Studying the Spatiotemporal Dynamics of Cortical Activity During REM-like State in Urethane Anesthetized Mice

Book excerpt: Sleep in mammals consists of two stages: non-rapid eye movement (NREM) and rapid eye movement (REM) sleep. NREM sleep is distinguished by slow and high-amplitude cortical EEG signals while REM sleep is characterized by "desynchronized" cortical rhythms. While until recently it was believed that cortical activity during REM sleep is globally desynchronized, using electrophysiological recording a recent study showed local slow waves in primary cortical areas during REM sleep (Funk et al, 2016). However, the sparse electrophysiological technique has been unable to resolve the regional structure of these activities. Here, we investigated local changes in neuronal activity during REM-like state using wide-field VSD imaging in the urethane model of sleep. We demonstrated that cortical desynchronization during REM-like state is indeed local; while midline and posterior areas typically show desynchronized patterns, anterior and lateral regions show synchronized activity. Our results also revealed that synchronized/desynchronized regions during individual REM-like episodes are dynamic.