As Stanislas Dehaene continues, he speaks of the difficulties which cause it to be more difficult to learn to read and those which make it difficult to become an effective reader. He emphasizes that reading is complex and that there are many potential interferences which can be present in isolation or in combinations. Most importantly, he emphasizes that, due to brain plasticity, children can learn to read who are given appropriate assistance, who remain engaged, and who are given time…
- Expert reading depends on a fortuitous combination of cerebral connections that luckily preexist in our primate brains and take years of training to convert to a new use. One mishap in the circuitry is enough to bring the fragile process of neuronal recycling to a grinding halt.
- Ramus and his colleagues do not deny, however, that a minority of dyslexic children presents with a visual deficit and no phonological impairment. In conclusion, we should perhaps question the very idea of a single cause for dyslexia. I therefore think it very likely that dyslexia arises from a joint deficit of vision and language.
- The left occipito-temporal region, at the precise location of the letterbox area, was the only part of the brain to be strongly underactivated in dyslexics. It showed reduced activity, not only for words, but, more surprisingly, for images. In brief, it seemed to be spectacularly dysfunctional.
- In dyslexics, the left occipito-temporal region does not seem able to simultaneously recognize all the letters that constitute a word – an anomaly that readily explains their slow reading and the persistence of the influence of the number of letters on reading time. This length effect often remains present in dyslexics when it has vanished in normal readers.
- Although I can certainly empathize with these feelings of despondency, they are totally misguided. They betray two frequent misconceptions about brain development. The first consists of thinking that biology rhymes with rigidity, as if genes dictated inalterable, ironclad laws that will govern our organisms for the rest of our lives.
- It is striking that one of the most sensitive tests for the detection of dyslexia consists of measuring the speed at which children name digits and pictures – a task that does not specifically target phonological processing. Across large groups of children, phonology and fast naming tests explain separate parts of the differences in reading scores – a finding which implies that while a majority of children predominantly suffer from phonological deficits, the difficulty in others comes from another source, perhaps the automatization of the links between vision and language.
- Progressively, however, our ventral system learns to break with symmetry. It stops considering “b” and “d” as two views of the same object. Ultimately, it assigns them neuronal populations that cease to generalize across mirror reversals.
- Visuospatial attention is of paramount importance to the normal development of reading. Good decoding skills do not arise from associations between letters and speech sounds alone – letters must be perceived in their proper orientation, at the appropriate spatial location, and in their correct left-right order. In the young reader’s brain, collaboration must take place between the ventral visual pathway, which recognizes the identity of letters and words, and the dorsal pathway, which codes for location in space and programs eye movements and attention. When any of these actors stumbles, reading falls flat on its face.
Reading in the Brain, Part 1 http://wp.me/p45V7Y-7a