Contrasting and convergent patterns of amygdala connectivity in mania and depression: a resting-state study

wMania and depression in bipolar disorder (BP) manifest two extremes of aberrant emotional, physiologic and behavioral arousal states despite similarities in treatment response and neurocognitive deficits. We used resting-state functional magnetic resonance imaging (rsfMRI) to explore the common and unique abnormal functional connectivity underlying acute manic or depressed state in BP.

18 Patients with bipolar mania (BM), 10 patients with bipolar depression (BD) and 28 healthy controls underwent resting-state functional magnetic resonance imaging scanning. Left and right amygdala seed-to-voxel based functional connectivity were assessed and compared among the three groups. The relationships between aberrant functional connectivity and the severity of clinical symptoms, number of episodes, illness duration were investigated.

Compared to healthy controls, both BM and BD groups showed reduced functional connectivity between bilateral amygdala and inferior frontal gyrus (orbital), striatum, right lingual gyrus and posterior cerebellar lobe. Furthermore right amygdala-hippocampal connectivity was decreased in BD but increased in BM. No significant correlations were found between strength of abnormal functional connectivity and clinical characteristic in BD or BM.

No euthymic subjects were recruited, and the patients in current study were all on medication.

The presence of substantial overlap in the pattern of disturbed connectivity between amygdala and frontal, striatal, lingual and cerebellar regions suggests mood state-independent dysconnectivity. The contrasting pattern of functional connectivity between right amygdala and hippocampus in BD and BM provides a novel lead to the probable mechanistic differences in these two extremes of mood states.