Free will takes flight: how our brains respond to an approach...( Wellcome Trust scientists have ident...),Health

Wellcome Trust scientists have identified for the first time how our brain's response changes the closer a threat gets. Using a "Pac Man"-like computer game where a volunteer is pursued by an artificial predator, the researchers showed that the fear response moves from the strategic areas of the brain towards more reactive responses as the artificial predator approaches.

When faced with a threat, such as a large bear, humans, like other animals, alter their behaviour depending on whether the threat is close or distant. This is because different defence mechanisms are needed depending on whether, for example, the bear is fifty feet away, when being aware of its presence may be enough, or five feet away, when we might need to fight or run away.

To investigate what happens in the brain in such a situation, researchers at the Wellcome Trust Centre for Neuroimaging at UCL, London, created a game where subjects were chased through a maze by an artificial predator if caught, they would receive a mild electric shock. The researchers then measured their brain activity using functional magnetic resonance imaging (fMRI). The results are published today in the journal Science.

When the artificial predator was in the distance, the researchers observed activity in lower parts of the prefrontal cortex just behind the eyebrows. Activity in this area known as the ventromedial prefrontal cortex increases during anxiety and helps control strategies on how to respond to the threat.

However, as the predator moved closer, the brain activity shifted to a region of the brain responsible for more primitive behaviour, namely the periaqueductal grey. The periaqueductal grey is associated with quick-response survival mechanisms, which include fight, flight and freezing. This region is also associated with the body's natural pain killer, opioid analgesia, preparing the body to react to pain.

Dr Dean Mobbs from UCL, lead author on the study,
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