Neuropsychological Mechinism Of Chinese Children With Dyslexia

Developmental dyslexia is characterized by an unexpected difficulty in reading in children and adults who otherwise possess the intelligence, motivation, and schooling considered necessary for accurate and fluent reading. Dyslexia is the most common of the learning disabilities, affecting 80% of all those identified as learning disabled. Once children present dyslexic, their behavior, cognition, emotion and social adaptation will be affected and thus be retarded to acquire any knowledge. There has been more than 100 years of studies on dyslexia in western countries. Many fields in dyslexia have been studied, including behavioral characteristics, cognitional model, disease mechanism and interventions. Chinese dyslexic study had not been developed because people thought that no one could be dyslexic within ideographic system for a long time. Until recent years, Chinese dyslexia turns into the focus. In this study, we discussed the mechanisms of Chinese dyslexic children using investigative research, cognitional research, neuropsychological research and genetic research in order to provide the epidemic features of this disorder in Chinese children and lay academic foundations for diagnosis, intervention and therapy of Chinese dyslexics.Epidemic Study on Chinese Dyslexic ChildrenIn order to study the epidemic characteristics of Chinese dyslexic children and disclose the risk factors of this disorder, 1200 children from four primary schools in Wuhan were randomly selected in this research. The questionnaires included family investigation, PRS(The Pupil Rating Scale Revised Screening for Learning Disabilities), DCCC(Dyslexia Checklist for Chinese Children) and WISC-CR(Wechsler Intelligence Scale for Children- Chinese Revision) were applied to investigate and collect data. The dyslexic children were diagnosed according to ICD-10 criteria.There were 69 children being found to be dyslexics. So the prevalence rate was 6.30%. The prevalence rate of boys was higher than that of girls (P<0.01). Simple factorial analysis showed that family environments (parents' occupation and nurture-ways) and children's own factors had influences on dyslexia. Multiple Logistic regression analysis showed the following 5 factors could be put into it. They were sex, learning pressure, being tired of school, father's educational background and satisfaction level of parents. Such 3 risk factors as gender (boy)(OR=2.087), higher pressures (OR=3.521) and being tired of school (OR=1.227) could induce the disorder. These are two protective factors: father's higher education (OR=0.594) and higher satisfaction level of parents (OR=0.393).In summary, since the number of Chinese dyslexic children was not low, parents and teachers should pay more attention to them. Many factors affected on this disorder including family environments (socioeconomic status, parents' occupation and nurturing-ways), children's own factors (being tired of school and high pressures). So, interventions and therapies of dyslexics need whole efforts not only from their families, but also from the schools and society, for example, positive education ways of parents and teachers, harmonious family environments and comfortable learning atmospheres.Cognitive deficits for reading in Chinese children with dyslexiaIn this part, we studied cognitive deficits of Chinese dyslexic children in phonological processing, characters' recognition and words access with the method of case-control. On the base of paradigm of phonetic awareness, phonological recognition task and phonological exchanging task were used to study the ability of onset/rhyme detection and phoneme synthesis. In order to explore the function of phonology and semanteme in Chinese characters' recognition, we used naming task and lexical decision task. At the same time, phonological priming/semantic priming in naming task and lexical decision task were also adopted.The results of phonological processing showed that reaction time of dyslexic group was longer than that of control group and correct rate of dyslexic group was lower than that of control group. Two factors using analysis of variance showed that both different group and different tasks affected the reaction time and correct rate. There was significant difference (P<0.01).The research of characters' recognition and words access: â‘ naming task without priming character results showed reaction time of dyslexic children was longer than that of control group(Dyslexia: 2.22±0.70, Control: 1.73±0.30), and the correct rate of dyslexics was lower(Dyslexia: 0.96±0.06, Control: 1.00±0.00). Both of them had significant difference (.P<0.05). Lexical decision task without priming character results showed reaction time of dyslexic children was longer than that of control group(Dyslexia: 4.81± 1.38, Control: 3.48±0.55), and the correct rate of dyslexics was iower(Dyslexia: 0.92±0.07, Control: 0.98±0.03). Both of them had significant difference (P<0.01).