| This course of research evaluates what the N400 event-related potential (ERP) component can inform us with regard to the organization of semantic memory and semantic processing for words and pictures. The N400 component differentiates between semantically primed and unprimed stimuli, and has been considered a linguistic processing component. The fact that the N400 is also elicited by pictorial stimuli lends itself to the hypothesis that the N400 reflects processing within an amodal semantic system. However, differing findings across studies leaves that hypothesis tentative at best. The present series of studies attempts to evaluate the discrepancies across studies and to provide a stronger test for that hypothesis.;Within a linguistic context, both words and pictures produce comparable N400 effects (differentiation between primed and unprimed stimuli). Within a pictorial context, words but not pictures were found to produce N400 effects. Evidence from the present course of experiments supports the existence of both modality-specific and shared memory systems. It appears that while normal linguistic processing necessarily entails activity within a semantic memory system (from which the N400 originates), processing of pictorial stimuli may or may not entail activity within that memory system. Explanations for such a pattern of findings are discussed in the context of prevalent models of semantic memory and evidence from other lines of research. |
