The physiological (EEG) nature of drowsiness and its relation to performance deficits in narcoleptics.

Ten narcoleptics off medication were compared to matched controls to determine the pattern and level of electroencephalographic (EEG) vigilance, and its relation to performance ability on the 1 h Wilkinson auditory vigilance task. The narcoleptics performed significantly more poorly and spent significantly less time in wakefulness than controls. The EEG of the patients revealed continual fluctuations between wakefulness, stage 1A (slowed and diffusing alpha) and stage 1B (theta activity). Stage 2 sleep only occurred briefly in 4 patients. Stages 3, 4 and REM sleep were never encountered. Controls were continually awake aside from very brief appearances of stage 1A in 5 subjects. Narcoleptic performance during stages 1B and 2 was characterized by lapses (response omissions). Patients also demonstrated significantly more lapses as well as false positive responses than controls during wakefulness and stage 1A. Poorer performance even during wakefulness was demonstrated to be related to inability to sustain wakefulness over time. The results clarify the temporal pattern of physiological vigilance during performance in narcoleptics and also demonstrate the insufficiency of the lapse-microsleep formulation in explaining performance deterioration in these patients.