Differential effects of moderate alcohol consumption on motion and contrast processing.

Although a moderate blood alcohol concentration already affects attention, an effect on early visual processing is still questionable. Using psychophysical measures and visually evoked potentials (VEP), we examined the effects of alcohol on the processing of contrast and motion features. In our tasks, two lateralized stimuli were briefly presented, and participants had to identify either the stimulus of higher contrast or motion coherence. In the contrast task, alcohol was found to decrease the discrimination ability and induced a global attenuation of VEP amplitudes. In the motion task, discrimination was not impaired. VEP amplitudes were reduced contralateral to the target position, indicating an effect of alcohol on the deployment of visuospatial attention. In sum, our data suggest that specialized areas for motion and contrast processing within the visual cortex are differently sensitive to moderate alcohol exposure.