Striatal and CMS activation, connectivity linked to depression in BD II
MedWire News: Striatal and cortical midline structure (CMS) activation and connectivity abnormalities are associated with depression in patients with bipolar II disorder, US research suggests.
Writing in the Journal of Affective Disorders, William Marchand (University of Utah, Salt Lake City) and team explain: "Considerable evidence implicates dysfunction of striatal and CMS circuitry in mood disorders."
But they add that it is not known whether such dysfunction is associated with depression in BD II patients.
To investigate, the researchers studied 16 unmedicated BD II patients with depression and 19 mentally healthy controls without a family history of psychiatric disorders in first-degree relatives. Only male participants were recruited to avoid gender-related differences.
Functional magnetic resonance imaging was used to assess striatal and CMS activation and connectivity among the participants while they performed a complex motor task.
The researchers found that, in the BD II patients, there were negative correlations between a history of suicidal ideation and activation of the left striatum (putamen).
In contrast, positive correlations were identified between depression severity, as measured using Montgomery-Asberg Depression Rating Scale scores, and activation of a cluster consisting of the left thalamus and surrounding region, and a cluster including portions of the left precentral gyrus.
Compared with controls, BD II patients had decreased functional connectivity between the left striatum (putamen) and a cluster containing portions of the bilateral CMS (precuneus).
Conversely, BD II patients demonstrated increased connectivity between the right striatum and a cluster involving portions of the right inferior parietal lobule and primary somatosensory cortex, compared with controls.
The team also found that depression severity was positively correlated with connectivity strength between the bilateral striatum and right lingual gyrus and surrounding region, as well as with the left cerebellum (declive).
Marchand and team conclude: "We provide the first evidence that functional abnormalities of the striatum and CMS, including connectivity between the two regions, are associated with BD II depression."
They add: "If replicated, the findings reported herein may advance our understanding of the general neurobiology of bipolar II depression as well as that of suicidal ideation, which is frequently associated with this condition."
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By Mark Cowen