Abstract
The foot of the left middle frontal gyrus is known as Exner's writing center ; however, its exact role in writing still remains unclear.
We report a right-handed Japanese male who showed selective kana agraphia following infarction restricted to Exner's area. Even five years after the infarction (at age 71), he still demonstrated kana agraphia. At this time, we investigated his agraphia in detail by moraic segmentation and kana dictation tests in which familiarity of kana notations and the number of syllables, morae and kana letters of the target words were controlled. The results showed, there was a familiarity effect in his agraphia：more errors appeared when he tried to write words whose notations in kana letters were unfamiliar. The errors consisted of substitutions of kana letters corresponding to you-on (contracted sound) and omissions of kana letters corresponding to chou-on (prolonged sound) and soku-on (contracted consonant). Furthermore, he showed difficulties in segmentation of those words containing chou-on and soku-on into morae.
From these observations, we suggest that his kana agraphia is best explained by a disturbance of moraic segmentation of words, especially of those containing special syllables, and by a deficit in translating phonemes into kana letters. Exner's area may be a location that plays an important role in segmenting a word into morae and translating phonemes into kana letters in Japanese.
