Phonological dyslexia and phonological dysgraphia following left and right hemispherectomy

Four adults who had hemispherectomies because of severe epilepsy following infantile of childhood damage to one hemisphere of the brain, are assessed on their reading and spelling abilities in an attempt to see if the two hemispheres are equipotential for these abilities in infancy. The psycholinguistic assessments of language processing in aphasia (PALPA) are used, and the results are interpreted from the viewpoint of hypotheses of "normal" right and left hemisphere reading abilities. Overall, the results suggest that the two hemispheres are equipotential at infancy for developing the skills underlying reading, but the left hemisphere is more specialized for the skills underlying spelling. All participants could read learnt regular and irregular words, and abstract and concrete words, suggesting that the reading lexicon develops in line with a normal left hemisphere lexicon, whichever hemisphere remains intact following hemispherectomy. However, poor reading of non-words suggests that the phonological reading route is severely impaired following left hemispherectomy (phonological dyslexia), and somewhat impaired following right hemispherectomy. The right-hemispherectomized participant is only mildly impaired on spelling real words, in contrast to the left-hemispherectomized participants who are markedly impaired. None of the participants could spell non-words, suggesting that the phonological spelling route is impaired following removal of either hemisphere (phonological dysgraphia).