[Neuronal circuits of reading and writing in Japanese language].

Japanese writing system consists of two different types of letters, kana (phonogram) and kanji (morphogram). Various types of alexia with or without agraphia in the Japanese language cause specific type of kanji/kanja dissociation. Upon the neuropsychological analysis of these dissociations, we have proposed a hypothesis of dual neuronal circuits of reading and writing process. Subsequent PET activation studies upon normal subjects confirmed the hypothesis; semantic reading pathway via area 37 on the inferior border of the left temporal lobe and phonological reading pathway via middle portion of the left lateral occipital lobe.