Training-induced brain plasticity in aphasia

It has long been a matter of debate whether recovery from aphasia after lef t perisylvian lesions is mediated by the preserved left hemispheric languag e zones or by the homologous right hemisphere regions. Using PET, we invest igated the short-term changes in the cortical network involved in language comprehension during recovery from aphasia. In 12 consecutive measurements of regional cerebral blood flow (rCBF), four patients with Wernicke's aphas ia, caused by a posterior left middle cerebral artery infarction, were test ed with a language comprehension task, Comprehension was estimated directly after each scan with a modified version of the Token Test, In the interval between the scans, the patients participated in brief, intense language co mprehension training. A significant improvement in performance was observed in all patients. We correlated changes in blood flow measured during the l anguage comprehension task with the scores achieved in the Token Test. The regions which best correlated with the training-induced improvement in verb al comprehension were the posterior part of the right superior temporal gyr us and the left precuneus. This study supports the role of the right hemisp here in recovery from aphasia and demonstrates that the improvement in audi tory comprehension induced by specific training is associated with function al brain reorganization.