Abstract
Little is known about the long-lasting effect of use of illicit stimulant drugs on learning of new motor skills. We hypothesised that abstinent individuals with a history of primarily methamphetamine and ecstasy use would exhibit normal learning of a visuomotor tracking task compared to controls. The study involved three groups: abstinent stimulant users (n = 21; 27 ± 6 yrs) and two gender-matched control groups comprising nondrug users (n = 16; 22 ± 4 yrs) and cannabis users (n = 16; 23 ± 5 yrs). Motor learning was assessed with a three-minute visuomotor tracking task. Subjects were instructed to follow a moving target on a computer screen with movement of the index finger. Metacarpophalangeal joint angle and first dorsal interosseous electromyographic activity were recorded. Pattern matching was assessed by cross-correlation of the joint angle and target traces. Distance from the target (tracking error) was also calculated. Motor learning was evident in the visuomotor task. Pattern matching improved over time (cross-correlation coefficient) and tracking error decreased. However, task performance did not differ between the groups. The results suggest that learning of a new fine visuomotor skill is unchanged in individuals with a history of illicit stimulant use.
Highlights
Learning of fine motor skills in humans is commonly investigated with tasks that involve visually guided movements of the hand [1, 2]
Performance of the visuomotor tracking task and grooved pegboard test improved over time
The improvement in performance is indicative of motor learning
Summary
Learning of fine motor skills in humans is commonly investigated with tasks that involve visually guided movements of the hand (i.e., visuomotor tasks) [1, 2]. Tasks that involve tracking a moving target on a computer screen with movements of the hand have been well characterised. Acute changes in the performance of visuomotor tasks have been observed following use of illicit drugs [6,7,8,9]. The ability to track a moving target on a computer screen with movements of the hand is impaired for up to seven hours after cannabis use [6,7,8] (cf [10]). Performance of a task that involves use of a joystick to keep a cursor centred in a target area (critical tracking test) is improved two hours after administration of 75 mg of 3,4methylenedioxymethamphetamine (MDMA or “ecstasy”) in adults with a history of illicit drug use [9]. Very little is known about the acute and long-lasting effect of illicit drug use on learning of these tasks
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