Abstract
The serotonergic pathway has been implicated in the pathogenesis of impulsivity, and sensitivity to aversive outcomes may be linked to serotonin (5-HT) levels. Polymorphisms in the gene that encodes the serotonin transporter (5-HTT), which have differential effects on the level of serotonin transmission, display alternate responses to aversive stimuli. However, recent studies have shown that 5-HT does not affect motor function, which suggests that the functioning of the serotonin-transporter-linked polymorphic region (5-HTTLPR) does not directly affect the behavioral regulatory process itself, but instead exerts an effect via the evaluation of the potential risk associated with particular behavioral outputs. The aim of the present study was to examine the effect of specific 5-HTTLPR genotypes on the motor regulatory process, as observed during a Go/Nogo punishment feedback task. 5-HTT gene-linked promoter polymorphisms were analyzed by polymerase chain reaction, using lymphocytes from 61 healthy Japanese volunteers. Impulsivity was defined as the number of commission errors (responding when one should not) made during a Go/Nogo task. We found that the s/s genotype group made fewer impulsive responses, specifically under aversive conditions for committing such errors, compared to those in the s/l group, without affecting overall motor inhibition. These results suggest that 5-HTTLPRs do not directly affect the behavioral regulatory process itself, but may instead exert an effect on the evaluation of potential risk. The results also indicate that under such aversive conditions, decreased expression of 5-HTT may promote motor inhibitory control.
Highlights
Impulsivity is characterized by actions based on sudden desires and whims rather than on careful thought
We found that different 5-HTTLPR genotypes have a specific influence on motor impulsivity, whereby s/s carriers made fewer commission errors than s/l carriers did, during the aversive conditions
Our findings correspond to findings from previous studies on motor impulsivity, which have reported that cautious people become even more cautious in terms of motor inhibition during a stop-signal task after an impulsive response is punished [25]
Summary
Impulsivity is characterized by actions based on sudden desires and whims rather than on careful thought. Amongst the different forms of impulsivity, motor impulsivity is the inability to inhibit planned or ongoing actions, and is usually associated with quick, possibly aggressive, reactions with little regard for consequences. Such rash actions of emotion-based dispositions are characterized by two subtypes; positive urgency, which is the tendency to engage in rash action in response to extreme positive affect, and negative urgency, which is the tendency to engage in rash action in response to extreme negative affect [6,7]
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