Journal
NEUROPSYCHOPHARMACOLOGY
Volume 30, Issue 7, Pages 1362-1373Publisher
NATURE PUBLISHING GROUP
DOI: 10.1038/sj.npp.1300704
Keywords
impulsivity; serotonin; reward certainty; motivation; self-control; tryptophan depletion
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Funding
- Wellcome Trust Funding Source: Medline
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Serotonin ( 5-HT) is well known to affect the motivational properties of stimuli predictive of rewards as well as the inhibitory control of behavior. Here, central 5-HT depletion was induced by the acute tryptophan ( TRP) depletion ( ATD) procedure in young healthy volunteers to examine the role of 5-HT in motivated action and prepotent response inhibition. A novel reaction-time task, tailored to individual differences in general cognitive speed, was employed to measure the guidance of behavior by motivationally relevant signals predictive of reinforcement likelihood, while the stop-signal reaction-time task was used to measure response inhibition. Following the TRP-balancing control drink, cues predictive of high-reinforcement certainty induced faster, but less accurate responses compared with cues predictive of lower reinforcement certainty. Depletion of central 5-HT modulated this coupling between motivation and action by slowing responses and increasing accuracy as a function of incentive certainty. These effects of ATD on motivated action correlated highly with individual differences in the personality trait of Nonplanning Impulsiveness ( Barratt Impulsivity Scale ( BIS-11)), so that strongest effects on motivated action were observed in high-impulsive individuals. By contrast, ATD left unaltered the ability to inhibit prepotent responses. Our findings may have implications for a variety of neuropsychiatric disorders including impulsive aggressive disorders and depression.
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