Tryptophan depletion alters the decision-making of healthy volunteers through altered processing of reward cues.

Full Abstract

While accumulating evidence suggests that effective real-life decision-making depends upon the functioning of the orbitofrontal cortex, much less is known about the involvement of the monoamine neurotransmitter systems and, in particular, serotonin. In the present study, we explored the impact of depleting the serotonin precursor, tryptophan, on human decision-making. Eighteen healthy volunteers consumed an amino-acid drink containing tryptophan and 18 healthy volunteers consumed an amino-acid drink without tryptophan, before choosing between simultaneously presented gambles, differing in the magnitude of expected gains (ie reward), the magnitude of expected losses (ie punishment), and the probabilities with which these outcomes were delivered. Volunteers also chose between gambles probing identified non-nomative biases in human decision-making, namely, risk-aversion when choosing between gains and risk-seeking when choosing between losses. Tryptophan-depleted volunteers showed reduced discrimination between magnitudes of expected gains associated with different choices. There was little evidence that tryptophan depletion was associated with altered discrimination between the magnitudes of expected losses, or altered discrimination between the relative probabilities with which these positive or negative outcomes were delivered. Risk-averse and risk-seeking biases were also unchanged. These results suggest that serotonin mediates decision-making in healthy volunteers by modulating the processing of reward cues, perhaps represented within the orbitofrontal cortex. It is possible that such a change in the cognition mediating human choice is one mechanism associated with the onset and maintenance of anhedonia and lowered mood in psychiatric illness.

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Author information

Author/s: Rogers, Robert D (RD); Tunbridge, Elizabeth M (EM); Bhagwagar, Zubin (Z); Drevets, Wayne C (WC); Sahakian, Barbara J (BJ); Carter, Cameron S (CS);

Affiliation: University Department of Psychiatry, University of Oxford, UK. robert.rogers(-atsign-)psych.ox.ac.uk

Journal and publication information

Publication Type: Clinical Trial; Journal Article; Randomized Controlled Trial; Research Support, Non-U.S. Gov't

Journal: Neuropsychopharmacology : official publication of the American College of Neuropsychopharmacology (Neuropsychopharmacology), published in United States. (Language: eng)

Reference: 2003-Jan; vol 28 (issue 1) : pp 153-62

Dates: Created 2002/12/23; Completed 2003/03/17; Revised 2006/11/15;

PMID: 12496952, status: MEDLINE (last retrieval date: 12/26/2008)

Sourced from the National Library of Medicine. Abstract text and other information may be subject to copyright.

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MeSH headings (categories)

This article was linked to the MESH Headings shown below.

Adult
Cues
Decision Making - physiology
Diet
Double-Blind Method
Female

Gambling - psychology
Humans
Male
Reward
Time Factors
Tryptophan - deficiency

Associated Chemicals: Tryptophan (73-22-3)

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