Subthalamic neuron activity related to tremor and movement in Parkinson's disease

Single cell activity recorded in the subthalamic nucleus (STN) of Parkinson 's patients and the effect of tremor, passive and voluntary movement upon t he same cells are described. Three types of cells were distinguished by the pattern of discharge: tonic, phasic and rhythmic. They all demonstrated hi gh mean firing rates (65, 59 and 69 Hz, respectively). Simultaneous recordi ngs of muscle activity and tremor helped in defining cell activity. The imp lantation of the definitive stimulating electrode in the patients was based on the number of STN cells related to tremor, active and passive movements (mean = 68%) along the track chosen. Cells were related to tremor (n = 21; 11%), modified the discharge with differences in the amplitude of tremor ( n = 4), and changed the rate and pattern when tremor stopped spontaneously or artificially (n = 6). Movement-related cells (n = 97; 51%) showed a cycl ic activity correlated with phases of the movement, or modified the firing rate along the performance of the movement. Tremor and movement-related cel ls (n = 11; 6%) revealed an interesting sensory-motor integrative function.