Vigilance and Behavioral State-Dependent Modulation of Cortical Neuronal Activity throughout the Sleep/Wake Cycle

GABAergic inhibitory neurons, through their molecular, anatomic, and physiological diversity, provide a substrate for the modulation of ongoing cortical circuit activity throughout the sleep/wake cycle. Here, we investigated neuronal activity dynamics of parvalbumin (PV), vasoactive intestinal polypeptide (VIP), and somatostatin (SST) neurons in naturally sleeping head-restrained mice at the level of layer 2/3 of the primary somatosensory barrel cortex of mice. Through calcium imaging and targeted single-unit loose-patch or whole-cell recordings, we found that PV action potential firing activity was largest during both rapid eye movement (REM) and nonrapid eye movement (NREM) sleep stages, that VIP neurons were most active during REM sleep, and that the overall activity of SST neurons remained stable throughout the sleep/wake cycle. Analysis of neuronal activity dynamics uncovered rapid decreases in PV cell firing at wake onset followed by a progressive recovery during wake. Simultaneous local field potential (LFP) recordings further revealed that except for SST neurons, a large proportion of neurons were modulated by ongoing delta and theta oscillations. During NREM sleep spindles, PV and SST activity increased and decreased, respectively. Finally, we uncovered the presence of whisking behavior in mice during REM sleep and show that the activity of VIP and SST is differentially modulated during awake and sleeping whisking bouts, which may provide a neuronal substrate for internal brain representations occurring during sleep.