Causes
“(It is) biological in origin, it tends to run in families, but environmental factors also contribute. Dyslexia can occur at any level of intellectual ability. It is not the result of poor motivation, emotional disturbance, sensory impairment or lack of opportunities, but it may occur alongside any of these. The effects of dyslexia can be largely overcome by skilled specialist teaching and the use of compensatory strategies.”
(The Dyslexia Institute, 2002)
There are various theories about the causes of dyslexia, however, several encompass that it’s a genetic condition that changes how the brain deals with information pertaining to language. The prime cells in the brain thought to be affected by this condition are a particular class of magnocellular nerve cells.
The manipulation and processing of words as required for reading, writing and spelling requires that several areas in the brain interact in a intricate manner. As a consequence, characteristics of an individual’s dyslexia depend on which areas are affected and how.
Problems resulting in Dyslexia could be due to problems with:
a) receiving sensory information through vision/hearing, b) retaining it or organizing it in the brain, c) retrieving it, d) processing it, e) a combination of the above.
Brain-imaging scans of dyslexic people differ from those of people without dyslexia, especially when they try to process information - indicating that their brains work differently.
Dyslexia and the brain
People with Dyslexia are thought to have problems with phonological processing because certain areas of their brain function in a way different from that of people without the condition.
During research the following areas in the left cerebral hemisphere have been studied:
• Broca’s area - involved in language abilities.
• Parietotemporal region - involved in analysing written words.
• Occipitotemproal region - involved in identifying written words.
Magnetic resonance imaging (MRI) scans have shown that activity levels in all three regions of the brain are much lower in people with dyslexia when they are trying to read. These low brain activity levels may contribute to their problems with phonological processing.
Impairment of the cerebellum has also been implicated with development of Dyslexia, and evidence for this comes from fMRI scans. It’s believed that the cerebellum plays an important role in helping to process language as well as in bodily coordination. This research might elucidate why several people with dyslexia often struggle with coordination and time management.
One must highlight that the areas of the brain discussed above are known to have a high degree of ‘plasticity’. This therefore makes it possible for people with Dyslexia to obtain suitable treatment to successfully ‘rewire’ areas of their brain with therapy and thus improve their phonological processing ability, directly improving their Dyslexia. Detailed information can be obtained in the ‘Treatment’ section of this website.
Developmental Dyslexia
Developmental dyslexia is not caused by a solitary, distinct defect. The manner in which dyslexia affects people differs from individual to individual, and each faces specific difficulties.
Children are believed to acquire their language skills best during a certain, brief "critical period". Being affected by conditions such as hearing problems (e.g. due to an ear infection) during this time could affect their language abilities and reading skills. Similarly, visual defects (e.g. blurred vision) may make reading difficult and thus this becomes a poorly developed ability. Children may also have trouble translating letters into the sounds they stand for, and thus experience difficulty understanding their meaning.
Genetics and the Phonological processing impairment theory have also been identified as potential causes of Dyslexia.