title: Mind matters: placebo enhances reward learning in Parkinson's disease.
abstract: Expectations have a powerful influence on how we experience the world. Neurobiological and computational models of learning suggest that dopamine is crucial for shaping expectations of reward and that expectations alone may influence dopamine levels. However, because expectations and reinforcers are typically manipulated together, the role of expectations per se has remained unclear. We separated these two factors using a placebo dopaminergic manipulation in individuals with Parkinson's disease. We combined a reward learning task with functional magnetic resonance imaging to test how expectations of dopamine release modulate learning-related activity in the brain. We found that the mere expectation of dopamine release enhanced reward learning and modulated learning-related signals in the striatum and the ventromedial prefrontal cortex. These effects were selective to learning from reward: neither medication nor placebo had an effect on learning to avoid monetary loss. These findings suggest a neurobiological mechanism by which expectations shape learning and affect.
authors.affiliation: Psychology Department, Columbia University, New York, New York, USA.
authors.forename: Liane
authors.initials: L
authors.lastname: Schmidt
authors.affiliation: Psychology Department, Columbia University, New York, New York, USA.
authors.forename: Erin Kendall
authors.initials: EK
authors.lastname: Braun
authors.affiliation: Psychology Department, University of Colorado at Boulder, Boulder, Colorado, USA.
authors.forename: Tor D
authors.initials: TD
authors.lastname: Wager
authors.affiliation: 1] Psychology Department, Columbia University, New York, New York, USA. [2] Kavli Center for Brain Science, Columbia University, New York, New York, USA.
authors.forename: Daphna
authors.initials: D
authors.lastname: Shohamy
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D000978:Antiparkinson Agents / Q000494:pharmacology / Q000627:therapeutic use; D005260:Female; D006801:Humans; D007858:Learning / Q000187:drug effects / Q000502:physiology*; D008279:Magnetic Resonance Imaging / Q000379:methods; D008297:Male; D008875:Middle Aged; D010300:Parkinson Disease / Q000188:drug therapy / Q000503:physiopathology* / Q000523:psychology*; D010775:Photic Stimulation / Q000379:methods; D017397:Prefrontal Cortex / Q000187:drug effects / Q000502:physiology; D012201:Reward; D013850:Thinking / Q000187:drug effects / Q000502:physiology*
chemical_list: D000978:Antiparkinson Agents