Walsh & Hoyt: Other Disconnection Alexias

The disconnection hypothesis involves two deafferentations of the left angular gyrus: the disconnection of right hemisphere vision and the disconnection or destruction of left hemisphere vision. Each of these has been described in isolation, as hemialexias. In left hemialexia, reading is impaired in the left hemifield only because of isolated damage to the posterior corpus callosum or callosal fibers elsewhere. This disconnection was visualized recently in one patient with a combination of fMRI and diffusion tensor imaging. Right hemialexia has been reported with a lesion of the left medial and ventral occipital lobe that spared other visual functions in the right field.