Language-related Field Potentials in the Anterior-medial Temporal Lobe: II. Effects of Word Type and Semantic Priming

Field potentials were recorded from intracranial electrodes in humans to study the role of the anterior medial temporal lobe (AMTL) in language-related processing. Subjects viewed lists of words in which orthography and word type varied, or in which words were primed by semantic associates. Large negative field potentials were elicited within the AMTL by isolated words. The amplitude and intracranial distribution of these AMTL field potentials were consistent with those in our previous study in which anomalous sentence-ending words were used as stimuli (McCarthy et al., in press). The neocortex, in the region of the collateral sulcus and anterior fusiform gyrus, was identified as the likely neural generator of this field potential. The AMTL field potential was diminished by semantic priming, and was larger for words with semantic content than for words serving grammatical function. Orthographically illegal nonwords did not elicit this field potential. The N400 scalp event-related potential (ERP) has been shown to respond in the same manner to these task manipulations (Nobre and McCarthy, 1994), and, thus, the AMTL field potential was proposed to contribute to the generation of N400. The possible roles in language processing reflected by the AMTL field potential were considered.