Research report: Electrophysiological correlates of visual categorization: evidence for cognitive dysfunctions in early Parkinson's disease

Our aim was to examine the electrophysiological correlates of perceptual categorization in Parkinson's disease (PD). We recorded visual event-related potentials (ERPs) in a natural scene categorization task in drug naive idiopathic PD patients and healthy control subjects. In the control group, there was a significant early difference (150-250 ms poststimulus) between ERPs elicited by pictures containing animals and scenes without animals. In spite of relatively preserved basic-level visual functions, this was not observable in the PD group. These results raise the possibility for striatal contributions to visual categorization and may provide a novel protocol for further clinical studies.