The relationship between dyslexia and the predominance manual
One study shows the existence of a genetic link between the predominantly manual, cerebral asymmetry and reading skills.
The recent genetic mapping of a sample of children with dyslexia made it possible to clarify the relationship between the dominance of the Manual, or the tendency to use one hand rather than the other, and language disorders, confirming at least in part a hypothesis formulated a long time. In the UK, scientists have discovered a gene variant called PCSK6 precisely related to manual dominance in children with dyslexia.
The study, published for the first time in the journal Human Molecular Genetics, has been partially funded by the project NEURODYS (Dyslexia genes and neurobiological pathways), which received more than 3 million € in reference to the thematic area ‘Life sciences , genomics and biotechnology for health in the Sixth Framework Programme (FP6), just to analyze the biological factors that underlie dyslexia.
It is a fact that there are many more right-handers: according to experts, the dominance is due to the fact that the left brain controls the right side of the body (and vice versa) and the control exercised by the left on motor functions. The left hemisphere is predominant also in terms of language. Some studies in the past had shown that people who reported damage to the left hemisphere of the brain showed the difficulties in terms of language.
“This study demonstrates for the first time the existence of a genetic link between the predominantly manual, cerebral asymmetry and reading skills,” said Professor Tony Monaco from the Wellcome Trust Centre for Human Genetics, University of Oxford ( United Kingdom), one of the authors of the study. “Although we were aware of the biological function of the gene PCSK6, this is the first study devoted to the predominantly manual. The fact that this association appears to manifest in people with dyslexia also provides an interesting starting point to analyze if indeed predominantly manual and speech disorders are connected “.
Until now, many researchers had theorized that the slope of the population to use the right hand was due to the evolution of language, thus assuming that there was a link between a preference for the use of a hand, developmental disorders of language such as specific disorders of language (specific language impairment – SLI) and autism. This recent study has highlighted a link between a specific gene variant PCSK6 and manual ability of children with reading difficulties.
By analyzing a sample of 192 persons (unrelated) with reading difficulties, the scientists found that those who had a new variant of the gene PCSK6 had a more pronounced capacity to use the right hand compared with subjects without this variant. The researchers acknowledge that the protein product of the gene NODAL PCSK6 interacts with the protein, which in turn plays an essential role in the formation of left-right symmetry in the early stages of embryonic development. The gene variants may contribute PCSK6, so the researchers say, the preliminary development of the system left-right in the embryo, affects the development of cerebral asymmetry and hence the predominance manual.
“In the be more like us, the hominids, it is apparent that the overwhelming predominance of the use of his right hand,” says William Brandler, one of the authors of the study and researcher at the Wellcome Trust Centre for Human Genetics. “Getting to understand the genetic basis of predominantly manual could then allow us to shed light on the evolutionary process.”
The results of this study could be used to carry out further research devoted to the biology of speech disorders and a possible connection between hand dominance and language.
