The state of cortical microcircuits during wakefulness and sleep.

Wakefulness and sleep are two qualitatively different behavioral states. The mechanisms underlying these behavioral states can be traced back to the coordinated functioning of cortical microcircuits. The stereotypical activity of cortical microcircuits during wakefulness and sleep shapes a cortical state, defined as an organized neuronal network functioning across time. Cortical microcircuits are conformed by pyramidal cells and several interneurons, organized into a six-layer structure that contains well defined connections across excitatory and inhibitory cells. In this organization, inhibitory interneurons play an important role in the transitions between wakefulness and sleep, through their actions in the regulation of the excitatory/inhibitory balance. Yet, we do not know what mechanisms underlie cortical microcircuits transitions between different behavioral states. The aim of this review is to examine how the action of specific interneurons can shape the outcome of cortical microcircuits. We discuss the role of interneurons, as main modulators of sleep and wake states and the communication regimes of microcircuits observed during different cortical states. The literature here reviewed suggests the importance of inhibitory interneurons as the main modulator of the function of cortical microcircuits. We finally discuss some future research perspectives about cortical states and their different interneurons subtypes.