Who are you talking about? Tracking discourse-level referential processing with event-related brain potentials

In this event-related brain potentials (ERPs) study, we explored the possibility to selectively track referential ambiguity during spoken discourse comprehension. Earlier ERP research has shown that referentially ambiguous nouns (e.g., “the girl” in a two-girl context) elicit a frontal, sustained negative shift relative to unambiguous control words. In the current study, we examined whether this ERP effect reflects “deep” situation model ambiguity or “superficial” textbase ambiguity. We contrasted these different interpretations by investigating whether a discourse-level semantic manipulation that prevents referential ambiguity also averts the elicitation of a referentially induced ERP effect. We compared ERPs elicited by nouns that were referentially nonambiguous but were associated with two discourse entities (e.g., “the girl” with two girls introduced in the context, but one of which has died or left the scene), with referentially ambiguous and nonambiguous control words. Although temporally referentially ambiguous nouns elicited a frontal negative shift compared to control words, the “double bound” but referentially nonambiguous nouns did not. These results suggest that it is possible to selectively track referential ambiguity with ERPs at the level that is most relevant to discourse comprehension, the situation model

Beyond gender stereotypes in language comprehension: self sex-role descriptions affect the brain’s potentials associated with agreement processing

We recorded Event-Related Potentials to investigate differences in the use of gender information during the processing of reflexive pronouns. Pronouns either matched the gender provided by role nouns (such as “king” or “engineer”) or did not. We compared two types of gender information, definitional information, which is semantic in nature (a mother is female), or stereotypical (a nurse is likely to be female). When they followed definitional role-nouns, gender-mismatching pronouns elicited a P600 effect reflecting a failure in the agreement process. When instead the gender violation occurred after stereotypical role-nouns the Event Related Potential response was biphasic, being positive in parietal electrodes and negative in anterior left electrodes. The use of a correlational approach showed that those participants with more “feminine” or “expressive” self sex-role descriptions showed a P600 response for stereotype violations, suggesting that they experienced the mismatch as an agreement violation; whereas less “expressive” participants showed an Nref effect, indicating more effort spent in linking the pronouns with the possible, although less likely, counter-stereotypical referent

Neural oscillations and a nascent corticohippocampal theory of reference

The ability to use words to refer to the world is vital to the communicative power of human language. In particular, the anaphoric use of words to refer to previously mentioned concepts (antecedents) allows dialogue to be coherent and meaningful. Psycholinguistic theory posits that anaphor comprehension involves reactivating a memory representation of the antecedent. Whereas this implies the involvement of recognition memory, or the mnemonic sub-routines by which people distinguish old from new, the neural processes for reference resolution are largely unknown. Here, we report time-frequency analysis of four EEG experiments to reveal the increased coupling of functional neural systems associated with referentially coherent expressions compared to referentially problematic expressions. Despite varying in modality, language, and type of referential expression, all experiments showed larger gamma-band power for referentially coherent expressions compared to referentially problematic expressions. Beamformer analysis in high-density Experiment 4 localised the gamma-band increase to posterior parietal cortex around 400-600 ms after anaphor-onset and to frontaltemporal cortex around 500-1000 ms. We argue that the observed gamma-band power increases reflect successful referential binding and resolution, which links incoming information to antecedents through an interaction between the brain’s recognition memory networks and frontal-temporal language network. We integrate these findings with previous results from patient and neuroimaging studies, and we outline a nascent cortico-hippocampal theory of reference

Verb aspect, event structure, and coreferential processing

We used an off-line story continuation task and an online ERP reading task to investigate coreferential processing following sentences that portrayed transfer-of-possession events as either ongoing or completed, using imperfective and perfective verb aspect (e.g., Amanda was shifting/shifted some poker chips to Scott). The story continuation task demonstrated that people were more likely to begin continuations with references to the Goal than to the Source, but that perfective aspect strengthened this bias. In the ERP task we probed expectations for Source and Goal referents by employing pronouns that matched one of the referents in gender. The ERP results were consistent with the biases revealed in the story continuation task and demonstrate that the difference in Goal bias for the two forms of aspect was manifested differently in the brain. These results provide novel behavioral and neurocognitive evidence that verb aspect influences the construction of situation models during language comprehension

An electrophysiological investigation of co-referential processes in visual narrative comprehension

