Effects of ethanol on eye movements in the monkey

Ethanol (0.25-2.0 g/kg) was administered by remotely controlled intravenous infusion to monkeys engaged in performance of a short-term memory task which required attention to and retention of visual stimuli. Eye movements were monitored and measured by recording the electrooculogram with implanted periorbital Ag/AgCl electrodes. Ethanol induced the following dose-dependent changes of ocular motility: (a) diminution of the frequency of saccades; (b) prolongation of fixation (immobility) periods, though stimulus-elicited fixations became shorter; (c) increase in saccade excursion; (d) increase in saccade duration; and (e) decrease in saccade velocity (preceded at low doses by a transient increase). These changes were correlated with an impairment of behavioral performance. The results of eye movement analysis complement the results obtained on studies of human subjects by oral administration of ethanol. The findings of the present study in the nonhuman primate are interpreted as a reflection of the deleterious effects of alcohol on the cerebral substrate of visual attention.