Association Between Resting-State Functional Connectivity and Reading in Two Writing Systems in Japanese Children With and Without Developmental Dyslexia

Abstract

Introduction: Japanese is unique, as it features two distinct writing systems that share the same sound and meaning: syllabic Hiragana and logographic Kanji scripts. Acquired reading difficulties in Hiragana and Kanji have been examined in older patients with brain lesions. However, the precise mechanisms underlying deficits in developmental dyslexia (DD) remain unclear. Materials and Methods: The neural signatures of Japanese children with DD were examined by using restingstate functional magnetic resonance imaging. We examined 22 dyslexic and 46 typically developing (TD) children, aged 7-14 years. Results: Reading performance in each writing system was correlated with neural connectivity in TD children. In contrast, in children with DD, weak associations between neural connectivity and reading performance were observed. In TD children, Hiragana-reading fluency was positively correlated with the left fusiform gyrus network. No significant correlations between Hiragana fluency and neural connectivity were observed in children with DD. Correspondingly, there were fewer correlations between Kanji accuracy and strength of reading-related connectivity in children with DD, whereas positive correlations with the bilateral fronto-parietal network and negative correlations with the left fusiform network were found in TD children. Discussion: These data suggest that positive and negative coupling with neural connectivity is associated with developing Japanese reading skills. Further, different neural connectivity correlations between Hiragana fluency and Kanji accuracy were detected in TD children but less in children with DD. Conclusion: The two writing systems may exert differential effects and deficits on reading in healthy children and in children with DD, respectively.

Academic achievements and brain volume development in children and adolescents

“…2010 ). In addition to visual word processing, letter-to-sound transformation in the fusiform network may be associated with the Japanese vocabulary with morphologically complex letters ( Hashimoto et al. 2020 ).…”

“…First, 144 children and adolescents aged 6–18 years were recruited through a newspaper advertisement as control subjects for studies of developmental disorders ( Hashimoto et al. 2020 , 2021 ).…”

Maternal education as an environmental factor related to reading in children with reading difficulties: A functional magnetic resonance imaging study

“…Future studies include diversifying the sample to include more mothers with lower education levels. In addition, we controlled for mean motion in our analysis for power; however, future analysis include employing a lenient exclusion criterion of mean motion >0.5 mm following Hashimoto et al (2020) due to paediatric populations having excessive motion (Power et al, 2014). We suggest that children with RDs may be relying more on visual imagery and semantic retrieval when listening to stories through the increased engagement of the receptive language network to visual processing regions when they have mothers with higher education levels.…”

Neural bases of reading fluency: A systematic review and meta-analysis

“…Reduced FC can also be seen in dysfluent readers when directly compared to those with typical reading development, especially in the reading network. When native Japanese speakers read in Hiragana, a Japanese syllabary with a very shallow orthography, individuals with DD (characterized by poor fluency) showed decreased FC between a seed region in the left fusiform gyrus and left ventrolateral prefrontal cortex (VLPFC), TPJ, IPL, MTG, insula, medial PFC, and right temporal pole, but increased connectivity with the left precentral gyrus, compared to typical readers (Hashimoto et al, 2020). A comparison of high- and low-fluency readers in English also showed reduced FC in low-fluency readers within two cognitive control networks: the cingulo-opercular (CO) and ventral attention (VA) networks (Freedman et al, 2020), the latter of which overlaps extensively with the traditional reading network’s frontal and temporal regions.…”