Temporal processing deficits in developmental dyslexia – a functional MRI study

Developmental dyslexia is defined as the difficulty in learning to read, and affects between 5 and 17.5 per cent of school-age children. The cause of dyslexia is unknown, but there may be a neurobiological basis. Current diagnostic tests for dyslexia are typically conducted by grade two or three, however by this time, the child already displays significant reading difficulties and may never catch up to their peers. Developing diagnostic tests to assess or predict reading difficulties at an earlier age could allow for earlier intervention and prevention of academic and social difficulties associated with dyslexia. For many children, the main problem in dyslexia involves sound (phonological) processing. For instance, the child may not be able to link sounds to letters, or break words up into their individual sounds. Also, people with dyslexia may show deficits in visual and auditory temporal processing, which is the perception and integration of rapidly presented stimuli. For example, the child may have difficulty with determining the direction of motion or sound. It is unknown whether there is a link between reading and temporal processing skills. Marita Partanen is examining whether reading and temporal processing use overlapping brain networks, and whether these brain areas are affected in children with dyslexia. She is using functional magnetic resonance imaging (fMRI) to track brain activation in children as they complete simple tasks. If a link between reading ability and temporal processing can be established, there is potential for simpler and earlier diagnostic tests for dyslexia that assess temporal processing. Ultimately, the ability to diagnose dyslexia at a younger age may lead to new programs that can improve academic and social outcomes for people with dyslexia.