Reuters has a report on how the brain reacts to fear. Subjects were instructed to play a pac-man like game where they tried to evade a predator. When they were caught, subjects received a mild shock. While the subjects were playing the research team was performing brain scans on them to determine how fear affects the brain.

Simultaneous brain scans measuring blood flow showed that when the predator was distant, lower parts of the prefrontal cortex area of the brain behind the eyebrows were active. This region is associated with complex decision-making, such as planning an escape. But when the predator moved closer, activity shifted to the periaqueductal grey area, responsible for quick-response survival mechanisms such as fighting, flight or freezing.

This builds on previous research on mice lacking a functioning prefrontal cortex. These mice did not handles stress as well as their wildtype counterparts. It is theorized that a healthy balance between prefrontal cortex and periaqueductal is required for successful resolution of stress.

People with anxiety problems may have a tendency to use parts of their brain more associated with quick-response survival. This would keep them perpetually “on their toes” and unable to form a long term plan to deal with stress.