// Research

My research activity is focused on the mechanisms of learning and memory systems in the brain, with particular emphasis on the hippocampal/prefrontal interactions, spatial cognition on rodents, and memory consolidation. I am investigating these problems with theoretical and experimental means

Some recent and active projects

  • Cerebral memory trace reactivation is a possible substrate for the consolidation processes taking place offline (after memory acquisition). These processes may depend upon plasticity mechanisms that ultimately promote the re-organization and stabilization of memories. Sleep plays a specific role in memory consolidation Slow-Wave Sleep (SWS) has been associated with the consolidation of declarative memories. SWS is characterized by slow oscillations of cortical field potentials, with bouts of intense firing separated by intervals of sparse  activity, reflecting the bistability of the cortical network. At the same time, the hippocampus engages in a more regular activity pattern, punctuated  by large irregular activity containing rapid bursts of cell activity (sharp waves). The two phenomena are tightly related Together with A. Peyrache and S. Wiener (Paris), we developed a novel measure for memory trace reactivation (Peyrache et al. Nature Neuroscience 2009, Peyrache et al. J. Computational Neuroscience 2009, see also  Hoffman et al.,(2007)), allowing to follow the precise time course of memory trace reactivation and its interaction with cortical and hippocampal collective phenomena. Hippocampal/prefrontal coherence was also found during active behavior in the theta (6-10 Hz) frequency range, as a function of behavioral demands, and related to cell assembly formation (Benchenane et al. Neuron 2010)
  • Entorhinal grid cells represent the most plausible mechanism for path integration in the brain and are therefore a key component of the spatial navigation system in rodents. Together with B. McNaughton (Tucson), O. Jensen (Nijmegen), E. and M.-B. Moser (Trondheim) we developed a model of grid cell functioning and development  (McNaughton et al., 2006).
  • Synaptic plasticity in the hippocampus is thought to be crucial for the learning of routes and goal locations. With Henrique Cabral and Cyriel Pennartz, and in collaboration with L. Rondi-Reig (Paris), we are recording the activity of CA1 ensembles in wild-type and NMDA NR-1 KO mice, in a spatial navigational task specifically designed to highlighted the impairments of the plasticity-lacking mutants. More information on Henrique’s page [link]
  • With Tara Arbab and Cyriel Pennartz, we are currently testing spatial correlates of hippocampal place cells in mouse models of Fragile-X mental retardation.
  • Memory consolidation  is the mechanism that gradually transfers newly acquired memories from a temporary store in the medial temporal lobe to a permanent storage involving the neocortex. In the process, memories change their character, losing context information and building up a more abstract model of the world (that is acquiring a “semantic” character). Together with Cyriel Pennartz and R. Bod (Amsterdam) we are applying theoretical models inspired to computational linguistics to analyze semantic memory formation.