Double dissociation between lexical decision and comprehension in a Japanese patient with semantic dementia: based on the characteristic processing of Kanji

We report the case of a Japanese-speaking patient with semantic dementia who showed lower kanji visual performance than auditory performance in a lexical decision task (LDT), but better visual performance in a reading comprehension task (RCT). In the RCT, the patient presumed meanings from single-character kanji (e.g., "rescue" /kyuʀzyo/ → ける "help" /tasukeru/) or orthographic neighbors (e.g., "rest" /kyuʀsoku/ → "rest" /kyuʀkeʀ/). In the LDT, he misidentified non-words as real words by relying on semantic associations of individual kanji characters. The logographic characteristics of kanji may have facilitated RCT while complicating LDT performance.