The detection of tremor during slow alternating movements performed by patients with early Parkinson's disease.

The present study demonstrates that tremor can be detected during slow alternating movements (SAM) performed by patients with early Parkinson's disease (PD) and that its relative amplitude is strongly correlated with patients' rest and postural hand tremor amplitudes (Rho=0.80 and 0.61, respectively, P<0.05). However, the tremor detected during SAM did not influence the accuracy of patients because of its relatively low amplitude. These results imply that the presence of tremor during movement is not restricted to advanced PD, but can also be detected in patients with early PD having relatively low amplitude tremor. Evidence that the tremor detected at rest, during posture and during voluntary movement share similar or overlapping neural substrates is also presented.