More generally, this highlights the fact that the meaning of a stimulus is not computed at a single point in time, but rather something that emerges through time, with the activity measured in the N400 representing an important aspect of that emergent process, but not, certainly, the final state. Indeed, at the time of the N400, meaning states may still be incoherent, either because a given stimulus elicits more than one disparate meaning (i.e., is ambiguous or, as in the case of unfamiliar nonwords, broadly elicits activity associated with similar inputs) or because context information has induced one state and the incoming stimulus a different one (e.g., in the case of semantic anomalies, but also more generally when unexpected words are encountered or contextually-induced predictions are disconfirmed). Thus, initial conceptual representations, as reflected in the N400, will often need to be refined with time, either through continued interactions within semantic memory or via the application of later-occurring processes that serve to select meaning features, revise initial interpretations, or otherwise update meaning representations (for example, adding information that might not have become available by the time the N400 was triggered; see discussion in Federmeier & Laszlo 2009).
