Objective: To investigate the effect of dopaminergic medication in Parkinson’s disease (PD) on learning to act and learning to withhold action based on rewarding versus punishing outcomes.

Background: There is an extensive literature on the role of dopamine in reward-based learning. Disorders associated with altered dopamine function in the Basal Ganglia, such as Parkinson’s disease, have been shown to disrupt this learning. Although the role of dopamine in learning to act has been investigated extensively, the role of dopamine in learning to withhold (or inhibit) action to influence outcomes is not as well understood.

Methods: We studied 19 Parkinson’s disease patients ‘On’ and ‘Off’ medication versus 30 healthy older adults on a probabilistic action-valence learning task. During this task subjects learned to act or withhold action to obtain reward or to avoid a punishment. Outcome valence and action were orthogonolized by this paradigm (action-reward, inaction-reward, action-punishment, inaction-punishment) and participants learned each of the four action-valence combinations.

Results: All participants demonstrated inherent learning biases preferring action with reward and inaction to avoid punishment and this was unaffected by dopamine in Parkinson’s disease. However, dopamine modulated the ability to learn less natural action-valence associations (withholding action to obtain a reward and acting to avoid punishment). ‘Off’ dopamine medication, patients demonstrated impairments in learning to withhold action to gain reward, whereas ‘On’ dopamine medication, patients showed a reduced ability to learn to act to avoid punishment.

Conclusions: The current findings suggest that dopamine in Parkinson’s disease is most critical when learning requires overriding natural action-valence tendencies in favor of less natural associations between action and valence. This paradigm could be useful to investigate learning biases in other basal ganglia disorders such as Huntington’s disease or Tourette’s disease and could provide insight into maladaptive action or valence biases in impulse control disorder. The findings might also have implications for rehabilitation learning and the motivators used in different medication states and with different movement disorders.

A similar abstract will be presented at CNS, NY, April 2016.

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MDS Abstracts - https://www.mdsabstracts.org/abstract/dopamine-modulates-learning-conflicting-action-valence-associations-in-parkinsons-disease/