The control of bimanual aiming movements in Parkinson's disease

The control of unimanual and bimanual aiming movements by Parkinson's disease and control subjects was examined. Despite greater bimanual movement initiation asynchrony and overall bradykinesia, the Parkinson's disease subjects were affected by the experimental manipulations in the same way as controls. Symmetrical and, more especially, asymmetrical bimanual movements required more preparation time and were executed more slowly by both groups than were unimanual movements. Both groups also showed temporal linkage of movements to targets of different extents--movements which have different movement times when performed unimanually, as well as of the faster and slower limbs. A majority in both groups over-compensated for asynchrony in bimanual movement initiation by modulation of movement times, but there was no group difference in this tendency. The results are discussed in terms of underlying motor control processes and with regard to previous evidence for impaired control of simultaneous movements in Parkinson's disease.