Event-related potentials study on cross-modal discrimination of Chinese characters

Event-related potentials (ERPs) were measured in 15 normal young subjects (18-22 years old) using the "cross-modal and delayed response" paradigm, which is able to improve inattention purity. The stimuli consisted of written and spoken single Chinese characters. The presentation probability of standard stimuli was 82.5% and that of deviant stimuli was 17.5%. The attention components were obtained by subtracting the ERPs of inattention condition from those of attention condition. The results of the N1 scalp distribution demonstrated a cross-modal difference. This result is in contrast to studies with non-verbal as well as with English verbal stimuli. This probably reflected the brain mechanism feature of Chinese language processing. The processing location of attention was varied along with verbal/ non-verbal stimuli, auditory/visual modalities and standard/deviant stimuli, and thus it has plasticity. The early attention effects occurred before the exogenous components, and thus provided evidence supporting the early selective theory of attention. According to the relationship of N1 and Nd1, the present result supported the viewpoint that the N1 enhancement was caused by endogenous components overlapping with exogenous one rather than by pure exogenous component.