Bimanual coordination dysfunction in early, untreated Parkinson's disease.

Bimanual coordination involves the simultaneous performance of either symmetrical (in-phase) or asymmetrical (anti-phase) movements with both hands and is known to be impaired in Parkinson's disease (PD). At present, it is unclear whether this aspect of motor function is already impaired in early stage, untreated PD patients. Therefore, we investigated the accuracy of bimanual coordination in 13 early stage, untreated PD patients and 13 age- and sex-matched healthy controls. Each subject performed bimanual coordination tasks at two different movement frequencies (1 and 1.75 Hz) and with two different phase relationships (in-phase and anti-phase). The percentage of unsuccessful trials (as a measure of overall task performance) in PD patients was significantly higher than in healthy subjects. PD patients performed high frequency in-phase and anti-phase bimanual coordination tasks less accurately with their non-dominant hand than healthy subjects. Furthermore, PD patients had more difficulty than healthy subjects in maintaining a constant phase relationship between the hands in the anti-phase condition at low movement frequency. This study demonstrates that bimanual coordination dysfunction is a very early sign of PD. Bimanual coordination tasks, in particular those involving high frequency anti-phase movements, might prove useful in the early diagnosis of PD.