Abnormal brain activation during emotion processing of euthymic bipolar patients taking different mood stabilizers

Area of Science:

• Neuroscience
• Psychiatry
• Neuroimaging

Background:

• Functional magnetic resonance imaging (fMRI) studies on emotion processing in bipolar disorder (BD) yield inconsistent results, partly due to varying medication histories.
• Existing research has not comprehensively investigated the brain functional effects of different mood stabilizers on emotion processing in BD patients.
• Understanding these effects is crucial for optimizing treatment strategies and addressing enduring impairments in euthymic BD.

Purpose of the Study:

• To compare emotion processing in euthymic bipolar disorder (BD) patients treated with lithium versus valproate, and healthy controls (HC).
• To investigate the brain functional effects of lithium and valproate on emotion processing using fMRI.
• To identify potential differences in neural activation patterns associated with different mood stabilizer treatments.

Main Methods:

• fMRI was used to assess brain activity during two emotional tasks (everyday objects/scenes and facial expressions) in three groups: BD patients on lithium (N=13), BD patients on valproate (N=16), and healthy controls (HC; N=16).
• Participants were euthymic at the time of the study.
• Statistical analyses compared brain activation patterns between the groups in response to positive versus neutral stimuli.

Main Results:

• Bipolar disorder (BD) patients treated with lithium exhibited significantly increased fMRI activation in the right dorsal anterior cingulate cortex and bilateral lingual gyrus in response to positive stimuli compared to neutral stimuli.
• This increased activation in BD patients on lithium was more pronounced than in BD patients on valproate and healthy controls.
• No abnormal amygdala activation was observed in any group, and no significant differences were found between BD patients on valproate and healthy controls.

Conclusions:

• Lithium and valproate appear to have differential effects on brain activity during emotion processing in euthymic bipolar disorder (BD) patients.
• The findings suggest that lithium may modulate neural responses to positive emotional stimuli differently than valproate.
• While suggestive of distinct treatment effects, the study's cross-sectional design and small sample size preclude establishing causality.