LOW-DOSE OF ETHANOL SUPPRESSES MISMATCH NEGATIVITY OF AUDITORY EVENT-RELATED POTENTIALS

The acute effect of a low dose of ethanol (0.5 g/kg) on attention and auditory event-related potentials (ERPs) was investigated in 10 social drinkers using a single-blind, placebo-controlled cross-over design. A dichotic listening task, in which the subjects were instructed to at tend selectively to stimuli to one ear while ignoring stimuli to the o ther, was used. The amplitudes of N1, P2, and the mismatch negativity (MMN) were significantly diminished by alcohol. The latencies of the M MN and N2b were also significantly increased after alcohol ingestion. The novel finding of the significant (>60% reduction in amplitude) sup pression of the MMN can be interpreted as indicating disturbed precons cious detection of acoustic changes outside the scope of attention. Be cause this is a prerequisite to an attentional shift, the MMN suppress ion may be related to increased risk for accidents after alcohol inges tion. The same dose of alcohol that suppressed the MMN left intact sel ective attention and conscious ''target'' detection, as reflected by t he processing negativity and P3 deflections, thus suggesting that the automatic functions of human information processing are more sensitive to alcohol than the controlled, attentional functions.