[Quasi-aphasia associated with thalamic lesions: relation between the language disorder and elective activation of the left hemisphere in 4 cases of left and right thalamic lesions].

The authors report on four patients with vascular lesions of the thalamus, three on the left side and one on the right, two of which were due to haemorrhage and two to infarcts. Language difficulties were observed in those cases with left thalamic lesions only. Speech was either slower or faster than normal, and there were verbal perseveration, semantic paraphasia, and more especially, reduction in verbal fluency with loss of control of logic, causing a true jargon in some tests in certain cases. Articulation, and phonemic programming were unaffected, as were comprehension, reading and writing. A comparison is made between these findings and those reported in the literature. Among the hypo-theses suggested, the authors subscribe to that which accepts the predominant role played by the interruption of the activating system of the left hemisphere by the thalamic lesion. The relative inactivation resulting from this could produce modifications in language dynamics and disturbances in attention in relation to language. The semantic paraphasia could be related to the intrusion of the right hemisphere apparatus into language, because of the lack of balance between the activation of each of the two hemispheres. The fact that thalamic lesions are characterized by language disorders would tend to show that sub-cortical dynamic factors constantly regulate the activation of the hemispheres.