Effects of ethanol on human fractionated response times.

The effects of ethanol (EtOH) on response components varying along a central vs. peripheral dimension were studied in five subjects. Reaction times (RTs) were fractionated by electromyographical recordings into premotor (central) and motor (peripheral, contractile) components. Highly practiced subjects performed a simple and discrimination RT task and related movement without significant impairment at the moderate blood ethanol concentration (BEC) (0.10%). At the higher BEC (0.17%), all components involving central processing (response time, RT and premotor time) were impaired in both simple and discrimination RT. More peripheral components (contractile time and movement time) were little affected. Contractile time was slowed slightly but significantly, but only in the combination of EtOH and the discrimination task which suggests that the stimulus discrimination stage of information processing can influence the activation of motor units involved in carrying out the movement.