Ethanol induced slowing of human reaction time and speed of voluntary movement.

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.