[The effect of alcohol on the control of the vestibulo-ocular reflex and gaze]

The effects of ethyl alcohol on vestibulo-ocular reflex (VOR) and gaze functions were investigated in normal adults. Twelve normal adults were administered whisky at the rate of 1.0ml/kg (ethyl alcohol 0.43g/kg), so that the mean peak concentration of breath alcohol amounted to 0.15mg/l. Before and after alcohol administration, the subjects underwent sinusoidal rotation tests with an amplitude of 40 degrees and frequencies of 0.2-0.85Hz and eye tracking tests of unidirectional motion at 30 degrees-70 degrees/sec. For the rotation test, 7 subjects were examined at the dose of 0.65g/kg ethyl alcohol. The following results were obtained. 1. The mean value of VOR gain under the condition of performing mental arithmetic in the dark was not significantly altered by alcohol. However, the magnitude of change in VOR gain showed a highly significant correlation with the gain before drinking; whereas small values were enlarged and large values were suppressed by alcohol. 2. The accuracy of spacial gaze fixation was scarcely affected by alcohol, even at the dose of 0.65g/kg. 3. Visual fixation on a head-fixed target (fixation-induced suppression of VOR) and smooth pursuit were significantly impaired by alcohol. 4. The present study indicated that VOR is regulated even in the dark by both gaze stabilizing functions, i.e., spacial gaze fixation and smooth pursuit.