Chinese aphasia

Overall there is a paucity of information and this article will be updated as I find more references. Much of this information is taken from an old book chapter "Aphasia in Chinese speakers" by Chen Ya-Huang in Chopra JS, Jagannathan K, Sawhney IMS, eds. Modern Trends in Neurology, New Delhi, Churchill-Livingstone, 1991. Other references are taken largely secondhand.

Chinese of course uses orthographic symbols to represent words. Whereas there is little or no difference in clinical characterisitcs of Brocas/Wernicke's aphasias in Chinese, several debates have emerged due to the nature of the written language.

Chinese words are monosyllabic, often, and simple tone differences may cause homophones to have different meanings. Since tone is processed by the right hemisphere, which hemisphere mediates processing of tone in Chinese, which is connected to meaning? H. Cohen et al. (Neuropsychologia, 1989; 27:241-5) studied Chinese and French Canadian subjects, and found that on dichotic listening tasks, both groups had a right ear superiority for consonant-vowel syllables, and a left ear superiority for non linguistic melodies and triple tones. However, Baudoin-Chial showed that in French subjects there is left hemisphere processing for Chinese consonant words, and right hemisphere processing for Chinese tone words; however among Chinese subjects there was no dominance for either task (J Neurolinguitics 1986; 2: 189-200).

Among Chinese left hemisphere-damaged nonfluent aphasics, a tonal production deficit exists that is "qualitatively and quantitatively equivalent" to an inability to produce consonants (Packard, Brain and Language 29:212-223). With right hemisphere damage, Chinese subjects become aprosodic but maintain tonal defferentiation for words (Hughes CP et al. Arch Neurol , 1983). In other words, when tone has a linguistic meaning, the left hemisphere processes it.

Chinese grammar is not built-in to words that do not have transitivity, inflections for tense, gender or plural markers on nouns. Subject-verb-object word order is like other languages and is maintained in Broca's and Wernicke's aphasics. Reading errors in Wernicke's aphasia include phoneme substitution, tone changes, morphological errors, and neologisms, with global reading errors and no differences based on the complexity of the logogram, part of speech, concreteness. Broca's errors are mostly phonologic or unclassifiable. Action naming is preferntially affected in Broca's aphasics (Tzeng and Chen, 1988, AAN poster).

Reading of orthographs is delayed among patients with Chinese word-form dyslexia or occipital strokes (author, unpublished). They found that activating an orthograph also activated semantically connected lexigraphs in the same orthographic string. In a case of alexia without agraphia, Chinese aphasics read out component radicles of the orthograph and then piece the radicles together into a single orthograph, even though that method is not normally used in reading. Reading stimulus activates similar orthographs (simlar morphologically, semantically, or phonologically).

Homophones can be constructed by putting together two real orthographs, and nonwords by putting together two normally unrelated orthographs. In Broca's, patients read bisyllabic real words better than homophones, while Wernicke's aphasics did not show homophone superiority to nonwords. The author has two potential explanations, see text.

Dysgraphia in Chinese in Broca's aphasics usually consist of visual errors wherein subjects write normal Chinese orthographs with either missing or excessive strokes. This compares to Western language in which errors use acceptable letter constraints, but make errors of compound or multiple letters rather than omission or substitution. Evidence suggest Chinese use all 3 routes, visual, semantic and phonologic.

Studies have shown equivalent, overwhelming left hemisphere dominance for speech in Chinese undergoing WADA tests or stimulation (Hung CC et al. , J Neurolinguistics, 1985: 1: 143-164) and Rapport RL, Tan CT and Whitaker HA, Brain and Lang 1983; 18: 342-366). Studies show a right hemisphere superiority for processing Chinese or Kanji logographs and a left hemisphere superiority for kana or syllabic symbols in Japanese. However, the studies that show a right hemisphere superiority in RECOGNIZING orthographs show a left hemisphere superiority for processing them semantically (semantic decision of relatedness) ( Tzeng OJL et al. 1979, Nature 282: 499-501; and Hossain R et al., Neuropsychologia1989; 27: 7-5-712; CK LEong et al, Brain and Lang, 1985). Crossed aphasia has not been found in higher rates among Chinese patients.