Time-Frequency Characterization of Resting Brain in Bipolar Disorder during Euthymia-A Preliminary Study

Area of Science:

• Neuroimaging
• Psychiatric Neuroscience
• Brain Activity Analysis

Background:

• Bipolar disorder (BD) is a complex mental health condition.
• Understanding baseline brain activity in euthymic BD patients is crucial for identifying neural correlates.
• Resting-state functional magnetic resonance imaging (rs-fMRI) offers insights into intrinsic brain function.

Purpose of the Study:

• To investigate baseline brain activity in euthymic bipolar disorder (BD) patients.
• To compare brain activity between euthymic BD patients and healthy controls (HC).
• To explore differences using various rs-fMRI analyses, including ALFF, f/ALFF, FC, and ReHo.

Main Methods:

• Utilized resting-state functional magnetic resonance imaging (rs-fMRI) on 42 participants (21 euthymic BD patients, 21 HC).
• Analyzed amplitude of low frequency fluctuations (ALFF), fractional ALFF (f/ALFF), ALFF-based functional connectivity (FC), and regional homogeneity (ReHo).
• Investigated specific frequency bands (slow-4 and slow-5) and performed seed-to-voxel FC analysis.

Main Results:

• BD patients showed increased ALFF in the left insula and increased slow-5 in the left middle temporal pole.
• Increased f/ALFF was observed in several left-sided regions and bilateral thalamus in BD patients.
• BD group had higher ReHo in the left superior medial frontal gyrus and lower ReHo in the right supplementary motor area; significant hyper-connectivity was found in the left insula and connected regions.

Conclusions:

• This study is the first to combine ReHo, ALFF, f/ALFF, and subdivided frequency bands in euthymic BD patients.
• ALFF, f/ALFF, slow-5, and ReHo analyses revealed significant group differences.
• While methods identified group-specific brain regions, no overlap was detected, suggesting complementary roles in understanding BD resting-state abnormalities.