EFFECTS OF ETHANOL ON THE PROCESSING OF LOW PROBABILITY STIMULI - AN ERP STUDY

The effect of a moderate dose of ethanol on the processing of low prob ability task-relevant and task-irrelevant stimuli was investigated usi ng event-related potentials (ERPs). Sixteen subjects received alcoholi c and placebo beverages on alternate days. ERPs were recorded from 15 locations on the scalp. The subjects were asked to press a button upon detection of rare target stimuli embedded among frequent standard and rare ''novel'' stimuli. Ethanol 1) reduced the amplitude of P3 to nov el stimuli, but not P3 to target stimuli, 2) did not affect the mismat ch negativity, and 3) delayed P3 latency and reaction time independent ly. These results suggest that 1) the processing of rare task-irreleva nt stimuli is more vulnerable to the effects of ethanol than is the pr ocessing of task-relevant stimuli, and 2) ethanol impacts stimulus eva luation time and response production stages of information processing.