Contextual novelty detection and novelty-related memory enhancement in amnestic mild cognitive impairment

Servais, Anaïs; Barbeau, Emmanuel J.; Bastin, Christine

doi:10.1016/j.cortex.2023.12.005

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CA1 ensembles expressing immediate-early genes are driven by context switch, shrink with sustained presence, and show no effect of change of task demands

Krajcovic,

Cernotova,

Buchtova

et al. 2025

Behavioural Brain Research

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CA1 ensembles expressing immediate-early genes are driven by context switch, shrink with sustained presence, and show no effect of change of task demands

Krajcovic,

Cernotova,

Buchtova

et al. 2025

Behavioural Brain Research

View full text Add to dashboard Cite

CA1 ensemble plasticity is coupled to context change and modulated by task familiarity

Krajcovic,

Cernotova,

Stuchlik

et al. 2024

Preprint

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When should plasticity mechanisms get recruited (stability-plasticity dilemma)? Environments change over time, re/entering a given context increases uncertainty and predicts the need for updating. The hippocampus (HPC) is key to tracking context change but also navigation relative to moving targets. CA1 ensembles expressing immediate-early genes (IEGs) are contextually specific, while the amount of IEG expression correlates with HPC-dependent task demands. However, task effects on the IEG-expressing ensembles per se remain unclear. In three experiments, we tested the effect of context change and HPC task demands on CA1 IEG+ ensembles in rats. Experiment 1 showed that the IEG+ (Arc, Homer1a RNA) ensemble size drops to baseline level during uninterrupted 30 min exploration, reflecting familiarization and decreasing uncertainty, unless context change is present; the ensemble sizes reflect both context identity and context change. Experiment 2 showed no evidence of task-specificity of IEG+ ensembles during highly HPC-dependent mobile robot avoidance nor HPC-independent stationary robot avoidance. Experiment 3 replicated the findings of Experiment 2 for c-Fos protein. Nonetheless, the data suggest that ensembles shrink with task mastery/familiarity and grow with novelty presented by the acquisition of behavioral extinction. Overall, our results shed light on the temporal dynamics, and the context and task control of CA1 IEG+ ensembles. The present results and the relevant literature suggest that context change resets the ensemble of IEG-expressing CA1 neurons and novelty delays the time-dependent ensemble shrinking.

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Contextual novelty detection and novelty-related memory enhancement in amnestic mild cognitive impairment

Cited by 2 publications

References 54 publications

CA1 ensembles expressing immediate-early genes are driven by context switch, shrink with sustained presence, and show no effect of change of task demands

CA1 ensembles expressing immediate-early genes are driven by context switch, shrink with sustained presence, and show no effect of change of task demands

CA1 ensemble plasticity is coupled to context change and modulated by task familiarity

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