Historical accounts of sleep loss studies have described changes in th
e content and patterns of speech, although to date these claims have n
ot been systematically studied. We examined the effects of sleep loss
on the spontaneous generation of words during a verbal word fluency ta
sk and the articulation of speech during a vocalized reading task. Nin
e subjects underwent two counterbalanced 36-hour trials involving slee
p deprivation (SD) and no sleep deprivation (NSD). After SD, there was
a significant deterioration in word generation and a tendency for sub
jects to become fixated within a semantic category. There was a signif
icant reduction in the subjects' use of appropriate intonation in the
voice after SD, with subjects displaying more monotonic or flattened v
oices. These findings are discussed in light of neuropsychological evi
dence concerning the functions of sleep in relation to the frontal cor
tex and in light of the implications for interpersonal communication i
n the event of sleep loss.