According to phonological theory, dyslexia, which is a specific impairment in learning to read and write, is characterised by a deficit in the ability to establish correspondence between graphemes (letters) and phonemes (sounds), due to the fact that the phonological representations of these words are insufficiently fine or detailed. ULg researchers have shown the existence of another deficient process: people with dyslexia show difficulties retaining ordered sequences of words in short-term memory. The researchers thus showed that the ability of children in the last year of nursery school to retain short-term verbal information in order was the strongest predictor of their ability to read one year later. The Liège researchers believe that this experimental data further strengthens the value of using the 'phonic method' of learning to read, based on the sequential decoding of letters making up words. Furthermore, by highlighting the importance of sequential processing, they open up one complementary avenue for rehabilitation as a means of treating children with dyslexia.
Language first developed some two million years ago. It is believed that this would have been some kind of sign language. Over the course of genetic evolution, the spoken word emerged, some 150,000 to 200,000 years ago. Written language did not appear until even more recently, with writing dating back only 4,000 years. This is such a recent development that the brain has not had the time to evolve and create specific 'modules' dedicated to the cognitive operations underlying reading and writing. So, as Stanislas Dahaene (1) writes in his publication The Neurons of Reading, the brain has to practice a form of 'recycling', turning to pre-existing cerebral regions used for other functions, the versatility of which the brain uses to redirect them towards the identification of written signs and to connect them with the spoken word.
In this way, reading circuits involving the visual areas and spoken language areas of the brain are created. In 2010, the journal Science published the results of a study conducted by an international team led by Stanislas Dehaene (1), from Inserm (France) and including Régine Kolinsky and José Morais, from the Université Libre de Bruxelles. This work addressed the cerebral activations in adults with varying degrees of literacy, when confronted with a battery of stimuli including written and spoken phrases, words and pseudo-words, i.e. words with no meaning such as 'tincheluche' or 'mupfteux', objects, faces and checker boards. Based on measurements conducted using functional magnetic resonance imaging (fMRI), their research took them to Brazil and Portugal, countries where education was not yet widespread as recently as a few decades ago. Sixty-three adult volunteers took part: 10 illiterate adults, 22 who became literate as adults, and 31 who were literate in childhood.
![Dyslexia]( "Dyslexia.")
What did this study show? By comparing reading scores and corresponding cerebral activity, the researchers showed that the impact of literacy on brain function is much more extensive than previous studies had led to believe, affecting areas of the brain used both for vision and for spoken language. Learning to read thus increased responses from the visual areas of the cortex, not only in the region specialising in the recognition of letters - the brain's 'letterbox' - but also in the primary visual area, where all visual information ends up. Similarly, reading increased responses to spoken language in the auditory cortex involved in coding phonemes. 'These results may correspond to the fact that illiterate people are unable to conduct language games such as deleting the first sound of a word' indicate the study authors. In other words, they can't extract the sound sequence 'aris' from 'Paris' for example.
