Behavioral impairments in response inhibition and initiation are common in Parkinson's disease (PD) and are associated with reduced impulse control. No prior study, however, has investigated the functional correlates of response inhibition in de novo PD. Twenty-one de novo PD patients and 37 matched healthy controls performed a stop-signal task during functional magnetic resonance imaging. The results showed that PD patients, compared with healthy controls, were slower on response initiation but not inhibition. Task-related activation of the response inhibition network, including the inferior frontal gyrus, was reduced in PD patients, and the activity in the inferior frontal gyrus correlated negatively with motor symptom severity. These findings show that de novo PD patients exhibit functional deficits in the response inhibition network, which are partly related to disease pathology and already evident before commencing dopamine replacement therapy. This study provides insights into the neural underpinnings of impulse control deficits, relevant for the study of the neural vulnerability factors involved in the development of impulse control disorders in PD.
Keywords: Dopamine transporter; Functional MRI; Impulse control disorders; Parkinson's disease; Response inhibition.
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