Increased slow wave activity in response to sleep deprivation is highest immediately after micro-arousals

Non-rapid eye movement (NREM) sleep is not uniform but characterized by brief intrusions of wake-like brain activity, known as micro-arousals or brief awakenings. Although micro-arousals are an inherent feature of both human and animal sleep, knowledge about the neural correlates of micro-arousals across the cortical column is sparse. We here developed an algorithm for automatic detection of micro-arousals based on EMG activity and used it to explore how micro-arousals modulate laminar neural activity in the motor cortex, and how this relationship is affected by sleep pressure in mice. Our analysis showed that micro-arousals were associated with a general suppression of local field potential (LFP) power across the cortical column. Slow wave activity (SWA, 1-4 Hz) immediately after micro-arousals was tightly correlated with sleep pressure and even surpassed average SWA levels during NREM sleep in sleep deprived animals. In addition, analysis of single-channel firing showed that some channels exhibited increased activity immediately prior to micro-arousals, while others exhibited decreased activity. This study provides new insights into the neural mechanisms underlying micro-arousals and identifies a new link between micro-arousals and sleep homeostasis.