Physical activity is associated with left corticospinal tract microstructure in bipolar depression

Area of Science:

• Neuroimaging
• Psychiatry
• Neuroscience

Background:

• Psychomotor retardation and reduced daily activities are key symptoms of bipolar disorder (BD) depression.
• Understanding the neural basis of motor deficits in BD is crucial for effective treatment.

Purpose of the Study:

• To investigate white matter microstructure in the motor system of BD patients during depression.
• To examine the association between motor activity levels and white matter integrity in the motor tracts of BD patients.

Main Methods:

• Diffusion tensor imaging (DTI) and tractography were used to analyze white matter microstructure of motor tracts (CST, M1, pre-SMA) in 19 BD patients and 19 healthy controls (HC).
• Quantitative motor activity was measured using 24-hour actigraphy.
• Tract-based spatial statistics (TBSS) and optic radiation analysis were used for comparison.

Main Results:

• BD patients exhibited lower activity levels (AL) compared to HC.
• A significant increase in fractional anisotropy (FA) was observed in the left corticospinal tract (CST) of BD patients.
• A significant group by activity level interaction indicated a positive association between FA and AL in the left CST of BD patients.

Conclusions:

• White matter microstructure of the left CST is altered in bipolar disorder during depression.
• The positive association between motor activity and left CST microstructure suggests a potential compensatory mechanism for psychomotor retardation in BD.