Topographical and Temporal Patterns of Brain Activity During the Transition From Wakefulness to Sleep

Transient topographical dynamics of the electroencephalogram predict brain connectivity and behavioural responsiveness during drowsiness

“…550 Importantly, it is not the full disappearance of all frontoparietal connectivity that drives the loss of 551 responsiveness, but specifically connectivity at alpha frequency. Indeed, literature shows that 552 connectivity shifts from alpha into lower-frequency theta and delta frequencies as consciousness 553 fades (Chennu et al, 2016(Chennu et al, , 2014Ogilvie, 2001;Tanaka et al, 2000Tanaka et al, , 1998Wright et al, 1995). In the 554 larger picture of states and levels of consciousness, our findings confirm long-range alpha networks 555 as a common marker of consciousness, whether this impairment is natural (sleep), pathological 556 (disorders of consciousness) or pharmacological (sedation).…”

“…Despite the subjective ability to classify 46 retrospectively one's own state as "awake" or "asleep" (Hori et al, 1994), research continues to 47 5 connectivity disintegrates at the onset of sleep, while lower-frequency theta and delta connectivity 76 increases (Tanaka et al, 2000(Tanaka et al, , 1998Wright et al, 1995). Several power and connectivity patterns 77 have been associated with the loss of consciousness, sometimes specifically with the loss of 78 responsiveness, such as the anteriorisation of alpha power and connectivity, which has been 79 described in drug-induced loss of responsiveness (Chennu et al, 2016), and frontoparietal 80 connectivity, which has been proposed as a key signature of consciousness (Laureys, 2005) and 81 linked to external awareness (Vanhaudenhuyse et al, 2011).…”

Power and coherent oscillations distinguish REM sleep, stage 1 and wakefulness

“…Many efforts have been directed toward differentiating stage 1 from wakefulness and stage 2 focused on the process of falling asleep, and although the precise moment of sleep onset is still a matter of debate, detailed studies have been carried out to determine the precise entrance into sleep considering behavioral, physiological and subjective changes (Ogilvie et al, 1991;Hasan and Broughton, 1994;Wright et al, 1995;Tanaka et al, 1997). In contrast, little is known about differences in EEG activity between stage 1 and REM sleep, except for a couple of studies focused on alpha activity only (Armitage, 1995;Cantero et al, 1999).…”

“…It has been proposed to be an intrinsic property of the brain involved in broader functions such as cognition and consciousness (Crick, 1994;Llinás and Paré, 1996;Singer, 1996). Analyses of coherent activity during sleep have revealed that spectral power is not enough to account for differences between sleep and wakefulness; several studies have demonstrated significant differences in inter-and intrahemispheric coherent activity between wakefulness (W), stage 2, stage 4 and REM sleep (Corsi-Cabrera et al, 1987, 1996, 2003Guevara et al, 1995;Wright et al, 1995;Morikawa et al, 1997;Achermann and Borbély, 1998;Cantero et al, 2000;Tanaka et al, 2000;Pérez-Garci et al, 2001); however, the differences between stage 1 and REM sleep, as already mentioned, have not been thoroughly investigated. The characterization of EEG activity and determination of differences between these two sleep stages may contribute to the understanding of REM sleep physiology and the process of falling asleep; therefore, in this study we analyzed spectral power and spectral correlation during stage 1 from the first non-REM sleep episode of the night and compared it with W and the first REM sleep episode.…”

Topographic mapping of EEG spectral power and coherence in delta activity during the transition from wakefulness to sleep

“…1,2 The SOP is neurophysiologically complex. 3 When the topographical behavior of EEG in SOP is of interest, however, the standard sleep stage criteria 4 are somewhat vague, especially for stage 1.…”