Biology subjects

Kuperberg, G.

Publications and source records attributed to Kuperberg, G..

5 recordsLinked to original sources

bioRxiv2023

A Predictive Coding Model of the N400

The N400 event-related component has been widely used to investigate the neural mechanisms underlying real-time language comprehension. However, despite decades of research, there is still no unifying theory that can explain both its temporal dynamics and functional properties. In this work, we show that predictive coding - a biologically plausible algorithm for approximating Bayesian inference - offers a promising framework for characterizing the N400. Using an implemented predictive coding computational model, we demonstrate how the N400 can be formalized as the lexico-semantic prediction error produced as the brain infers meaning from linguistic form of incoming words. We show that the magnitude of lexico-semantic prediction error mirrors the functional sensitivity of the N400 to various lexical variables, priming, contextual effects, as well as their higher-order interactions. We further show that the dynamics of the predictive coding algorithm provide a natural explanation for the temporal dynamics of the N400, and a biologically plausible link to neural activity. Together, these findings directly situate the N400 within the broader context of predictive coding research, and suggest that the brain may use the same computational mechanism for inference across linguistic and non-linguistic domains.

neuroscience↗

bioRxiv2021

Dynamic predictive coding across the left fronto-temporal language hierarchy: Evidence from MEG, EEG and fMRI

We used MEG and ERPs to track the time-course and localization of evoked activity produced by expected, unexpected plausible and implausible words during incremental language comprehension. We interpret the full pattern of evoked responses and functional connectivity within a hierarchical predictive coding framework in which evoked activity reflects residual information (error) that is passed up and down the cortical hierarchy. Between 300-500ms, the three conditions produced progressively larger responses within left temporal cortex (lexico-semantic prediction error), while implausible inputs produced a selectively enhanced response within left inferior frontal cortex (event-level prediction error). Between 600-1000ms, unexpected plausible words activated left inferior frontal and middle temporal cortices (feedback activity that induced top-down shifts of event-level and lexico-semantic representations), while highly implausible inputs activated posterior fusiform and medial temporal cortices, supporting orthographic reanalysis and new learning. Therefore, predictive coding may provide a unifying theory that links language comprehension to other domains of cognition.

neuroscience↗

bioRxiv2021

Domain-general conflict monitoring predicts neural and behavioral indices of linguistic error processing during reading comprehension

The ability to detect and respond to linguistic errors is critical for successful reading comprehension, but these skills can vary considerably across readers. In the current study, healthy adults (age 18-35) read short discourse scenarios for comprehension while monitoring for the presence of semantic anomalies. Using a factor analytic approach, we examined if performance in non-linguistic conflict monitoring tasks (Stroop, AX-CPT) would predict individual differences in neural and behavioral measures of linguistic error processing. Consistent with this hypothesis, domain-general conflict monitoring predicted both readers end-of-trial acceptability judgments and the amplitude of a late neural response (the P600) evoked by linguistic anomalies. Interestingly, the influence on the P600 was non-linear, suggesting that online neural responses to linguistic errors are influenced by both the effectiveness and efficiency of domain-general conflict monitoring. These relationships were also highly specific and remained after controlling for variability in working memory capacity and verbal knowledge. Finally, we found that domain-general conflict monitoring also predicted individual variability in measures of reading comprehension, and that this relationship was partially mediated by behavioral measures of linguistic error detection. These findings inform our understanding of the role of domain-general executive functions in reading comprehension, with potential implications for the diagnosis and treatment of language impairments.

neuroscience↗

bioRxiv2018

A Tale of Two Positivities (and the N400): Distinct neural signatures are evoked by confirmed and violated predictions at different levels of representation

It has been proposed that hierarchical prediction is a fundamental computational principle underlying neurocognitive processing. Here we ask whether the brain engages distinct neurocognitive mechanisms in response to inputs that fulfill versus violate strong predictions at different levels of representation during language comprehension. Participants read three-sentence scenarios in which the third sentence constrained for a broad event structure, e.g. {Agent caution animate-Patient}. High constraint contexts additionally constrained for a specific event/lexical item, e.g. a two-sentence context about a beach, lifeguards and sharks constrained for the event, {Lifeguards cautioned Swimmers} and the specific lexical item, \"swimmers\". Low constraint contexts did not constrain for any specific event/lexical item. We measured ERPs on critical nouns that fulfilled and/or violated each of these constraints. We found clear, dissociable effects to fulfilled semantic predictions (a reduced N400), to event/lexical prediction violations (an increased late frontal positivity), and to event structure/animacy prediction violations (an increased late posterior positivity/P600). We argue that the late frontal positivity reflects a large change in activity associated with successfully updating the comprehenders current situation model with new unpredicted information. We suggest that the late posterior positivity/P600 is triggered when the comprehender detects a conflict between the input and her model of the communicator and communicative environment. This leads to an initial failure to incorporate new unpredicted input, which may be followed by second-pass attempts to make sense of the discourse through reanalysis, repair, or reinterpretation. Together, these findings provide strong evidence that confirmed and violated predictions at different levels of representation manifest as distinct spatiotemporal neural signatures.

neuroscience↗

bioRxiv2018

Neural evidence for representationally specific prediction in language processing

Previous studies suggest that people generate predictions during language comprehension at multiple linguistic levels. It has been hypothesized that, under some circumstances, this can result in the pre-activation of specific lexico-semantic representations. We asked whether such representationally specific semantic pre-activation can be detected in the brain ahead of encountering bottom-up input. We measured MEG activity as participants read highly constraining sentences in which the final word could be predicted. We found that both spatial and temporal patterns of the brain activity prior to the onset of this word were more similar when the same words were predicted than when different words were predicted. This pre-activation was transient and engaged a left inferior and medial temporal region. These results suggest that unique spatial patterns of neural activity associated with the pre-activation of distributed semantic representations can be detected prior to the appearance of new sensory input, and that the left inferior and medial temporal regions may play a role in temporally binding such representations, giving rise to specific lexico-semantic predictions.

neuroscience↗