Exploring the connections between platelet monoamine oxidase activity and behavior. II. Impulsive personality without neuropsychological signs of disinhibition in air force pilot recruits.

Platelet monoamine oxidase (MAO) activity and serum levels of the adrenal androgen metabolite dehydroepiandrosterone sulfate (DHAS) were measured in 18 male air force pilot recruits and 19 randomly selected male conscripts. Personality scales from three inventories were given, and computerized neuropsychological tests were performed: finger tapping and alternation, reaction time, perceptual maze, perspective fluctuation and lexical decision. The pilot recruits had higher scores in sensation-seeking-related scales suggesting disinhibited behavior in the social sphere, interest in sports and activities involving some danger, and a need for change. They also had higher scores on an impulsivity scale which comprises sensation-seeking content. In the neuropsychological tasks, the pilot recruits were faster in finger-tapping alternation and performed more efficiently in the perceptual-maze test than the conscripts. In a linear discriminant analysis, neuropsychological-task performance discriminated significantly between the pilot and conscript groups. In the biochemical measures, the pilot recruits had higher DHAS levels but similar MAO activity levels compared to the conscripts, which is in contrast to what has been found in other sensation-seeking groups in comparison to controls. This result is in accordance with the normal scores in one of the impulsivity scales in the pilot recruits, and with the absence of signs of disinhibition in neuropsychological tasks. It is proposed that only some aspects of the impulsivity concept might be critical for the association with low MAO activity.