Spatiotemporal dynamics of reading Kana (syllabograms) and Kanji (morphograms)

Reading engages complex neural networks integrating visual, phonological, and semantic information. The dual-stream model posits ventral and dorsal pathways for lexical and sublexical processing in the left hemisphere and is well-supported in alphabetic languages. However, its applicability to non-a...

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Main Authors: Kazuto Katsuse, Kazuo Kakinuma, Shin-Ichiro Osawa, Shoko Ota, Hana Kikuchi, Ai Kawamura, Kazushi Ukishiro, Kazuyo Tanji, Nobuko Kawakami, Chifumi Iseki, Shigenori Kanno, Yuichiro Shirota, Masashi Hamada, Tatsushi Toda, Hidenori Endo, Nobukazu Nakasato, Kyoko Suzuki
Format: Article
Language:English
Published: Elsevier 2025-08-01
Series:NeuroImage
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Online Access:http://www.sciencedirect.com/science/article/pii/S1053811925003192
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author Kazuto Katsuse
Kazuo Kakinuma
Shin-Ichiro Osawa
Shoko Ota
Hana Kikuchi
Ai Kawamura
Kazushi Ukishiro
Kazuyo Tanji
Nobuko Kawakami
Chifumi Iseki
Shigenori Kanno
Yuichiro Shirota
Masashi Hamada
Tatsushi Toda
Hidenori Endo
Nobukazu Nakasato
Kyoko Suzuki
author_facet Kazuto Katsuse
Kazuo Kakinuma
Shin-Ichiro Osawa
Shoko Ota
Hana Kikuchi
Ai Kawamura
Kazushi Ukishiro
Kazuyo Tanji
Nobuko Kawakami
Chifumi Iseki
Shigenori Kanno
Yuichiro Shirota
Masashi Hamada
Tatsushi Toda
Hidenori Endo
Nobukazu Nakasato
Kyoko Suzuki
author_sort Kazuto Katsuse
collection DOAJ
description Reading engages complex neural networks integrating visual, phonological, and semantic information. The dual-stream model posits ventral and dorsal pathways for lexical and sublexical processing in the left hemisphere and is well-supported in alphabetic languages. However, its applicability to non-alphabetic scripts remains unclear. The Japanese writing system, comprising Kana (syllabograms) and Kanji (morphograms) with distinct orthographic, phonological, and semantic properties, provides a unique framework to investigate neural dissociation between phonological and orthographic-semantic processing. Previous studies suggest that Kanji relies on the ventral route for whole-word recognition and semantic processing, whereas Kana depends mainly on the dorsal route for phonological decoding via grapheme-to-phoneme conversion; however, their spatiotemporal dynamics remain unknown. Using high-gamma power analysis from electrocorticography recordings in 14 patients with epilepsy and subdural implants, we examined the spatiotemporal neural dynamics of Kana and Kanji reading. Participants completed a visual lexical decision task with Kana and Kanji words and pseudowords. Across 912 electrodes, differential high-gamma power analysis showed that Kanji activated bilateral occipitotemporal fusiform regions early (120–550 ms) and the left inferior temporal gyrus (150–240 ms). Conversely, Kana showed prolonged late activation (270–750 ms) in the left-lateralised superior temporal, supramarginal, and inferior frontal gyri, especially during pseudoword processing. These findings indicate that Kanji relies on bilateral ventral stream earlier, while Kana depends on the left dorsal stream, with slower processing reflecting the extra grapheme-to-phoneme conversion. This underscores the value of non-alphabetic languages in elucidating both universal and script-specific neural mechanisms, advancing a cross-linguistic understanding of the reading network.
