Unit activity of the human thalamus during voluntary movements.

The quantitative functional analysis of firing patterns has made it possible to classify human VL neurons into two basic types: (1), units with irregular unitary 3-to 20-imp/s activity (A type) and (2) units with short (10-30 ms) rhythmic (3-6 Hz) burst discharges (B type). These two basic types of VL neurons, determined by differences of their discharge patterns and functional properties, are theorized to play a significant role in motor and rhythmic thalamic mechanisms related to parkinsonian tremor. Despite the absence of any direct relationship between rhythmic (3-6 Hz) bursting VL and Rt neurons of the B type and parkinsonian tremor, some indirect relations between them were found.