Different Interhemispheric Transfer of Kanji and Kana Writing Evidenced by a Case With Left Unilateral Agraphia Without Apraxia

Abstract

Recent neuropsychological studies have revealed that the processing of kanji (the Japanese morphograms) and kana (the Japanese syllabograms) involves different intrahemispheric mechanisms. We describe a patient showing left unilateral agraphia without apraxia for kanji, but not for kana, who was diagnosed by magnetic resonance imaging as having a lesion of the posterior body of the corpus callosum. This patient indicates that different neural pathways are used for kanji and kana not only intrahemispherically, but also interhemispherically.

Somesthetic Disconnection Syndromes in Patients with Callosal Lesions

“…None of the cases exhibited aphasia, and their ability to read aloud under conditions of free vision was excellent. Callosal signs other than somesthetic ones have been reported previously for cases 1 [4]and 2 [5, 6, 7]. …”

“…The autopsy in case 1 revealed lesions localized to the posterior truncus of the corpus callosum (for MRI of case 1, see Kawamura et al [4]). MRI in case 2 revealed lesions throughout the corpus callosum except in the rostrum [5, 6], and in case 3 it revealed lesions in the caudoventral part of the posterior truncus (fig.…”

Morphometry of the corpus callosum in Chinese children: relationship with gender and academic performance

“…Several clinical studies have also alluded to this hypothesis. Global and permanent alexia and apraxia, as well as other disorders of language, have been shown to relate to the interference of flow from the left hemisphere to the right across the posterior corpus callosum [6,7]. Egaas et al [34] examined 51 autistic patients (age 3-42 years) and found that the overall size reduction in the corpus callosum was concentrated in the posterior subregions where parietal lobe fibres are known to project [13].…”

Kinesthetic Alexia due to Left Parietal Lobe Lesions

“…6, *2). The somatosensory information from the left hand necessary for kinesthetic reading is thought to be transferred to the left superior parietal lobule via the anterior or dorsal part of the posterior truncus of the corpus callosum [13], although kana and kanji may not be transferred via exactly the same portion of the corpus callosum [29]. …”