[Preserved implicit reading and the recovery of explicit reading in a pure alexic]

We described a 55-year-old, right-handed, university-educated Japanese man who showed pure alexia after an infarction in the territory of the left posterior cerebral artery. Damage to the corpus callosum was limited to the most caudal part of the splenium. In the early days of his illness, he demonstrated the inability to read aloud on either Kana (Japanese syllabograms) or Kanji (Japanese morphograms). In contrast, he could semantically categorize Kanji-words such as animals or non-animals. Subsequently, he gradually regained the ability of reading aloud Kanji as well as Kana. At that time, we further investigated the relation between his reading ability and the attributes of 881 Kanji characters including hieroglyphicity, concreteness, and familiarity. We found that he could more readily read Kanjis with higher hieroglyphicity, concreteness, and familiarity. The reading times for Kanji-words were significantly shorter than those of corresponding Kana-words. Moreover, he showed some difficulty to read Kana-words and Kana combinations without meaning when asked to perform repetitive opposing movements with his thumb and little finger inhibiting kinesthetic reading. The effect was not observed when he read Kanji-words. These results lead us to suggest the following: (1) the two components of reading, reading aloud and comprehension abilities, are dissociable in a pure alexic, especially in Kanji reading; and (2) recovery mechanisms underlying Kanji and Kana reading were different in our case. Namely, restitution of the direct connection through the residual splenium fibers between the visual word form processing area in the right hemisphere and the left angular gyrus was attributed to Kanji reading, and utilization of kinesthetic reading played an important role in Kana reading.