Ethanol Induced Slowing of Human Reaction Time and Speed of Voluntary Movemen

Abstract

This study tested the hypothesis that a CNS depressant (ethanol) would affect self-initiated psychomotor movement speed as much as the speed of an homologous movement made in response to an external stimulus. Four normal Ss (three male, one female, aged between 33–45 years) provided well-practiced measures of reaction time and a simple homologous traverse movement (a) in response to a signal from the E and (b) initiated at the S's own discretion. Performance by each S under ethanol conditions (B. A. L. .22%) was compared with his own baseline (pre- and postdrug) scores. Traverse originated by the S was consistently faster in the nondrug condition. Under peak-ethanol, both forms of traverse were slowed significantly in all Ss. Speed reductions were similar but consistently greater for self-initiated movement. A single S who repeated the experimental sequence under a minimally effective dosage (B. A. L. .08%) showed no important reduction in reactive movement speed, but was slowed significantly in self-initiated traverse measured concomitantly. The selective sensitivity of self-initiated movement to ethanol provides added evidence that a higher level of neural organization underlies control of human voluntary action.