THE ROLE OF THE THALAMUS AND BASAL GANGLIA IN PARKINSONIAN TREMOR

The mechanism of parkinsonian tremor may involve a central oscillator, peripheral feedback to the central nervous system (CNS), or both. The thalamus or the globus pallidus is the most likely site for a central oscillator and would be predicted to generate thalamic tremor-related activity characterized, respectively, by calcium spike-associated bur sts and by maximal tremor-related activity in the pallidal relay nucle us of thalamus. Thalamic spike trains demonstrate neither of these cha racteristics. However, cross-correlation, latency, and transfer functi on analysis indicate that sensory feedback is a critical element in th e relationship between thalamic activity and parkinsonian tremor. Ther efore, thalamic spike train activity is most consistent with parkinson ian tremor being mediated by peripheral inputs involved in either an u nstable reflex loop or sensory modulation of a central oscillator.