Does Damage to the Cerebellum cause Dyslexia?
The cerebellum has been referred to as “a neuronal learning machine”, but only recently has there been an increasing appreciation of its role in development and developmental disorders.
Developmental dyslexia is defined as a specific learning impairment in reading which cannot be accounted for by a general intellectual disability or lack of educational opportunity. Dyslexia is associated with slow, laborious reading. Poorer performance with motor tasks have been reported in dyslexia; including balance, rapid pointing peg-moving, and control of eye movements. These are all motor functions controlled mainly by the cerebellum. These findings have led to the proposal that cerebellar dysfunction is a core neurobiological factor of dyslexia.
Scientists believe that cerebellar dysfunction plays a critical role in neurodevelopmental disorders. They focus on three developmental disorders in which cerebellar abnormalities have been well-documented (autism spectrum disorder [ASD], attention deficit-hyperactivity disorder [ADHD], and developmental dyslexia.
However, there has been controversy over the cause of dyslexia, the catalyst of this dispute being the claim of two British scientists claiming that the cerebellum is involved in the cause of dyslexia.
According to NewScientist Rod Nicholson and Angela Fawcett of the University of Sheffield say there is an “extremely high correlation between dyslexia in children and impairments in the cerebellum.” They have been measuring the performance of children with dyslexia and children with more general learning difficulties with tests to measure damage to the cerebellum. The children were asked to hold their arms out in front of them, with their hands dangling. They measured the angle between the child’s hand and wrist on both the left and the right side to see if there are any differences. Fawcett claimed that with dyslexics, the results showed consistent differences of
about 10 degrees. With slow learners and normal children there were virtually no differences.
Even if a correlation is present, new brain imaging research has disproved the theory that the cerebellum could be involved in causing dyslexia. According to Neurosciencenews, Researchers at Georgetown University used functional magnetic resonance imaging to look for brain activation during reading. They also tested for functional connections between the cerebellum and the cortex during reading.
They found no cerebellar involvement during reading. In fact, when just examining the communications between brain regions at rest — the cerebellum was communicating with the cortex more strongly in the children with dyslexia.
It is estimated that 5-10% of people in the United States has dyslexia, but this number can also be as high as 17%.
It is not uncommon to know someone in Harborfields High School that is, or has struggled with dyslexia. When asked if they knew anyone in HF that has dyslexia Melissa Neder (Freshman) responded, “Yeah I know 3 people in my grade that has dyslexia but all work around it really well.” She claimed that they all receive accommodations and help in school. Kathryn Morgan (junior) responded, “I know 4 people that have it, 2 of them are really good students in advanced classes.” When asked if they thought if damage to the cerebellum caused dyslexia they both said yes. Their reasoning was that they “knew that the cerebellum had to do with balance and coordination so I guess it could cause dyslexia.”
Many people believe in this common misconception, which could be counterproductive when trying to understand dyslexia. There is still so much we don’t understand about the brain, and continued research is being conducted to further understand learning disabilities.