title: Cortical and subcortical blood flow effects of subthalamic nucleus stimulation in PD.
abstract: OBJECTIVE
  To assess whether subthalamic nuclei (STN) stimulation's primary mechanism of action is to drive or inhibit output neurons.
  
  
  METHODS
  Cerebral blood flow responses to STN stimulation were measured using PET in 13 patients with Parkinson disease. Patients were scanned with stimulators off and on (six scans each condition). Clinical ratings, EMG, and videotaping of movements were obtained at each scan. Scans with observable tremor or movement were eliminated from analysis. Brain regions where STN stimulation significantly altered blood flow were identified.
  
  
  RESULTS
  STN stimulation increased blood flow in midbrain (including STN), globus pallidus, and thalamus, primarily on the left side, but reduced blood flow bilaterally in frontal, parietal, and temporal cortex.
  
  
  CONCLUSIONS
  These data suggest that STN stimulation increases firing of STN output neurons, which increases inhibition of thalamocortical projections, ultimately decreasing blood flow in cortical targets. STN stimulation appears to drive, rather than inhibit, STN output neurons.
mesh_terms: D000200:Action Potentials; D001921:Brain / Q000098:blood supply / Q000000981:diagnostic imaging*; D002540:Cerebral Cortex / Q000098:blood supply / Q000000981:diagnostic imaging; D002560:Cerebrovascular Circulation; D004525:Efferent Pathways / Q000502:physiology; D004599:Electric Stimulation Therapy; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009474:Neurons / Q000502:physiology; D010300:Parkinson Disease / Q000000981:diagnostic imaging / Q000503:physiopathology / Q000628:therapy*; D020531:Subthalamic Nucleus / Q000503:physiopathology*; D014055:Tomography, Emission-Computed