The Effect of Stimulation of the Subthalamic Nucleus (STN) or Globus Pallidus (GPi) On executive function in Parkinson's Disease

Abstract:
Abstract: Parkinson's disease (PD), electrical stimulation of the STN but not GPi is associated with increased activation of frontal cortices with PET. In light of such differences in frontal activation, our aim was to compare the effects of stimulation on executive function in 13 PD patients, 7 with stimulators implanted in STN and 6 in GPi. Patients were assessed off medication with stimulators off vs on. The STN and GPi groups showed significant differential change with stimulation for Reitan Trail B (STN more improved) and for random number generation (STN improved, GPi worse with stimulation). For both groups, stimulation significantly speeded up responding and improved performance on two tests requiring attention and working memory (paced serial addition, missing digit). For both groups, trial and error visual conditional learning (VCL) was significantly worse with stimulation. The results are consistent with the neuroimaging findings. In support of current models of PD, 'releasing the subcortical brake' on frontal function with stimulation improved aspects of executive function. Conversely, disruption of basal ganglia outflow during stimulation impaired VCL, suggesting that basal ganglia output is essential for such learning.