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).

Conclusions: STN stimulation reduces working memory and response inhibition performance under conditions of greater challenge to cognitive control despite significant improvement of motor function.