ASA 126th Meeting Denver 1993 October 4-8

3aPP13. Effects of vigilance on cortical processing.

D. M. Daly

Box 210855, Dallas, TX 75211

Normal persons significantly deprived of sleep show impaired vigilance with slowing of motor responses, errors in cognitive processing, and defects in recall. Pupillometry measures autonomic correlates of vigilance. Effects of sustained and of fluctuating vigilance on cortical processing using standard sets of synthetic acoustic stimuli are reported. [Daly et al., J. Neurophysiol. 44(1), 200--222 (1980)]. A 60-yr-old woman had lifelong difficulty awakening, and if not awakened might sleep 14 h continuously. A single 7 am 30-mg dose of methylphenidate aided arousal; once awake she could remain alert. In 2-h sessions of unmedicated continuous testing she classified stimuli consistently [p((chi)[sup 2]>G[sup 2])0.0001] and appropriately (p0.001, re: 32 normal adults). Her performance after 1 1/2 h was as consistent as the best controls. A 54-yr-old man had since adolescence slept less than 3 h per night (typically 2--5 pm). Unlike other reported philagrypniacs, for 30 yr he has also napped for an hour in late morning. Despite diminished sleep requirements, he does not remain alert while awake. Performance with FM transients in CVs fluctuated widely (p<0.01 to p<0.0001), but remained consistent with relatively CF vowels (p<0.0001). His performance improved temporarily with caffeinated (but not decaffeinated) coffee. These results are consistent with evidence that vigilance modulates cortical auditory processing; they suggest that like capacity for sleep, individual capacity to remain alert may also vary in a Gaussian distribution.