EXPLORING THE LAMINAR ORGANIZATION OF AUDITORY PROCESSING DURING SLEEP STATES AND WAKEFULNESS

Sleep is characterized by sensory disconnection of our brain from the external world. Paradoxically, several studies have demonstrated that external sensory stimuli, in particular sounds, evoke subcortical and cortical responses highly similar to those observed in the awake state, meaning that the loss of responsiveness is not due to an absence of sensory processing. However, we have recently observed that during NREM sleep, sounds, intermittently fail to recruit population responses in the layer 2/3 of the auditory cortex, indicating that sleep produces interruptions of some of the information flow in the cortex, that we observe to be more frequent in deeper sleep.
To better understand the spatial extent of these interruptions and their relationship to more global fluctuations of the brain state (e.g. slow-wave activity, 0.5-4Hz) we have started to perform large-scale translaminar electrophysiological recordings, with Neuropixels 2.0, in the auditory cortex of head-fixed mice, naturally alternating between sleep and wake states. Our experimental approach allows us to probe layer-dependent differences in sensory encoding and information propagation during sleep, and can be extended to simultaneous recording of multiple areas such as the auditory, visual or prefrontal cortex.
Our preliminary results suggest that the modulation of auditory responses by NREM sleep occurs synchronously across the vertical and horizontal axes of the auditory cortex and could be phased with ongoing UP/DOWN states.