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Seminaire LNC : Abdel-Mouttalib OUAGAZZAL

ATTENTION : Exceptionnellement, ce séminaire aura lieu à l’amphi Charve.

Abdel-Mouttalib OUAGAZZAL

Institut de Génétique et de Biologie Moléculaire et Cellulaire CNRS et Université de Strasbourg

New insight on the function of hippocampal N/OFQ peptide and memory-updating processes

In the first part of my talk I will present set of studies addressing the contribution of nociceptin/orphanin-FQ peptide (N/OFQ) to hippocampal functions. We have used central approach to manipulate N/OFQ signaling in dorsal hippocampus and found that this neuropeptide plays a predominant role in modulation of specific behavioral processes, particularly those involving cognitive function and emotional responses associated to despair state. Unlike other neurotransmitters, such as GABA and acetylcholine, N/OFQ does not seem to regulate anxiety states in the dorsal hippocampus. These findings support the view that anxiety and despair behaviors are subserved by overlapping but not identical neural substrates and suggest that dysfunction of hippocampal N/OFQ signalling may contribute to development of specific neuropsychiatric complications such as cognitive impairments and mood disturbances. In the second part of my talk I will introduce a novel mouse task that provides a way to assess context recognition memory, a form of declarative memory, without the use of motivational reinforcers. The task relies on spontaneous discrimination of spatial cues (nose-poke holes), which makes it particularly suitable for studying memory-updating processes and retroactive interference phenomenon, the most common cause of forgetting. Thus far, the brain processes underpinning dynamic malleability of spatial or contextual memory have been mostly investigated by mean of electrophysiological recording of hippocampal principal cells. Using well-defined environmental manipulations we demonstrate that updating of behavioral memory can occur either through pattern separation, which consists of building a new integrated memory representation by consolidation-like mechanism, or through pattern completion, which consists of remodeling original memory trace with novel information by reconsolidation mechanism. We further show that memory interference effects are mitigated when encoding of updating information involves reconsolidation than consolidation mechanisms. Our findings, taken together with neurophysiological data provide a basis for mechanistic framework of how interplay between pattern completion and pattern separation processes engages encoding by reconsolidation or consolidation to support reorganization of hippocampal-dependent memories when new relevant information need to be integrated with stored knowledge.