APHASIA

also called Dysphasia, brain-generated defect in sounding words. Symptoms are associated with the location and extent of the brain tissues involved. An afflicted person, for example, although able to move his mouth parts and utter sounds and able to understand spoken words, may be totally unable to form words himself. Another aphasic person may be able to say the word hopper but be unable to say the word hop. The term aphasia is extended to a group of related disturbances. In agraphia (dysgraphia) the patient may be totally or partially unable to write words, although he is perfectly competent in speaking, reading, and drawing pictures. Perceptual aphasias are called agnosias; e.g., a person can see perfectly but be unable to recognize what he sees, even though he may be able to recognize it by feeling, hearing, or smelling it. A specific form of visual agnosia seen as a reading difficulty (alexia, dyslexia) may be found in otherwise normal, intelligent people. Also known are agnosias of smell, touch, and taste. All of the aphasias are of importance in psychology and psychiatry because they show that the apparent unity of what is commonly called mind rests on the interaction of functionally independent parts of the brain, each of which may be damaged without interfering with the function of other parts. Thus, there seems to be no such unitary power as memory, because visual memories may be abolished without affecting auditory, olfactory, tactile, or any other memory functions.