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•ERPs reflect error-based learning processes that support linguistic adaptation.•Error propagation explains the P600 using the same mechanism as the N400.•Explains data from three ...N400, five P600, one semantic P600, and three learning related studies.•Production-based prediction error ERPs in comprehension will differ from non-ERP comprehension measures.•ERPs are biological evidence for a neural learning algorithm that propagates error.
Event-related potentials (ERPs) provide a window into how the brain is processing language. Here, we propose a theory that argues that ERPs such as the N400 and P600 arise as side effects of an error-based learning mechanism that explains linguistic adaptation and language learning. We instantiated this theory in a connectionist model that can simulate data from three studies on the N400 (amplitude modulation by expectancy, contextual constraint, and sentence position), five studies on the P600 (agreement, tense, word category, subcategorization and garden-path sentences), and a study on the semantic P600 in role reversal anomalies. Since ERPs are learning signals, this account explains adaptation of ERP amplitude to within-experiment frequency manipulations and the way ERP effects are shaped by word predictability in earlier sentences. Moreover, it predicts that ERPs can change over language development. The model provides an account of the sensitivity of ERPs to expectation mismatch, the relative timing of the N400 and P600, the semantic nature of the N400, the syntactic nature of the P600, and the fact that ERPs can change with experience. This approach suggests that comprehension ERPs are related to sentence production and language acquisition mechanisms.
To understand how neural networks in the left (LH) and right (RH) cerebral hemispheres contribute to different aspects of language comprehension, in two experiments we measured event-related ...potentials (ERPs) as right-handed participants read sentences, some of which contained morphosyntactic and thematic role violations. Replicating prior work (Kuperberg et al., 2006), in Experiment 1 thematic role violations elicited both an N400 and a (semantic) P600 effect. Morphosyntactic violations elicited effects that differed as a function of participants’ familial sinistrality (the presence FS+ or absence FS- of a left-handed biological relative): FS+ participants showed a (syntactic) P600 effect whereas FS- participants showed a biphasic N400 and P600 response. To assess whether this difference reflects different underlying patterns of lateralization, in Experiment 2 target words were presented using visual half-field (VF) presentation. Indeed, for morphosyntactic violations, the FS- group elicited an asymmetric pattern, showing a P600 effect only with LH-biased presentation and an N400 effect in both VFs (cf. Lee and Federmeier, 2015). In contrast, FS+ participants showed a bilateral (N400-only) response pattern. This provides further evidence of FS-based differences in hemispheric contributions to syntactic processing. Strikingly, we found that, when lateralized, thematic role violations did not elicit a P600 effect, suggesting that this effect requires contributions from both hemispheres. The different response patterns for morphosyntactic and thematic role animacy violations across FS and VF also point to a processing difference in the comprehension mechanisms underlying the semantic and syntactic P600, which had heretofore been assumed to be variants of the same component.
•Familial sinistrality (FS) influenced the brain's response to syntactic violations.•For FS- group, hemifield of presentation influenced processing of syntactic violations.•FS+ group showed symmetrical brain responses for syntactic/thematic violations.•Normal processing of thematic role violations seems to require both hemispheres.•Syntactic and semantic P600s have different eliciting conditions.
