More specifically, one early line of N400 work tested long-standing questions about whether semantic memory is best thought of as a single, amodal system (similarly accessed by stimuli with different surface forms, such as pictures and words) or as comprising a number of distinct (sub)systems (reviewed in Kutas & Federmier 2000). The answer provided by N400 data – namely, yes and yes -- raised serious questions about the validity of this debate. For, although there were broad similarities (in waveshape, timecourse, and functional sensitivity of the N400 effect), there were also important differences (especially in terms of scalp topography) in the response to different types of meaningful items. Although much of the debate focused on comparisons of pictures and words, a wide range of stimulus types have been investigated, including faces, environmental sounds, and even odors. Pictures elicited a similar but more frontally-distributed N400, similar to that for concrete words (Ganis, Kutas & Sereno 1996). The N400 effects for familiar faces completed by mismatching versus matching internal features had an occipital maximum (Olivares et al 1999). Within-subject comparisons of words
