On the Proper Treatment of the N400 and P600 in Language Comprehension

Event-Related Potentials (ERPs)—stimulus-locked, scalp-recorded voltage fluctuations caused by -synaptic neural activity—have proven invaluable to the study of language comprehension. interest in the ERP signal are systematic, reoccurring voltage fluctuations called components, are taken to reflect the neural activity underlying specific computational operations carried in given neuroanatomical networks (cf. Näätänen and Picton, 1987). For language processing, N400 component and the P600 component are of particular salience (see Kutas et al., 2006, a review). The typical approach to determining whether a target word in a sentence leads differential modulation of these components, relative to a control word, is to look for effects mean amplitude in predetermined time-windows on the respective ERP waveforms, e.g., 350–550 ms for the N400 component and 600–900 ms for the P600 component. The common of operation in psycholinguistics, then, is to tabulate the presence/absence of N400- and/or 600-effects across studies, and to use this categorical data to inform neurocognitive models attribute specific functional roles to the N400 and P600 component (see Kuperberg, 2007; -Schlesewsky and Schlesewsky, 2008; Brouwer et al., 2012, for reviews). , we assert that this Waveform-based Component Structure (WCS) approach to ERPs to inconsistent data patterns, and hence, misinforms neurocognitive models of the of language processing. The reason for this is that the WCS approach ignores latent component structure underlying ERP waveforms (cf. Luck, 2005), thereby leading to about component structure that do not factor in spatiotemporal component overlap of N400 and the P600. This becomes particularly problematic when spatiotemporal component interacts with differential P600 modulations due to task demands (cf. Kolk et al., 2003). While the problem of spatiotemporal component overlap is generally acknowledged, and invoked to account for within-study inconsistencies in the data, its implications are overlooked in psycholinguistic theorizing that aims to integrate findings across studies. We WCS-centric theorizing to be the single largest reason for the lack of convergence regarding processes underlying the N400 and the P600, thereby seriously hindering the advancement of theories and models of language processing.