State-dependent pontine ensemble dynamics and interactions with cortex across sleep states

The pontine nuclei play a crucial role in sleep-wake regulation. However, pontine ensemble dynamics underlying sleep regulation remain poorly understood. By monitoring population activity in multiple pontine and adjacent brainstem areas, here we show slow, state-predictive pontine ensemble dynamics and state-dependent interactions between the pons and the cortex in mice. On a timescale of seconds to minutes, pontine populations exhibit diverse firing across vigilance states, with some of these dynamics being attributed to cell type-specific activity. Pontine population activity can predict pupil dilation and vigilance states: pontine neurons exhibit longer predictable power compared with hippocampal neurons. On a timescale of sub-seconds, pontine waves (P-waves) are observed as synchronous firing of pontine neurons primarily during rapid eye movement (REM) sleep, but also during non-REM (NREM) sleep. Crucially, P-waves functionally interact with cortical activity in a state-dependent manner: during NREM sleep, hippocampal sharp wave-ripples (SWRs) precede P-waves. On the other hand, P-waves during REM sleep are phase-locked with ongoing hippocampal theta oscillations and are followed by burst firing in a subset of hippocampal neurons. Thus, the directionality of functional interactions between the hippocampus and pons changes depending on sleep states. This state-dependent global coordination between pontine and cortical regions implicates distinct functional roles of sleep.