# 1.1.1 Lateralisation

Unusual patterns of cerebral lateralisation (i.e., the ‘division of labour’ between left and right hemispheres of the brain) may be linked to dyslexia.

Postmortem and neuroimaging studies show that the left hemisphere’s structure and function differ in individuals with dyslexia (Krafnick and Evans, 2019). Altarelli et al. (2013) observed reduced cortical thickness in the left hemisphere of dyslexic children. The evidence shows differences between dyslexic and neurotypical individuals, but not between genders. However, there is no consensus on the specific ‘contribution[s] of individual brain regions to dyslexia’ (Krafnick and Evans, 2019, p. 4).

## Left and right

Early researchers thought left-handedness was common among dyslexic people, but in fact most are right-handed. However, ambidexterity (using different hands for different tasks) is more common (Eglington and Annett, 1994).

A fun fact: while we often hear about ‘left-brained’ and ‘right-brained’ people, this is a generalisation, since both hemispheres cooperate in most activities. Many language-processing regions are in the left hemisphere, which works on producing understandable sentences, and understanding speech. However, other language functions, like associating emotions with phrases, occur on the right side of the brain.

Figure 1 The left/right brain

OpenLearn - Understanding dyslexia
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