Spatiotemporal Brain Activity During Hiragana Word Recognition Task

Abstract

The 19-channel Event-Related Potentials (ERPs) we recorded during recognition of hiragana (one type of Japanese phonetic characters) were simultaneously and independently presented as a word and a nonword to opposite eyes using a field-sequential stereoscopic 3D display with a liquid-crystal shutter, a word and a non-word were simultaneously and independently presented to the left (right) and the right (left) eyes, respectively. Each word consists of 3 hiragana characters. Three subjects were instructed to press a button when they understood the meaning of the visual stimuli after 3,000 ms poststimulus. Equivalent Current Dipole source Localization (ECDL) with 3 unconstrained ECDs was applied to the ERPs. In the case of right-handed subjects, the ECDs were localized to the Wernicke’s area at around 600 ms. In the case of left-handed subject, the ECD was localized to the Wernicke’s homologue. After that ECDs were then localized to the prefrontal area, the superior frontal gyrus, and the middle frontal gyrus. At around 800 ms, the ECDs were localized to the Broca’s area, then after that ECDs were relocalized to the the Wernicke’s area and to the Broca’s area.