eliciting perceptual signal. Rather than reflecting the activation of “a word’s meaning”, then, the N400 region of the ERP is more accurately described as reflecting the activity in a multimodal long-term memory system that is induced by a given input stimulus during a delimited timewindow as meaning is dynamically constructed (see discussion in Laszlo & Federmeier submitted). Such activity is observed for nonwords as for words, rendering the system more robust to input noise and providing a mechanism for implicit conceptual-level learning of novel stimuli (Gratton et al 2009). Baseline activity levels, however, will be higher for some stimuli than for others – because they are similar to or associated with many other things stored in memory (e.g., have high orthographic neighborhood sizes, large cohorts, or many lexical associates) and/or because they are linked to more meaning features (e.g., are ambiguous, more polysemous, concrete as opposed to abstract, etc.). Given evidence that the semantic feature information being accessed is widely distributed across the neural network, it also follows that different stimuli and types of stimuli (e.g., words and pictures) elicit functionally similar but spatially different activity patterns across this distributed network, resulting in the observed differences in the topography of
