Impulse control disorder in Parkinson ’s disease is associated with abnormal frontal value signalling

AbstractDopaminergic medication is well established to boost reward- versus punishment-based learning in Parkinson ’s disease. However, there is tremendous variability in dopaminergic medication effects across different individuals, with some patients exhibiting much greater cognitive sensitivity to medication than others. We aimed to unravel the mechanisms underlying this individual variability in a large het erogeneous sample of early-stage patients with Parkinson’s disease as a function of comorbid neuropsychiatric symptomatology, in particular impulse control disorders and depression.One hundred and ninety-nine patients with Parkinson’s disease (138 ON medication and 61 OFF medication) and 59 heal thy controls were scanned with functional MRI while they performed an established probabilistic instrumental learning task. Reinforcement learning model-based analyses revealed medication group differences in learning from gains versus losses, but only in patients with impulse control disorders. Fur thermore, expected-value related brain signalling in the ventromedial prefrontal cortex was increased in patients with impulse control disorders ON medication compared with those OFF medication, while striatal reward prediction error signalling remained unaltered.These data substantiate the hypothes is that dopamine’s effects on reinforcement learning in Parkinson’s disease vary with individual differences in comorbid impulse control disorder and suggest they reflect defici...

Source: Brain - May 16, 2023 Category: Neurology Source Type: research