Sleep deprivation suppresses the increase of rapid eye movements across sleep cycles.

Introduction: Sleep Inertia (SI) denotes a period of hypovigilance, confusion and impaired cognitive and behavioral performance that immediately follows awakening. Objectives: Here we examined regional differences between presleep and postsleep waking period. Moreover, we compared REM and stage 2 NREM awakenings by a within-subject design. Methods: Presleep and postsleep waking EEG (i.e., 5 min with eyes-closed and 5 min with eyes-open) of 18 subjects (12 M; age 23.8±2.3 yrs) were recorded from 19 derivations. Partecipants slept for 2 consecutive nights in sleep laboratory, and in one night were awakened from stage 2 NREM, while in the other night from REM sleep. EEG power were calculated across: delta (1 4 Hz), theta (5 7 Hz), alpha (8 12 Hz), beta1 (13 16 Hz), and beta2 (17 24 Hz) bands. Results: Low-activity bands (i.e., delta-theta-alpha) exhibit a prevalence in morning awakening as compared to presleep, while beta activity increases in presleep compared to postsleep. The increase of delta power upon awakening showed a posterior prevalence, whereas presleep exhibited a predominance of desyncronized activity almost overall scalp locations for the beta2, and in correspondence of fronto-temporal areas for beta1. The difference between postsleep and presleep waking was more prominent in eyes-closed than in eyes-open condition upon REM awakenings. Moreover, NREM awakening is characterized by a higher beta-1 and beta-2 EEG power than REM awakening. Conclusions: These findings support the hypothesis that generalized reduction in beta activity and increased delta activity in more posterior areas upon awakening may represent the EEG substratum of SI phenomenon. An enhanced posterior EEG synchronization may represent an electrophysiological basis of the reduced sensory-motor performance upon sleep offset. On the other hand, the decreased EEG synchronization on anterior brain locations may be associated to better performances in processes involving associative prefrontal areas.