The objective of our work was to find whether the subthalamic nucleus (STN) is directly involved in cognitive activities, specifically in executive functions. Ten patients with idiopathic Parkinson's disease had P3 potentials recorded by externalized deep brain electrodes that were implanted in the STN or in its immediate vicinity. Two contacts of each electrode were positioned inside the STN according to clinical effect, perioperative microrecording, and stimulation. The P3 waves were recorded following the auditory stimulus in a standard oddball paradigm. They were compared with the P3 waves elicited from a protocol modified by a dual task with an increased demand on executive functions. The P3 potentials with a steep amplitude gradient evoked by the modified protocol were detected by the contacts in 8 of the 14 available electrodes, located either inside the STN or in its immediate vicinity. The modified protocol led to an increased latency of the P3 potential in 8 of 14 electrodes. No local field potentials of the standard P3 potentials were recorded. The P3 potentials related to the increased demand on executive functions were detected by the STN contacts known to have the best effect on Parkinsonian motor signs. This could suggest that the STN takes part in the executive function processing. (c) 2007 Movement Disorder Society.

Department of Neurology Movement Disorders Centre St Anne's University Hospital Medical School of Masaryk University Pekarska 53 Brno Czech Republic