Abstract: The N400 component of ERP implies anomalous processing in language semantics, its amplitude reflects the difficulty of semantic integration during processing. The N400 can be used as an important index to observe how meaning is constructed under discourse context. Discourse context can be categorized into linguistic context and nonlinguistic context. Previous studies on discourse processes using the N400 indicated that the linguistic context plays a constraining and coordinating role in sentence comprehension, which were found to specifically function in aspects of semantic priming in words, scenario goodness-of-fit, text message and causal inference; whereas the nonlinguistic context plays a constraining and complementary role in sentence comprehension, with its functional mechanism not known very well. The semantic information from the two different sources may probably be processed in parallel during the on-line comprehension

Key words: discourse context, ERP, semantic processing, N400