Stimulation of STN impairs aspects of cognitive control in PD

Objective: To test the hypothesis that subthalamic nucleus (STN) stimulation in Parkinson disease (PD) patients affects working memory and response inhibition performance, particularly under conditions of high demand on cognitive control. Methods: To test this hypothesis, spatial working memory ( spatial delayed response [SDR]) and response inhibition (Go - No - Go [GNG]) tasks requiring varying levels of cognitive control were administered to patients with PD with previously implanted bilateral STN stimulators (n = 24). Patients did not take PD medications overnight. Data were collected while bilateral stimulators were on and off, counterbalancing the order across subjects. Results: On the SDR task, STN stimulation decreased patients' working memory performance under a high but not low memory load condition ( effect of stimulator condition on high load only and condition x load interaction, p < 0.05). On the GNG task, STN stimulation reduced discriminability on a high but not medium inhibition condition ( effect of stimulator condition on high inhibition level only, p = 0.05; condition x inhibition level interaction, p = 0.07). Conclusion: STN stimulation reduces working memory and response inhibition performance under conditions of greater challenge to cognitive control despite significant improvement of motor function.