Damage of White Matter in the Parietal Lobe Results in Anomic Alexia of Kana

Abstract

The reading and writing of two different types of Japanese words, "kana" and "kanji", are processed by different neural pathways. For example, kana are phonographic representations of words that are processed though the dorsal route related to phonological processing in a manner similar to that for words of phonetic languages (e.g., English). Investigators have reported that the left angular gyrus is critical for the process of writing kana 1,2 . By contrast, kanji are logographic representations of words and are processed through the ventral route related to visual processing in a manner similar to that for logographic languages (e.g., Chinese) [3][4][5] . Investigators have reported that the left posterior inferior or middle temporal cortex is critical for the process of reading or writing kanji 2,[6][7][8] . THE CANADIAN JOURNAL OF NEUROLOGICAL SCIENCES 113 BRIEF COMMUNICATIONSPatients with alexia and anomic aphasia, namely anomic alexia for kanji, present with lesions that correspond to the middle temporal gyrus and its subcortical area 9 . Conversely, alexia and anomic aphasia for English are induced by lesions of the left occipital and medial temporal lobe 10 . To date, there are no reports that characterize lesions responsible for anomic alexia for kana and the relationship between reading of kana and neural tracts remain unclear.Newer, noninvasive diagnostic modalities have enabled characterization of the neuroanatomic distribution of various language functions within the human brain. Of these new diagnostic modalities, diffuse tensor imaging (DTI) provides information regarding the trajectories of cerebral white matter Fig. 1A and Fig. 1B quantitatively,