Conférence CRNL de Niels Neithard "Sleep and Plasticity: New insights from in vivo calcium imaging"

Sleep concurrently contributes to homeostatic down-regulation and  mnemonic synaptic up-regulation in cortical networks. We used two-photon imaging of calcium activity to examine how these seemingly opposing functions are established. We found that neuronal excitability on average decreases across sleep, whereas subsets of neurons increase firing rates across sleep. Studies of the excitation/inhibition balance in cortical circuits suggest that both processes are connected to a specific inhibitory regulation of cortical principal neurons, characterized by an enhanced perisomatic inhibition via parvalbumin positive (PV+) cells, together with a release from dendritic inhibition by somatostatin positive (SOM+) cells. Such shift towards increased perisomatic inhibition of principal cells appears to be a general motif which underlies the plastic synaptic changes observed during sleep, regardless of whether towards up or downregulation.