Although aphasiology is the historical core of neurolinguistics, in recent years the field has broadened considerably, thanks in part to the emergence of new brain imaging technologies (such as PET and fMRI) and time-sensitive electrophysiological techniques (EEG and MEG), which can highlight patterns of brain activation as people engage in various language tasks; electrophysiological techniques, in particular, emerged as a viable method for the study of language in 1980 with the discovery of the N400, a brain response shown to be sensitive to semantic issues in language comprehension. The N400 was the first language-relevant event-related potential to be identified, and since its discovery EEG and MEG have become increasingly widely used for conducting language research.