NEUROPHYSIOLOGICAL IDENTIFICATION OF THE SUBTHALAMIC NUCLEUS IN SURGERY FOR PARKINSONS-DISEASE

Microelectrode recording methods for stereotactic localization of the subthalamic nucleus (STN) and surrounding structures are described. Th ese methods accurately define targets for chronic deep brain stimulati on in the treatment of Parkinson's disease. Mean firing rates and a bu rst index were determined for all recorded neurons, and responses to a ctive and passive lime, and orofacial movements were tested. STN neuro ns had a mean firing rate of 37 +/- 17 Hz (n 248) and an irregular fir ing pattern (median burst index, 3.3). Movement-related activity and t remor cells were identified in the STN. Ventral to the STN, substantia ni,ora pars reticulata neurons had a mean rate of 71 +/- 23 Hz (n = 5 6) and a more regular firing pattern (median burst index, 1.7). Short trains (1-2 seconds) of electrical microstimulation of STN could produ ce tremor arrest but were not found to be useful for localization. Com pared with data from normal monkeys our findings suggest that STN neur onal activity is elevated in Parkinson's disease.