Electroencephalographic activity in a flanker interference task using Japanese orthography

The neural activities for color word interference effects were investigated using event-related brain potentials (ERPs) recorded in a flanker-type interference task. Kanji words (Japanese morphograms) and kana words (Japanese phonograms) were used as the flanker stimuli to obtain insights about hemispheric specialization for processing two types of Japanese orthographies. Interference effects in reaction time were larger when kanji words were presented in the left visual field and when kana words were in the right visual field. ERPs were modulated by the incongruent flankers, which generated a negative ERP component with the different onset and offset depending on flanker attributes. Consistent with the behavioral data, the interference-related negativity was observed for kanji words presented in the left visual field and for kana words in the right visual field. The negativity distributed maximally over the fronto-central site. The early part of the negativity distributed strongly over the frontal midline area, whereas it extended bilaterally over the frontal area in the late phase. The present results support the view of preferential processing of kanji in the right hemisphere and that of kana in the left hemisphere. The temporal profile of scalp topographies for the interference-related neural activity suggests that the medial and dorsolateral prefrontal regions may be involved in maintaining attentional set and conflict resolution.