New brain imaging research debunks a controversial theory about dyslexia that can impact how it is sometimes treated. The cerebellum, a brain structure traditionally considered to be involved in motor function, has been implicated in the reading disability, developmental dyslexia, however, this ‘cerebellar deficit hypothesis’ has always been controversial. The new research shows that the cerebellum is not engaged during reading in typical readers and does not differ in children who have dyslexia.

The cerebellum, a brain structure traditionally considered to be involved in motor function, has been implicated in the reading disability, developmental dyslexia, however, this «cerebellar deficit hypothesis» has always been controversial. The new research shows that the cerebellum is not engaged during reading in typical readers and does not differ in children who have dyslexia.

That is the finding of a new study involving children with and without dyslexia published October 9, 2019, in the journal Human Brain Mapping.

It is well established that dyslexia, a common learning disability, involves a weakness in understanding the mapping of sounds in spoken words to their written counterparts, a process that requires phonological awareness. It is also well known that this kind of processing relies on brain regions in the left cortex. However, it has been argued by some that the difficulties in phonological processing that lead to impaired reading originate in the cerebellum, a structure outside (and below the back) of the cortex.

«Prior imaging research on reading in dyslexia had not found much support for this theory called the cerebellar deficit hypothesis of dyslexia, but these studies tended to focus on the cortex,» says the study’s first author, Sikoya Ashburn, a Georgetown PhD candidate in neuroscience. «Therefore, we tackled the question by specifically examining the cerebellum in more detail. We found no signs of cerebellar involvement during reading in skilled readers nor differences in children with reading disability.»

The researchers 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.

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Materials provided by Georgetown University Medical Center. Note: Content may be edited for style and length.