[Endogenous cortical evoked potentials in parkinsonism].

Averaged cortical evoked potentials (EP) to light stimuli were studied in 19 Parkinsonian patients and 12 healthy subjects under the conditions of passive perception ("the background") and during different psycho-motor reactions. Differential EP waves between "the reaction" and "the background" were analysed, i.e. the endogenous potentials. A retardation of the psycho-motor reactions in patients was found to be accompanied by a decrease of endogenous EP in the frontal recording. This decrease mainly concerned the potentials connected rather with the motor acts than with the cognitive operations. The retardation of the voluntary movements in parkinsonism is assumed to be connected with a "deficit" of the frontal activation due to a disfunction of the basal ganglia.