Bilateral subthalamic nucleus stimulation improves frontal cortex functionin Parkinson's disease - An electrophysiological study of the contingent negative variation

Parkinson's disease involves impaired activation of frontal cortical areas, including the supplementary motor area and prefrontal cortex, resulting fr om impaired thalamocortical output of the basal ganglia, Electrophysiologic ally, such impaired cortical activation may be seen as a reduced amplitude of the contingent negative variation (CNV), a slow negative potential shift reflecting cognitive processes associated with the preparation and/or anti cipation of a response. Surgical interventions aimed at increasing basal ga nglia-thalamic outflow to the cortex, such as electrical stimulation of the subthalamic nucleus with chronically implanted electrodes, have been shown to be effective in improving the clinical symptoms of Parkiuson's disease. This study examined changes in cortical activity, as reflected in the CNV, associated with bilateral subthalamic nucleus stimulation in Parkinson's d isease, The CNV was recorded from 10 patients with Parkinson's disease when on and off bilateral subthalamic nucleus stimulation, and was compared wit h the CNV of 10 healthy control subjects. Without subthalamic nucleus stimu lation, Parkinson's disease patients showed reduced CNV amplitudes over the frontal and frontocentral regions compared with control subjects. With bil ateral subthalamic nucleus stimulation, however, CNV amplitudes over the fr ontal and frontocentral regions were significantly increased. Results there fore suggest that impaired cortical functioning in Parkinson's disease, par ticularly within the frontal and premotor areas, is improved by subthalamic nucleus stimulation.