Abstract
Parkinson’s disease (PD) is a neurodegenerative disease that causes motor impairments, such as tremor or slowing. Here we investigate whether these deficits extend to goal-directed eye and hand movements and sensorimotor decisions. Sixteen early stage PD patients with mild to moderate symptoms and 18 age-matched healthy controls performed baseline smooth pursuit tracking, pro- and anti-saccades (Munoz & Everling, 2004), and go/no-go manual interceptions. During the go/no-go interception task observers had to predict whether a moving target would pass through (go required) or miss (no-go required) a designated strike box. Only the initial launch (300 or 500 ms) of the target was shown, requiring observers to extrapolate the target trajectory to decide whether and when to intercept. Eye and hand movements were recorded with a video-based eye and magnetic hand tracker. Patients made more catch-up saccades than controls during baseline pursuit, showed systematic eye movement impairments during visually guided (pro-) saccades, and made a higher number of corrective saccades (changes of mind) during the anti-saccade task. Yet, eye movements were unimpaired compared to the control group during the track-intercept task and patients exhibited similar interception timing and go/no-go decision accuracy. Interestingly, PD patients initiated hand movements earlier than controls, indicating the ability to compensate for motor slowing by adapting eye and hand movement timing. These results suggest that early stage PD patients show most impairments during visually guided pursuit and saccades, but seem to preserve function in higher-level tasks.