Dyslexia linked to profound impairment in the magnocellular medial geniculate nucleus

Abstract

The neurological basis of dyslexia, a common reading disorder, remains unclear but is hypothesized to be caused by either dysfunction of the magnocellular system in the brain, abnormal temporal processing, and/or deficient phonological skills. Using functional magnetic resonance imaging, we measured activity in the magnocellular portion of the medial geniculate nucleus, the auditory relay in the thalamus, and observed profoundly attenuated responses to non-linguistic transient but not sustained sounds in every subject with dyslexia we tested, compared to normal readers. Our finding unifies these three hypotheses and identifies a core deficit causing dyslexia.