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Brain region responsible for perceiving sound space identified

Scientists have identified a region in the brain that is responsible for perceiving sound space i.e. the location of sounds.

Washington, September 20 : Scientists have identified a region in the brain that is responsible for perceiving "sound space" i.e. the location of sounds.

Leon Y. Douell of The Hebrew University of Jerusalem and University of California at Berkeley and colleagues claim that their study settles a controversy in earlier studies that failed to establish the auditory region called the planum temporale as responsible for perceiving auditory space.

Previous studies had shown that the planum temporale was activated when people were asked to perform tasks in which they located sounds in space. But many researchers believed that the region was responsible only for intentional processing of such information.

Earlier studies had also failed to establish that the planum temporale was responsible for automatic, nonintentional representation of spatial location, according to background information in a report in the journal Neuron, published by Cell Press.

In the present study, Deouell and colleagues used an improved experimental design, which enabled them to determine the brain's auditory spatial location centre more sensitively.

The researchers presented human subjects with sounds against a background of silence, used headphones that more accurately reproduced sound location, used noise with a rich spectrum that has been shown to be more readily locatable in space, and created an individually tailored sound space for each subject by using sounds previously recorded directly from the subjects' own ears.

During the course of study, the volunteers wearing the headphones were exposed to bursts of the noise, and their brains were scanned by functional magnetic resonance imaging.

The subjects had been instructed to ignore the sounds. In order to divert their attention, the subjects either watched a movie with the sound turned off or were given a simple button-pushing task.

Upon varying the position of the noise bursts in space, the researchers found that the planum temporale in the subjects' brain was activated.

The greater the number of distinct sound locations subjects heard during test runs, the greater the activity in the planum temporale, said the researchers.

They said that their experiments "suggest that neurons in this region represent, in a nonintentional or preattentive fashion, the location of sound sources in the environment."

"Space representation in this region may provide the neural substrate needed for an orientation response to critical auditory events and for linking auditory information with information acquired through other modalities," the researchers added.

ANI