â‘¡When priming task was phonological, the correct rate of naming characters in dyslexia group was significant lower than that of controls(Dyslexia: 0.960±0.057, Control: 0.995±0.014, P<0.05); the reaction time of lexical decision in dyslexia group was longer(Dyslexia: 2.22±0.48,Control: 1.75±0.37, P<0.01). â‘¢When priming task was semantic, the reaction time of naming characters in dyslexia group was longer (Dyslexia: 5.67±1.73, Control: 4.38±0.96, P<0.05); the reaction time of lexical decision in dyslexia group was obviously longer (Dyslexia: 5.26±1.70, Control 1: 3.56±0.74, P<0.01) and correct rate was lower (Dyslexia: 0.92±0.04, Control: 0.97±0.03,P<0.01).In summary, there existed phonological awareness deficits and disability of phonological processing in Chinese children with dyslexia, one of the possible causes for reading disability. Naming task and lexical-decision task without priming character performances of dyslexic children was worse than that of the control children. The significant difference between two groups showed effects of both phonological and semantic priming influenced performing these tasks. Dyslexic children had not only phonological deficits but also disability of semanteme. We inferred that dyslexic children possessed processing deficits in these two accesses: the first one was from grapheme to meaning; the second one was from grapheme-phonology to meaning.Brain mechanism for phonological deficits in Chinese children with dyslexia: a fNIRI studyIn present brain functional imaging study, we aimed to explore the state of brain functions in dyslexic children during phonological processing and further more to explore the neuropsychological mechanism of dyslexics. We used functional near-infrared imaging (fNIRI) technique to observe prefrontal cerebral blood flowing and metabolically characteristic of 20 dyslexic children from elementary school and 20 healthy children who have the normal reading ability from the same school as the case-control.Based on the results of fNIRI observed, the changes of oxyhemoglobin(HbO₂) and totle hemoglobin (THb ) of dyslexics were lower than that of normal readers. Taking the channel 3 as the example, deoxyhemoglobin (Hb) was negative correlation with HbO₂ and THb in control group with the correlation coefficient -0.95 , -0.72 respectively, and HbO₂ between THb was positive correlation(r=0.90) . In dyslexic group, Hb between HbO₂ was negative correlation(r=-0.46), and Hb between THb (r=0.35) and HbO₂ between THb( r = 0.68)both were positive correlation. There were significant differences in these correlation coefficients. The results also showed that during onset detection task the value of Hb was significant different between two groups in channel 13(Dyslexia: 0.0108, Control: -0.0033, P<0.05 ), the value of HbO₂ was different in channel 12(Dyslexia: 0.0005, Control: 0.0336, P<0.05). During rhyme detection task, the value of Hb was different in channel 10(Dyslexia: -0.0089, Control: 0.0014, P<0.05), the value of HbO₂ was different in channel 3(Dyslexia: -0.0114, Control: 0.0282, P<0.01) and in channel 11(Dyslexia: -0.0317, Control: 0.0758, P<0.01), and the value of THb was different in channel 3(Dyslexia: 0.0000, Control: 0.0328, P<0.05) and in channel 11(Dyslexia: -0.0118, Control: 0.0617, P<0.05). During consonant exchanging task, the value of Hb was different in channel 10(Dyslexia: -0.0174, Control: 0.0008, P<0.05), the value of HbO₂ was different in channel 11 (Dyslexia: -0.0555, Control: 0.0510, P<0.05 ), and the value of THb was different in channel 9(Dyslexia: -0.0137, Control: 0.0104, P<0.05). During vowel exchanging task, the value of HbO₂ was different in channel 3(Dyslexia: -0.1579, Control: 0.0366, P<0.05) , in channel 5(Dyslexia: 0.0003, Control: 0.0131, P<0.05) and channel 11 (Dyslexia: -0.0845, Control: 0.0394 , P<0.05); the value of THb was different in channel 10(Dyslexia: -0.1110, Control: 0.0091, P<0.05).In conclusion, the cortexes of prefrontal lobe in dyslexia children group were less activated when performing phonological processing. The cerebral blood flowing couldn't increase as the cognitive task flash on the screen and the oxyhemoglobin reduced. Especially the Broca Area and left dorsolateral prefrontal cortex were less activated obviously. It suggested there exited significant difference both the prefrontal metabolizable mechanism and the pattern of activity between two groups. The biological foundation for dyslexia could be hypothesized. The association of gene polymorphisms and dyslexia in Chinese childrenThis study was aimed to search the genetic factors for Chinese dyslexics and provide some practical experience for the further study of this disorder. The method of case-control was used. Children's buccal cells were collected as a source of DNA for polymorphism analysis and allele specific analysis (ASA). The genotypes were tested by polymerase chain reaction following restriction fragment length polymorphism analysis (PCR-RFLP).There were no significant difference in the distribution of genotypes and alleles frequencies of the -3 position in the second extron of DYX1C1 gene between dyslexic group and normal group (P>0.05). After adjusting for sex with multiple logistic regression analysis, no significant higher risk was found in any genotype of this position (P>0.05).In summary, it was suggested that genetic polymorphism of this position in DYX1C1 gene might be not the susceptible factor of Chinese dyslexia. More researches should be done about other positions in DYX1C1. It was feasible and valid for collecting buccal cells as a source of DNA for study on genetic mechanism of dyslexia.