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Retrieval (N400) and integration (P600) in expectation-based comprehension. PLoS One 2021; 16:e0257430. [PMID: 34582472 PMCID: PMC8478172 DOI: 10.1371/journal.pone.0257430] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/16/2021] [Accepted: 08/31/2021] [Indexed: 11/24/2022] Open
Abstract
Expectation-based theories of language processing, such as Surprisal theory, are supported by evidence of anticipation effects in both behavioural and neurophysiological measures. Online measures of language processing, however, are known to be influenced by factors such as lexical association that are distinct from—but often confounded with—expectancy. An open question therefore is whether a specific locus of expectancy related effects can be established in neural and behavioral processing correlates. We address this question in an event-related potential experiment and a self-paced reading experiment that independently cross expectancy and lexical association in a context manipulation design. We find that event-related potentials reveal that the N400 is sensitive to both expectancy and lexical association, while the P600 is modulated only by expectancy. Reading times, in turn, reveal effects of both association and expectancy in the first spillover region, followed by effects of expectancy alone in the second spillover region. These findings are consistent with the Retrieval-Integration account of language comprehension, according to which lexical retrieval (N400) is facilitated for words that are both expected and associated, whereas integration difficulty (P600) will be greater for unexpected words alone. Further, an exploratory analysis suggests that the P600 is not merely sensitive to expectancy violations, but rather, that there is a continuous relation. Taken together, these results suggest that the P600, like reading times, may reflect a meaning-centric notion of Surprisal in language comprehension.
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Delogu F, Brouwer H, Crocker MW. When components collide: Spatiotemporal overlap of the N400 and P600 in language comprehension. Brain Res 2021; 1766:147514. [PMID: 33974906 DOI: 10.1016/j.brainres.2021.147514] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/26/2021] [Revised: 03/30/2021] [Accepted: 05/04/2021] [Indexed: 01/23/2023]
Abstract
The problem of spatiotemporal overlap between event-related potential (ERP) components is generally acknowledged in language research. However, its implications for the interpretation of experimental results are often overlooked. In a previous experiment on the functional interpretation of the N400 and P600, it was argued that a P600 effect to implausible words was largely obscured - in one of two implausible conditions - by an overlapping N400 effect of semantic association. In the present ERP study, we show that the P600 effect of implausibility is uncovered when the critical condition is tested against a proper baseline condition which elicits a similar N400 amplitude, while it is obscured when tested against a baseline condition producing an N400 effect. Our findings reveal that component overlap can result in the apparent absence or presence of an effect in the surface signal and should therefore be carefully considered when interpreting ERP patterns. Importantly, we show that, by factoring in the effects of spatiotemporal overlap between the N400 and P600 on the surface signal, which we reveal using rERP analysis, apparent inconsistencies in previous findings are easily reconciled, enabling us to draw unambiguous conclusions about the functional interpretation of the N400 and P600 components. Overall, our results provide compelling evidence that the N400 reflects lexical retrieval processes, while the P600 indexes compositional integration of word meaning into the unfolding utterance interpretation.
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Affiliation(s)
- Francesca Delogu
- Department of Language Science and Technology, Saarland University, Building C7.1, 66123 Saarbrücken, Germany.
