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How Learning To Read Changes The Brain. Extent And Origins Of Expertise For Reading In The Visual System| old_uid | 9088 |
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| title | How Learning To Read Changes The Brain. Extent And Origins Of Expertise For Reading In The Visual System |
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| start_date | 2010/09/24 |
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| schedule | 11h-12h |
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| online | no |
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| location_info | salle des Voûtes |
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| summary | One of most intriguing issues concerning how culture affects the brain is the question of how learning to read changes existing cerebral
mechanisms. Reading was invented only ~5400 years ago and there was no sufficient time to evolve a brain system devoted to visual word recognition. Reading is thus very different from spoken language, which appeared in our history about 100,000 years ago, and is most likely a biologically evolved capacity with a genetic background. Yet, learning to read leads to specific and very reproducible changes in brain circuitry. Here we used functional Magnetic Resonance Imaging in normal human subjects to address two outstanding questions about the impact of reading on the visual brain.
1) An intriguing fact about reading is that it always activates a very specific part of the high level visual system in the left
occipitotemporal sulcus (~0.5 cm SD between subjects’ peak activations). Since the capacity to read is not an evolved one, it is difficult to explain why reading systematically draws upon the same cortical location in all subjects and cultures. Here we demonstrate that the reading areas fall into a part of the high-level object recognition system that is particularly sensitive to the presence of line junctions such as T or Y. Since it has been shown previously that such line junctions are features useful for object recognition, the acquisition of reading skills might result from a “recycling” of occipito-temporal circuitry for object recognition into neural networks specialized for visual word recognition. This would explain the reproducible location of reading areas.
2) Which levels of the visual system are actually modified through the acquisition of literacy? The visual system has a hierarchical
architecture. Simple feature analysis (e.g. the detection line orientation) is being done in early visual areas which then converge on
high-level visual areas responding to complex stimuli such as faces or objects. Several neuroimaging studies have shown that reading skills can be linked to a particular sub-region of the high-level visual system. Here we investigated whether reading also relies on perceptual learning within early visual areas (perceptual learning is a form of implicit learning that involves improvement in sensory discrimination by repeated exposure to stimuli). To that aim, we matched written words and line-drawings of objects for their low-level visual features, and designed control images by scrambling procedures that keep local features intact. Greater responses to words than objects were found not only in high level visual areas, but also early visual areas V1-V4.
These early visual activations might express the consolidated effects from prior perceptual learning under the pressure for fast, parallel
processing that is more prominent in reading than other visual cognitive processes. The impact of literacy on the brain is thus more widespread than previously thought. |
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| responsibles | Pélissier |
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