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Published on: March 11, 2021
Two scripts, two pathways: dorsal-ventral biases in post-stroke kana-kanji agraphia
Takeshi Ito1,2, Yuichi Higashiyama1, Masayo Urano1,2,3
1Department of Neurology and Stroke Medicine, Yokohama City University Graduate School of Medicine, Kanazawa-ku, Yokohama, Kanagawa 236-0004, Japan.
Brain : a Journal of Neurology
|June 30, 2026
Summary
This study reveals distinct brain pathways for writing Japanese kana (phonograms) and kanji (morphograms) in stroke patients with aphasia. Findings show dorsal pathways for kana and ventral pathways for kanji, advancing understanding of writing disorders.
Area of Science:
- Neuroscience
- Linguistics
- Neurology
Background:
- Stroke-induced writing impairments offer insights into neural writing mechanisms.
- The Japanese writing system, with kana (phonograms) and kanji (morphograms), allows distinct analysis of writing pathways.
- Previous research on kana vs. kanji processing is limited by small cohorts and pure agraphia.
Purpose of the Study:
- To identify anatomical differences underlying phonogram (kana) versus morphogram (kanji) processing in a large stroke-induced aphasia cohort.
- To investigate distinct neural substrates for kana and kanji writing using advanced neuroimaging techniques.
- To explore script-specific neural processing in aphasia.
Main Methods:
- Analysis of 315 post-stroke aphasia patients with comprehensive language assessments (kana/kanji writing tests) and MRI.
- Multivariate support vector regression-based lesion-symptom mapping to correlate lesion locations with writing deficits.
- Structural disconnection analyses (disconnectome mapping) and tract-level regression to identify affected white matter pathways.
Main Results:
- Lesion-symptom mapping indicated left frontal regions for kana impairments and white matter under the supramarginal/angular gyri for kanji impairments.
- Disconnectome analyses implicated left dorsal pathways (arcuate fasciculus, superior longitudinal fasciculus) for kana writing and left ventral pathways (inferior fronto-occipital, inferior longitudinal fasciculus) for kanji writing.
- Tract-level regression confirmed a dissociation: kana outcomes associated with dorsal pathways, kanji outcomes with ventral pathways.
Conclusions:
- Distinct neural pathways exist for writing phonograms (kana) and morphograms (kanji).
- A dorsal-ventral pathway dissociation underlies kana and kanji writing impairments in aphasia.
- Findings enhance understanding of script-specific neural processing and may guide aphasia rehabilitation strategies.
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