Bimanual coordination in Parkinson's disease: deficits in movement frequency, amplitude, and pattern switching

Six patients with idiopathic Parkinson's disease (PD) and six age-matched controls participated in a variety of rhythmic bimanual coordination tasks. The main goal of the task was to perform inphase or antiphase patterns of pronation and supination of the forearms at a specified tempo, and to switch from one pattern to the other upon presentation of a visual cue. The availability of advance information was varied to examine whether deficits would emerge under choice versus pre-cue constraints. In pre-cue conditions, the subjects knew in advance which hand would be cued to initiate pattern change. In choice conditions, the cued hand was not known until the imperative stimulus was presented. Overall, the PD patients made movements with significantly lower frequencies and smaller amplitudes relative to controls. Patients exhibited spontaneous pattern switching from antiphase to inphase at significantly lower movement frequencies than controls. During intentional switching trials, the control group was significantly faster at initiating pattern change. PD and control groups differed in the time to initiate pattern switching to a greater extent under choice conditions, suggesting that patients used advance information to increase the speed of their response. The control group exhibited a preference for spontaneous switching and intentional switching through the subdominant hand. Patients exhibited a switching preference using the impaired limb (whether or not it was subdominant). The control group made more correct responses when the subdominant side was either pre-cued or presented in choice conditions. The patients maintained the subdominant/impaired side advantage under pre-cue conditions but not choice. In the maintenance of rhythmic movement, individuals with PD were able to use advance information in terms of both speed and accuracy.