Dopamine and performance in a reinforcement learning task: evidence from Parkinson’s disease Full Text
Shiner T et al. – 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.Methods
- The authors studied patients in a two-stage reinforcement learning task, while they were ON and OFF dopamine replacement medication.
- Contrary to expectation, they 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 the 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.
- The data indicate that dopamine modulation of nucleus accumbens and ventromedial prefrontal cortex exerts a specific effect on choice behaviour distinct from pure learning.