| | - Harm Brouwer
- Department of Language Science and Technology, Saarland University, Building C7.1, 66123 Saarbrücken, Germany
| | - Matthew W Crocker
- Department of Language Science and Technology, Saarland University, Building C7.1, 66123 Saarbrücken, Germany
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Broderick MP, Di Liberto GM, Anderson AJ, Rofes A, Lalor EC. Dissociable electrophysiological measures of natural language processing reveal differences in speech comprehension strategy in healthy ageing. Sci Rep 2021; 11:4963. [PMID: 33654202 PMCID: PMC7925601 DOI: 10.1038/s41598-021-84597-9] [Citation(s) in RCA: 27] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/14/2020] [Accepted: 02/08/2021] [Indexed: 12/17/2022] Open
Abstract
Healthy ageing leads to changes in the brain that impact upon sensory and cognitive processing. It is not fully clear how these changes affect the processing of everyday spoken language. Prediction is thought to play an important role in language comprehension, where information about upcoming words is pre-activated across multiple representational levels. However, evidence from electrophysiology suggests differences in how older and younger adults use context-based predictions, particularly at the level of semantic representation. We investigate these differences during natural speech comprehension by presenting older and younger subjects with continuous, narrative speech while recording their electroencephalogram. We use time-lagged linear regression to test how distinct computational measures of (1) semantic dissimilarity and (2) lexical surprisal are processed in the brains of both groups. Our results reveal dissociable neural correlates of these two measures that suggest differences in how younger and older adults successfully comprehend speech. Specifically, our results suggest that, while younger and older subjects both employ context-based lexical predictions, older subjects are significantly less likely to pre-activate the semantic features relating to upcoming words. Furthermore, across our group of older adults, we show that the weaker the neural signature of this semantic pre-activation mechanism, the lower a subject’s semantic verbal fluency score. We interpret these findings as prediction playing a generally reduced role at a semantic level in the brains of older listeners during speech comprehension and that these changes may be part of an overall strategy to successfully comprehend speech with reduced cognitive resources.
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Affiliation(s)
- Michael P Broderick
- School of Engineering, Trinity Centre for Bioengineering and Trinity College Institute of Neuroscience, Trinity College Dublin, Dublin 2, Ireland.
| | - Giovanni M Di Liberto
- Laboratoire des Systèmes Perceptifs, Département d'études Cognitives, École Normale Supérieure, PSL University, CNRS, 75005, Paris, France
| | - Andrew J Anderson
- Department of Biomedical Engineering, University of Rochester, Rochester, NY, 14627, USA.,Department of Neuroscience, and Del Monte Institute for Neuroscience, University of Rochester, Rochester, NY, 14627, USA
| | - Adrià Rofes
- Department of Neurolinguistics and Language Development, University of Groningen, Oude Kijk in Het Jatstraat 26, 9712 EK, Groningen, The Netherlands
| | - Edmund C Lalor
- School of Engineering, Trinity Centre for Bioengineering and Trinity College Institute of Neuroscience, Trinity College Dublin, Dublin 2, Ireland.,Department of Biomedical Engineering, University of Rochester, Rochester, NY, 14627, USA.,Department of Neuroscience, and Del Monte Institute for Neuroscience, University of Rochester, Rochester, NY, 14627, USA
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Brouwer H, Delogu F, Venhuizen NJ, Crocker MW. Neurobehavioral Correlates of Surprisal in Language Comprehension: A Neurocomputational Model. Front Psychol 2021; 12:615538. [PMID: 33643143 PMCID: PMC7905034 DOI: 10.3389/fpsyg.2021.615538] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/09/2020] [Accepted: 01/11/2021] [Indexed: 11/13/2022] Open
Abstract
Expectation-based theories of language comprehension, in particular Surprisal Theory, go a long way in accounting for the behavioral correlates of word-by-word processing difficulty, such as reading times. An open question, however, is in which component(s) of the Event-Related brain Potential (ERP) signal Surprisal is reflected, and how these electrophysiological correlates relate to behavioral processing indices. Here, we address this question by instantiating an explicit neurocomputational model of incremental, word-by-word language comprehension that produces estimates of the N400 and the P600-the two most salient ERP components for language processing-as well as estimates of "comprehension-centric" Surprisal for each word in a sentence. We derive model predictions for a recent experimental design that directly investigates "world-knowledge"-induced Surprisal. By relating these predictions to both empirical electrophysiological and behavioral results, we establish a close link between Surprisal, as indexed by reading times, and the P600 component of the ERP signal. The resultant model thus offers an integrated neurobehavioral account of processing difficulty in language comprehension.
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Affiliation(s)
- Harm Brouwer
- Department of Language Science and Technology, Saarland University, Saarbrücken, Germany
| | - Francesca Delogu
- Department of Language Science and Technology, Saarland University, Saarbrücken, Germany
| | - Noortje J Venhuizen
- Department of Language Science and Technology, Saarland University, Saarbrücken, Germany
| | - Matthew W Crocker
- Department of Language Science and Technology, Saarland University, Saarbrücken, Germany
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