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Research Projects

Presynaptic plasticity in hippocampal circuits

Project Leader(s): TBD

It is widely accepted that storage, and recall of information depend on multiple forms of activitydependentsynaptic and intrinsic plasticity processes with distinct temporal dynamics. Within the hippocampus, most of the attention has focused on long-term changes in synaptic efficacy occurring on the postsynaptic side. Neurons often encode information not as spikes in isolation but as bursts of 2–20 spikes at high frequency (>20Hz), which trigger a wide range of presynaptic forms of synaptic plasticity (short- and long-term), depending on the synaptic contacts and on the previous history of synapse activity. The cell-biological mechanisms and the functional consequences of presynaptic plasticity have been much less explored than postsynaptic forms of plasticity (LTP, LTD), in particular in relation to memory. We hypothesize that structural and functional plasticity on the presynaptic side, acting in a concerted fashion, shape the dynamics of neural processing in hippocampal circuits, which ultimately underlies mechanisms of memory encoding and recall. This line of thinking fills an important but largely unexplored research area, as previous studies considered either structural or functional plasticity in isolation but not both together, and have mostly focused on long-term postsynaptic forms of plasticity. This project focuses on the connections between the dentate gyrus and the CA3 region of the hippocampus, which can rapidly encode an episodic-like memory, within a single trial. We first address the mechanisms for both functional and structural presynaptic plasticity at synapses formed by mossy fibers (Mf) with CA3 pyramidal cells (PCs) as well as with CA3 interneurons. We address then how the close interplay between presynaptic functional and structural plasticity determines the dynamics of information transfer, excitation/inhibition balance, neural processing and memory encoding in the hippocampus.



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