Reading and comprehension disturbances of Kanji and Kana in Alzheimer's disease and frontotemporal dementia

We assessed the kanji- and kana-word processing ability in eight Japanese patients with Alzheimer's disease (AD; n +AD0- 4) or frontotemporal dementia (RD; n +AD0- 4). All the patients underwent an experimental test that consisted of 20 kanji word oral reading, 20 kana word oral reading, 20 kanji word-picture matching and 20 kana word-picture matching. Frequency and notation familiarity of the employed words were controlled. The AD patients scored lower in word-picture matching than in oral reading on both kanji and kana modalities. The results suggested the dysfunction is restricted to the semantic system. The FTD patients could read most of the kana words, but showed deterioration on the performances of kanji oral reading, kanji word-picture matching and kana word-picture matching. We assume that the preserved ability of character-sound conversion enables the FTD patients to read kana words in a character-by-character manner, whereas the dysfunction of word lexicons results in the disturbed oral reading of kanji words, and the dysfunction of the semantic system causes the deficits in word-picture matching. These findings underline a possible disease specificity in the pattern of kanji- and kana-processing impairments.