Analysis of kanji and kana word reading process by H215O-PET

Regional cerebral blood flow was measured during kanji or kana word reading with the intravenous H215O bolus injection technique by positron emission tomography. Reading aloud tasks of kana non-word, kana word and kanji word were given to five subject each. Three times intra-subject averaging and region of interest(ROI) - based regional cerebral blood flow (rCBF) change analyses revealed as follows. Both kana non-word and kana word tasks activated widespread regions including bilaterally the medial and lateral occipital gyri and the left posterior inferior temporal area (PIT), while the kanji word task only activated the PIT of both hemispheres. The medial and lateral occipita gyri were activated almost equally by both kana non-word and kana word tasks, but the PIT was activated left-side dominantly by the kana word task. In addition, there were significantly more rCBF increases in the left PIT in the kana word task than in the kana non-word task. The parietal lobe was not activated at all, on the contrary, the left angular gyrus was significantly deactivated by all the tasks. For language output, the left or both posterior inferior frontal gyri were activated together with the supplementary motor area, the left or both basal ganglia, and the left or both thalamus and cerebellum. The left-side dominant activation of Broca's area was obtained only in the kanji word task. (author) 59 refs