Link between handedness and dyslexia

January, 2011

A genome study has found a gene variant that leads to greater right-hand skill in dyslexics, but not others. The gene is implicated in embryonic development.

While brain laterality exists widely among animal species, the strong dominance of right-handedness in humans is something of an anomaly. As this implies a left-hemisphere dominance for motor function, it’s been suggested that the evolution of language (also mainly a function of the left hemisphere) may be behind the right-handed bias, leading to a search for a connection between hand preference and language disorders. To date, no convincing evidence has been found.

However, a genetic study of 192 dyslexic children has now revealed a strong link between a variant of a gene called PCSK6 and relative hand skill in these children. Specifically, those who carried the variant in PCSK6 were, on average, more skilled with their right hand compared to the left than those not carrying the variant. However, among the general population, this gene variant is associated with less right-hand skill.

The findings provide evidence for a link between brain lateralization and dyslexia. The gene’s protein is known to interact with another protein (NODAL) that plays a key role in establishing left-right asymmetry early in embryonic development, suggesting that the gene may affect the initial left-right patterning of the embryo, with consequences for cerebral lateralization.

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