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Deep dyslexia for kanji and phonological dyslexia for kana: Different manifestations from a common source

2008; Taylor & Francis; Volume: 14; Issue: 6 Linguagem: Inglês

10.1080/13554790802372135

1465-3656

Hitomi Sato, Karalyn Patterson, Takao Fushimi, Jane Maxim, Karen Bryan,

Hearing Impairment and Communication

Abstract A Japanese-speaking stroke patient with disrupted phonology but relatively good semantics was severely impaired in nonword reading, with better preserved and imageability-modulated word-reading in both kanji and kana. This basic similarity of reading in the two Japanese scripts was accompanied by the following differences: (i) distinct error patterns (prominent semantic errors for kanji vs. phonological errors for kana); (ii) a more pronounced imageability effect for kanji; and (iii) a remarkable pseudohomophone advantage for kana. The combination of deep dyslexia for kanji and phonological dyslexia for kana in a single patient suggests that these are not two distinct reading disorders. Keywords: Deep dyslexiaPhonological dyslexiaJapanese orthographyPhonological impairment Our extreme gratitude goes to YT for her participation in this research. We also wish to express our appreciation to Professor Taeko N. Wydell for providing us her database of imageability (1991); to Dr M. Hatta, Dr R. Sato, and Dr R. Yoshida for referring YT, providing and explaining her MRI; and to Dr E. Otomo (Director of Yokufukai Hospital), by whose approval H.S. was able to study in London. Notes 1The percentage of semantic errors (out of all errors) varies considerably from one deep dyslexic patient to another. For example, it was 54% in PW (CitationPatterson, 1978) and 10% in PS (CitationShallice & Coughlan, 1980). 2Morae, or moras, are the time-based units of spoken Japanese. There are 108 distinct morae in the corpora of Japanese speech and more than 70% of morae are consonant-vowel combinations (CV) (CitationOtake, 1990). Additional moras consist of vowels on their own (the five canonical vowels of Japanese, /a/, /i/, /u/, /e/, /o/), more complex combinations of consonant and vowel (CjV), and the two special moras corresponding to nasal (N) and geminate consonants (Q). For instance, the katakana word caramel, pronounced /kja-ra-me-ru/, consists of one CjV morae (kja) and three CV moras (ra, me, and ru), and the kanji word stairs, pronounced /kai-daN/, consists of two CV moras (ka and da), one V morae (i) and one nasal (N). Both and are 4-mora words. 3Although some single morae in Japanese correspond to words (e.g., /me/ eye, /ki/ tree), such words are commonly written in kanji characters, not in kana characters. Therefore, single-kana characters can be considered as non-homophonic nonwords or pseudohomophones. 4Hiragana transcriptions are not misspelled, but psycholinguistically they are similar to pseudohomophones, as CitationColtheart, Patterson, and Marshall (1987) pointed out. 5This flexibility of the Japanese writing system led CitationKondo and Amano (1999) to propose a new psycholinguistic variable called orthographic plausibility. This is similar to orthographic wordlikeness and reflects a sort of subjective acceptability of writing a particular lexical item in kanji, katakana or hiragana. The degree of orthographic plausibility (on a 5-point scale) for a kanji word which is normally written in kanji is of course high, whereas this value for its transcriptions is low. For example, the word meaning magnificent, pronounced /ka-rei/, is usually written in kanji, and this representation () has a plausibility value of 4.75; when written in hiragana (), the plausibility value drops to 2.75; and if written in katakana (), it drops still further to 1.60. For the subset of words that are frequently written in either kanji or kana, such a pattern is not observed (e.g., apple /ri-N-go/: = 4.30, = 4.15, = 4.05). 6YT's lesion is consistent with reports that the usual lesion site in deep dyslexia is the left-temporo-parietal region and 'typically larger, encompassing at least the perisylvian area and often extending to include much of the left hemisphere' (CitationLambon Ralph & Graham, 2000, p. 142). 7 CitationPatterson et al. (1995) modified this test for investigating a Japanese neurological patient and created 49 test items. We added three new items to this version in order to match the number of items to the original test. 8This is called 'Gojyu-On-Hyou' (a Japanese syllabary list), in which kana characters are arranged in order, and this list is used for learning kana. 9The assignment of concrete and abstract words was based on the author's subjective judgment, in which object names (e.g., desk) were classified as concrete words, and nouns representing non-visible things (e.g., honesty) or time and space (e.g., present, left) were classified as abstract words. 10Each constituent character of 2-character consistent kanji words has only one possible pronunciation. YT's reading accuracy for these high/low frequency kanji words was 15/20 = 75% and 10/20 = 50%, respectively.