Physical causes of dyslexia
Since the late 19th century it is assumed that dyslexia is related to structural defects in the brains. These assumptions were confirmed by medical research into the processing of language in the brains. Neurologists Geschwind and Galaburda examined the brains of deceased dyslectics and found slight variations in the anatomy of the linguistic centres.
Dyslectics have a different way of arranging the sensory information that enters the brains compared to other people. The ability to read is acquired in the right half of the brain. Eventually, the left half of the brain takes over this function when it becomes automatic. The halves of the brains of dyslectics take over tasks from one another, thereby influencing the process of learning.
The origin of this is found in the process of neuronal migration. It is the method by which neurons that are created in the central areas of the brains move to the cerebral cortex during the development of the fetus. The differences primarily affect the left half of the brain. According to Geschwind it is caused by an overdose of testosterone.
It is a fact that dysletic children often experience CNSLD (eczema, allergies, bronchitis, asthma) symptoms, are frequently troubled by otitis media and are more often left-handed. All of these symptoms seem to have the same cause, namely the male sex hormone testosterone. This hormone appears to play an important role in the 25th week of pregnancy, at which time the linguistic areas of the brains are developed. The amount of testosterone produced is hereditary.
Scientists have managed to isolate the chromosomes that are probably involved in the development of reading disorders. Other studies have shown that the same chromosomes are responsible for autoimmune diseases, such as asthma and allergy.
Researchers at the university of Helsinki and the Swedish Karolinska Institute have found a gene that may be the basis of dyslexia, one of the most frequently occurring development disorders in children. Research was conducted in 20 Finnish families in which dyslexia had been diagnosed. In a number of these families a mutation on gene DYXC1 was found. The influence of this mutation is yet unknown. According to the scientists, it does not account for all the cases of dyslexia.