Discharge of Purkinje and cerebellar nuclear neurons during rapidly alternating arm movements in the monkey.

Abstract

Cerebellar unit activity was recorded in monkeys at rest and during learned rapid alternating movements of each arm. Purkinje cells (Pc) and nuclear cells (Nc) were identified by anatomical location and discharge pattern. A Pc generated spikes of two shapes: a "simple" spike resembled the parallel fiber response and a "complex" spike the climbing fiber response that Eccles and colleagues have recorded intracellularly from the Purkinje cell. At rest, the simple spike of most Pc''s occurred at high frequencies (sometimes over 100/ sec) occasionally interrupted by the complex spike (at around 1/sec). During movement (for Pc''s related to movement) the simple spike frequency alternated between rates higher (up to 400-500/sec) and lower than the resting rate, these modulations consistently occurring at certain phases of the movement; the complex spike occurred as during rest. Nc''s generated spikes of one shape, which at rest also fired at high frequencies (sometimes over 80/sec). During movement (for Nc''s related to movement) the frequency also alternated between rates higher (up to 400-500/sec) and lower than the resting rate and in time with the movement. Pc''s and Nc''s were related to ipsilateral movements only. These observations are discussed with regard to the inputs which might have been driving Pc''s and Nc''s during these movements.