Mental set change and parallel processing in Parkinson's disease: a multimodal P3 analysis

Abstract

The purpose of our study was to demonstrate working-memory impairment in nondemented early stage mild Parkinson's disease patients (PDPs) electrophysiologically using a multimodal event-related potentials (ERP) paradigm. Multimodal ERP paradigm was performed in 21 nondemented medicated early stage PDPs (MMSE>24) and 16 age-matched normal control subjects (NCs). Twenty channels of ERP were recorded from scalp. The global field power (GFP) was employed for ERP components analysis. The new modified Wisconsin Card Sorting Test (WSCT) was used to evaluate frontal lobe function. No novelty P3s were detected in PDPs. P3 GFP latency to nontarget novel stimulus in visual and auditory modalities was significantly longer in PDPs than in the NCs. P3 GFP amplitude for the target stimulus (P3b) was higher in PDPs in both auditory and visual modalities. P3b GFP latency, however, was not different between the two groups. PDPs showed a significantly lower score of achieved categories and deterioration of perseverative errors in WSCT compared to the NCs. Our results suggest that nondemented mild PDPs do not have sufficient mental resources to allocate to the central executive as indicated by the lack of novelty P3 which may be due to the disability of the working memory.