The present study uses event-related potentials to investigate the role of prediction in the processing of information structure, a domain of language that belongs to the level of the discourse. ...Twenty-three native speakers of English read short contexts including three Noun Phrases (NPs) (e.g., Either an adviser or an agent can be helpful to a banker), followed by a wh-question that established the discourse role of each referent (In your opinion, which of the two should a banker hire?). The NP that the question was about (banker) was the Topic, and the two NPs that could fill the slot opened by the wh-question (adviser, agent) were the Focus NPs. The participants’ brain activity was recorded with EEG while they read the responses to the wh-questions, which differed along two dimensions: (1) the availability of the it-cleft construction (In my opinion, it is an agent…), a Focus-devoted device that makes Focus assignment predictable in the response; and (2) the discourse role of the target noun (Focus, Topic), which corresponds to the first referent in the response (In my opinion, it is an agent/a banker…). Crucially, we manipulated the phonological properties of the Focus and Topic nouns such that, if the Topic noun began with a consonant (e.g., a banker), both nouns that could fill the slot opened by the wh-question began with a vowel (e.g., an agent, an adviser) (counterbalanced in the overall design). This allowed us to measure effects of prediction at the prenominal article, before the integration of semantic and discourse information took place. The analyses on prenominal articles revealed an N400 effect for articles that were unexpected based on the phonological properties of the Focus nouns, but only in the conditions with the it-cleft. This effect emerged between 250 and 400 ms, with a frontal bias. The analyses on the noun revealed that violations of information structure (i.e., cases where the it-cleft was followed by the Topic noun) yielded a broadly distributed P600 effect, relative to appropriately clefted (i.e., focused) nouns. A similar (but numerically less robust) effect emerged for Topic relative to Focus NPs in the conditions without the it-cleft, suggesting that, in the absence of a constraining cue, comprehenders still assigned Focus to the first referent in the response. Overall, these results suggest that, when reading answers to wh-questions, comprehenders use information structure constraints (i.e., prior context + the it-cleft) to anticipate the form that the response should take (i.e., how information should be packaged).
•Comprehenders use cleft constructions predictively for Focus assignment.•Effects of prediction emerged on articles preceding focused nouns.•Information structure violations yielded a P600.•Clefted nouns showed a positive brain response related to information delivery.
Since its discovery in the 1960s, the P300 has been contributing both directly and indirectly to language research. Perhaps most notably, it has been suggested that the P600, an ERP component that ...was first characterized in the context of syntactic processing, could be a variant of the P3b subcomponent of the P300. Here, we review studies on both sides of the debate. We also review the “semantic P600,” a positivity with a similar time course and distribution to the P600 seen for syntactic manipulations but that is obtained in response to some types of semantic anomalies. Because most current theories of the P600 try to account for both the syntactic and the semantic variant, linking the syntactic P600 to the P3b might also imply a similar link for the semantic P600. However, we describe emerging research in our lab that casts doubt on the idea that the syntactic P600 and the semantic P600 are the same effect. We argue that grouping ERP responses primarily by domain (language vs. nonlanguage) is likely to be misleading and suggest alternative ways of determining whether ERP effects reflect similar or different processing mechanisms.
ERP components are commonly categorized according to cognitive domain, such as language or memory. The current article discusses this convention in relation to the P300 component and the semantic and syntactic variants of the traditionally language‐related P600. Existing and emerging evidence is presented to support the idea that alternate categorization methods could inform extant lines of research and potentially open up new ones.
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•Processing of pseudohomophones requiring morphological analysis increases N400 amplitude.•Pseudohomophones based on the traditional writing principle modulate P600.•Both ...pseudohomophones activate the left inferior frontal gyrus.•Pseudohomophones based on traditional principles activate additional postcentral areas.
Spelling in any writing system is governed by fundamental principles. We examined the processing of two types of pseudohomophones constructed from words whose spellings are based on different principles – on the traditional principle of writing, requiring memorization of their spelling, and on the morphological principle, allowing the determination of their spelling from another word with the same morpheme (root) to examine the dependence of the occurrence of orthography–phonology conflict on spelling principles. Event-related potentials were recorded from 22 volunteers during silent reading. Pseudohomophones based on the morphological principle increased the N400 amplitude, emphasizing semantic and morphological processing importance. The P600 component showed significant effects for differentiating words and pseudohomophones based on the traditional principle, predominantly indicating the involvement of memory and reanalysis processes. Source reconstruction demonstrates that both pseudohomophones activate the left inferior frontal gyrus. However, pseudohomophones based on the traditional principle additionally activate the right and left postcentral gyrus, indicating the involvement of additional areas in the differentiation process. The earlier differences for stimuli based on the morphological principle indicate access to smaller units (morphemes), whereas stimuli based on the traditional principle require whole word processing. Our findings underscore the significant role of spelling principles in orthographic processing.
