Brain Disorders and Language Analysis

Separate regions of the cortex form complicated systems for the analysis and synthesis of visual, auditory, kinaesthetic and motor stimuli. Focal lesions of the brain produce a break-down in such analysis and synthesis and lead to a secondary disturbance of a whole complex of functions. Lesions in the left temporal zone cause a break-down in the discrimination and generalisation of sound patterns, and above all in phonemic auditory perception. This in turn affects pronunciation and writing, and also the structure of word-meanings. This failure at the lexical level affects the various parts of a word in different degrees: the roots of words, which carry the more concrete meaning, are lost, while suffixes, with their more abstract meaning, are retained. Clinical observation of different cases throws light on the distinction between the “communication of events” and the “communication of relations”. Lesions in the parietal and parieto-occipital areas produce a failure in dealing with “communications of relations”, a failure to combine a number of elements into a single whole. When these lesions extend to the borders of the speech area, they entail a further break-down in operations that require the abstraction of a scheme of reference. “Communication of relations” necessitates precisely this operation and this explains why patients with parieto-occipital lesions are often unable to deal with such communications. Lesions in the fronto-temporal areas affect the synthesis of successive elements and hence lead to a failure in “propositionizing”. In all cases of parieto-occipital lesion the “regulating” function of speech remains intact. Animal experiments have shown that ablation of the frontal sections of the cortex completely upsets the regulation of the animal's behaviour. In man, frontal lesions interfere with the regulating function of speech without affecting other speech functions.