Cognitive and Systems Neuroscience Group, Swammerdam Institute for Life Sciences, University of Amsterdam, Science Park 904, 1098XH, Amsterdam, NH, The Netherlands.
During the sleep-wake cycle, consciousness changes, and this is thought to relate to how brain areas integrate. Recent work found that people can have conscious experiences during NREM sleep, which is usually considered unconscious. This study tested whether functional connectivity between neurons varies within brain states in a way that matches fluctuating consciousness. Researchers examined directed functional connectivity between neurons across the wake-sleep cycle in rats, over seconds. They observed that NREM sleep contains epochs where inter-areal connectivity patterns resemble those during wakefulness and REM sleep, and vice versa. Thus, circuit-level connectivity patterns are not fixed by brain state but may reflect other factors, such as changes in consciousness level within as well as between brain states.
Consciousness is thought to fluctuate with the integration of brain areas across the wake-sleep cycle, but recent evidence suggests consciousness may not be uniformly present or absent within a given brain state, as conscious reports can occur during Non-REM sleep. This study tested whether functional connectivity between neurons varies within brain states in a way that reflects changing levels of consciousness. In rats, directed functional connectivity between neurons was examined across the wake-sleep cycle at a scale of a few seconds. The analysis aimed to determine whether Non-REM sleep contains epochs with inter-areal integration comparable to wakefulness and REM sleep, and vice versa. The findings could reveal circuit-level connectivity patterns consistent with alternating levels of consciousness both between and within brain states.