title: Amygdala excitability to subliminally presented emotional faces distinguishes unipolar and bipolar depression: an fMRI and pattern classification study.
abstract: BACKGROUND
  Bipolar disorder and Major depressive disorder are difficult to differentiate during depressive episodes, motivating research for differentiating neurobiological markers. Dysfunctional amygdala responsiveness during emotion processing has been implicated in both disorders, but the important rapid and automatic stages of emotion processing in the amygdala have so far never been investigated in bipolar patients.
  
  
  METHODS
  fMRI data of 22 bipolar depressed patients (BD), 22 matched unipolar depressed patients (MDD), and 22 healthy controls (HC) were obtained during processing of subliminal sad, happy and neutral faces. Amygdala responsiveness was investigated using standard univariate analyses as well as pattern-recognition techniques to differentiate the two clinical groups. Furthermore, medication effects on amygdala responsiveness were explored.
  
  
  RESULTS
  All subjects were unaware of the emotional faces. Univariate analysis revealed a significant group × emotion interaction within the left amygdala. Amygdala responsiveness to sad>neutral faces was increased in MDD relative to BD. In contrast, responsiveness to happy>neutral faces showed the opposite pattern, with higher amygdala activity in BD than in MDD. Most of the activation patterns in both clinical groups differed significantly from activation patterns of HC--and therefore represent abnormalities. Furthermore, pattern classification on amygdala activation to sad>happy faces yielded almost 80% accuracy differentiating MDD and BD patients. Medication had no significant effect on these findings.
  
  
  CONCLUSIONS
  Distinct amygdala excitability during automatic stages of the processing of emotional faces may reflect differential pathophysiological processes in BD versus MDD depression, potentially representing diagnosis-specific neural markers mostly unaffected by current psychotropic medication.
authors.affiliation: Department of Psychiatry, University of Münster, Germany.
authors.forename: Dominik
authors.initials: D
authors.lastname: Grotegerd
authors.forename: Anja
authors.initials: A
authors.lastname: Stuhrmann
authors.forename: Harald
authors.initials: H
authors.lastname: Kugel
authors.forename: Simone
authors.initials: S
authors.lastname: Schmidt
authors.forename: Ronny
authors.initials: R
authors.lastname: Redlich
authors.forename: Peter
authors.initials: P
authors.lastname: Zwanzger
authors.forename: Astrid Veronika
authors.initials: AV
authors.lastname: Rauch
authors.forename: Walter
authors.initials: W
authors.lastname: Heindel
authors.forename: Pienie
authors.initials: P
authors.lastname: Zwitserlood
authors.forename: Volker
authors.initials: V
authors.lastname: Arolt
authors.forename: Thomas
authors.initials: T
authors.lastname: Suslow
authors.forename: Udo
authors.initials: U
authors.lastname: Dannlowski
mesh_terms: D000328:Adult; D000679:Amygdala / Q000098:blood supply* / Q000187:drug effects / Q000503:physiopathology; D000928:Antidepressive Agents / Q000627:therapeutic use; D001714:Bipolar Disorder / Q000145:classification / Q000175:diagnosis* / Q000188:drug therapy; D001931:Brain Mapping; D003865:Major Depressive Disorder / Q000145:classification / Q000175:diagnosis* / Q000188:drug therapy; D004644:Emotions / Q000187:drug effects / Q000502:physiology*; D005145:Face; D005149:Facial Expression; D005260:Female; D006801:Humans; D007091:Image Processing, Computer-Assisted; D008279:Magnetic Resonance Imaging; D008297:Male; D008875:Middle Aged; D010100:Oxygen / Q000097:blood; D010364:Pattern Recognition, Visual / Q000187:drug effects / Q000502:physiology; D010775:Photic Stimulation; D011930:Reaction Time / Q000187:drug effects; D017603:Signal Detection, Psychological
chemical_list: D000928:Antidepressive Agents; D010100:Oxygen
keywords: amygdala; bipolar disorder; depression; fMRI; pattern classification; subliminal emotion processing
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