| Objective To document the suspected high error rate of selective damage in producing shengmu and to address whether there are specific factors that lead to the unequal distribution of errors for shengmu and yunmu, this study examined the breakdown in a patient with acquired language aphasia caused by lesions in the frontal lobe.Methods①Experiment 1 was designed to measure the effect of the frequency of Chinese characters on the rate of the patient's shengmu and yunmu errors. From to the Modern Chinese Frequency Dictionary, 444 Chinese characters were analysed, including 140 high-frequency characters, 140 intermediate-frequency characters, and 164 low-frequency characters.②In our study, there were 316 pairs of Chinese characters, of which 152 were meaningful pairs (e.g.'大脑'(brain),'山羊'(goat), and'公鸡'(cock) and 164 were meaningless pairs (e.g.'芹刷','手豆', and'衣鸡'), defined as phrases and pseudo phrases respectively.③In experiment 3, there were 280 characters whose yunmu contained only vowel(s) and 176 whose yunmu contained vowels and consonants as different types of groups. The 456 Chinese characters were presented in randomised order. The patient was asked to discriminate every Chinese character and pronounce it aloud (Chinese pinyin) as clearly as possible. The patient was given sufficient time to respond to each item, and all the experimental tasks were tape-recorded.Results①Experiment 1: The critical comparison of the rate of shengmu and yunmu errors in each group is highly significant (high-frequency group, HFG:χ~2 = 52.986, P < 0.01; intermediate-frequency group, IFG:χ~2 = 33.158, P < 0.01; low-frequency group, LFG):χ~2 = 19.617, P < 0.01). The differences between errors on shengmu and tone were also examined, and it was found that performance is significantly different from chance. In contrast, the rate of yunmu errors in each group is close to the tone, which is not significantly different from chance. Our findings suggest that the performance on shengmu, yunmu, and tone does not support significant grouping when these characters are classified by frequency (χ~2 = 6.343, P > 0.05).②Experiment 2: Comparisons between phrase and pseudo phrase groups showed similar performance: The patient performed poorly on shengmu but much better on yunmu and tone. The comparison between shengmu 1 and shengmu 2 in the phrase group (χ~2 = 0.844, P > 0.05) and pseudo phrase group (χ~2 = 0.196, P > 0.05) did not differ, indicating a high rate of shengmu errors as compared to yunmu errors and tone errors was irrelevant to its initial position and the neural priming effect.③Experiment 3: The significant difference between shengmu and yunmu does not vary with the two types of yunmu (χ~2 = 50.493, P <0.01;χ~2 = 59.031, P <0.01). The performance error rate of yunmu does not differ in the two conditions (χ~2 = 0.053, P > 0.05), indicating that in Chinese, the distinction between vowels and consonants does not contribute to the observed contrastive error performance on shengmu and yunmu.Conclusions Our data show that in the speech production task, the patient with lesions in the left inferior frontal gyrus displayed contrasting patterns of error rates in shengmu relative to yunmu. Therefore, this study suggests that in the processing of Chinese syllables, shengmu are more vulnerable than yunmu in the Chinese Broca's aphasic. Likewise, this case as a model of focal brain damage argues for the role of Broca's area in the coordination of articulatory movements because of her poor articulation but relatively preserved comprehension, phonemic discrimination and auditory word recognition. We claim that Broca's area plays a significant role for articulation of shengmu which need complex articulatory movements. |
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