Scientists using a computer game have discovered how the brain's response to fear changes as a threat gets nearer in a development that could help people suffering from panic attacks.
Two key areas of the brain are involved in fear, with the more impulsive region taking over as a threat looms closer. A malfunctioning in the balance between the two could explain some anxiety disorders, researchers believe.
To find out exactly where our fear resides, British scientists scared volunteers with a Pac Man-like computer game, in which subjects were chased through a maze by an artificial predator. If caught, they received a mild electric shock.
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.
The findings by Dean Mobbs and colleagues at the Wellcome Trust Centre for Neuroimaging at University College London were reported in the journal Science on Thursday.
"It's a bit like a see-saw — both regions play a role but one becomes more dominant at different stages of threat," Mobbs said.
Understanding the shifts in activities between the forebrain and midbrain regions may be crucial.
In particular, it seems the prefrontal cortex helps control more primitive systems in the brain and loss of this regulation could explain why people with panic disorders overreact to situations that pose no immediate threat.
The new research builds on similar findings in animals, including a test on rodents in 2005. That found rats with a non-functioning prefrontal cortex did not cope with stress as well as those with normal brains.
From an evolutionary perspective, maintaining the correct balance between the different regions of the brain that handle fear helps animals escape being eaten.
"The most efficient survival strategy will depend on the level of threat we perceive," Mobbs said.
"This makes sense as sometimes being merely wary of a threat is enough, but at other times we need to react quickly. The closer a threat gets, the more impulsive your response will be -- in effect, the less free will you will have."
