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. 2010;3:99-111.
doi: 10.4137/ijtr.s4317. Epub 2010 Jun 10.

Effects of Acute Tryptophan Depletion on Three Different Types of Behavioral Impulsivity

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Free PMC article

Effects of Acute Tryptophan Depletion on Three Different Types of Behavioral Impulsivity

Donald M Dougherty et al. Int J Tryptophan Res. .
Free PMC article

Abstract

Introduction: While central nervous system serotonin has been implicated in a variety of problematic impulsive behaviors, biological manipulation of brain serotonin using acute tryptophan depletion for studying changes in impulsive behavior has received little attention.

Methods: Using identical treatment conditions, we examined the effects of reduced serotonin synthesis for each of three matched groups using acute tryptophan depletion. Thirty healthy men and women (ages 18-45) were assigned to perform one of three tasks assessing different types of behavioral impulsivity: response initiation, response inhibition, and consequence sensitivity (N = 90). Participants completed two experimental days during which each consumed either a tryptophan-depletion or balanced-placebo amino-acid formulation and completed 5 sessions of their respective tasks at 0.25 h before and 1.5, 4.0, 5.0, and 6.0 h after beverage consumption.

Results: During peak effectiveness (5.0 h to 6.0 h following amino-acid consumption), depletion produced selective differences dependent on the type of impulsivity being tested. Specifically, relative to baseline testing (pre-depletion), response initiation impulsivity was significantly increased during the peak effects of depletion. And, when compared to placebo control, both response initiation and consequence sensitivity impulsivity were increased during the peak effects of depletion.

Conclusion: Though response initiation and consequence sensitivity impulsivity were affected by tryptophan depletion, response inhibition impulsivity was not, suggesting that other biological processes may underlie this specific component of impulsivity. Future research in other populations or using different pharmacological agents is warranted to further examine the biological processes underlying these components of impulsivity.

Keywords: adults; behavior; humans; impulsivity; task comparison; tryptophan.

Figures

Figure 1.
Figure 1.
The effects of two amino-acid conditions on IMT (top panel), GoStop (middle panel), and SKIP (bottom panel) performance across pre-drink baseline and post-drink testing times (mean ± SEM). For the SKIP, data were transformed using a reflection strategy to correct non-normal negative skew. *Indicates significant differences between Trp depletion and the balanced placebo. §Indicates a significant difference from pre-drink baseline performance.

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