Neuropsychological effects of amphetamine may correlate with personality characteristics

Although the stimulant properties of amphetamine are well established, its effects on cognitive test performance in unfatigued normal adults are poorly documented. Seventeen healthy individuals received a single oral dose of dextroamphetamine (0.25 mg/kg) in a double-blind, placebo-controlled, crossover study. Neurocognitive tests, motor tests, and behavioral observations were performed. Personality information, based on the Tridimensional Personality Questionnaire (TPQ) was also gathered to explore a relationship between personality factors and response to the stimulant. With the exception of two measures of reaction time, there were no overall changes in performance on measures of memory or other cognitive functions. There was decreased reaction time on the continuous performance task (CPT) and increased accuracy of performance under minimal delay conditions in the spatial delay response task while subjects were receiving amphetamine. In addition, the novelty-seeking subscale was found to correlate with a measure of verbal memory. Individuals with higher scores on the novelty-seeking scale deteriorated under amphetamine, while those who had lower scores improved. These results suggest that some cognitive abilities of persons who may have relatively high dopaminergic tone are disrupted by amphetamine, while those with relatively low dopaminergic tone may have their performance enhanced.