Frontal pure agraphia for kanji or kana: dissociation between morphology and phonology.

We present two patients with frontal pure agraphia more impaired for either kanji or kana (two separate writing systems for the Japanese language). The lesion of patient 1 (preferentially disturbed for kanji) was restricted to the foot of the middle frontal gyrus and the adjacent anterior precentral gyrus, whereas the lesion of patient 2 (preferentially disturbed for kana) included the posterior two thirds of the middle frontal gyrus. Both patients made agraphic errors (impaired recall) for kanji and agraphic or paragraphic errors (changing into other symbols) for kana. The double dissociation and the difference in types of errors between kanji writing and kana writing suggests that there are two pathways involved in writing, i.e., a morphologic route and a phonologic route. We concluded that damage to the morphologic route may yield agraphia for kanji and that damage to the phonologic route may yield agraphia for kana.