Within this dys-constellation, we are now going to talk about the co-occurrence of dyslexia with oral language difficulties. First of all, a distinction should be made between oral language difficulties at the level of production and at the level of perception. For production, in his publication, in his latest book, the French neurologist Michel Habib considers that about half of the dyslexic learners display a history of delays in the acquisition of spoken language. Now, when this concerns pronunciation, usually a few months of visiting a speech and language therapist will do. However, conversely when these concern the acquisition of the syntax, the vocabulary, and the grammar, then the possibility of underlying dyslexia is greater. This was for production. Now let's move to the perception of spoken language. Categorical perception studies have repeatedly shown that representation of full names are 'fuzzier', less well defined in dyslexics compared to non-dyslexics. This may be related to the fact that learners - that dyslexic learners - are oversensitive to what is called 'allophonic variation'. For example, the 'a' in 'bar', 'cap', and 'mat' are not the in those three words, ... ... exactly the same. But we, or non-dyslexic learners, have learned to ignore those small variations which are not relevant for the meaning. However, dyslexic learners do hear those small variations, and that's the reason why they build representations of phonemes which are not as accurate as the ones in non-dyslexic readers. Other studies say that's not exactly the case. There is recent controversy here which is not solved yet. Some studies suggest that the phonological representations in the dyslexic are intact, that the problem is accessing those representations. Studies by Ramus and a team of Leuven in Belgium, Boets, have shown, and suggest that phonological representations are intact. As speech is also a fast signal, another group, Tallal and collaborators have suggested that dyslexic learners have difficulties in identifying fast temporal changes which occur in speech. Furthermore, as Jenny has already told you, Heiki Lyttinen and his colleagues have interviewed over 200 families and have classified the new borns as at risk for dyslexia, versus non-at risk for dyslexia, depending on the familial risk for dyslexia, which is often heredity, as we said in the definition. They showed that a test administered only six months after birth, was a good predictor of future dyslexia or not. You should know that in Finnish, there is a distinction between the short consonant as in 'ata' and a long consonant, as in 'atta'. And, not only, the children at risk for dyslexia, who've became dyslexic later on, needed more time to make the distinction between the two the two consonants, the short and the long one but also the electric activity of the brain was different compared to the children not at risk for dyslexia. So, linking to productive language and vocabulary, the study also found that the children who were late talkers, they started talking at around two years, two years and a half, and also had genetic risk in combination with a strong risk factor for dyslexia. So those children had difficulties perceiving a consonant contrast contrast at six months and they were also late talkers. Evoked potentials, which is a technique used in measuring the electric activity of the brain through electrodes put on the head, measured when learners are five years old robustly predicts eventual risks for dyslexia, this was shown by Giraud and collaborators. Finally, functional magnetic resonance studies show, before learning to read and write, the density of the grey substance is rarefied in the temporal region which (is) the region where reading occurs, and that this region is less activated in children proving to be dyslexic compared to non-dyslexic. There is a sort of continuum between difficulties in oral language development called specific language impairment, or SLI, and dyslexia - most children with SLI will develop dyslexia afterwards, will display subsequent reading difficulties. In fact, we can say, to put it simply, that SLI is often co-occurring with dyslexia, and that it's a sort of 'stronger form' which start with difficulties with the oral language first, then subsequently with the written language. These two conditions should be seen as complementary. And there is also genetic overlap between the two. Researchers usually make a distinction between three types of specific language impairments. Receptive for comprehension, expressive for production, and mixed. But be aware that these categories should not be taken straightforwardly - these are generalizations. And even kids with a predominantly ... expressive profile are likely to have some subtle receptive issues as well. Severe forms of specific language impairment can lead to silence sometimes. And specific language impairment acquired by adults who have acquired oral language normally and then have lost this ability, is called Dysphasia in the US and Alexia in Europe.
