Effects of Secobarbital and d-Amphetamine on Tracking Performance During Angular Acceleration

Abstract

Thirty young men wore randomly assigned in equal numbers to one of the following groups: placebo (lactose), secobarbital (100 mg), or tj-amphetamine (l0 mg). The drugs or placebo wore administered in capsules in a double- blind procedure following practice at a tracking task and baseline determinations of tracking performance levels in both static (stationary) and dynamic (angular acceleration) conditions. Tests wore scheduled 1, 2, and 4 hours after capsule ingestion; all tests were conducted inside a St:lle-Werner rotator and were in total darkness with the exception of the illuminated tracking display. With the rotator stationary, d-amphetamino subjects performed significantly better than controls during the 2-hour and 4-hour post-drug sessions; no other static differences among the groups wore significant. However, during angular acceleration, secobarbital subjects made significantly more tracking errors and had significantly more vestibular nystagmus than both the control and the d-amphetamine groups for all post-drug sessions. These findings agree with our previous studies of alcohol effects: dopressant drugs may have little or no deleterious influence on tracking performance in static environments, but may produce marked performance degradation during angular motion. The primary cause of this performance impairment appears to be a vestibulo-ocular one; the ability to inhibit vestibular nystagmus by visual fixation is impaired.