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Differences in Dyslexic and Normal Brains
n an article published in the June 20th issue of the Lancet (351:1849-52), Dr. Caroline Rao, et al., studied whether the neurologic and physiologic deficits noted in dyslexic individuals manifested as biochemical changes in the brain.
In her study, they performed proton magnetic resonance spectra bilaterally from the temporal and parietal cortices, and the cerebellum on 14 well-defined dyslexics between the ages of 20 and 40, and 15-age matched controls. The individuals identified as dyslexics in this study had been formally diagnosed formally by an outside education psychologists based on a large discrepancy between the reading and spelling achievement based on age-defined and intelligence norms.
The biochemical differences found between the brains of dyslexic and normal men: (i) A difference in the ratio of choline-containing compounds (like serotonin and other neurotransmitters) compared to N-acetylaspartate compounds in the left parieto-temporal cortex; (ii) A difference in the ratio of creatine to N-acetylaspartate compounds in the right cerebellum.
The authors conclude that the differences seen in their study reflect changes in the cell density in these areas and that the altered structural symmetry seen in dyslexia is a manifestation of the abnormal development of the associated neurons or the their intercellular connections, or both.
With involvement of the temporoparietal and cerebellar areas of the brain and with neurons from the inner ear that enter these areas or have intercellular connections from neurons in the involved areas, it is not hard to see how the cerebello-vestibular system may be affected.
Though the size of the study was small, it did show a difference in the spectroscopy of dyslexic versus normal brains. These differences in the neurochemical makeup require more research to identify which neurotransmitters are more specifically involved and to understand how current therapeutic modalities help improve dyslexia. Understanding this will further lead to a better understanding of the biochemical basis and plasticity of learning.
As you can see, these findings give additional support for a cerebellar-vestibular origin of dyslexia as I have been postulating since the late 1970's.
In the article, the authors' state:
"Dyslexic people are often uncoordinated, with poor balance and delayed motor milestones such as crawling, walking, or learning to ride a bicycle. Anti-motion sickness medications, which may be considered 'cerebellar-vestibular stabilizers,' have been shown to improve reading performance in dyslexia... The changes (noted by the study in neurotransmitter levels) are indicative of altered cell patterns of density in the cerebellum of a dyslexic individual."
The references that they provide to support these comments do not substantiate these statements. However, they do reflect my theories and support my clinical outcomes. For more about this please read Lancetgate.