Visual narratives make use of various means to convey referential and co-referential meaning, so comprehenders must recognize that different depictions across sequential images represent the same character(s). In this study, we investigated how the order in which different types of panels in visual sequences are presented affects how the unfolding narrative is comprehended. Participants viewed short comic strips while their electroencephalo- gram (EEG) was recorded. We analyzed evoked and induced EEG activity elicited by both full panels (showing a full character) and refiner panels (showing only a zoom of that full panel), and took into account whether they preceded or followed the panel to which they were co-referentially related (i.e., were cataphoric or anaphoric). We found that full panels elicited both larger N300 amplitude and increased gamma-band power compared to refiner panels. Anaphoric panels elicited a sustained negativity compared to cataphoric panels, which appeared to be sensitive to the referential status of the anaphoric panel. In the time-frequency domain, anaphoric panels elicited reduced 8–12 Hz alpha power and increased 45–65 Hz gamma-band power compared to cataphoric panels. These findings are consistent with models in which the processes involved in visual narrative compre- hension partially overlap with those in language comprehension

A compositional neural architecture for language

Hierarchical structure and compositionality imbue human language with unparalleled expressive power and set it apart from other perception–action systems. However, neither formal nor neurobiological models account for how these defining computational properties might arise in a physiological system. I attempt to reconcile hierarchy and compositionality with principles from cell assembly computation in neuroscience; the result is an emerging theory of how the brain could convert distributed perceptual representations into hierarchical structures across multiple timescales while representing interpretable incremental stages of (de) compositional meaning. The model's architecture—a multidimensional coordinate system based on neurophysiological models of sensory processing—proposes that a manifold of neural trajectories encodes sensory, motor, and abstract linguistic states. Gain modulation, including inhibition, tunes the path in the manifold in accordance with behavior and is how latent structure is inferred. As a consequence, predictive information about upcoming sensory input during production and comprehension is available without a separate operation. The proposed processing mechanism is synthesized from current models of neural entrainment to speech, concepts from systems neuroscience and category theory, and a symbolic-connectionist computational model that uses time and rhythm to structure information. I build on evidence from cognitive neuroscience and computational modeling that suggests a formal and mechanistic alignment between structure building and neural oscillations and moves toward unifying basic insights from linguistics and psycholinguistics with the currency of neural computation

Linguistic Focus Promotes the Ease of Discourse Integration Processes in Reading Comprehension: Evidence From Event-Related Potentials

Psycholinguistic studies of focus processing have yielded varying results regarding how focus affects language processing. We report the results of an event-related potential (ERP) experiment that used question-answer pairs in a discourse to manipulate whether a target word was contextually focused, contrastively focused, contextually defocused, or contextually neutral. We found a negative-going waveform that was sustained in the time-course (250–800 ms after the target word onset) with a maximum over frontal-central scalp sites. As the structure of the discourse made the target word more focused, the negative-going deflection was systematically reduced. We also observed a frontal positive-going waveform that was larger for the focus-marked words relative to the neutral target word in an earlier time window (150–250 ms, P200), which may reflect increased attention allocated to the focused items. We propose that the reduced negative ERPs for the focused words reflects facilitation of meaning integration when focus functions to establish reference in the discourse representation. This can be attributed to extra attention paid to the focus-marked items that in turn promotes the prominence of focus-marked referent and prompts the contextual priming mechanism that facilitates the access of propositionally relevant items in text memory during reading

What does "it" mean anyway? Examining the time course of semantic activation in reference resolution

Pronouns (e.g. ‘it’) are commonly studied in research on anaphoric reference, because they appear to carry out the linguistic function of referring back to an entity, while providing little or no new information about the referent. However, differing viewpoints have emerged in the psycholinguistic literature on what cognitive processes are engaged when reading or hearing a pronoun. One view is that encountering a pronoun leads the comprehender to reactivate the semantics of its antecedent. We examined this hypothesis by manipulating the concreteness of a noun antecedent and assessing whether an Event Related Potential (ERP) concreteness effect was elicited at a downstream pronoun. We observed a robust concreteness effect at the noun, but no evidence of a concreteness effect at the pronoun. In a secondary analysis, we examined whether N400 semantic priming from the antecedent would increase on content words shortly following the pronoun, relative to those preceding it. Again, although we observed robust semantic priming from the noun antecedent at positions following it, we did not observe an increase in the size of this effect following the pronoun. Taken together with the broader literature, our data suggest that pronouns do not induce the activation of (much) new semantic information in long-term memory, perhaps instead triggering an attentional shift towards their antecedents’ active semantic representations within working memory. This, in turn, suggests that the process of linking an anaphor to its antecedent is attentionally mediated and does not entail long-term memory access, in contrast with ACT-R inspired models (Lewis & Vasishth, 2005)