Is beta in agreement with the relatives? Using relative clause sentences to investigate MEG beta power dynamics during sentence comprehension.

There remains some debate about whether beta power effects observed during sentence comprehension reflect ongoing syntactic unification operations (beta-syntax hypothesis), or instead reflect maintenance or updating of the sentence-level representation (beta-maintenance hypothesis). In this study, we used magnetoencephalography to investigate beta power neural dynamics while participants read relative clause sentences that were initially ambiguous between a subject- or an object-relative reading. An additional condition included a grammatical violation at the disambiguation point in the relative clause sentences. The beta-maintenance hypothesis predicts a decrease in beta power at the disambiguation point for unexpected (and less preferred) object-relative clause sentences and grammatical violations, as both signal a need to update the sentence-level representation. While the beta-syntax hypothesis also predicts a beta power decrease for grammatical violations due to a disruption of syntactic unification operations, it instead predicts an increase in beta power for the object-relative clause condition because syntactic unification at the point of disambiguation becomes more demanding. We observed decreased beta power for both the agreement violation and object-relative clause conditions in typical left hemisphere language regions, which provides compelling support for the beta-maintenance hypothesis. Mid-frontal theta power effects were also present for grammatical violations and object-relative clause sentences, suggesting that violations and unexpected sentence interpretations are registered as conflicts by the brain's domain-general error detection system.

The parser consults the lexicon in spite of transparent gender marking: EEG evidence from noun class agreement processing in Zulu.

In sentence comprehension, the parser in many languages has the option to use both the morphological form of a noun and its lexical representation when evaluating agreement. The additional step of consulting the lexicon incurs processing costs, and an important question is whether the parser takes that step even when the formal cues alone are sufficiently reliable to evaluate agreement. Our study addressed this question using electrophysiology in Zulu, a language where both grammatical gender and number features are reliably expressed formally by noun class prefixes, but only gender features are lexically specified. We observed reduced, more topographically focal LAN, and more frontally distributed alpha/beta power effects for gender compared to number agreement violations. These differences provide evidence that for gender mismatches, even though the formal cues are reliable, the parser nevertheless takes the additional step of consulting the noun's lexical representation, a step which is not available for number.

THE POWER OF NEURAL OSCILLATIONS TO INFORM SENTENCE COMPREHENSION: A LINGUISTIC PERSPECTIVE.

The field of psycholinguistics is currently experiencing an explosion of interest in the analysis of neural oscillations - rhythmic brain activity synchronized at different temporal and spatial levels. Given that language comprehension relies on a myriad of processes, which are carried out in parallel in distributed brain networks, there is hope that this methodology might bring the field closer to understanding some of the more basic (spatially and temporally distributed, yet at the same time often overlapping) neural computations that support language function. In this review we discuss existing proposals linking oscillatory dynamics in different frequency bands to basic neural computations, and review relevant theories suggesting associations between band-specific oscillations and higher-level cognitive processes. More or less consistent patterns of oscillatory activity related to certain types of linguistic processing can already be derived from the evidence that has accumulated over the past few decades. The centerpiece of the current review is a synthesis of such patterns grouped by linguistic phenomenon. We restrict our review to evidence linking measures of oscillatory power to the comprehension of sentences, as well as linguistically (and/or pragmatically) more complex structures. For each grouping, we provide a brief summary and a table of associated oscillatory signatures that a psycholinguist might expect to find when employing a particular linguistic task. Summarizing across different paradigms, we conclude that a handful of basic neural oscillatory mechanisms are likely recruited in different ways and at different times for carrying out a variety of linguistic computations.

Assessing the utility of frequency tagging for tracking memory-based reactivation of word representations.

Reinstatement of memory-related neural activity measured with high temporal precision potentially provides a useful index for real-time monitoring of the timing of activation of memory content during cognitive processing. The utility of such an index extends to any situation where one is interested in the (relative) timing of activation of different sources of information in memory, a paradigm case of which is tracking lexical activation during language processing. Essential for this approach is that memory reinstatement effects are robust, so that their absence (in the average) definitively indicates that no lexical activation is present. We used electroencephalography to test the robustness of a reported subsequent memory finding involving reinstatement of frequency-specific entrained oscillatory brain activity during subsequent recognition. Participants learned lists of words presented on a background flickering at either 6 or 15 Hz to entrain a steady-state brain response. Target words subsequently presented on a non-flickering background that were correctly identified as previously seen exhibited reinstatement effects at both entrainment frequencies. Reliability of these statistical inferences was however critically dependent on the approach used for multiple comparisons correction. We conclude that effects are not robust enough to be used as a reliable index of lexical activation during language processing.

Gender agreement violations modulate beta oscillatory dynamics during sentence comprehension: A comparison of second language learners and native speakers.

For native speakers, many studies suggest a link between oscillatory neural activity in the beta frequency range and syntactic processing. For late second language (L2) learners on the other hand, the extent to which the neural architecture supporting syntactic processing is similar to or different from that of native speakers is still unclear. In a series of four experiments, we used electroencephalography to investigate the link between beta oscillatory activity and the processing of grammatical gender agreement in Dutch determiner-noun pairs, for Dutch native speakers, and for German L2 learners of Dutch. In Experiment 1 we show that for native speakers, grammatical gender agreement violations are yet another among many syntactic factors that modulate beta oscillatory activity during sentence comprehension. Beta power is higher for grammatically acceptable target words than for those that mismatch in grammatical gender with their preceding determiner. In Experiment 2 we observed no such beta modulations for L2 learners, irrespective of whether trials were sorted according to objective or subjective syntactic correctness. Experiment 3 ruled out that the absence of a beta effect for the L2 learners in Experiment 2 was due to repetition of the target nouns in objectively correct and incorrect determiner-noun pairs. Finally, Experiment 4 showed that when L2 learners are required to explicitly focus on grammatical information, they show modulations of beta oscillatory activity, comparable to those of native speakers, but only when trials are sorted according to participants' idiosyncratic lexical representations of the grammatical gender of target nouns. Together, these findings suggest that beta power in L2 learners is sensitive to violations of grammatical gender agreement, but only when the importance of grammatical information is highlighted, and only when participants' subjective lexical representations are taken into account.

Fast oscillatory dynamics during language comprehension: Unification versus maintenance and prediction?

The role of neuronal oscillations during language comprehension is not yet well understood. In this paper we review and reinterpret the functional roles of beta- and gamma-band oscillatory activity during language comprehension at the sentence and discourse level. We discuss the evidence in favor of a role for beta and gamma in unification (the unification hypothesis), and in light of mounting evidence that cannot be accounted for under this hypothesis, we explore an alternative proposal linking beta and gamma oscillations to maintenance and prediction (respectively) during language comprehension. Our maintenance/prediction hypothesis is able to account for most of the findings that are currently available relating beta and gamma oscillations to language comprehension, and is in good agreement with other proposals about the roles of beta and gamma in domain-general cognitive processing. In conclusion we discuss proposals for further testing and comparing the prediction and unification hypotheses.