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.

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Working memory (WM) performance is considered to change according to the nature of the task by adequate and prompt activation of corresponding functional connectivity in the brain. In the present study, we examined continuous prefrontal hemodynamic changes depending on reciprocal disposition of WM and non-WM tasks using two-channel near-infrared spectroscopy. To investigate possible functional connectivity deficits in autism spectrum disorder (ASD) during these tasks, relative concentration changes in oxygenated hemoglobin (Hb), deoxygenated Hb, and total Hb were compared between high-functioning ASD subjects (n = 11) and controls (n = 22). Instant evoked cerebral blood oxygenation changes were observed in response to the task switch in controls but not in ASD subjects, although the task performance rate was almost equivalent. Delayed or altered response of functional connectivity to incoming stimuli is considered a characteristic feature of ASD.

IntroductionWe investigated the neural processing of reading Japanese Kanji characters, which involves unique hierarchical visual processing, including the recognition of visual components specific to Kanji, such as “radicals.”MethodsWe performed functional MRI to measure brain activity in response to hierarchical visual stimuli containing (1) real Kanji characters (complete structure with semantic information), (2) pseudo Kanji characters (subcomponents without complete character structure), (3) artificial characters (character fragments), and (4) checkerboard (simple photic stimuli).ResultsAs we expected, the peaks of the activation in response to different stimulus types were aligned within the left occipitotemporal visual region along the posterior–anterior axis in order of the structural complexity of the stimuli, from fragments (3) to complete characters (1). Moreover, only the real Kanji characters produced functional connectivity between the left inferotemporal area and the language area (left inferior frontal triangularis), while pseudo Kanji characters induced connectivity between the left inferotemporal area and the bilateral cerebellum and left putamen.ConclusionsVisual processing of Japanese Kanji takes place in the left occipitotemporal cortex, with a clear hierarchy within the region such that the neural activation differentiates the elements in Kanji characters' fragments, subcomponents, and semantics, with different patterns of connectivity to remote regions among the elements.

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