Aphasia

Aphasia may be defined as a total or partial loss of the use or understanding of language, the receptive and expressive organs of speech remaining intact. Since speech is an intellectual function, dependent upon the physiological activity of the underlying neural arrangements, the component units of which have an anatomical localization, the problem of aphasia may be considered from the psychological, the physiological, or the anatomical point of view. Aphasia may, therefore, be considered as a symptom, or external manifestation, of a disorder of one or more of the component parts of the basic speech mechanism. While speech, either internal or external, is the usual mode of expression of thought, it must be distinguished from that higher intellectual function which may proceed without symbolic representation. Historical. Broca2, in I86I, described a lesion in the left thirc frontal convolution associated with aphasia. The speech disorder was characterized by a reduction or complete loss of vocabulary , the intelligence and phonation remaining intact. In some cases there was loss of the mental picture of phrases and sentences, the so-called inner language, while in others this function remained intact. From these findings, Broca postulated a center for speech, later designated as the motor speech area, in the third frontal convolution of the left hemisphere for right-handed people, and on the right for left-handed people. Somewhat later, in I874, Wernicke'5 located a speech-center in the posterior third of the left first temporal convolution. A lesion at this point was found to be characterized chiefly by an inability to understand spoken language (word-meaning deafness). These patients were able to pronounce words but were unable to interpret the words spoken by themselves or by others. From these findings, Wernicke assumed the presence of an auditory speech-center, located in the posterior third of the first temporal convo-lution, controlling the motor speech-center of Broca. Dejerine", in I88 i, observed a third form of aphasia in which there was an inability to understand written or printed