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Characterization of the spatial and mnemonic functions of the hippocampus in the non-human primate

Final Activity Report Summary - SPATIAL MEMORY (Characterization of the spatial and mnemonic functions of the hippocampus in the non-human primate)

Our project aimed at understanding the neural bases of mnemonic and spatial functions of the hippocampus. To this end, we developed behavioural testing approaches which were designed to mimic real life situations and used electrophysiological techniques to study the neural patterns underlying these memories.

Our report was articulated over two research lines:
1. the neural correlates underlying visuo-spatial learning in primates including human;
2. the neural correlates of voice-face pair associates in the monkey within the hippocampus.

These two projects both aimed at understanding the neural basis of episodic memory, which allowed us to remember events, where they took place, when they occurred and who they involved. Using virtual reality techniques, we studied oscillatory activity in human subjects performing navigational tasks. The results associated with our first project showed larger oscillatory activity before environments became familiar, which suggested a broad recruitment of the population before learning. With learning, oscillatory activity tended to be observed in tighter time periods, which suggested that formed memory was supported with smaller neurones’ population.

Our second project combined single unit recording and behavioural techniques in macaques and aimed at understanding how hippocampal neurones combined multimodal information to represent identity. Using spontaneous recognition techniques we showed that monkeys, like human, oriented towards familiar speakers based on their voice. Single unit recordings showed that the neural response elicited by a face was enhanced if it followed the voice matching it. This suggested a cross-sensory preparedness of the hippocampal neuronal network that conveyed information about identity through multisensory elements.