Scientists find brain mechanism that counters fear

London: Scientists have identified a brain mechanism which makes a person fearless, a discovery they say could lead to a new treatment for those suffering from regular anxiety attacks.

More than one in four people are likely to experience a bout of anxiety at some point in their lives. With symptoms like sweating, raised heart rate and churning stomach, the condition sometimes becomes so severe that it can be classified as a psychiatric disorder.

But, researchers at Stanford University in California found that by stimulating a brain circuit within a structure of grey matter could help counter fear, the Daily Mail reported.

Tests on mice showed that triggering the mechanism with pulses of light boosted their willingness to take risks, while inhibiting it rendered them more timid.

Professor Karl Deisseroth, who led the research, said the finding opened the possibility of improved medications to help control anxiety disorders because the human brain is structured in the same way.

The team were able to pinpoint the phenomenon by working with a technology called optogenetics, where nerve cells are rendered photo-sensitive so their action can be turned on or off by different wavelengths of light.

They targeted a circuit within the amygdala region of the brain and found dramatic changes in the behaviour of mice.

"They suddenly became much more comfortable in situations they would ordinarily perceive as dangerous and, therefore, be quite anxious in," said Prof Deisseroth.

For example, rodents ordinarily try to avoid wide-open spaces such as fields because such places leave them exposed to predators.

But in simulations of both open and covered areas the willingness of mice to explore the open areas increased profoundly as soon as light was pulsed into the brain circuit.

Pulsing that same circuit with a different, inhibitory frequency of light produced the opposite result — the mice instantly became more anxious and "hunkered down".

The new findings were published online in journal Nature.