dyslexia

Malfunction in the brain's synthesis and interpretation of written information, popularly known as ‘word blindness’.

Dyslexia may be described as specific or developmental to distinguish it from reading or writing difficulties which are acquired. It results in poor ability in reading and writing, though the person may excel in other areas, for example, in mathematics. A similar disability with figures is called dyscalculia. Acquired dyslexia may occur as a result of brain injury or disease.

Research by UK cognitive scientists 1996 showed that dyslexia may be due to a failed connection between Broca's area and Wernicke's area in the brain. Both areas are involved with the way language is processed and are connected by part of the brain known as the insula. Brain activity of both dyslexics and nondyslexics was studied using positron emission tomography (PET). In nondyslexics the three areas were active during linguistic tests; in dyslexics the insula remained inactive and Broca's and Wernicke's areas acted in isolation.

In 1994 US researchers linked the occurrence of dyslexia in families to a region on chromosome 6.