Wh-movement vs. scrambling: The brain makes a difference

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Toward a Neurobiologically Plausible Model of Language-Related, Negative Event-Related Potentials

Language-related event-related potential (ERP) components such as the N400 have traditionally been associated with linguistic or cognitive functional interpretations. By contrast, it has been considerably more difficult to relate these components to neurobiologically grounded accounts of language. Here, we propose a theoretical framework based on a predictive coding architecture, within which negative language-related ERP components such as the N400 can be accounted for in a neurobiologically plausible manner. Specifically, we posit that the amplitude of negative language-related ERP components reflects precision-weighted prediction error signals, i.e., prediction errors weighted by the relevance of the information source leading to the error. From this perspective, precision has a direct link to cue validity in a particular language and, thereby, to relevance of individual linguistic features for internal model updating. We view components such as the N400 and LAN as members of a family with similar functional characteristics and suggest that latency and topography differences between these components reflect the locus of prediction errors and model updating within a hierarchically organized cortical predictive coding architecture. This account has the potential to unify findings from the full range of the N400 literature, including word-level, sentence-, and discourse-level results as well as cross-linguistic differences

Waves and Words: Oscillatory activity and language processing

Successful language comprehension depends not only on the involvement of different domain-specific linguistic processes, but also on their respective time-courses. Both aspects of the comprehension process can be examined by means of event-related brain potentials (ERPs), which not only provide a direct reflection of human brain activity within the millisecond range, but also allow for a qualitative dissociation between different language-related processing domains. However, recent ERP findings indicate that the desired one-to-one mapping between ERP components and linguistic processes cannot be upheld, thus leading to an interpretative uncertainty. This thesis presents a fundamentally new analysis technique for language-based ERP components, which aims to address the ambiguity associated with traditional language-related ERP effects. It is argued that this new method, which supplements ERP measures with corresponding frequency-based analyses, not only allows for a differentiation of ERP components on the basis of activity in distinct frequency bands and underlying dynamic behaviour (in terms of power changes and/or phase locking), but also provides further insights into the functional organisation of the language comprehension system and its inherent complexity. On the basis of 5 EEG experiments, I show (1) that it is possible to dissociate two superficially indistinguishable language-related ERP components on the basis of their respective underlying frequency characteristics (Experiment 1), thereby resolving the vagueness of interpretation inherent to the ERP components themselves; (2) that the processing nature of the ‘classical’ semantic N400 effect can be unambiguously specified in terms of its underlying frequency characteristics, i.e. in terms of (evoked and whole) power and phase-locking differences in specific frequency bands, thereby allowing for a first interpretative categorisation of the N400 effect with respect to its underlying neuronal processing dynamics; and (3) that frequency-based analyses may be employed to distinguish the semantic N400 effect from N400-like effects that appear in contexts which cannot readily be characterised as semantic-interpretative processes. Experiments 2 – 5 investigated the processing of antonym relations under different task conditions. Whereas in Experiment 2, the processing of antonym pairs (black – white) was compared to that of related (black – yellow) and non-related (black – nice) word pairs in a sentence context, Experiments 3 to 5 presented isolated word pairs. The frequency-based analysis showed that the observed N400 effects were not uniform in nature, but rather resulted from the superposition of functionally different frequency components. Task-relevant targets elicited a specific frequency modulation, which showed up as a P300-like positivity in terms of ERP measures. In addition, lexical-semantic processing elicited a pronounced increase in a different frequency range that was independent of the experimental context. For antonyms (Experiments 2 and 3), the task-related positive component appeared almost simultaneously to the N400 deflection for non-related words, thereby giving rise to a substantial N400 effect. In contrast, for pseudowords (Experiment 5), this positivity appeared in temporal succession to the N400. In sum, in the present results provide converging evidence that N400 effects should not be regarded as functionally uniform. Depending on the respective task and stimulus manipulations, the N400 effect appears as a result of the superposition of functionally different activities, which can be clearly distinguished in terms of their underlying frequency characteristics. In this way, the proposed frequency-based methods directly bear upon the interpretation of language-related ERP effects and thus have straightforward consequences for psycholinguistic theory. In view of the phenomenon that language-related processes have, in a number of cases, been directly attributed to the lexical-semantic processing domain on account of the observation of an N400, these results not only call for a reinterpretation of previous findings but also for a reinterpretation of their theoretical consequences

Neighborhood consistency in mental arithmetic: Behavioral and ERP evidence

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Individual differences in peripheral hearing and cognition reveal sentence processing differences in healthy older adults

When viewed cross-sectionally, aging seems to negatively affect speech comprehension. However, aging is a heterogeneous process, and variability among older adults is typically large. In this study, we investigated language comprehension as a function of individual differences in older adults. Specifically, we tested whether hearing thresholds, working memory, inhibition, and individual alpha frequency would predict event-related potential amplitudes in response to classic psycholinguistic manipulations at the sentence level. Twenty-nine healthy older adults (age range 61–76 years) listened to English sentences containing reduced relative clauses and object-relative clauses while their electroencephalogram was recorded. We found that hearing thresholds and working memory predicted P600 amplitudes early during reduced relative clause processing, while individual alpha frequency predicted P600 amplitudes at a later point in time. The results suggest that participants with better hearing and larger working memory capacity simultaneously activated both the preferred and the dispreferred interpretation of reduced relative clauses, while participants with worse hearing and smaller working memory capacity only activated the preferred interpretation. They also suggest that participants with a higher individual alpha frequency had a higher likelihood of successfully reanalysing the sentence toward the reduced relative clause reading than participants with a lower individual alpha frequency. By contrast, we found no relationship between object-relative clause processing and working memory or hearing thresholds. Taken together, the results support the view that older adults employ different strategies during auditory sentence processing dependent on their hearing and cognitive abilities and that there is no single ability that uniformly predicts sentence processing outcomes

Resolving complex anaphors. Evidence from online comprehension

This study investigates the question of whether the processing of complex anaphors require more cognitive effort than the processing of NP-anaphors. Complex anaphors refer to abstract objects which are not introduced as a noun phrase and bring about the creation of a new discourse referent. This creation is called “complexation process”. We describe ERP findings which provide converging support for the assumption that the cognitive cost of this complexation process is higher than the cognitive cost of processing NP-anaphors

Parafoveal versus foveal N400s dissociate spreading activation from contextual fit

Using concurrent electroencephalogram and eye movement measures to track natural reading, this study shows that N400 effects reflecting predictability are dissociable from those owing to spreading activation. In comparing predicted sentence endings with related and unrelated unpredicted endings in antonym constructions (‘the opposite of black is white/yellow/nice’), fixation-related potentials at the critical word revealed a predictability-based N400 effect (unpredicted vs. predicted words). By contrast, event-related potentials time locked to the last fixation before the critical word showed an N400 only for the nonrelated unpredicted condition (nice). This effect is attributed to a parafoveal mismatch between the critical word and preactivated lexical features (i.e. features of the predicted word and its associates). In addition to providing the first demonstration of a parafoveally induced N400 effect, our results support the view that the N400 is best viewed as a component family