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

Abstract

Ten years ago, researchers using event‐related brain potentials (ERPs) to study language comprehension were puzzled by what looked like a Semantic Illusion: Semantically anomalous, but structurally well‐formed sentences did not affect the N400 component—traditionally taken to reflect semantic integration—but instead produced a P600 effect, which is generally linked to syntactic processing. This finding led to a considerable amount of debate, and a number of complex processing models have been proposed as an explanation. What these models have in common is that they postulate two or more separate processing streams, in order to reconcile the Semantic Illusion and other semantically induced P600 effects with the traditional interpretations of the N400 and the P600. Recently, however, these multi‐stream models have been called into question, and a simpler single‐stream model has been proposed. According to this alternative model, the N400 component reflects the retrieval of word meaning from semantic memory, and the P600 component indexes the integration of this meaning into the unfolding utterance interpretation. In the present paper, we provide support for this “Retrieval–Integration (RI)” account by instantiating it as a neurocomputational model. This neurocomputational model is the first to successfully simulate the N400 and P600 amplitude in language comprehension, and simulations with this model provide a proof of concept of the single‐stream RI account of semantically induced patterns of N400 and P600 modulations.

Modeling the N400 ERP component as transient semantic over-activation within a neural network model of word comprehension

“…John & McClelland, 1990). It is also important to extend the approach to address the properties of other comprehension-related ERP components, such as the P600 and its apparent complementary sensitivity to syntactic but not semantic violations (Friederici 1995; Hagoort, Brown & Groothusen 1993; but see Brouwer, Fitz & Hoeks 2012; Brouwer & Hoeks 2013; Brouwer, Crocker, Venhuizen & Hoeks in press; Kuperberg 2007 for an interesting alternative perspective in which the relevant distinction is between lexical-level vs. sentence-level integration).…”

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

“…Brouwer et al, (2012) adapt this perspective on the N400 as part of the Retrieval-Integration hypothesis and argue that the process of integrating word meaning with the unfolding utterance representation is instead reflected in P600 amplitude, a late positive deflection of the ERP signal. Under this view, our comprehension-centric formalization of surprisal is predicted to be reflected in the P600; surprisal is a measure of how likely a transition is from one interpretative state to the next, and P600 amplitude is a reflection of the neurophysiological processing involved in this transition (see also Brouwer, 2014;Brouwer, Crocker, Venhuizen, & Hoeks, 2017;Crocker, Knoeferle, & Mayberry, 2010).…”

Event‐related brain potentials reveal how multiple aspects of semantic processing unfold across parafoveal and foveal vision during sentence reading

“…Although widely reported in rapid serial visual presentation (RSVP) ERP studies, PNP effects have not been explicitly tested for nor reported in ERP studies of parafoveal processing. Given that recent eye‐tracking findings (reviewed in more detail below) have presented evidence for parafoveal detection of plausibility violations in eye movement behavior during natural reading (e.g., Schotter & Jia, ; Veldre & Andrews, ), it remains an open question whether the LPC, which has been linked to plausibility‐related integration failures (Brouwer, Crocker, Vanhuizen, & Hoeks, ; DeLong, Quante, & Kutas, ; Van Petten & Luka, ), can be elicited from parafoveal stimulation. Thus, in the current study, our goal was to elucidate the nature and time course of higher‐level integrative processing across parafoveal and foveal vision by studying the posterior LPC component of the ERP during sentence reading in a flanker‐RSVP paradigm that permits the measurement of ERP effects elicited by words in parafoveal vision.…”

“…Similarly, many studies have reported biphasic ERP responses to semantic congruity violations, such that large N400 amplitudes to semantically anomalous words are often immediately followed by a posterior LPC, with a similar morphology and distribution to the (semantic) P600 (Leckey & Federmeier, ; Van Petten & Luka, ). Indeed, Brouwer and colleagues () have recently proposed a neurocomputational model accounting for the biphasic N400/LPC complex in terms of a single‐stream “retrieval‐integration” cycle, in which the N400 reflects semantic memory retrieval and the LPC reflects a process where the activated memory representation is integrated into an updated message‐level representation. A major goal of the current study was to examine whether the LPC to plausibility violations can be initiated in parafoveal vision.…”