Language Laterality in Left - Handed Aphas 1 Cs

LATERALITY refers to the relationship of a cerebral function, or the symptom of its disturbance, to one cerebral hemisphere. Although the term is used mostly in connexion with handedness, aphasias, and agnosias, it has much wider implications and, in its broader sense, it constitutes the basis for localizing the lesion in cerebral hemiplegia in the opposite hemisphere. The association of right hemiplegia and speech disturbance can be found in the description of aphasia by Goethe (1796) and others. The idea of localization of speech in the left hemisphere was first conceived by Marc Dax in 1811 and presented at a lecture in 1836, but was not published until 1865 (Broca, 1865). It was reiterated by his son, Gustave Dax, in 1863 (Souques, 1928). When Broca, too, concluded that the posterior part of the third frontal convolution, especially on the left, was essential for intactness of the faculty of speech (1861-1864); he offered no explanation for this lateralization, nor suggested any significance in terms of handedness or cerebral dominance (Broca, 1863«, b). The idea of the linkage of handedness and speech was first formulated by Bouillaud in April 1865, when he spoke of "gaucherie cerebrale," again by Baillarger in May 1865, and Broca in June 1865 (See Broca, 1865: Souques, 1928; Riese, 1947). In 1874 Jackson spoke of the "leading hemisphere " and of'the localization of both propositional and emotional speech in the left hemisphere, and of emotional speech alone in the right hemisphere. Jackson (1880), and Ogle (1871) contributed some cases of left-handed individuals who had been rendered aphasic by right cerebral lesions. In 1877 Kussmaul stated that innervation centres are bilateral for all manual work but most people are right-handed and train the left hemisphere for most skills. "On this fact and the preponderance of aphasic disturbances in lesions of the left hemisphere rests the hypothesis that most people are 'left-brained speakers'."