Spatial distortion related to time compression during spatiotemporal production in Parkinson's disease
To produce coordinated manual actions within specific space and time, their relationship must be properly dealt with in a sensorimotor system. This study examined how such a coordination system might be impaired in normal aging and in Parkinson's disease (PD). Using a tablet device, young participants, elderly participants, and patients with PD were tested for concurrent production of distance and duration as well as single production of distance or duration alone. Results were analyzed in relation to deficiency of presynaptic dopamine transporter (DaT) in the striatum. We observed different patterns of impairment between normal aging and PD. Elderly participants exhibited duration overproduction when they had to produce distance and duration concurrently, but were normal in single production of either distance or duration. In contrast, PD patients exhibited normal distance production and marked underproduction of duration when either distance or duration was produced alone, but both duration and distance were underproduced when they were concurrently produced. These findings suggest that aging yields impaired performances in both elderly people and PD patients, but that temporal underproduction in PD patients entrains spatial production as if the distance to be produced were made consistent with their duration underproduction. We also observed that striatal DaT deficit was correlated with the extent of duration underproduction in PD patients. The deficit may be associated with the severe time compression and the entrainment during spatiotemporal production in PD patients.