Orthographic Knowledge of Hangul Syllable in Alzheimer’s Disease

Abstract

Objectives: Alzheimer’s disease (AD) can cause visuoconstructional and linguistic dysfunction due to bilateral involvement of the tempoparietal-frontal hemispheric areas. At the later stages of disease, the patients often manifest written language impairment. Generalized orthographic knowledge/representation, that is, knowledge of symbol and letter patterns within and across words, is important for written language. The aim of this study was to delineate the basic knowledge of the graphemic or syllabic shapes in Hangul as well as Hangul writing ability of those with AD. We hypothesized that the orthographic representation of Hangul syllable might withstand the impact of AD, because the basic knowledge of a letter shape of Hangul might be preserved in this clinical population. Methods: Seventy-five AD patients were included in this study. The patient group was divided into four subgroups according to the clinical dementia rating (CDR): 16 were very mild cases (CDR0.5); 37, mild (CDR1); 19, moderate (CDR2); and 3, severe (CDR3). We administered dictation and representation tasks of Hangul syllables and compared the performances among groups. Results: In the writing-to-dictation and representation tasks, the number of correct responses significantly differed according to CDR (p<.001). Interestingly, the patients at a later stage of the disease received scores of below 10% on the Hangul writing to dictation task, and 41.5% on the Hangul representation tasks. Conclusion: This finding supports the hypothesis that orthographic knowledge/representation of Hangul grapheme/syllable may partly withstand the impact of AD.