LANGUAGE PROCESSING IN APHASIA - CHANGES IN LATERALIZATION PATTERNS DURING RECOVERY REFLECT CEREBRAL PLASTICITY IN ADULTS

During single word processing the negative cortical DC-potential revea ls a left frontal preponderance in normal right-handers as well as in patients with a history of transient aphasia. Lateralization of DC-neg ativity therefore provides a reliable and robust method for the assess ment of language dominance. In 11 stroke patients with permanent aphas ia this physiological pattern changed to bilateral activation reflecti ng an additional right-hemispheric involvement in compensatory mechani sms in aphasia. Along with complete clinical recovery the classical ap hasic syndromes revealed specific differences in changes of their late ralization patterns. In Broca's aphasia the initial right-hemispheric preponderance changed to a left frontal lateralization while in Wernic ke's aphasia a presumably permanent shift towards the right hemisphere occurred. Differences in lateralization patterns might reflect differ ent mechanisms of recovery such as the initial disinhibition of homolo gous areas contralaterally and subsequent collateral sprouting and syn aptic modulation. The assessment of changes in lateralization of the c ortical DC-potential during language tasks is a non-invasive, safe met hod with excellent time resolution that might provide further insights in the neural basis of recovery from aphasia. (C) 1997 Elsevier Scien ce Ireland Ltd.