Oculomotor impairment after 1 night of total sleep deprivation: a dissociation between measures of speed and accuracy

Objectives: The present study examined the effects of 40 h of sleep depriva tion and of time-of-day on saccadic and smooth pursuit oculomotor performan ce. Methods: Nine normal subjects slept for 3 consecutive nights in the laborat ory (one adaptation, one baseline, one recovery). Baseline and recovery wer e separated by a period of 40 h of continuous wakefulness, during which sub jects were tested every 2 h. Oculomotor performance assessed at the followi ng hours: 10:00, 12:00, 14:00, 16:00, 18:00, 20:00, 22:00, of both the days preceding and following the sleep deprivation night, as well as at 24:00, 02:00, 04:00, 06:00 and 08:00 h during the deprivation period. Results: Saccade latency increased and peak velocity decreased significantl y during the post-deprivation day; saccadic accuracy was unaffected. As reg ards smooth pursuit performance, phase (a measure of accuracy) was not affe cted by sleep loss, while velocity gain significantly decreased during the day that followed the sleep deprivation night. Significant time-of-day effe cts on the considered oculomotor variables except saccadic accuracy were al so found, indicating an overall performance impairment during the night. Conclusions: It is concluded that 40 h of sleep deprivation significantly i mpaired diurnal performance in pursuit and saccadic tasks. This performance worsening is limited to the measures of speed, while accuracy is not affec ted by sleep loss. A significant operational relevance of these results is suggested, since saccadic velocity has recently been found to be negatively correlated with simulator vehicle crash rates. (C) 2000 Elsevier Science I reland Ltd. All rights reserved.