Medial-Vowel Writing Difficulty in Korean Syllabic Writing: A Characteristic Sign of Alzheimer's Disease

BACKGROUND AND PURPOSE: Korean-speaking patients with a brain injury may show agraphia that differs from that of English-speaking patients due to the unique features of Hangul syllabic writing. Each grapheme in Hangul must be arranged from left to right and/or top to bottom within a square space to form a syllable, which requires greater visuospatial abilities than when writing the letters constituting an alphabetic writing system. Among the Hangul grapheme positions within a syllable, the position of a vowel is important because it determines the writing direction and the whole configuration in Korean syllabic writing. Due to the visuospatial characteristics of the Hangul vowel, individuals with early-onset Alzheimer's disease (EOAD) may experiences differences between the difficulties of writing Hangul vowels and consonants due to prominent visuospatial dysfunctions caused by parietal lesions. METHODS: Eighteen patients with EOAD and 18 age-and-education-matched healthy adults participated in this study. The participants were requested to listen to and write 30 monosyllabic characters that consisted of an initial consonant, medial vowel, and final consonant with a one-to-one phoneme-to-grapheme correspondence. We measured the writing time for each grapheme, the pause time between writing the initial consonant and the medial vowel (P1), and the pause time between writing the medial vowel and the final consonant (P2). RESULTS: All grapheme writing and pause times were significantly longer in the EOAD group than in the controls. P1 was also significantly longer than P2 in the EOAD group. CONCLUSIONS: Patients with EOAD might require a higher judgment ability and longer processing time for determining the visuospatial grapheme position before writing medial vowels. This finding suggests that a longer pause time before writing medial vowels is an early marker of visuospatial dysfunction in patients with EOAD.