Concurrent Parkinson tremors

1. Concurrent resting and postural tremors of patients with idiopathic Park inson's disease were monitored using transducers responding to angular velo city of rotation. Spectra and correlation functions were calculated for eac h pair of records. 2. When concurrent tremor spectra share indistinguishable fundamental frequ encies, have statistically significant peaks in their coherence spectra at those fundamental frequencies, and show significant peaks in their cross-co rrelation functions near zero delay, they are classified as linearly depend ent. When such tremor records are superimposed, their phase locked behaviou r is evident. 3. Pairs of correlated concurrent tremors, of varying duration, have been o bserved in both hands, both feet and in either hand and the contralateral o r ipsilateral foot. Correlated tremors may be concurrent with other tremors that are independent. We hypothesize that correlated Parkinson tremors ari se from one or more common (and possibly unilateral) central sources.