A time and place for language comprehension: mapping the N400 and the P600 to a minimal cortical network

Abstract

We propose a new functional-anatomical mapping of the N400 and the P600 to a minimal cortical network for language comprehension. Our work is an example of a recent research strategy in cognitive neuroscience, where researchers attempt to align data regarding the nature and time-course of cognitive processing (from ERPs) with data on the cortical organization underlying it (from fMRI). The success of this “alignment” approach critically depends on the functional interpretation of relevant ERP components. Models of language processing that have been proposed thus far do not agree on these interpretations, and present a variety of complicated functional architectures. We put forward a very basic functional-anatomical mapping based on the recently developed Retrieval-Integration account of language comprehension (Brouwer et al., 2012). In this mapping, the left posterior part of the Middle Temporal Gyrus (BA 21) serves as an epicenter (or hub) in a neurocognitive network for the retrieval of word meaning, the ease of which is reflected in N400 amplitude. The left Inferior Frontal Gyrus (BA 44/45/47), in turn, serves a network epicenter for the integration of this retrieved meaning with the word's preceding context, into a mental representation of what is being communicated; these semantic and pragmatic integrative processes are reflected in P600 amplitude. We propose that our mapping describes the core of the language comprehension network, a view that is parsimonious, has broad empirical coverage, and can serve as the starting point for a more focused investigation into the coupling of brain anatomy and electrophysiology.

A Neurocomputational Model of the N400 and the P600 in Language Processing

“…The functional role of these pathways is, however, subject to an ongoing debate (Baggio & Hagoort, 2011; Bornkessel‐Schlesewsky & Schlesewsky, 2013; Friederici, 2009, 2011, 2012; Hickok & Poeppel, 2004, 2007; Saur et al., 2008; Tyler et al., 2011; Weiller, Musso, Rijntjes, & Saur, 2009), which turns out to be difficult to settle as DTI does not allow for the determination of pathway directionality (Friederici, 2011). Nonetheless, the existence of these pathways clearly shows that there is white matter connectivity that supports the bi‐directional information sharing between the lpMTG and lIFG required for RI processing cycles (see Brouwer & Hoeks, 2013, for further discussion).…”

Combinatorial semantics strengthens angular-anterior temporal coupling

“…Most of these models have offered detailed proposals about the neural correlates underlying meaning composition, involving different perisylvian left-lateralized brain regions (Binder & Desai, 2011;Friederici, 2012;Hagoort, 2013;Lau, Phillips, & Poeppel, 2008;Patterson, Nestor, & Rogers, 2007). Although these models present notable differences with respect to the main nodes involved and the interactions between them during semantic processes, all of them agree on the participation and roles of the posterior middle/superior temporal gyrus (MTG/STG) and inferior frontal gyrus (IFG) during language processing (see also Brouwer & Hoeks, 2013;Jefferies, 2013). In many of these models, accessing lexical/semantic information related to single words is associated with posterior MTG/STG activation (e.g., Friederici, 2012;Hagoort, 2013;Lau et al, 2008;Snijders et al, 2009) while the left IFG appears to orchestrate the activity of the whole semantic network via controlled retrieval of lexical/semantic information based on top-down processes (Badre & Wagner, 2007;Hagoort, 2013;Thompson-Schill, D'Esposito, Aguirre, & Farah, 1997;Thompson-Schill, D'Esposito, & Kan, 1999).…”

Expectation-based Comprehension: Modeling the Interaction of World Knowledge and Linguistic Experience

“…Frank and colleagues (2015), for instance, report a reliable correlation between N400 amplitude and surprisal. Critically, however, the RetrievalIntegration account predicts that an increase in N400 amplitude typically cooccurs with an increase in P600 amplitude (Brouwer et al, , 2012Brouwer & Hoeks, 2013;). An increase in P600 amplitude, on the other hand, does not necessarily cooccur with an increase in N400 amplitude (see Bornkessel-Schlesewsky & Schlesewsky, 2008;Brouwer et al, 2012;Kuperberg, 2007;for reviews).…”