نبذة مختصرة : Wakefulness, non rapid eye movement (NREM) and rapid eye movement (REM) sleep are characterized by specific brain activities. However, recent experimental findings as well as various clinical conditions (parasomnia, sleep inertia) have revealed the presence of transitional states. Brief intrusions of wakefulness into sleep, namely arousals, appear as relevant phenomena to characterize how brain commutes from sleep to wakefulness. Using intra-cerebral recordings in 8 drug-resistant epileptic patients we analyzed electroencephalographic (EEG) activity during spontaneous or nociceptive-induced arousals in NREM and REM sleep. Wavelet spectral analyses were performed to compare EEG signals during arousals, sleep and wakefulness, simultaneously in the thalamus, and primary, associative or high order cortical areas. We observed that: 1) thalamic activity during arousals is stereotyped and its spectral composition corresponds to a state in-between wakefulness and sleep 2) patterns of cortical activity during arousals are heterogeneous, their manifold spectral composition being related to several factors such as sleep stages, cortical areas, arousal modality ("spontaneous" vs nociceptive-induced) and homeostasis; 3) spectral compositions of EEG signals during arousal and wakefulness differ from each other. Thus, stereotyped arousals at the thalamic level seem to be associated with different patterns of cortical arousals due to various regulation factors. These results suggest that human cortex does not shift from sleep to wake in an abrupt binary way. Arousals may be considered more as different states of the brain than as "short awakenings". This phenomenon may reflect the mechanisms involved in the compromise needed to be found between two main contradictory functional necessities, preserving the continuity of sleep and maintaining the possibility to react ; Trois états de vigilance, caractérisés par une activité cérébrale spécifique, sont habituellement décrits chez l'Homme: la veille, le sommeil lent et le sommeil ...
Processing Request
No Comments.