[Functional brain basis of pathophysiology in depression].

Recently, numerous brain imaging studies have been performed to clarify the pathophysiology of depression. These studies suggest that the neural network, physiological function, and their interaction are related to the development of depressive symptoms. In this article, we present our neuroimaging studies employing functional magnetic resonance imaging (fMRI) and magnetoencephalography (MEG) on the functional basis of depression involving the brain. At first, because of the influence of stressful life events on depression, sex differences in the cognition of psychosocial stressors, the change in the sensory gating system under stressful conditions, and the mechanism of psychological ways to adapt to stressful events were examined. The results revealed the importance of prefrontal cortex (PFC) function in stress regulation. Next, some important changes in the PFC were shown in depression using well-known neuropsychological tasks and originally created tasks related to depressive symptoms. Moreover, these changes in the brain might be a possible biological marker of the treatment response and functional recovery. Then, we focused on the neurophysiological role of serotonin in higher cognitive function in the human brain. It was found that serotonin differentially regulated reward-predictive activities at different time scales in the striatum-PFC network. Finally, the brain mechanism of cognitive behavioral therapy (CBT) was examined. Brain activation in the PFC and functional connectivity between the PFC and amygdala on receiving negative emotional stimuli were weakened after CBT. From these findings, the functional basis of the pathophysiology of depression in the brain was discussed.