Parallel cholinergic circuit in oculomotor nucleus to control eye movements and REM sleep

Sleep suppresses most motor output, yet rapid eye movement sleep (REMs) is marked by brief muscle twitches, including eye movements (EMs), indicating selective motor preservation. How these opposing features are coordinated remains unclear. Here we show that cholinergic neurons in the oculomotor nucleus (nIIIChAT) possess dual functional organization governing REMs termination and oculomotor execution in mice. We identify a ventrolateral periaqueductal gray-projecting nIIIChAT subset whose activity dissociates from EMs but undergoes a progressive increase prior to REMs termination. Optogenetic activation of this subset suppresses REMs without affecting EMs, whereas extraocular muscles-projecting nIIIChAT neurons reliably induced EMs without altering sleep-wake states. These motor and sleep-modulating functions of nIIIChAT neurons are coordinated by genetically distinct Vglut2- and Vgat-expressing neurons in the upstream nucleus papilio. Collectively, our findings revealed a microcircuitry underlying REMs exit, where motor related function of nIII is preparing the mammal to enter the subsequent wakefulness with elevated motor capabilities. While eye movements (EMs) serve as a critical physiological marker for distinguishing NREM from REM sleep, they have traditionally been characterized as a secondary byproduct of the sleep state. Here authors show that a dual role for cholinergic neurons of the oculomotor nucleus (nIII) in coordinating REM sleep and its associated EMs. This work provides insights into oculomotor activity during the late phase of REM sleep, suggesting a mechanism that prepares mammals to transition into wakefulness with enhanced motor readiness.