by Aruna on  October 20, 2009 at 9:13 AM Mental Health News
How Does The Brain Respond To Footsteps In The Dark
Researchers say that the rapid response to approaching footsteps in the dark is hard-wired in the brain.

The study showed that changes in the visual cortex boost brain's sensitivity primed to identify the pursuer in dim light.

The changes occur before people are even conscious of a 'looming sound', the sounds that indicate that something is approaching rapidly.

Lead researcher Vincenzo Romei of the University of Glasgow, UK, recruited 15 volunteers and played them selection of sounds, some of which sounded like they were approaching, while others seemed to be receding or stationary.

They also used transcranial magnetic stimulation (TMS) to stimulate the visual cortex at the back of the brain. It uses magnetic fields to generate weak electrical currents that excite brain cells.

When the researchers used TMS on the visual cortex, it could make people see illusory spots of light called phosphenes. The more sensitive the visual cortex is, the higher the chance of seeing phosphenes.

While all the sounds made the volunteers more likely to see phosphenes during TMS, the looming showed the strongest effect.

The study revealed that volunteers saw phosphenes in 70 per cent of trials in which the looming sound was played, compared with 50 per cent when the sound was stationary, 45 per cent when it was receding and 36 per cent when no sound was played.

"The visual cortex is responding to non-visual stimuli," New Scientist quoted Romei as saying.

Making the visual cortex more sensitive when we hear something approaching could help us to spot threats more quickly in the dark, according to Romei.

"It's important for our survival to respond as fast as possible to something that's approaching fast," Romei added.

"Auditory processing is faster than visual processing, so if the brain gets an auditory signal first, it will be likely to influence the interpretation of subsequent incoming stimuli," said Vincent Walsh of University College London, who was not involved in the study.

The study appears in journal Current Biology.

Source: ANI

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