Appetitive motivational deficits in individuals with Parkinson's disease

Parkinson's disease is known for its effects on sensorimotor coordination caused by degeneration of the nigrostriatal dopamine pathway. Dopamine-innervated areas of the ventral striatum also become compromised in Parkinson's disease, and little is known about the potential impact of this pathology on motivational processes mediated by the mesolimbic dopamine system. The current study tested the hypothesis that patients with Parkinson's disease would show a deficit in appetitive motivational arousal. Patients with Parkinson's disease and age-matched healthy controls completed a visual discrimination task in which control and appetitive food images (incidental to the task) were presented in the background. Response rate changes indicated appetitive motivational arousal. The healthy controls showed an increase in response rate on the task when appetitive food cues were present compared with control stimuli. In contrast, the Parkinson's disease group showed an inverse pattern to the healthy controls. The reduction in appetitive motivation correlated with an individual's Parkinsonian symptomology. Patients with Parkinson's disease demonstrated an impairment in appetitive motivational arousal consistent with the progression of dopaminergic degeneration across the course of the disease. Dysfunction of this system affects quality of life in Parkinson's disease, and a blunting of the anticipatory motivation may contribute to the high prevalence of depression in Parkinson's disease.