Dorsolateral prefrontal hemodynamic responses during a verbal fluency task in hypomanic bipolar disorder

Area of Science:

• Neuroscience
• Psychiatry
• Medical Imaging

Background:

• Neuroimaging studies indicate prefrontal cortex dysfunction in bipolar disorder (BD).
• The specific characteristics of prefrontal hemodynamic responses during manic states in BD remain unclear.
• Understanding these differences is crucial for accurate diagnosis and treatment.

Purpose of the Study:

• To compare prefrontal hemodynamic responses during a cognitive task between hypomanic and depressive states in BD patients.
• To longitudinally assess changes in prefrontal hemodynamics from hypomanic to euthymic states.
• To investigate the utility of near-infrared spectroscopy (NIRS) in evaluating state-dependent prefrontal function in BD.

Main Methods:

• Near-infrared spectroscopy (NIRS) was used to measure prefrontal hemodynamic responses during a verbal fluency task (VFT).
• Participants included 27 patients with BD (11 hypomanic, 16 depressed) and 12 healthy controls (HCs).
• Eight hypomanic patients underwent a follow-up NIRS measurement after symptom resolution.

Main Results:

• No significant differences in VFT performance were observed among hypomanic, depressed, and HC groups.
• Both BD groups showed reduced prefrontal activation compared to HCs.
• Hypomanic patients exhibited greater left dorsolateral prefrontal cortex (DLPFC) activation than depressed patients, correlating positively with symptom severity.

Conclusions:

• Prefrontal hemodynamic responses during cognitive activation vary between hypomanic and depressive states in BD.
• NIRS is a valuable tool for objectively assessing state-dependent prefrontal hemodynamics in BD.
• These findings highlight the potential of NIRS for characterizing mood-state specific brain alterations in bipolar disorder.