X. - Diurnal variation in oculomotor performance

Abstract

Summary 1. In 18 subjects kept awake for more than 24 hours, on one or more occasions, there was a diurnal variation in oculomotor performance, as judged by the blinking rate, binocular fixation, and lateral oscillations of the eyes. 2. Poorest performance occurred in the early hours of the morning, coinciding with the development of drowsiness. 3. Without intervening sleep, there was a spontaneous recovery of oculomotor performance, along with an increase in alertness, later in the morning or afternoon. 4. An intermediate degree of oculomotor impairment manifested itself in poorer oscillations in post-fixation, as compared to pre-fixation, trials, and in the appearance of diplopia toward the end of the five-minute fixation period. 5. In the execution of lateral sweeps, the templeward moving eye completed its excursion faster than did the nasalward moving eye. This disparity also held in drowsiness, when the sweep was slowed in both eyes. 6. Amphetamine had no effect on oculomotor performance of subjects when the subjects were wide-awake,but ledto improvement of impaired performance observed during drowsiness. 7. Small amounts of alcohol often imitated the impairment of oculomotor performance that occurred in drowsiness.