title: Dopamine modulates reward-related vigor.
abstract: Subjects routinely control the vigor with which they emit motoric responses. However, the bulk of formal treatments of decision-making ignores this dimension of choice. A recent theoretical study suggested that action vigor should be influenced by experienced average reward rate and that this rate is encoded by tonic dopamine in the brain. We previously examined how average reward rate modulates vigor as exemplified by response times and found a measure of agreement with the first suggestion. In the current study, we examined the second suggestion, namely the potential influence of dopamine signaling on vigor. Ninety healthy subjects participated in a double-blind experiment in which they received one of the following: placebo, L-DOPA (which increases dopamine levels in the brain), or citalopram (which has a selective, if complex, effect on serotonin levels). Subjects performed multiple trials of a rewarded odd-ball discrimination task in which we varied the potential reward over time in order to exercise the putative link between vigor and average reward rate. Replicating our previous findings, we found that a significant fraction of the variance in subjects' responses could be explained by our experimentally manipulated changes in average reward rate. Crucially, this relationship was significantly stronger under L-Dopa than under Placebo, suggesting that the impact of average reward levels on action vigor is indeed subject to a dopaminergic influence.
authors: Centre for Computational Neuroscience and Cognitive Robotics, University of Birmingham, Edgbaston, UK. u.beierholm@bham.ac.uk
authors: Ulrik
authors: U
authors: Beierholm
authors: Marc
authors: M
authors: Guitart-Masip
authors: Marcos
authors: M
authors: Economides
authors: Rumana
authors: R
authors: Chowdhury
authors: Emrah
authors: E
authors: Düzel
authors: Ray
authors: R
authors: Dolan
authors: Peter
authors: P
authors: Dayan
mesh_terms: D000293:Adolescent; D000328:Adult; D015283:Citalopram / Q000494:pharmacology; D004298:Dopamine / Q000502:physiology*; D004311:Double-Blind Method; D005260:Female; D006801:Humans; D007980:Levodopa / Q000494:pharmacology; D008297:Male; D009042:Motivation / Q000187:drug effects / Q000502:physiology*; D010775:Photic Stimulation / Q000379:methods; D011597:Psychomotor Performance / Q000187:drug effects / Q000502:physiology*; D011930:Reaction Time / Q000187:drug effects / Q000502:physiology; D012201:Reward; D055815:Young Adult
chemical_list: D015283:Citalopram; D007980:Levodopa; D004298:Dopamine