High-density mapping in an N400 paradigm: evidence for bilateral temporal lobe generators

Objective: The aim of this study was to obtain a more detailed description of N400 scalp topography than has previously been reported. Methods: High-density (128 channel) visual event-related potentials were me asured in an N400 paradigm using semantically incongruous sentence endings. Results: The stimuli elicited an N400 with a centroparietal scalp distribut ion. In addition, P400s with similar timing and functional characteristics were observed at non-standard recording locations inferior to the temporal lobes. Conclusions: The data are consistent with intracranial evidence for bilater al activation of anterior medial temporal lobe structures. These structures are oriented such that the positive regions of their scalp fields lie larg ely outside of the area sampled by standard electrode montages. P400s at ot her non-standard scalp locations, including infraorbital and infraoccipital sites, may reflect volume conduction from the same generators, or activati on of non-temporal lobe generators. (C) 2000 Elsevier Science Ireland Ltd. All rights reserved.