| Dyslexia is a specific learning disability characterized by difficulties with accurate and/or fluent word recognizing, spelling and decoding abilities despite adequate intelligence, education, and socioeconomic status and is one of the main subtypes of learning disability. The prevalence rate of dyslexia was 4.5%～17.5% and at least 80% of the learning disability children was combined or suffering from dyslexia in the alphabetic languages. According to the phonological processing deficiency theory, the early belief was that it was only a problem for people using the alphabetic languages, but not for the nonalphabetic languages, such as Chinese. However, current researchs suggested the prevalence rate of dyslexia in Chinese population was also as high as alphabetic languages, with a rate at about 3.26%-10%. Studies on dyslexia can trace back to about 100 years ago and there were plenty results about different aspects of dyslexia from different fields. There already existed many theories and recently the cognition model of working memory can well explain all the results from different views. Thus the working memory deficiency was tested in many studies and more evidences indicated that the executive dysfunction in dyslexia may beyond their impairment in phonological processing and maybe the core deficit of dyslexia.The present study orientated on the executive dysfunction theory, and with the aim to study the epidemic characteristies of Chinese dyslexia children and understand the risk factors, and also, understand the executive function of Chinese dyslexia children with the data from the behavioral and event-related potentials(ERP). The study is essential to the etiology of Chinese dyslexia and can provide evidence for the diagnosis and intervene. The specific ERPs can also provide an index for the diagnosis of dyslexia. Part 1:Epidemic Study on Chinese Dyslexia ChildrenObjective:To study the epidemic characteristies of Chinese dyslexia children and understand the risk factors.Methods:Three elementary schools were selected representatively according to randomized cluster sampling methods, and totally 1048 children were selected in this investigation. The questionnaires including family investigation, PRS (The Pupil Rating Scale Revised Sereening for Leaning Disabilities), DCCC (Dyslexia Cheeklist for Chinese Children),and Combined Raven's Test.Results:74 children were diagnosed as having developmental dyslexia, the prevalence rate was 7.1%, and the rate on the subtype of the code deficiency were 2.7%-3.4%.The Logistic analysis was undertaken on the basis of single factor, and revealed that the risk factors to dyslexia including difficulty in finishing homework(OR=8.117) and no special time on reading (OR=2.250); and the protocol factors to dyslexia including education of father (OR=0.552) and the same parental style (OR=0.334).Conclusions:The prevalence rate of Chinese dyslexia was high according to the broad sense, and its influence referred to the factors about individual and parent. Thus the diagnosis, prevention and intervene should need the cooperation of parent and school.Part 2:The behavioral study on executive functions of Chinese dyslexia childrenObjective:To explore the Chinese developmental dyslexic children's executive functions.Methods:26 dyslexic children were chosen according to the International Classification of Diseases-10 (ICD-10), and the control group included 26 children matched for gender, age. All subjects took the Flank Task and Number Switch Task. The reaction time, accurate and switch cost were analyzed.Results:In the consistent condition, there is no significant difference on results of the accurate, reaction time (t=-1.10, P=0.28;t=-0.80, P=0.43). In the inconsistent condition, there is a significant difference on the accurate (t=-2.29, P=0.03) and the discrimination ability (t=-2.34, P=0.02). The error rate of dyslexic children was significantly higher on the switch trials (P<0.01)and marginal significantly higher on the non-switch trials (P=0.07) compared to the normal readers. And no significant difference both in the switch cost and the RTs between dyslexic and normal readers (P>0.01)Conclusions:Chinese dyslexic children had a deficiency in the executive functions.Part 3:The ERP study on executive function of Chinese dyslexia childrenObjective:To understand the brain mechanisms of executive dysfunction for Chinese developmental dyslexic children.Methods:16 dyslexic children were chosen according to the International Classification of Diseases-10 (ICD-10), and the control group included 16 children matched for gender, age. All subjects took the Flank Task and Number Switch Task. The ERPs of both groups were recorded and analyzed with the Neuroscan equipment.Results:There was no significant behavioral difference between the two groups, thus the experiment was suitable for the ERP study. In the inhibitory task, the dyslexia showed decreased P300 amplitude in the frontal site (t=2.19, P=0.036); and in switch task, the dyslexia showed significant difference in N2, P3b amplitudes(all Ps<0.05) and longer latency for P3b(t=-2.059, P=0.049).Conculsion:The executive dysfunction for dyslexia happened both in the rule-representation and task-set reconfiguration stages and also the conflict monitoring. |
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