title: Regional fMRI hypoactivation and altered functional connectivity during emotion processing in nonmedicated depressed patients with bipolar II disorder.
abstract: OBJECTIVE
  Although the amygdala and ventrolateral prefrontal cortex have been implicated in the pathophysiology of bipolar I disorder, the neural mechanisms underlying bipolar II disorder remain unknown. The authors examined neural activity in response to negative emotional faces during an emotion perception task that reliably activates emotion regulatory regions.
  
  
  METHODS
  Twenty-one nonmedicated depressed bipolar II patients and 21 healthy comparison subjects underwent functional MRI (fMRI) while performing an emotional face-matching task. Within- and between-group whole-brain fMRI activation and seed-based connectivity analyses were conducted.
  
  
  RESULTS
  In depressed bipolar II patients, random-effects between-group fMRI analyses revealed a significant reduction in activation in several regions, including the left and right ventrolateral prefrontal cortices (Brodmann's area [BA] 47) and the right amygdala, a priori regions of interest. Additionally, bipolar patients exhibited significantly reduced negative functional connectivity between the right amygdala and the right orbitofrontal cortex (BA 10) as well as the right dorsolateral prefrontal cortex (BA 46) relative to healthy comparison subjects.
  
  
  CONCLUSIONS
  These findings suggest that bipolar II depression is characterized by reduced regional orbitofrontal and limbic activation and altered connectivity in a fronto-temporal circuit implicated in working memory and emotional learning. While the amygdala hypoactivation observed in bipolar II depression is opposite to the direction seen in bipolar I mania and may therefore be state dependent, the observed orbitofrontal cortex hypoactivation is consistent with findings in bipolar I depression, mania, and euthymia, suggesting a physiologic trait marker of the disorder.
authors: David Geffen School of Medicine , University of California, Los Angeles, CA, USA. vizuetan@gmail.com
authors: Nathalie
authors: N
authors: Vizueta
authors: Jeffrey D
authors: JD
authors: Rudie
authors: Jennifer D
authors: JD
authors: Townsend
authors: Salvatore
authors: S
authors: Torrisi
authors: Teena D
authors: TD
authors: Moody
authors: Susan Y
authors: SY
authors: Bookheimer
authors: Lori L
authors: LL
authors: Altshuler
mesh_terms: D000328:Adult; D000679:Amygdala / Q000503:physiopathology; D001714:Bipolar Disorder / Q000503:physiopathology*; D001921:Brain / Q000503:physiopathology*; D016022:Case-Control Studies; D004644:Emotions / Q000502:physiology*; D005260:Female; D005625:Frontal Lobe / Q000503:physiopathology; D059907:Functional Neuroimaging; D006801:Humans; D008279:Magnetic Resonance Imaging; D008297:Male; D009434:Neural Pathways / Q000503:physiopathology; D017397:Prefrontal Cortex / Q000503:physiopathology