Evoked potential correlates of recovery from aphasia after focal left hemisphere injury in adults.

An evoked potentials (EPs) paradigm that has been effective in demonstrating asymmetries in hemispheric activation during cognitive tasks was used to assess cerebral reorganization for language in recovered aphasics. Cortical click EPs were recorded bilaterally in normal volunteers, recovered aphasics who had sustained focal left hemisphere injury, and nonaphasic patients with diffuse injuries during a control condition of attending only to the click and during a verbal memory task. During that task, EP amplitude attenuation occurred in the left hemisphere for the normal subjects and the nonaphasic patients and in the right hemisphere for the recovered aphasics. These contrasting asymmetries in hemispheric activation suggest that a shift of hemispheric specialization for verbal processing contributes to the recovery of linguistic competence in adult aphasics.