Abstract
Human beings are known as “Homo sapiens” meaning humans who know or possess knowledge. Among related species, only Homo sapiens are known to have developed speech abilities. This probably came about because they were equipped with vocal speech organs as well as speech functions in specific areas of the brain. Since the latter half of the nineteenth century, Broca's, Wernicke's, and the left angular gyrus have been considered as the only neurological basis for speech and language activities. Recent studies focusing on the correspondence between lesions and symptoms by using either the PET scan or the functional MRI, however, have revealed that much wider areas of the brain also provide bases for linguistic abilities. It is necessary, therefore, to analyze and utilize the results of such research more fully in clinical practice.
