Functionality of the N400 component and its application in studies of figurative language processing: a systematic review

Electrophysiological studies have increased in the field of Neuroscience of Language as they allow for detailed analyses of the temporal course of language processing. In figurative language research, the most employed technique is Event Related Potentials (ERPs). The N400 is the most studied ERP component and is usually described as a marker of difficulty or effort in semantic processing. However, many controversial results about N400 have been found. Two main reasons can be raised for these results: (1) methodological difficulties in controlling psycholinguistic variables that are known to affect language processing and (2) different interpretations regarding what the N400 indexes. In this systematic review our main goals are: (1) providing a general panorama of studies on the N400 component applied to metaphoric and idiomatic language and (2) discussing the different views adopted by researchers regarding functional N400 theories and how ERP studies of figurative processing fit into each of those theories. We found two main interpretations about the process which is indexed by the N400: N400 as a marker of lexical access or as a marker of semantic integration. We also found that this dichotomy has an impact on the choice of models to explain the results about figurative language processing.