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Dopamine promotes instrumental motivation, but reduces reward-related vigour.

Published version
Peer-reviewed

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Authors

Sandhu, Timothy R 
Hu, Michele T 

Abstract

We can be motivated when reward depends on performance, or merely by the prospect of a guaranteed reward. Performance-dependent (contingent) reward is instrumental, relying on an internal action-outcome model, whereas motivation by guaranteed reward may minimise opportunity cost in reward-rich environments. Competing theories propose that each type of motivation should be dependent on dopaminergic activity. We contrasted these two types of motivation with a rewarded saccade task, in patients with Parkinson's disease (PD). When PD patients were ON dopamine, they had greater response vigour (peak saccadic velocity residuals) for contingent rewards, whereas when PD patients were OFF medication, they had greater vigour for guaranteed rewards. These results support the view that reward expectation and contingency drive distinct motivational processes, and can be dissociated by manipulating dopaminergic activity. We posit that dopamine promotes goal-directed motivation, but dampens reward-driven vigour, contradictory to the prediction that increased tonic dopamine amplifies reward expectation.

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Keywords

Parkinson's disease, dopamine, human, motivation, neuroscience, reward, vigour, Aged, Anticipation, Psychological, Dopamine, Eye Movement Measurements, Female, Humans, Male, Motivation, Parkinson Disease, Reward, Saccades

Journal Title

Elife

Conference Name

Journal ISSN

2050-084X
2050-084X

Volume Title

9

Publisher

eLife Sciences Publications, Ltd
Sponsorship
Medical Research Council (MR/M024962/1)
Medical Research Council (MR/L023784/1)