A novel method to assess motor planning deficits in patients with parkinson’s disease and mild cognitive impairment

It is well established that patients with Parkinson's disease (PD) show deficits with movement execution, however experiences of motor planning dysfunction, and how they relate to the severity of motor symptoms, remains unclear. To investigate motor planning in PD, we designed a novel precision-grip task. PD patients showed significantly higher uncertainty in task performance compared to healthy controls, indicative of motor planning deficits. Performance of PD patients did not correlate with indicators of disease severity or subtype, yet patients on a higher daily levodopa dosage showed reduced motor planning deficits. Interestingly, these deficits were present even in recently diagnosed patients, implying that this measure may have potential as an early marker of motor planning impairment. These results suggest that the motor planning deficits revealed by our task may arise from separate pathological processes to that of motor execution dysfunction in PD, though might be alleviated with higher treatment dosages.