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Stabilization of the hippocampal map during spatial learning| old_uid | 15747 |
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| title | Stabilization of the hippocampal map during spatial learning |
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| start_date | 2018/04/06 |
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| schedule | 11h |
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| online | no |
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| location_info | Amphi Broca-Nouvelle Aquitaine |
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| details | Séminaire Impromptu - Invitant : Erwan Bézard, Directeur de l'IMN (Institut des maladies neurodégénératives |
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| summary | The formation of episodic and spatial memories requires a two-stage process that includes an "online" encoding phase, during which the memory trace is initially labile and vulnerable to interference, followed by an "offline" consolidation phase. Stabilization of the memory trace is thought to rely on reactivations of hippocampal networks, which would facilitate the progressive strengthening of the connections that represent the original experience. Reactivations are mainly coordinated by network events called sharp wave ripple oscillations (SPW-Rs) which occur during slow wave sleep, rest and consummatory behaviors. Rodent studies showed that during SPW-Rs, neurons coding for specific locations in space ("place cells") replay previous waking activity patterns, corresponding to entire spatial trajectories. We hypothesized that activity during SPW-Rs mediates the stabilization of the hippocampal network during learning. We reasoned that if SPW-Rs are necessary for the network stabilization, disrupting neuronal activity specifically during those events would result in an altered mental representation of space coded by hippocampal place cells (the "cognitive map").
Mice performed a spatial memory task requiring daily learning of three goal locations (hidden rewards) on a familiar multi-well maze. SPW-Rs occurred regularly during reward consumption. We used online position tracking, high-density extracellular recordings and closed-loop manipulations to trigger optogenetic silencing of a subset of CA1 pyramidal neurons, selectively during SPW-Rs at goal locations.
Control place cells (non-silenced or silenced outside SPW-Rs) largely maintained the location of their place fields after learning and showed increased spatial information content. In contrast, the place fields of SPW-R-silenced place cells remapped, and their spatial information remained unaltered. SPW-R silencing did not impact the firing rates or the proportions of place cells. These results suggest that interference with SPW-R-associated activity during learning prevents the stabilization and refinement of the hippocampal map. |
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| responsibles | Deris |
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