Developmental dyslexia is a neurobiological disorder of the language system and involves deficits in phonological processing. Cognitive and neurobiological profiles were investigated at the individual level for adults with varying reading/phonological skills including several with developmental dyslexia. Neurobiological variance was measured by three independent neuroimaging methods including functional magnetic resonance imaging (fMRI), diffusion tensor imaging (DTI) and magnetic resonance spectroscopy (MRS).

The fMRI results replicated and extended previous findings indicating functional deficits exist in fusiform gyrus regions. Bilateral inferior frontal as well as right hemisphere fusiform regions were negatively related to reading and phonological skills. Leftward laterality of both fusiform regions was less for individuals with developmental dyslexia and was negatively related to reading/phonological skills. Together the results suggest that right hemisphere regions may be engaged as compensatory mechanisms. Correlational evidence indicates these mechanisms are engaged by reading disabled individuals and nonimpaired individuals with increasing engagement being associated with decreasing reading/phonological skills across a wide range of ability.

Diffusion imaging provided evidence that white matter integrity in various structures of the cortico-spinal motor pathway was associated with reading and phonological skills. In the superior corona radiata, white matter integrity was positively related to reading comprehension. In more inferior regions, white matter integrity was related to both reading and phonological measures.

According to the MRS results, metabolite concentrations in the angular gyrus are associated with reading and phonological skill. Choline levels were elevated in dyslexic individuals, indicating higher rate of white mater turnover. As a whole, the results suggest that white matter microstructure may be directly related to atypical functional activation patterns including less leftward lateralization of posterior language regions.