The Brain During Stress
The prefrontal cortex (Figure 3) is another key brain region in the regulation of mood. It is a very specialized and advanced area present at the front of the brain, and is highly developed in humans. This is where advanced thinking, planning, and problem solving can occur. The prefrontal cortex is highly interconnected with the limbic system, and plays a very important role in the regulation of mood.
How can stress be harmful to the brain?
Some of the symptoms of depression such as recurrent negative thought patterns and lack of motivation are thought to arise from dysfunction in this area. Brain images from depressed individuals show different patterns of metabolism in key prefrontal regions of the brain when compared with people without depression.
Depression most likely occurs when there is dysregulation between important circuits involved in the regulation of mood. Areas that are known to be important are parts of the cortex, especially regions known as the prefrontal cortex (Figure 3). These areas are closely connected with the hippocampus and amygdala. When these areas are not functioning properly, alterations in mood can result.
It is not known exactly how stress has its harmful effects on the brain, but it is known that stress is associated with cell loss in specific brain regions, especially the hippocampus and prefrontal cortex. Brain scans of patients with depression have shown that these areas are smaller on average in people with depression. Following antidepressant treatment, these effects are reversed. It is thought that antidepressant treatment can cause neurons to become healthy again to support normal mood regulation. It is thought that stress causes degeneration of healthy neurons, and suppresses the formation of new neurons. When there is a net loss of cells in a particular brain region, this region can no longer interact adequately with other brain regions in supporting normal brain function.
Once there is dysregulation in one part of the brain, it will affect how that area interacts with other brain regions. This can lead to a series of convergent symptoms such as depressed mood, over-emphasis on negative thoughts, increased anxiety and anxiety-related memories. The amygdala, hippocampus and prefrontal cortex all interact with the hypothalamus, a region of the brain important for regulation of feeding, sleeping, and sexual function. All of these things are also typically dysregulated in mood disorders. One goal of treatment, therefore, is to try to restore neurons to a healthy state of functioning, which in turn restores the functioning of the circuits that interact with that brain region.