SPATIAL-FREQUENCY DISCRIMINATION, BRAIN LATERALIZATION, AND ACUTE INTAKE OF ALCOHOL

The effect of alcohol (breath-alcohol level of 0.1%) on perceptual dis crimination of low (1.5 cycles deg(-1)) and high (8 cycles deg(-1)) sp atial frequencies in the left and right visual field was measured in e ighteen right-handed males, in a double-blind, balanced placebo design . Discrimination thresholds for briefly (180 ms) presented sinusoidal gratings were determined by two-alternative forced-choice judgments wi th four interleaving psychophysical staircases providing random trial- to-trial variation of reference spatial frequency and visual field, in addition to a random (+/-10%) jitter of reference spatial frequency. Alcohol produced overall higher discrimination thresholds but did not alter the visual-field balance: no main effect of visual field was obs erved, but in both placebo and alcohol conditions spatial frequency in teracted with visual field in the direction predicted by the spatial-f requency hypothesis of hemispheric asymmetry in visual-information pro cessing, with left-visual-field/right-hemisphere superiority in discri mination of low spatial frequencies and right-visual-field/left-hemisp here superiority in discrimination of high spatial frequencies.