The efficacy of the levodopa on cognitive function in patients with de novo Parkinson's disease

Abstract

We investigated the efficacy of the levodopa on cognitive function in patients with de novo Parkinson's disease (PD) using the event-related potential (ERP) measure and neuropsychological test batteries. We studied 12 PD patients who had never received anti-Parkinson medications. The ERP with auditory oddball P3 paradigm and neuropsychological tests such as Mini-Mental State Examination (MMSE), New Modified Wisconsin Card Sorting Test (WCST) and Trail Making test were repeated in the patients before and after administration of levodopa plus benserazide daily 300 mg. For the ERP's components, reference-independent measures (global field power, GFP) were determined, and P3 GFP peak, peak latency and topography were assessed. After administration of levodopa, the patients revealed significant increase of the achieved categories and decrease of perseveration errors in the WSCT, shortening of time in Trail Making test, although MMSE score showed no significant difference. The P3 GFP peak attenuated, although there were no differences in peak latency or on scalp topography. These findings suggest that levodopa affect to the neural circuit connect frontal cortex with the striatum and normalize its function, and it causes decrease of P3 GFP peak reflecting appropriate resource allocation.