Modifications of vestibulo-ocular reflex induced by diazepam: experiments in the macaque.

The vestibulo-ocular reflex in the macaque was tested before and after intravenous administration of diazepam. The drug effect was marked by decrease in gain and increase in time constant of nystagmus in response to a modified Bárány test and by reduction in directional asymmetry of nystagmus. Because the time course of reduction in gain differed from the time course of increase in time constant, diazepam probably has more than one site of action. These results emphasize the complexity of neural processing in the vestibulo-ocular reflex arc.