Contribution of functional imaging techniques to the study of subcortical aphasia

This paper reviews a number of studies devoted to subcortical aphasia. Functional imaging techniques (either isotopic or electrophysiological) allowed to analyze the possible contribution of cortical remote effects to the pathophysiology of the clinical disorders. Sufficient cortical dysfunction proved to be necessary to give rise to language disorders. According to a network approach, different cortico-subcortico-cortical loops might be involved. In thalamic lesions, a diffuse remote cortical metabolism reduction, probably representing damage to a non-specific thalamic activating system, might be related to injuries of ventro-antero-lateral nuclei. Injury to the posterior part of the thalamus would give rise to lexical-semantic impairment. In non-thalamic lesions, the cortical dysfunction concerned mainly frontal and sylvian regions including classical cortical language areas. Some features of the clinical pictures (reduction in verbal output, perseverations, phonological disorders, auditory comprehension disorders, ...) might be attributed to the involvement of specific cortical areas. (C) 1997 Elsevier Science Ltd. All rights reserved.