Abstract
Recent near-infrared spectroscopy (NIRS) studies have shown frontotemporal hypofunction in depression by using a verbal fluency task, but the regions of impairment affecting respective depressive symptoms still remain unclear. We investigated the frontotemporal function during a word production task in patients with depression by multi-channel NIRS. Further, we aimed to clarify whether any depressive symptoms affect frontotemporal dysfunction. One hundred seventy-seven major depressive patients and 50 healthy control volunteers participated in this study. After we provided complete explanations to the subjects, the study was approved by the ethics committee of Nippon Medical School Chiba Hokusoh Hospital. Their cerebral activations were compared during the verbal fluency task. Significant hypoactivation in the bilateral frontotemporal regions was observed in depressed patients, compared with controls. Left lateral frontotemporal activation was significantly reduced in the group with the mandatory symptom, which is a depressed mood, or loss of interest or pleasure, compared with the patients that still had residual depressive symptoms in spite of major depressive disorder having been remitted. Our findings indicate hypofunction of the bilateral frontotemporal regions in depression during the verbal fluency task. Further, hypofunction of the left frontotemporal including the dorsolateral prefrontal cortex by this task could reflect whether the subjects recovered from the depressed mood, or loss of interest or pleasure.
