GABAergic interneurons are known to play a central role in sensory processing, circuit plasticity in the developing cortex and several neurological disorders. However, the role of specific interneuron subtypes in the emergence of functional properties or in the modulation of spontaneous cortical dynamics is still unclear. In this project, we propose to study interneuron micro-circuits in two primary sensory areas of the mouse.Extensive work has emphasized the role of feedforward thalamo-cortical projections in the formation of orientation tuned cells in the primary visual cortex. However, the precise interplay between these afferent synaptic inputs and the participation of recurrent cortical connections is still largely debated. During the outgoing phase, we will use 2-photon calcium imaging together with fluorescent labeled interneurons and optogenetics technologies to dissect out, in the mouse V1, the specific role of two interneurons subtypes (parvalbumin- (PV+) and calretinin-expressing (CR+)) in the orientation tuning and the emergence of simple-like receptive fields in pyramidal cells.Recent works in the mouse barrel cortex have shown that different interneuron subtypes are correlated to animal behaviors in specific ways. The spiking activity of PV+ cells decreases when the mouse undergoes a transition from a resting state to a whisking behavior whereas other GABAergic cells increase their firing rate. We hypothesize that specific PV- interneurons play a central role in the filtering of sensory information during whisking whereas PV+ interneurons could participate in the emergence of slow oscillations that are present during quiet wakefulness. During the return phase of the project, techniques that have been applied during the outgoing phase will be used to address these questions.This work would provide detailed micro-circuit models of mice V1 and S1 superficial layers responsible for the emergence and modulation of pyramidal cells sensory responses.