Brain Mechanism of Language

Abstract

Several cortical areas of the left cerebral hemisphere other than the classical language areas, the Broca's and Wernicke's areas and the left angular gyrus, have recently been found to play an important role in the brain mechanism of human language. It has been generally assumed that the left basal temporal area stores lexicons and that the fiber tract from this area to the Wernicke's area through the subcortical white matter of the middle temporal gyrus realizes the naming process. Clinical studies on alexias and agraphias in the Japanese language have revealed an important role played by the left posterior inferior temporal region in the semantic reading process which is essential in kanji word reading. Recent PET-scan activation studies confirmed these findings and also revealed that the cortical area responsible for phonological reading is not the left angular gyrus as has been proposed in classical theories but the left lateral occipital area.