Sleep deprivation affects speech.

Historical accounts of sleep loss studies have described changes in the content and patterns of speech, although to date these claims have not been systematically studied. We examined the effects of sleep loss on the spontaneous generation of words during a verbal word fluency task and the articulation of speech during a vocalized reading task. Nine subjects underwent two counterbalanced 36-hour trials involving sleep deprivation (SD) and no sleep deprivation (NSD). After SD, there was a significant deterioration in word generation and a tendency for subjects to become fixated within a semantic category. There was a significant reduction in the subjects' use of appropriate intonation in the voice after SD, with subjects displaying more monotonic or flattened voices. These findings are discussed in light of neuropsychological evidence concerning the functions of sleep in relation to the frontal cortex and in light of the implications for interpersonal communication in the event of sleep loss.