For the first time, genes linked to dyslexia have been identified: the “reading disorder”, which affects 1 in 10 children. “Knowing the candidate genes for dyslexia will allow us to carry out early screening in boys and girls, especially in those more at risk (children of parents with dyslexia) “, explains the doctor Deny MenghiniPsychologist and Psychotherapist at the Complex Operating Unit of Childhood or Adolescent Neuropsychiatry of the Bambino Gesù Pediatric Hospital in Rome.
Genetic origin
That dyslexia was of genetic origin was a discovery 20 years ago and published in the Journal of Medical Genetics: the area of the genome “guilty” of the disorder is chromosome 15. The recent study, published in the journal Nature Genetics, identifies 42 genetic variants, some previously linked to cognitive abilities, but for the most part entirely new and never associated with this disorder. The database is the richest ever created: the DNA of 50 thousand dyslexic adults and over a million people not affected by the disorder were analyzed.
According to Michelle Luciano, lead researcher at the University of Edinburgh School of Philosophy and Language Sciences who participated in the research, “the results show that genetic variants have very similar effects in both boys and girls, and that there is a genetic link between dyslexia and ambidextrousism. , the ability to be able to use both hands indiscriminately “. But let’s try to understand more.
Doctor Menghini, dyslexia is one of the most common learning disabilities: which areas of the brain are involved?
“In the brain there are two regions that play an important role for reading: the parieto-temporal regions for the analysis of words, where graphemes, i.e. written letters, are translated into phonemes, the sounds of letters, and the occipito-temporal regions, responsible for fluent reading. The latter is the area of the visual form of the word. It is involved in accessing and automatically reading whole words and is a critical area for word recognition and fast, fluent reading. A third area, located in the frontal lobe (Broca’s area), is instead mainly involved in the articulation and phonological analysis (of sounds) of speech “.
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What are the difficulties in reading for a child with dyslexia and why?
“Children with dyslexia read imprecisely, with many errors and, often, not very fluently and slowly. They have difficulty in understanding the read text, not grasping the relationships, or the internal passages and the more implicit meanings. This deficit persists over time. , although it expresses itself and manifests itself differently in different ages. The child struggles to blend the individual sounds to compose the syllable or word from the earliest stages. In fact, there is no characteristic error of the child, which, in reality, he makes the same mistakes as his classmates, but he does it more frequently. “
What are the most common mistakes?
“During the first years of primary school the classic errors of all children and therefore also of those with dyslexia are the substitutions of similar sounds such as f / v (” mouth “instead of” voice “), t / d (” your “instead of” two “), s / z (” solle “instead of” clods “), c / g (” care “instead of” races “), p / b (” ball “instead of” balla “) or letters visually similar, due to their shape, such as p / q (” skin “instead of” those “), d / b (” where “instead of” bove “), d / p (” from “instead of” ball “). Growing up, errors affect the complex groups that make up words or spelling rules: the use of doubles, gn, sch, sc. The number of errors the child makes is progressively reduces and at the end of primary school or secondary school the reading is not very rapid and fluid “.
The deficit in addition to reading the words also affects spelling, rapid naming and phonology. How? Can you give some examples?
“Learn to read bene it requires the presence of the “learning prerequisites”: such as the ability to distinguish and manipulate the sounds of the spoken language, how to be able to orally divide the syllables that make up a word. Some examples: listening to the word motor and saying mo-to-re, listening to the syllables mo-to-re and saying the word motor, or identifying a word that ends the same way as another (identifying the word that rhymes with another one). Or the ability to quickly name elements, such as colors or numbers. Hence the difficulty in quickly and automatically associating the grapheme with the phoneme, a process at the basis of a fluent reading. These prerequisites, in general, are also considered essential for other learning disorders that usually arise in association with dyslexia: the comorbidity with dysorthography is known (difficulty in respecting the specific spelling rules of the language) “.
Can you give me an example?
“A dysorthographic child exchanges graphemes that represent similar phonemes such as,” f “with” v “,” t “with” d “,” b “with” p “or between visually similar graphemes” d “and” b “or” q “and” p “. Or he makes mistakes in the accent, in the apostrophe, in the use of the h of the verb to have, in the double consonant (ball-shovel)”.
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The study reveals that genetic variants have very similar effects in both boys and girls, and that there is a genetic link between dyslexia and ambidextrousism. How come?
“The results of the study support the hypothesis that there is a relationship between manifesting dyslexia and ambidextrousism, while the hypothesis that left-handers are more at risk for dyslexia is not confirmed. It is not easy to find an explanation for this result. of the hypothesis is that being left-handed, right-handed or ambidextrous depends on brain dominance. So the particular brain architecture of those who are ambidextrous could be genetically determined and be related to dyslexia. However, the study did not collect direct data on the brain and this remains only a ‘ hypothesis”.
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The cognitive processes underlying the function that leads us to learn to read do not depend on the type of language used. Because?
“Dyslexia is present in all languages, regardless of the conventional system used. What varies is the prevalence, which in Italy is around 3.5%. The prevalence indicated in the study (between 5 and 17.5% ) refers, above all, to English-speaking countries and to the specific characteristics of that language and spelling which, unlike Italian, are not “transparent”, but “opaque.” In our language, words are written with a grapheme correspondence ( written letter) – almost unique phoneme (sound of the letter). In English, words can be written in the same way, but be read differently depending on the meaning. This is the case, for example, of pint which is read / paInt / or / pint / depending on whether it indicates a local unit of measurement or a verb. And again, the words that are read in the same way can be written very differently depending on the context (for example: where, were, weare) In summary, the differences between languages and related spelling systems can produce multiple reading difficulties in different countries. In the case of languages with “transparent” spelling, such as Italian, the high correspondence between grapheme and phoneme can benefit the reading accuracy compared to other English-speaking languages, such as English, in which generally the phoneme grapheme correspondence is not followed. Studies in the literature show that children with reading difficulties in languages with transparent spelling show better decoding levels in accuracy than children with languages with “opaque” spelling “.
Is dyslexia therefore more common in English-speaking countries?
“The problem is related to these elements that make the task of learning to read and write more complex. It is assumed that the proportion of people with dyslexia is so high in English-speaking countries and, more generally, in countries with little or no spelling. semi-transparent is precisely for these difficulties. Compared to ADHD, it is estimated that at least 50% of children with ADHD also have a specific learning disorder (SLD) and that those with SLD in about 20% of cases also have ADHD. commonality of genes, therefore, is not surprising “.
Why is this study so important?
“This study, using data with a very high number of people with dyslexia, validates the hypothesis that the disorder, such as those of neurodevelopment (for example, ADHD, Autism, Intellectual Disability), has a neurobiological basis and is the result of genetic alterations . It also clarifies better the characteristics of those who can manifest dyslexia, for example that the genetic predisposition is present in both males and females “.
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What could be the future developments?
“Knowing the candidate genes for dyslexia would allow us to identify them and intervene promptly, with therapies, even in the preschool phase when dyslexia cannot yet be diagnosed because the boy / girl needs at least 2 years of reading-writing training ( and the diagnosis can only be made at the end of the second year of primary school). This would include late diagnoses and therapies, which often cause the child / child to emotional problems, such as anxiety and depression, due to the non-recognition of the problem and feeling different from peers for years. This study, identifying 23 loci (13 new) in independent groups of people with dyslexia, is a further step towards this possibility “.