Measurements of visual evoked potentials in Parkinson's disease.

Visual evoked potentials elicited by reversing grating patterns were recorded in 35 patients with Parkinson's disease and in 26 controls. The average latency of evoked potentials in patients with Parkinson's disease exceeded by two standard deviations the average of the age-matched control group of other neurological patients. Over two-thirds of all patients with Parkinson's disease had abnormal latency. In these patients latency did not correlate with age. In 5 patients the latency became less prolonged on levodopa therapy, suggesting that catecholaminergic pathways have either indirect or direct effects on the generation of visual evoked potentials. Extrapyramidal connections of the visual cortex, as well as retinal dopaminergic neurons, require further study in Parkinson's disease.