Developmental dyslexia: The role of the cerebellum

Children with dyslexia suffer from unexpected problems in reading, writing and spelling. The dominant causal hypothesis has been that the deficits arise from some impairment in phonological processing ability. Initial studies revealed that children with dyslexia suffered severe deficits in skills including not only phonological skill but also picture naming speed, bead threading and balance. Given the growing evidence that the cerebellum is directly involved in acquiring 'language dexterity', all the above deficits are directly consistent with cerebellar impairment. Further studies established that the panel of children with dyslexia showed severe deficits on clinical and theoretical tests of cerebellar function, among the largest obtained in our research programme. The cerebellar impairment hypothesis provides a causal explanation for developental dyslexia, subsuming the phonological deficit account within a broader framework.