title: Dopamine and performance in a reinforcement learning task: evidence from Parkinson's disease.
abstract: The role dopamine plays in decision-making has important theoretical, empirical and clinical implications. Here, we examined its precise contribution by exploiting the lesion deficit model afforded by Parkinson's disease. We studied patients in a two-stage reinforcement learning task, while they were ON and OFF dopamine replacement medication. Contrary to expectation, we found that dopaminergic drug state (ON or OFF) did not impact learning. Instead, the critical factor was drug state during the performance phase, with patients ON medication choosing correctly significantly more frequently than those OFF medication. This effect was independent of drug state during initial learning and appears to reflect a facilitation of generalization for learnt information. This inference is bolstered by our observation that neural activity in nucleus accumbens and ventromedial prefrontal cortex, measured during simultaneously acquired functional magnetic resonance imaging, represented learnt stimulus values during performance. This effect was expressed solely during the ON state with activity in these regions correlating with better performance. Our data indicate that dopamine modulation of nucleus accumbens and ventromedial prefrontal cortex exerts a specific effect on choice behaviour distinct from pure learning. The findings are in keeping with the substantial other evidence that certain aspects of learning are unaffected by dopamine lesions or depletion, and that dopamine plays a key role in performance that may be distinct from its role in learning.
authors.affiliation: Wellcome Trust Centre for Neuroimaging, UCL, London, WC1N 3BG, UK. tamarashiner@gmail.com
authors.forename: Tamara
authors.initials: T
authors.lastname: Shiner
authors.forename: Ben
authors.initials: B
authors.lastname: Seymour
authors.forename: Klaus
authors.initials: K
authors.lastname: Wunderlich
authors.forename: Ciaran
authors.initials: C
authors.lastname: Hill
authors.forename: Kailash P
authors.initials: KP
authors.lastname: Bhatia
authors.forename: Peter
authors.initials: P
authors.lastname: Dayan
authors.forename: Raymond J
authors.initials: RJ
authors.lastname: Dolan
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001245:Association Learning / Q000187:drug effects; D002230:Carbidopa / Q000494:pharmacology* / Q000627:therapeutic use; D002755:Choice Behavior / Q000187:drug effects; D015259:Dopamine Agents / Q000494:pharmacology* / Q000627:therapeutic use; D004305:Dose-Response Relationship, Drug; D004338:Drug Combinations; D005260:Female; D005793:Generalization, Psychological / Q000187:drug effects*; D006801:Humans; D007091:Image Processing, Computer-Assisted; D007980:Levodopa / Q000494:pharmacology* / Q000627:therapeutic use; D008279:Magnetic Resonance Imaging; D008297:Male; D008875:Middle Aged; D009714:Nucleus Accumbens / Q000098:blood supply / Q000187:drug effects; D010100:Oxygen / Q000097:blood; D010300:Parkinson Disease / Q000188:drug therapy / Q000473:pathology / Q000503:physiopathology*; D010775:Photic Stimulation; D017397:Prefrontal Cortex / Q000098:blood supply / Q000187:drug effects; D011597:Psychomotor Performance / Q000187:drug effects; D012054:Reinforcement, Psychology
chemical_list: D015259:Dopamine Agents; D004338:Drug Combinations; C009265:carbidopa, levodopa drug combination; D007980:Levodopa; D002230:Carbidopa; D010100:Oxygen