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Alcohol impairs the cognitive component of reaction time to an omitted stimulus: a replication and an extension.

OBJECTIVE
Research from a recent study indicates that cognitive performance is impaired by an acute dose of alcohol at blood alcohol concentrations (BACs) that do not affect motor performance. That study measured reaction time (RT) to the omission of a recurring stimulus and used behavioral criteria to fractionate premotor (cognitive) and motor components of RT when stimuli occurred at slow, 2-second intervals (0.5 Hz). The present experiment tested the generality of the evidence when stimuli occurred at slow or fast, 0.143-second intervals (7 Hz). Using muscle potential to fractionate RT, we tested the reproducibility of the findings obtained by a behavioral fractionation procedure.


METHOD
Thirty male social drinkers were randomly assigned to two groups (n = 15 each) that received 0.8 g/kg alcohol or a placebo (0 g/kg). All participants performed a drug-free baseline test and a test during rising BACs. A test presented fast and slow frequency auditory stimuli in counterbalanced order within groups.


RESULTS
Tests using both fast and slow frequency stimuli showed that alcohol slowed premotor RT and had no detectable effect on motor RT.


CONCLUSIONS
Fractionated RT based on muscle potential reproduced the findings based on behavioral fractionation. The generality of the deleterious effects of alcohol on premotor RT was demonstrated by manipulating the frequency of the recurring stimuli. The consistent results obtained with the omitted stimulus paradigm provide a basis for new alcohol research that incorporates electrophysiological measures of the brain potential that are associated with the omission of a stimulus.