Prefrontal activation during a working memory task differs between patients with unipolar and bipolar depression: A...

Area of Science:

• Neuroscience
• Psychiatry
• Medical Imaging

Background:

• Distinguishing bipolar depression (BD) from unipolar depression (UD) in early stages is a significant clinical challenge.
• Functional brain activity patterns may reveal underlying neural differences between BD and UD.
• This study investigates neural activity differences during executive tasks in BD and UD patients.

Purpose of the Study:

• To explore distinct neural activity patterns in the prefrontal cortex between bipolar depression and unipolar depression patients.
• To assess the potential of near-infrared spectroscopy (NIRS) as a diagnostic marker for differentiating between BD and UD.

Main Methods:

• A 52-channel near-infrared spectroscopy (NIRS) scan was conducted on 39 BD patients, 35 UD patients, and 36 healthy controls (HCs).
• Changes in oxygenated hemoglobin ([oxy-Hb]) and deoxygenated hemoglobin ([deoxy-Hb]) were measured during a 1-back working memory task.
• Clinical characteristics, including current mood, were assessed within one week prior to the NIRS examination.

Main Results:

• Both BD and UD patients exhibited reduced [oxy-Hb] activation in the inferior prefrontal region compared to HCs.
• BD patients showed less decreased [oxy-Hb] changes in the left frontopolar cortex (FPC) and Broca's area compared to UD patients.
• No significant correlation was found between clinical characteristics and NIRS measurements.

Conclusions:

• Distinct prefrontal activation patterns observed in BD and UD suggest different neural mechanisms.
• The left frontopolar cortex and Broca's area showed particular differences between BD and UD.
• NIRS-based prefrontal activation measurement shows promise as a potential biomarker for differentiating bipolar from unipolar depression.