Abnormal amygdala-prefrontal effective connectivity to happy faces differentiates bipolar from major depression.
BACKGROUND
Bipolar disorder is frequently misdiagnosed as major depressive disorder, delaying appropriate treatment and worsening outcome for many bipolar individuals. Emotion dysregulation is a core feature of bipolar disorder. Measures of dysfunction in neural systems supporting emotion regulation might therefore help discriminate bipolar from major depressive disorder.


METHODS
Thirty-one depressed individuals-15 bipolar depressed (BD) and 16 major depressed (MDD), DSM-IV diagnostic criteria, ages 18-55 years, matched for age, age of illness onset, illness duration, and depression severity-and 16 age- and gender-matched healthy control subjects performed two event-related paradigms: labeling the emotional intensity of happy and sad faces, respectively. We employed dynamic causal modeling to examine significant among-group alterations in effective connectivity (EC) between right- and left-sided neural regions supporting emotion regulation: amygdala and orbitomedial prefrontal cortex (OMPFC).


RESULTS
During classification of happy faces, we found profound and asymmetrical differences in EC between the OMPFC and amygdala. Left-sided differences involved top-down connections and discriminated between depressed and control subjects. Furthermore, greater medication load was associated with an amelioration of this abnormal top-down EC. Conversely, on the right side the abnormality was in bottom-up EC that was specific to bipolar disorder. These effects replicated when we considered only female subjects.


CONCLUSIONS
Abnormal, left-sided, top-down OMPFC-amygdala and right-sided, bottom-up, amygdala-OMPFC EC during happy labeling distinguish BD and MDD, suggesting different pathophysiological mechanisms associated with the two types of depression.
Almeida
Jorge Renner Cardoso de
JR
Department of Psychiatry, University of Pittsburgh, School of Medicine, Pittsburgh, Pennsylvania, USA.
Versace
Amelia
A
Mechelli
Andrea
A
Hassel
Stefanie
S
Quevedo
Karina
K
Kupfer
David Jerome
DJ
Phillips
Mary Louise
ML
D000328:Adult; D000679:Amygdala / Q000503:physiopathology*; D001714:Bipolar Disorder / Q000175:diagnosis* / Q000503:physiopathology*; D016022:Case-Control Studies; D003865:Major Depressive Disorder / Q000175:diagnosis* / Q000503:physiopathology*; D003937:Diagnosis, Differential; D004644:Emotions / Q000502:physiology; D005149:Facial Expression; D005260:Female; D006801:Humans; D008297:Male; D008959:Models, Neurological; D009434:Neural Pathways / Q000503:physiopathology; D017397:Prefrontal Cortex / Q000503:physiopathology*