Researchers call brain 'task machine'
The portion of the brain responsible for visual reading doesn't require vision at all, according to new research. Presented in the journal Current Biology, the study was funded in part by the EU-funded SEEING WITH SOUNDS (Neural and behavioural correlates of seeing without visual input using auditory-to-visual sensory substitution in blind and sighted') project. SEEING WITH SOUNDS received a Marie Curie International Reintegration Grant worth EUR 100,000 under the Seventh Framework Programme (FP7). Scientists came to this conclusion after brain imaging studies of blind people as they read words in Braille showed activity in precisely the same part of the brain that lights up when sighted readers read. They said their findings challenged the textbook notion that the brain is divided up into regions that are specialised for processing information coming in via one sense or another. 'The brain is not a sensory machine, although it often looks like one; it is a task machine,' says Dr Amir Amedi, senior lecturer at Hebrew University of Jerusalem which led the study. 'A brain area can fulfil a unique function, in this case reading, regardless of what form the sensory input takes.' Unlike other tasks that the brain performs, reading is a recent invention - only about 5,400 years old - and Braille has been in use for less than 200 years. 'That's not enough time for evolution to have shaped a brain module dedicated to reading,' Dr Amedi explains. Previous studies by co-author Laurent Cohen from the Pierre and Marie Curie University in France had showed in sighted readers that a very specific part of the brain, known as the visual word form area (VWFA), has been co-opted for this purpose. But no one knew what happened in the brains of blind people who learn to read without any visual experience. Dr Amedi's team used functional magnetic resonance imaging (fMRI) to measure neural activity in eight people who had been blind since birth while they read Braille words or nonsense Braille. If the brain were organised around processing sensory information, Braille reading would likely depend on regions dedicated to processing tactile information, according to Dr Amedi. If instead the brain were task oriented, the peak of activity should be found across the entire brain in the VWFA, right where it occurs in sighted readers. That is exactly what the researchers discovered. Further comparison of brain activity in blind and sighted readers showed that the patterns in the VWFA were indistinguishable between the two groups. 'The main functional properties of the VWFA as identified in the sighted are present as well in the blind, are thus independent of the sensory modality of reading, and even more surprisingly do not require any visual experience,' the researchers wrote. 'To the best of our judgment, this provides the strongest support so far for the metamodal theory [of brain function]', which suggests that brain regions are defined by the tasks they perform. 'Hence, the VWFA should also be referred to as the tactile word form area, or more generally as the (metamodal) word form area.' The researchers suggest that the VWFA is a multi-sensory integration area that binds simple features into more elaborate shape descriptions, making it ideal for the relatively new task of reading. 'Its specific anatomical location and its strong connectivity to language areas enable it to bridge high-level perceptual word representation and language-related components of reading,' they wrote. 'It is therefore the most suitable region to be taken over during reading acquisition, even when reading is acquired via touch without prior visual experience.' Dr Amedi said the researchers now plan to examine brain activity as people learn to read Braille for the first time, to find out how rapidly this takeover happens. 'How does the brain change to process information in words?' he asks. 'Is it instantaneous?'For more information, please visit: Marie Curie International Reintegration Grant:http://cordis.europa.eu/mariecurie-actions/irg/home.htmlResearch in FP7:http://ec.europa.eu/research/fp7/index_en.cfmCurrent Biology:http://www.cell.com/current-biology/
Countries
France, Israel