Objective: To evaluate the effects of explicit and implicit task prioritization on reaching and foot-pedal tracking in people with Parkinson disease (PD).

Background: PD affects attention, dual-task performance, and ability to initiate or change movement based on implicit cues. We hypothesized that PD reduces ability to shift focus between arm tasks and foot tasks based on implicit cues but does not affect ability to shift focus based on explicit task prioritization.

Methods: 15 participants with PD (tested ON and OFF medication a week apart; counterbalanced) and 15 age-matched healthy adults performed a reaching task and a foot-pedal tracking task, concurrently (dual-task; DT) and separately (single-task; ST). Attention shifts during DT were explicitly cued by instructing participants to prioritize one task or the other. To cue attention implicitly, we manipulated the accuracy required: participants reached to, lifted and replaced either an empty glass or one filled with water that would spill if tilted >3º, while tracking a target moving in either steep/fast or gradual/slow ramp patterns.

Results: Participants with PD reached more slowly overall than controls, but only when OFF had more delayed reaction time and slower return to the start position. All participants demonstrated DT costs, relative to ST, on the reaching task (reaction time, movement time, and peak velocity of return movement) and pedal tracking task (root mean square error from target traces); participants with PD had greater DT cost to reaching movement time than controls. When explicitly instructed to prioritize one of the tasks, all participants performed better on the instructed task compared with no instruction. In the implicitly cued ST conditions, all participants took longer to reach for a full than an empty glass and had greater error tracking the steep than the gradual ramp. However, in implicitly cued DT conditions, participants took the same time to reach for a full or an empty glass, but had even greater error tracking the steep compared to the gradual ramp.

Conclusions: In dual-task conditions, participants with PD were able to prioritize tasks as instructed and generally responded to implicit cues, prioritizing the reaching task over the foot-pedal task. However, their slowed and delayed reach and less accurate pedal control may put drivers with PD at greater risk of impaired driving.

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MDS Abstracts - https://www.mdsabstracts.org/abstract/multi-limb-dual-task-cost-in-parkinson-disease-evaluating-effects-of-implicit-and-explicit-cues/