Evaluation of cognitive function in spinocerebellar ataxia—a study using event-related potential

Abstract

The purpose of this study is to determine the profile of cognitive impairment of spinocerebellar ataxia, especially the cortical cerebellar atrophy (CCA), using event-related potential (ERP) measures and neuropsychological test batteries. We studied 13 CCA patients and 13 age- and sex-matched controls. For ERP recording, we submitted not only conventional auditory oddball task but also the continuous performance test (CPT), which investigates the attentional performance and the ability to control a motor response, i.e. to execute (Go) or inhibit a motor reaction (NoGo). Brain electric data was obtained from 20 channels and recomputed into a series of potential distribution maps using Biologic Brain Atlas. For the ERPs components, reference-independent measures (global field power=GFP; Lehmann D. and Skrandies W 1980) were determined. Furthermore, low resolution electromagnetic tomography (LORETA) was used to compute the three-dimensional intracerebral distribution of electric activity of Go/NoGo P3 components. The Mini-Mental State Examination (MMSE), the Japanese version of Wechsler Adult Intelligence Scale-Revised (WAIS-R) and the New Modified Wisconsin card sorting test (WCST) were also assessed. The CCA patients showed prolonged GFP peak latency and attenuated GFP peak in NoGo condition, although there were no differences in auditory oddball task and in Go condition. LORETA indicated that CCA patients showed decreased activation of frontal source in NoGo P3 of NC. However, the patients revealed no significant differences both in the WSCT and in the MMSE compared with NC. These findings suggest that degeneration of cerebellum contribute greatly to the frontal dysfunction. And this dysfunction is characterized by the impairment of inhibitory system.