Effects of sleep deprivation on signal detection measures of vigilance: implications for sleep function.

In an attempt to tease out the extent to which the performance decline during sleep deprivation might be due to a fall in the inherent capacity (d') of a subject, the parameters of the theory of signal detection were applied to auditory vigilance data obtained five times per 24 h during 60 h of continuous wakefulness. Eight subjects were exposed to both control and deprivation conditions in a balanced design. Oral temperature and self-assessed alert-drowsy reports were taken at three hourly intervals. The value of d' exhibited a significant stepwise decline during deprivation, falling sharply within the usual sleep period and levelling out during the daytime. Both temperature and self-assessment data exhibited clear circadian rhythms overlying the declines due to deprivation. The changes in d' were seen to be consistent with a brain "restitutive" role for sleep function.