Dynamics of tremor-related oscillations in the human globus pallidus: A single case study

Physiological evidence indicates that the resting tremor of Parkinson's dis ease originates in oscillatory neural activity in the forebrain, but it is unknown whether that activity is globally synchronized or consists of paral lel, independently oscillating circuits. In the present study, me used dual microelectrodes to record tremor-related neuronal activity from eight site s in the internal segment of the globus pallidus (GPi) from an awake Parkin son's disease patient undergoing stereotaxic pallidotomy. me utilized spect ral analysis to evaluate the temporal correlations between multiunit activi ty at spatially separated sites and between neural and limb electromyograph ic activity. We observed that some GPi neural pairs oscillated synchronousl y at the tremor frequency, whereas other neural pairs oscillated independen tly. Additionally, we found that GPI tremor-related activity at a given sit e could fluctuate between states of synchronization and independence with r espect to upper limb tremor. Consistent with this finding, same paired reco rding sites within GPi showed periods of transient synchronization. These o bservations support the hypothesis of independent tremor-generating circuit s whose coupling can fluctuate over time.