Auditory areas in the brain are split into two pathways for recognizing what a sound is and where it is coming from, which are similar to those used in visual processing.
A study published online in Nature Neuroscience reports conclusive evidence for auditory brain areas being segregated by whether they contribute to recognizing an object -- the 'what' pathway -- or processing where an object is located -- the 'where' pathway.
Previous work had suggested that such segregation might exist for auditory brain areas, but the idea has been controversial. Stephen Lomber and Shveta Malhotra used cooling coils laid on the surface of the brain to reversibly deactivate specific brain areas in cats. They found that when a part of the brain, known as the posterior auditory field, was deactivated by cooling, the cats were unable to indicate where a sound was coming from. However, they could still distinguish between different types of sound patterns, indicating that the 'what' auditory pathway was intact. Conversely, when another nearby part of the brain, the anterior auditory field was deactivated instead, the cats now lost the ability to tell apart different sound patterns, but they could still correctly indicate where a sound was coming from. This suggests that the 'where' pathway was still intact with the anterior auditory field was deactivated. This shows that the posterior auditory field is involved in working out where an auditory object is, and the anterior auditory field is involved in working out what an auditory object is.
The existence of similar segregation in visual and auditory processing suggests that this could be a general organization principle in the brain.
Stephen Lomber (University of Western Ontario, Canada)
Abstract available online.
(C) Nature Neuroscience press release.
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