Abstract
To explore the neural mechanisms underlying recovery of language output, we investigated, using functional MRI, the pattern of brain activity during explicit word retrieval to initial letter cues in five aphasic patients and six normal control subjects. The aphasic patients presented with mild to moderate degree of language impairment with word list generation < 50% as evidenced by the Standard Language Test of Aphasia. One of the patients was examined twice in the course of recovery. The cerebral activation of normal control subjects during word retrieval to letter cues was most prominently observed in Broca's area with additional activation in the surrounding areas including the left anterior prefrontal and medial frontal cortices, the insula and the superior temporal lobe. The modification of language-related brain function of each aphasic patient was evaluated and compared with the activation pattern of normal controls. Overall activation in Broca's area of the aphasic patients appeared less significant than normal controls. Good word retrieval was related to the relative functional spare/restoration of Broca's and adjacent areas. Insufficient functional recovery of Broca's and ipsilateral adjacent area may lead to functional activation of the right-sided homologous regions, which presumably is related to partial language recovery. The findings suggest that the functional restoration of language appeared variable in individual patients. Future studies using longitudinal functional neuroimaging evaluation are warranted to further clarify across-subject variability in aphasia recovery.
