Cognitive and motor performance of narcoleptic and normal subjects living in temporal isolation.
Six unmedicated narcoleptic subjects and nine normal controls lived in a temporal isolation laboratory for 18-22 days. They were permitted to "free-run" for the last 9-13 days. Brief cognitive and motor performance tests were repeated on average six times per subjective day. They consisted of serial search, complex verbal reasoning tasks and manual dexterity of each hand. Only minor differences in performance were found between the narcoleptic subjects and controls. Narcoleptic subjects showed mild impairment of accuracy on the search task that could be explained by occasional lapses and an afternoon dip in performance. Narcoleptic subjects also tended to perform some tasks more slowly, but the group differences were not significant. Neither speed nor accuracy of performance of narcoleptic subjects decreased over the course of the experiment. By one standard of performance, therefore, all or nearly all of the sleep need of these subjects was met by the sleep they obtained in the laboratory. That amount, in turn, did not exceed the total sleep obtained by the normal controls. Significant time-of-day effects were found in narcoleptic subjects for speed of verbal reasoning (progressive slowing over the course of the day), manual dexterity (fluctuations in speeds) and accuracy of serial search (afternoon dip). These variations in performance could not be attributed to changes in core body temperature or to occurrences of naps or meals.