Two different readers in the same brain after a posterior callosal lesion.

Two different types of reading, one in each hemifield, were exhibited by a patient with a lesion of the posterior half of the corpus callosum. The patient read normally when words and non-words were presented to his right visual field. However, with left visual field presentations, the patient could not read non-words and vocalized real words very slowly, especially abstract words, inflected verbs and function words. He often replaced concrete words by semantic associates. Such an abnormal reading pattern is similar to that known as deep dyslexia. This unilateral deficit reveals the competence of the right hemisphere to initiate some semantic processing and its inability to manage phonological coding. The hypothesis that deep dyslexia is due to right hemisphere reading is reinforced by the present case.