information into episodic memories has been studied in great detail, how social information is encoded in the brain has received less attention. Emerging evidence suggests that the hippocampus area CA2 plays an essential role for social recognition memories, and previous studies show that silencing area CA2 impairs social recognition in mice. To determine how social, spatial and object information is computed in the different areas of the hippocampus, we recorded