Characteristics of oxygenated hemoglobin concentration change during pleasant and unpleasant image-recall tasks in patients with depression: Comparison with healthy subjects.

Aim: Patients with major depressive disorder (MDD) have been reported to show cognitive impairment in attention, cognition control, and motivation. The prefrontal cortex plays an important role in the pathophysiology of depression. Neurophysiological abnormalities have been examined in MDD patients by several neuroimaging studies. However, the underlying neural mechanism is still unclear. We evaluated brain function during pleasant and unpleasant image-recall tasks using multichannel near-infrared spectroscopy (NIRS) in MDD patients.

Methods: The subjects were 25 MDD patients and 25 age- and sex-matched healthy controls. Patients were classified according to DSM-IV-TR criteria. We measured the oxygenated hemoglobin concentration change (δoxyHb) in the forehead and temporal lobe during image-recall task with pleasant (e.g., puppy) and unpleasant (e.g., snake) images using NIRS. To check whether all subjects understood the task, they were asked to draw pictures of both image tasks after NIRS measurement.

Results: The δoxyHb in the healthy group was significantly higher than that in the MDD group in the bilateral frontal region during the unpleasant condition. A significant negative correlation between the Hamilton Rating Scale for Depression score and δoxyHb was observed in the left frontal region during the unpleasant condition.

Conclusion: We suggest that image-recall tasks related to emotion measured by NIRS might be a visually useful psychophysiological marker to understand the decrease in the frontal lobe function in MDD patients. In particular, we suggest that the decrease in δoxyHb in the left frontal lobe is related to the severity of depression.