Norman Geschwind, M.D.
Experimental studies of animals permit us to investigate many aspects of the physiology of the nervous system, or of the effects of brain damage on behavior. This means of investigation fails, however, when we consider the problem of language in relation to the brain. As far as we know, no animal has language in the human sense, and indeed, even if forerunners of this ability exist, they must be very rudimentary. Our knowledge of the neurological bases of language has been derived overwhelmingly from the effects of disease on the brain of man.
The term "aphasia" is used to describe disorders of language resulting from damage to the brain. The aphasias are, unfortunately, very common disorders, and occur very frequently as the result of the disease of the blood vessels supplying the brain. There are literally millions of people throughout the world suffering from aphasia. Consequently, this disorder has great theoretical interest as the major source of knowledge of the brain mechanisms involved in language. It is also a great practical problem for which we have as yet no very satisfactory solution. Research in this area therefore has a double motivation: as we increase our knowledge of how the brain functions in language we may be able to devise more rational approaches to the treatment of these disorders.
As was the case with many other branches of science, the foundations of our knowledge of aphasia were established in the last half of the nineteenth century. The history of this field began in the early 1860s when a French physician named Paul Broca described a patient who had lost his faculty of speech,