By carrot or by stick: cognitive reinforcement learning in parkinsonism

Science. 2004 Dec 10;306(5703):1940-3. doi: 10.1126/science.1102941. Epub 2004 Nov 4.


To what extent do we learn from the positive versus negative outcomes of our decisions? The neuromodulator dopamine plays a key role in these reinforcement learning processes. Patients with Parkinson's disease, who have depleted dopamine in the basal ganglia, are impaired in tasks that require learning from trial and error. Here, we show, using two cognitive procedural learning tasks, that Parkinson's patients off medication are better at learning to avoid choices that lead to negative outcomes than they are at learning from positive outcomes. Dopamine medication reverses this bias, making patients more sensitive to positive than negative outcomes. This pattern was predicted by our biologically based computational model of basal ganglia-dopamine interactions in cognition, which has separate pathways for "Go" and "NoGo" responses that are differentially modulated by positive and negative reinforcement.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Aged
  • Antiparkinson Agents / therapeutic use
  • Basal Ganglia / physiopathology*
  • Cognition*
  • Computer Simulation
  • Dopamine / physiology*
  • Feedback, Psychological
  • Female
  • Frontal Lobe / physiopathology
  • Humans
  • Learning*
  • Male
  • Matched-Pair Analysis
  • Middle Aged
  • Models, Neurological
  • Parkinson Disease / drug therapy
  • Parkinson Disease / physiopathology*
  • Parkinson Disease / psychology*
  • Probability
  • Reinforcement, Psychology*


  • Antiparkinson Agents
  • Dopamine