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In the present study, topical gel and emulsion gel were formulated using Acrylamide/ Sodium Acryloyldimethyl taurate copolymer (Sepineo P600) as a gelling agent, and their rheological ...attributes and physical stability were evaluated upon incorporation of API. Lidocaine, a free base drug (pKa 7.92) was used as a model drug in all formulations. Medium- chain Triglycerides (MCT) was used as a dispersed phase to prepare the emulgel. Results show that the rheological properties of both gel and emulgel such as viscosity, elastic moduli and yield stress were significantly influenced by the pH of the topical formulations and API concentration. A lower pH (pH < pKa) leads to the increase in number of cationic species of lidocaine, which results in the weakening of the structure of the gel matrix by charge screening of polymer-polymer repulsions. Interactions between API and polymer chains through electrostatic attraction may play a major role in altering the rheology, which could potentially impact the physical stability against phase separation of the internal phase in emulsion gel samples. This study provides valuable insights into rheological behaviors of Sepineo P600 gel and emulgel which can be modified or tuned though the interplay of the API properties and critical formulation parameters such as pH. The tunable rheological properties with simpler manufacturing process make Sepineo P600 gel and emulsion gel very suitable systems for use in semisolid topical formulations.
Although it is widely known that high‐pass filters can reduce the amplitude of slow ERP components, these filters can also introduce artifactual peaks that lead to incorrect conclusions. To ...demonstrate this and provide evidence about optimal filter settings, we recorded ERPs in a typical language processing paradigm involving syntactic and semantic violations. Unfiltered results showed standard N400 and P600 effects in the semantic and syntactic violation conditions, respectively. However, high‐pass filters with cutoffs at 0.3 Hz and above produced artifactual effects of opposite polarity before the true effect. That is, excessive high‐pass filtering introduced a significant N400 effect preceding the P600 in the syntactic condition, and a significant P2 effect preceding the N400 in the semantic condition. Thus, inappropriate use of high‐pass filters can lead to false conclusions about which components are influenced by a given manipulation. The present results also lead to practical recommendations for high‐pass filter settings that maximize statistical power while minimizing filtering artifacts.
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.
In traditional theories of language comprehension, syntactic and semantic processing are inextricably linked. This assumption has been challenged by the ‘Semantic Illusion Effect’ found in studies ...using Event Related brain Potentials. Semantically anomalous sentences did not produce the expected increase in N400 amplitude but rather one in P600 amplitude. To explain these findings, complex models have been devised in which an independent semantic processing stream can arrive at a sentence interpretation that may differ from the interpretation prescribed by the syntactic structure of the sentence. We review five such multi-stream models and argue that they do not account for the full range of relevant results because they assume that the amplitude of the N400 indexes some form of semantic integration. Based on recent evidence we argue that N400 amplitude might reflect the retrieval of lexical information from memory. On this view, the absence of an N400-effect in Semantic Illusion sentences can be explained in terms of priming. Furthermore, we suggest that semantic integration, which has previously been linked to the N400 component, might be reflected in the P600 instead. When combined, these functional interpretations result in a single-stream account of language processing that can explain all of the Semantic Illusion data.
•The functional interpretation of the N400 and the P600 is still a matter of debate.•In a single ERP study, we tested the competing hypotheses about both components.•The results show that the N400 ...indexes retrieval rather than integration processes.•The P600 indexes general integration difficulty, not syntactic processes alone.•Findings suggest spatiotemporal overlap between the N400 and P600 components.
The functional interpretation of two salient language-sensitive ERP components – the N400 and the P600 – remains a matter of debate. Prominent alternative accounts link the N400 to processes related to lexical retrieval, semantic integration, or both, while the P600 has been associated with syntactic reanalysis or, alternatively, to semantic integration. The often overlapping predictions of these competing accounts in extant experimental designs, however, has meant that previous findings have failed to clearly decide among them. Here, we present an experiment that directly tests the competing hypotheses using a design that clearly teases apart the retrieval versus integration view of the N400, while also dissociating a syntactic reanalysis/reprocessing account of the P600 from semantic integration. Our findings provide support for an integrated functional interpretation according to which the N400 reflects context-sensitive lexical retrieval – but not integration – processes. While the observed P600 effects were not predicted by any account, we argue that they can be reconciled with the integration view, if spatio-temporal overlap of ERP components is taken into consideration.
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