Electroencephalographic sleep inertia of the awakening brain

• Published in: Neuroscience Vol. 176; pp. 308 - 317
• Main Authors: Marzano, C, Ferrara, M, Moroni, F, De Gennaro, L
• Format: Journal Article
• Language: English
• Published: Amsterdam Elsevier Ltd 10-03-2011; Elsevier
• Subjects: awakening; Biological and medical sciences; Brain - physiology; Brain Mapping; cortical topography; EEG power; Electroencephalography; Female; Fundamental and applied biological sciences. Psychology; Humans; local EEG changes; Male; Neurology; Signal Processing, Computer-Assisted; sleep inertia; Sleep Stages - physiology; Sleep. Vigilance; Vertebrates: nervous system and sense organs; Wakefulness - physiology; Young Adult; slow wave sleep; transcranial magnetic stimulation; HRV; WASO; FFT; heart rate variability; awakening; blood flow; EC; EMG; eyes closed; blood pressure; EEG; electrooculogram; cortical topography; TBT; EO; sleep efficiency index; electromiogram; electroencephalogram; high-density electroencephalography; TST; SEI; cerebral blood flow; EEG power; wake after sleep onset; eyes open; BF; CBF; NREM; cerebral blood flow velocity; total bed time; BP; analyses of variance; ANOVA; SI; hd-EEG; total sleep time; EOG; SWA; non-rapid eye movements; rapid eye movements; slow wave activity; fast Fourier transform; SWS; CBFV; sleep inertia; local EEG changes; REM; TMS; positron emission tomography; PET; Sleep; Central nervous system; Electrophysiology; Electroencephalography; Encephalon
• ISSN: 0306-4522; 1873-7544
• DOI: 10.1016/j.neuroscience.2010.12.014

Abstract Sleep inertia (SI) denotes a period of hypovigilance, confusion and impaired cognitive and behavioral performance that immediately follows awakening. Based on the observation that the reactivation of some cortical areas is faster than other upon awakening, here we examined regional differences between presleep and postsleep waking period. Moreover, we also compared rapid eye movements (REM) and stage 2 non-rapid eye movements (NREM) awakenings in a within-subject design. Presleep and postsleep waking electroencephalogram (EEG; 5 min with eyes-closed and 5 min with eyes-open) of 18 healthy subjects (12 males, mean age=23.8±2.3 years) were recorded from 19 derivations. Participants slept for two consecutive nights in the laboratory. In one night they were awakened from stage 2 NREM, while in the other from REM sleep. EEG power spectra were calculated across the following bands: delta (1–4 Hz), theta (5–7 Hz), alpha (8–12 Hz), beta-1 (13–16 Hz) and beta-2 (17–24 Hz). Moreover, a detailed hertz-by-hertz analysis has been repeated in the 2–4 Hz frequency range. Postsleep wakefulness, compared to presleep, is characterized by a generalized decrease of higher beta-1 and beta-2 EEG power over almost all scalp locations. A detailed analysis of topographical modifications in the low-frequency range showed that postsleep wakefulness is characterized by an increased delta activity in the posterior scalp locations, and by a concomitant frontal decrease compared to presleep. Moreover, it was found a prevalence of EEG power in the high frequency ranges (beta-1 and beta-2) upon awakening from stage 2 compared to REM awakenings over the left anterior derivations. Altogether these findings support the hypothesis that a generalized reduction in beta activity and increased delta activity in more posterior areas upon awakening may represent the EEG substratum of the sleep inertia phenomenon.