OFF-periods reduce the complexity of neocortical activity during sleep

Abstract

Field recordings decrease their temporal complexity during slow-wave sleep (SWS), however, the neural mechanism for this decrease remains elusive. Here, we show that this complexity reduction is caused by synchronous neuronal OFF-periods by analysing in-vivo recordings from neocortical neuronal populations. We find that OFF-periods trap cortical dynamics, disrupting causal interactions and making the population activity more recurrent, deterministic, and less chaotic than during REM sleep or Wakefulness. Moreover, when we exclude OFF-periods, SWS becomes indistinguishable from Wakefulness or REM sleep. In fact, for all states, we show that the spiking activity has a universal scaling compatible with critical phenomena. We complement these results by analysing a critical branching model that replicates the experimental findings, where we show that forcing OFF-periods into a percentage of neurons suffices to generate a decrease in complexity that replicates SWS.