title: Deep brain stimulation of the subthalamic nucleus improves cognitive flexibility but impairs response inhibition in Parkinson disease.
abstract: BACKGROUND
  Deep brain stimulation of the subthalamic nucleus (STN) improves motor symptoms of Parkinson disease. Although several studies have assessed cognitive functions before surgery and after long-term STN stimulation, only a few have assessed patients while stimulation is on and off to more specifically address the short-term cognitive effects of STN deep brain stimulation.
  
  
  OBJECTIVE
  To examine the short-term effects of STN stimulation on several tests sensitive to executive function and the long-term effects of STN stimulation on a global cognitive scale.
  
  
  METHODS
  Twenty-three patients with Parkinson disease were tested 6 to 12 months after surgery with STN stimulation switched on and off in a random order while taking their regular medication. The Unified Parkinson's Disease Rating Scale motor score was also rated in the on and off stimulation condition. The neuropsychological battery included digit span, verbal fluency, Stroop color test, and random number generation in a single- and dual-task condition.
  
  
  RESULTS
  Short-term stimulation improved the results on the Random Number Generation Task, requiring suppression of habitual responses, but induced more errors in the interference task of the Stroop color test. Digit span, verbal fluency, and dual-task performance results did not change. There was a significant correlation (r = 0.47, P =.02) between improved performance on the Random Number Generation Task and impaired response inhibition in the Stroop interference condition. A preoperative to postoperative comparison showed no changes in global cognitive function with long-term STN deep brain stimulation.
  
  
  CONCLUSIONS
  Short-term STN stimulation improves cognitive flexibility (giving up habitual responses) but impairs response inhibition. Long-term STN stimulation does not change global cognitive function.
authors.affiliation: Department of Neurology, Christian-Albrechts-University Kiel, Kiel, Germany.
authors.forename: Karsten
authors.initials: K
authors.lastname: Witt
authors.forename: Ulrich
authors.initials: U
authors.lastname: Pulkowski
authors.forename: Jan
authors.initials: J
authors.lastname: Herzog
authors.forename: Delia
authors.initials: D
authors.lastname: Lorenz
authors.forename: Wolfgang
authors.initials: W
authors.lastname: Hamel
authors.forename: Günther
authors.initials: G
authors.lastname: Deuschl
authors.forename: Paul
authors.initials: P
authors.lastname: Krack
mesh_terms: D003071:Cognition / Q000502:physiology*; D004599:Electric Stimulation Therapy; D005260:Female; D006801:Humans; D007266:Inhibition, Psychological; D008297:Male; D008875:Middle Aged; D009483:Neuropsychological Tests; D010300:Parkinson Disease / Q000628:therapy*; D020531:Subthalamic Nucleus / Q000502:physiology*