Priming effects in Chinese character recognition for Chinese children with developmental dyslexia

BACKGROUND： Dyslexic children exhibit reading ability unmatched to age, although they possess normal intelligence and are well educated. OBJECTIVE： To examine the performance of dyslexic children in Chinese characters visual recognition tasks and to investigate the relationship between priming effect in character recognition and dyslexia. DESIGN, TIME AND SETTING： A case-control study was performed at the Department of Children and Adolescent Health and Maternal Care, School of Public Health, Tongji Medical College, Huazhong University of Science and Technology between March and June 2007. PARTICIPANTS： A total of 75 primary school students in grades 3 and 5 were selected from two primary schools in Wuhan City, Hubei province, China, and were assigned to three groups. （1） Reading disability （RD, n = 25）; （2） chronological age （CA） group （n = 25 normal readers that were intelligence quotient and age-matched to the RD group）; （3） reading level （RL） group （n = 25 normal readers that were intelligence quotient and RL-matched to the RD group）. All children were right-handed and had normal or corrected-to-normal vision. METHODS： Recognition of target characters was performed in each child using a masked prime paradigm. Recognition speed and accuracy of graphic, phonological, and semantic characters were examined. Simultaneously, data, with respect to response time for each target character and error rate, were recorded to calculate facilitation values （unrelated RT-related RT）. MAIN OUTCOME MEASURES： Response time, facilitation, and error rate in Chinese character recognition task were calculated. RESULTS： The baseline-adjusted facilitation of graphic, phonological, and semantic priming for dyslexic children was -0.010, -0.010, and 0.001, respectively. Dyslexic children displayed inhibition in graphic and phonological prime conditions. Facilitations under the three prime conditions were 0.026, 0.026, and 0.022 for the CA group. In the RL group, results were 0.062, 0.058, and 0.031 respectively. The differences of baseline-adjusted facilitation across the three groups were significant [F （2, 216） = 17.91, P 〈 0.01 ], whereas the main effect of prime condition IF （2, 216） = 0.49, P 〉 0.05] and the interaction of group x prime condition [F （4, 216） = 0.91, P 〉 0.05] were not significant. The error rate under the three prime conditions was 0.066, 0.077, and 0.079 for the RD group. As for the CA group, the results were 0.057, 0.071, and 0.074 accordingly, and in the RL group, the results were 0.119, 0.111, and 0.121, respectively. The difference of error rate across the three groups was significant （F = 6.61, P = 0.002）. The error rate was significantly greater in the RL group, compared with the CA and RD groups, while no significant difference existed between the RD and CA groups. CONCLUSION： Dyslexic children were slower to recognize target characters than normal readers, and did not exhibit significant prime effects in graphic and phonological primer condition. These results suggested that dyslexic children exhibited general deficits in phonological and graphic processing, and presented a different pattern in character recognition. These results could be interpreted by parallel-distributed processing models.

DCDC2 gene polymorphisms are associated with developmental dyslexia in Chinese Uyghur children

Developmental dyslexia is a complex reading and writing disorder with strong genetic components. In previous genetic studies about dyslexia, a number of candidate genes have been identified. These include DCDC2, which has repeatedly been associated with developmental dyslexia in various European and American populations. However, data regarding this relationship are varied according to population. The Uyghur people of China represent a Eurasian population with an interesting genetic profile. Thus, this group may provide useful information about the association between DCDC2 gene polymorphisms and dyslexia. In the current study, we examined genetic data from 392 Uyghur children aged 8–12 years old from the Xinjiang Uyghur Autonomous Region of China. Participants included 196 children with dyslexia and 196 grade-, age-, and gender-matched controls. DNA was isolated from oral mucosal cell samples and fourteen single nucleotide polymorphisms（rs6456593, rs1419228, rs34647318, rs9467075, rs793862, rs9295619, rs807701, rs807724, rs2274305, rs7765678, rs4599626, rs6922023, rs3765502, and rs1087266） in DCDC2 were screened via the SNPscan method. We compared SNP frequencies in five models（Codominant, Dominant, Recessive, Heterozygote advantage, and Allele） between the two groups by means of the chi-squared test. A single-locus analysis indicated that, with regard to the allele frequency of these polymorphisms, three SNPs（rs807724, rs2274305, and rs4599626） were associated with dyslexia. rs9467075 and rs2274305 displayed significant associations with developmental dyslexia under the dominant model. rs6456593 and rs6922023 were significantly associated with developmental dyslexia under the dominant model and in the heterozygous genotype. Additionally, we discovered that the T-G-C-T of the four-marker haplotype（rs9295619-rs807701-rs807724-rs2274305） and the T-A of the two-marker haplotype（rs3765502-1087266） were significantly different between cases and controls. Thus, we conclude that DCDC2 gene polymorphisms are associated with developmental dyslexia in Chinese Uyghur children.