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spelling doaj-art-5c0876281dde477799b9e4c42e7f673e2025-08-20T03:31:24ZengElsevierNeuroImage1095-95722025-08-0131712131610.1016/j.neuroimage.2025.121316Spatiotemporal dynamics of reading Kana (syllabograms) and Kanji (morphograms)Kazuto Katsuse0Kazuo Kakinuma1Shin-Ichiro Osawa2Shoko Ota3Hana Kikuchi4Ai Kawamura5Kazushi Ukishiro6Kazuyo Tanji7Nobuko Kawakami8Chifumi Iseki9Shigenori Kanno10Yuichiro Shirota11Masashi Hamada12Tatsushi Toda13Hidenori Endo14Nobukazu Nakasato15Kyoko Suzuki16Department of Behavioral Neurology and Cognitive Neuroscience, Tohoku University Graduate School of Medicine, Japan; Department of Neurology, Graduate School of Medicine, The University of Tokyo, JapanDepartment of Behavioral Neurology and Cognitive Neuroscience, Tohoku University Graduate School of Medicine, JapanDepartment of Neurosurgery, Tohoku University Graduate School of Medicine, Japan; Department of Epileptology, Tohoku University Graduate School of Medicine, JapanDepartment of Behavioral Neurology and Cognitive Neuroscience, Tohoku University Graduate School of Medicine, JapanDepartment of Behavioral Neurology and Cognitive Neuroscience, Tohoku University Graduate School of Medicine, JapanDepartment of Behavioral Neurology and Cognitive Neuroscience, Tohoku University Graduate School of Medicine, JapanDepartment of Epileptology, Tohoku University Graduate School of Medicine, JapanDepartment of Psychiatry, Koishikawa Tokyo Hospital, JapanDepartment of Behavioral Neurology and Cognitive Neuroscience, Tohoku University Graduate School of Medicine, JapanDepartment of Behavioral Neurology and Cognitive Neuroscience, Tohoku University Graduate School of Medicine, JapanDepartment of Behavioral Neurology and Cognitive Neuroscience, Tohoku University Graduate School of Medicine, JapanDepartment of Neurology, Graduate School of Medicine, The University of Tokyo, JapanDepartment of Neurology, Graduate School of Medicine, The University of Tokyo, JapanDepartment of Neurology, Graduate School of Medicine, The University of Tokyo, JapanDepartment of Neurosurgery, Tohoku University Graduate School of Medicine, JapanDepartment of Epileptology, Tohoku University Graduate School of Medicine, JapanDepartment of Behavioral Neurology and Cognitive Neuroscience, Tohoku University Graduate School of Medicine, Japan; Corresponding author at: Department of Behavioral Neurology and Cognitive Neuroscience, Tohoku University Graduate School of Medicine, 2-1 Seiryo, Sendai 980-8575, Japan.Reading engages complex neural networks integrating visual, phonological, and semantic information. The dual-stream model posits ventral and dorsal pathways for lexical and sublexical processing in the left hemisphere and is well-supported in alphabetic languages. However, its applicability to non-alphabetic scripts remains unclear. The Japanese writing system, comprising Kana (syllabograms) and Kanji (morphograms) with distinct orthographic, phonological, and semantic properties, provides a unique framework to investigate neural dissociation between phonological and orthographic-semantic processing. Previous studies suggest that Kanji relies on the ventral route for whole-word recognition and semantic processing, whereas Kana depends mainly on the dorsal route for phonological decoding via grapheme-to-phoneme conversion; however, their spatiotemporal dynamics remain unknown. Using high-gamma power analysis from electrocorticography recordings in 14 patients with epilepsy and subdural implants, we examined the spatiotemporal neural dynamics of Kana and Kanji reading. Participants completed a visual lexical decision task with Kana and Kanji words and pseudowords. Across 912 electrodes, differential high-gamma power analysis showed that Kanji activated bilateral occipitotemporal fusiform regions early (120–550 ms) and the left inferior temporal gyrus (150–240 ms). Conversely, Kana showed prolonged late activation (270–750 ms) in the left-lateralised superior temporal, supramarginal, and inferior frontal gyri, especially during pseudoword processing. These findings indicate that Kanji relies on bilateral ventral stream earlier, while Kana depends on the left dorsal stream, with slower processing reflecting the extra grapheme-to-phoneme conversion. This underscores the value of non-alphabetic languages in elucidating both universal and script-specific neural mechanisms, advancing a cross-linguistic understanding of the reading network.http://www.sciencedirect.com/science/article/pii/S1053811925003192Japanese readingDual-route modelNon-alphabetic scriptElectrocorticographyKana and Kanji
spellingShingle Kazuto Katsuse
Kazuo Kakinuma
Shin-Ichiro Osawa
Shoko Ota
Hana Kikuchi
Ai Kawamura
Kazushi Ukishiro
Kazuyo Tanji
Nobuko Kawakami
Chifumi Iseki
Shigenori Kanno
Yuichiro Shirota
Masashi Hamada
Tatsushi Toda
Hidenori Endo
Nobukazu Nakasato
Kyoko Suzuki
Spatiotemporal dynamics of reading Kana (syllabograms) and Kanji (morphograms)
NeuroImage
Japanese reading
Dual-route model
Non-alphabetic script
Electrocorticography
Kana and Kanji
title Spatiotemporal dynamics of reading Kana (syllabograms) and Kanji (morphograms)
title_full Spatiotemporal dynamics of reading Kana (syllabograms) and Kanji (morphograms)
title_fullStr Spatiotemporal dynamics of reading Kana (syllabograms) and Kanji (morphograms)
title_full_unstemmed Spatiotemporal dynamics of reading Kana (syllabograms) and Kanji (morphograms)
title_short Spatiotemporal dynamics of reading Kana (syllabograms) and Kanji (morphograms)
title_sort spatiotemporal dynamics of reading kana syllabograms and kanji morphograms
topic Japanese reading
Dual-route model
Non-alphabetic script
Electrocorticography
Kana and Kanji
url http://www.sciencedirect.com/science/article/pii/S1053811925003192
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