Abnormal functional connectivity of the medial cortex in euthymic bipolar II disorder

Area of Science:

• Neuroscience
• Psychiatry
• Medical Imaging

Background:

• Bipolar II disorder is characterized by mood fluctuations.
• Understanding neural circuitry in the euthymic state is crucial for identifying trait pathology.
• Cortical midline structures (CMS) are implicated in mood regulation and cognitive functions.

Purpose of the Study:

• To investigate functional connectivity within CMS in euthymic individuals with bipolar II disorder.
• To identify aberrant neural circuits associated with bipolar II disorder.
• To explore the potential of CMS dysfunction as a trait marker for bipolar II disorder.

Main Methods:

• Functional magnetic resonance imaging (fMRI) was used.
• A motor activation paradigm was employed.
• Functional connectivity analyses were performed on 19 subjects with bipolar II disorder and 18 healthy controls.

Main Results:

• Increased functional connectivity was observed in two CMS circuits in bipolar subjects compared to controls.
• Aberrant connectivity involved medial and dorsolateral regions of the superior frontal gyrus.
• Specific circuits identified included connections within the left and right superior frontal gyri and right medial frontal gyrus.

Conclusions:

• CMS circuit dysfunction persists in the euthymic state of bipolar II disorder, suggesting trait pathology.
• These findings may inform future research on the role of superior frontal circuitry in default mode network and cognitive processes.
• Further studies are needed to determine if these circuits contribute to illness relapse.