Neural clues to anxiety disorders
Fear is one of the most primitive emotions, having evolved deep in evolutionary history to make sure our ancestors stayed away from bigger, toothier or more poisonous animals. There is a very good reason why some of the most common fears around the world concern snakes and spiders, animals that, if given the chance, could kill in a single bite.
But, if fear is a natural response to external dangers, why is there such a range in the degree to which fear is expressed? Why do some people show almost no fear, while some people are crippled by chronic anxiety disorders such as phobia, panic attacks and OCD?
The scientists implicated two brain regions which act unusually in those individuals vulnerable to anxiety, using fMRI data collected from 23 healthy adults watching a scary scene – a virtual man screaming.
The first of these – the amygdala – is a part of the limbic system, and is responsible for creating feelings that motivate. This includes fear, but also encompasses the pleasurable feelings of eating when hungry, and sexual desires. People with higher levels of anxiety had an overactive amygdala.
The second region, the ventral prefrontal cortex (vPFC), acts to mediate fears and worries. The region is under conscious control, enabling us to stop feelings of terror which would otherwise incapacitate us, such as when we watch a horror film. Participants who had a reduced activity in the vPFC felt more anxiety and fear.
The author’s of the paper hope that this finding may help sufferers of anxiety disorders to overcome their afflictions. “If we can train those individuals who are not naturally good at this to be able to do this, we may be able to help chronically anxious individuals as well as those who live in situations where they are exposed to dangerous or stressful situations” said Sonia Bishop, lead author of the paper.