Running Scared

One very promising approach to understanding many psychological problems is to look at them from an evolutionary perspective: to see if clinical observations can be re-framed around the evolution of the brain.

Our brains are a hodgepodge of bits and pieces that have evolved over millions of years. We still have regions that evolved in reptiles, as well as the stunningly complex neocortex that has been developing over the last few hundred thousand years. Most of the time the different systems and circuits cooperate, but that cooperation falls apart if people are under the influence of alcohol or dugs, or in different types of neurological and psychological problems. Then the older and more “primitive” regions of the brain take over. That is typically what happens when a drunk wants becomes irritable or wants to fight. It is also what can happen in people who have sustained damage or have abnormal development of the frontal lobes of the brain. Alternatively it may happen if something over-stimulates the primitive regions of the brain.

Colleagues in London have been doing experiments with a computer game that could be immensely valuable for people with panic attacks and some types of anxiety disorders.

Working with healthy volunteers, Dean Mobbs and colleagues at the Wellcome Trust Centre for Neuroimaging at University College, London, used 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.

At the same time, brain scans measuring blood flow showed that when the predator was a long way off, lower parts of the prefrontal cortex area of the brain 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 gray area, which is responsible for rapid response survival mechanisms such as fighting, flighting or freezing.

This shows us that the brain’s response to fear changes as a threat gets nearer: the more impulsive region takes over from the decision-making regions as a threat looms closer. A problem in the balance between the two regions could explain some anxiety disorders. Most sufferers report that they “know” that their fears are illogical, but they react anyway. So the key question is what is it that shifts the balance of activities between the forebrain and midbrain regions of the brain?

This new research is published in the journal Science, and builds on similar findings in animals, including tests on rats that were performed at the University of Colorado in Boulder and published in 2005. In those experiments 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 help animals to avoid or escape predators.

There are some situations where we only have to be wary about potential threats, but other times we need to react without thought. The closer a threat, the more impulsive will be your response. If the threat is large enough and close enough we lose any semblance of free will and just take action.

Just as happens when someone is in the throes of a severe anxiety attack.