title: Mapping the "Depression Switch" During Intraoperative Testing of Subcallosal Cingulate Deep Brain Stimulation.
abstract: OBJECTIVE
  The clinical utility of monitoring behavioral changes during intraoperative testing of subcallosal cingulate deep brain stimulation is unknown.
  
  
  OBJECTIVE
  To characterize the structural connectivity correlates of deep brain stimulation-evoked behavioral effects using probabilistic tractography in depression.
  
  
  METHODS
  Categorization of acute behavioral effects was conducted in 9 adults undergoing deep brain stimulation implantation surgery for chronic treatment-resistant depression in a randomized and blinded testing session at Emory University. Patients were studied from September 1, 2011, through June 30, 2013. Post hoc analyses of the structural tractography patterns mediating distinct categories of evoked behavioral effects were defined, including the best response overall. Data analyses were performed from May 1 through July 1, 2015.
  
  
  METHODS
  Categorization of stimulation-induced transient behavioral effects and delineation of the shared white matter tracts mediating response subtypes.
  
  
  RESULTS
  Among the 9 patients, 72 active and 36 sham trials were recorded. The following stereotypical behavior patterns were identified: changes in interoceptive (noted changes in body state in 30 of 72 active and 4 of 36 sham trials) and in exteroceptive (shift in attention from patient to others in 9 of 72 active and 0 sham trials) awareness. The best response was a combination of exteroceptive and interoceptive changes at a single left contact for all 9 patients. Structural connectivity showed that the best response contacts had a pattern of connections to the bilateral ventromedial frontal cortex (via forceps minor and left uncinate fasciculus) and to the cingulate cortex (via left cingulum bundle), whereas behaviorally salient but nonbest contacts had only cingulate involvement. The involvement of the 3 white matter bundles during stimulation of the best contacts suggests a mechanism for the observed transient "depression switch."
  
  
  CONCLUSIONS
  This analysis of transient behavior changes during intraoperative deep brain stimulation of the subcallosal cingulate and the subsequent identification of unique connectivity patterns may provide a biomarker of a rapid-onset depression switch to guide surgical implantation and to refine and optimize algorithms for the selection of contacts in long-term stimulation for treatment-resistant depression.
authors.affiliation: Department of Psychiatry and Behavioral Sciences, Emory University School of Medicine, Atlanta, Georgia.
authors.forename: Ki Sueng
authors.initials: KS
authors.lastname: Choi
authors.affiliation: Department of Psychiatry and Behavioral Sciences, Emory University School of Medicine, Atlanta, Georgia.
authors.forename: Patricio
authors.initials: P
authors.lastname: Riva-Posse
authors.affiliation: Department of Neurosurgery, Emory University School of Medicine, Atlanta, Georgia.
authors.forename: Robert E
authors.initials: RE
authors.lastname: Gross
authors.affiliation: Department of Psychiatry and Behavioral Sciences, Emory University School of Medicine, Atlanta, Georgia3Department of Neurology, Emory University School of Medicine, Atlanta, Georgia.
authors.forename: Helen S
authors.initials: HS
authors.lastname: Mayberg
mesh_terms: D000328:Adult; D001931:Brain Mapping / Q000379:methods*; D003337:Corpus Callosum / Q000503:physiopathology*; D046690:Deep Brain Stimulation / Q000379:methods*; D003865:Major Depressive Disorder / Q000503:physiopathology* / Q000628:therapy; D061218:Depressive Disorder, Treatment-Resistant / Q000503:physiopathology* / Q000628:therapy; D005260:Female; D006179:Gyrus Cinguli / Q000503:physiopathology*; D006801:Humans; D064795:Intraoperative Neurophysiological Monitoring / Q000379:methods; D008279:Magnetic Resonance Imaging; D008297:Male; D008875:Middle Aged; D009415:Nerve Net / Q000503:physiopathology*; D009434:Neural Pathways / Q000503:physiopathology; D016037:Single-Blind Method; D066127:White Matter / Q000503:physiopathology*