With the growing sense of the N400 as an index of semantic memory and the dynamic processing that unfolds within it, it became of interest to localize the source(s) of this activity, to answer the question of not only what brain areas might be involved but when and how they might contribute (reviewed in Van Petten & Luka 2006; Lau et al. 2008). Some attempts have been made to model the scalp-recorded signal, but more exciting developments involved the use of intracranial recording techniques, typically in individuals with epilepsy prior to surgical intervention. Such studies have identified a widely distributed set of brain regions co-active with the scalp-recorded N400. These include a source in the anterior medial temporal lobe (functionally akin to the scalp N400 with respect to manipulations of semantic priming, semantic congruity, repetition, and recognition (verbal) memory), in middle and superior temporal areas, inferior temporal areas, and prefrontal areas. Essentially these same brain areas in both hemispheres (although perhaps stronger in the LH) also have been identified by other neuroimaging techniques such as the magnetic counterpart of the
