[Neural mechanism of reading].

We conducted positron emission tomography studies on reading and found that two distinct areas were activated, i.e. the left fusiform/inferior temporal gyri (posterior inferior temporal cortex, Area 37) by kanji words and the fusiform/inferior occipital gyri (posterior occipital gyri, Area 18/19) by kana words. Clinically, alexia and agraphia for kanji is caused by a posterior inferior temporal cortex lesion. Moreover, pure alexia more impaired for kanji results from a fusiform gyrus lesion, whereas pure alexia for kana occurs because of damage to the posterior occipital gyri. These experimental and clinical findings suggest that impaired letter identification in Area 18/ 19 causes pure alexia for kana, disrupted visual images of words in Area 37 results in alexia with agraphia for kanji, and impaired access to the visual image storage (Area 37) yields pure alexia dominantly disturbed for kanji.