Cognitive dysfunction in cortical cerebellar atrophy correlates with impairment of the inhibitory system.

The aim of the present study was to evaluate the profile of cognitive impairment in patients with cortical cerebellar atrophy (CCA) by measurement of event-related potentials (ERP) and neuropsychological tests. We studied 13 CCA patients and 13 age-, sex- and education-matched normal controls. For ERP recording, we used the conventional auditory oddball task as well as the continuous performance task, which evaluates the attentional performance and ability to control a motor response, i.e., to execute ("Go") or inhibit a motor reaction ("No Go"). Brain electric activity was recorded using 20 scalp electrodes and computed into series of potential distribution maps. For components of ERP, reference-independent measures [global field power (GFP)] were determined, and low-resolution brain electromagnetic tomography (LORETA) was used to compute the three-dimensional intracerebral distribution of electric activity of the P3 component of Go and No Go responses. A comprehensive neuropsychological test battery was also assessed. GFP peak latency was prolonged and GFP peak was attenuated under the No Go condition in patients with CCA, although there were no differences in the auditory oddball task and in the Go condition between the two groups. LORETA showed low activation of frontal source in CCA patients in No Go P3 compared with the controls. However, neuropsychological tests revealed no differences between the two groups. Our results indicate that degeneration of the cerebellum contributes to frontal dysfunction, and suggest this dysfunction is characterized by an impairment of the inhibitory system.