Mechanism of Reading Aloud and Covert Reading: Positron Emission Tomography Studies

Abstract

Using Statistical Parametric Mapping, we reanalyzed our positron emission tomography (PET) study on reading of Japanese kanji (morphogram) words, kana (phonogram) words and kana nonwords. Common activation between kanji and kana was observed in the superior temporal, lingual, inferior occipital, fusiform and inferior temporal gyri, among which activity was most pronounced in the fusiform/inferior temporal gyri with kanji and in the inferior occipital gyrus with kana, suggesting that kanji and kana are processed differently. We also compared covert reading with reading aloud. The anterior insula, primary sensorimotor cortex and supplementary motor area were activated separately in reading aloud compared with covert reading, i.e., articulation or vocalization, whereas the anterior precentral gyrus adjoining the middle frontal gyrus, medial parietal operculum and middle superior temporal gyrus were activated in a conjunction involving these two reading task pairs, suggesting that they are process components in reading itself.