What is sleep exactly? Global and local modulations of sleep oscillations all around the clock.

Local sleep significantly influences behavior and cognition, highlighting its importance in both wakefulness and different sleep stages. Evidence from studies involving over 500 participants indicates that local sleep can occur independently of global NREM and REM states, affecting attention and consciousness. This phenomenon is linked to dreaming, inattention, and mind wandering. Understanding local sleep may unravel complex interactions within the brain's neurophysiology, offering insights into how sleep impacts metabolism and plasticity, while also addressing various pathological conditions related to sleep disturbances.

Study at a glance

Abstract

Wakefulness, non-rapid eye-movement (NREM) and rapid eye-movement (REM) sleep differ from each other along three dimensions: behavioral, phenomenological, physiological. Although these dimensions often fluctuate in step, they can also dissociate. The current paradigm that views sleep as made of global NREM and REM states fail to account for these dissociations. This conundrum can be dissolved by stressing the existence and significance of the local regulation of sleep. We will review the evidence in animals and humans, healthy and pathological brains, showing different forms of local sleep and the consequences on behavior, cognition, and subjective experience. Altogether, we argue that the notion of local sleep provides a unified account for a host of phenomena: dreaming in REM and NREM sleep, NREM and REM parasomnias, intrasleep responsiveness, inattention and mind wandering in wakefulness. Yet, the physiological origins of local sleep or its putative functions remain unclear. Exploring further local sleep could provide a unique and novel perspective on how and why we sleep.