Pre-stimulus alpha (8–12 Hz) and beta (16–20 Hz) oscillations have been frequently linked to the prediction of upcoming sensory input. Do these frequency bands serve as a neural marker of linguistic prediction as well? We hypothesized that if pre-stimulus alpha and beta oscillations index language predictions, their power should monotonically relate to the degree of predictability of incoming words based on past context. We expected that the more predictable the last word of a sentence, the stronger the alpha and beta power modulation. To test this, we measured neural responses with magnetoencephalography of healthy individuals during exposure to a set of linguistically matched sentences featuring three levels of sentence context constraint (high, medium and low constraint). We observed fluctuations in alpha and beta power before last word onset, and modulations in M400 amplitude after last word onset. The M400 amplitude was monotonically related to the degree of context constraint, with a high constraining context resulting in the strongest amplitude decrease. In contrast, pre-stimulus alpha and beta power decreased more strongly for intermediate constraints, followed by high and low constraints. Therefore, unlike the M400, pre-stimulus alpha and beta dynamics were not indexing the degree of word predictability from sentence context.

Within the sensory domain, alpha/beta oscillations have been frequently linked to the prediction of upcoming sensory input. Here, we investigated whether oscillations at these frequency bands serve as a neural marker in the context of linguistic input prediction as well.Specifically, we hypothesized that if alpha/beta oscillations do index language prediction, their power should modulate during sentence processing, indicating stronger engagement of underlying neuronal populations involved in the linguistic prediction process. Importantly, the modulation should monotonically relate to the degrees of predictability of incoming words based on past context. Specifically, we expected that the more predictable the last word of a sentence, the stronger the alpha/beta power modulation. To test this, we measured neural responses with magnetoencephalography of healthy individuals (of either sex) during exposure to a set of linguistically matched sentences featuring three distinct levels of sentence context constraint (high, medium and low constraint). We observed fluctuations in alpha/beta power before last word onset, and also modulations in M400 amplitude after last word onset that are known to gradually relate to semantic predictability. In line with previous findings, the M400 amplitude was monotonically related to the degree of context constraint, with a high constraining context resulting in the strongest amplitude decrease. In contrast, alpha/beta power was non-monotonically related to context constraints. The strongest power decrease was observed for intermediate constraints, followed by high and low constraints. While the monotonous M400 amplitude modulation fits within a framework of prediction, the nonmonotonous oscillatory results are not easily reconciled with this idea. SIGNIFICANCE STATEMENTNeural activity in the alpha (8-10Hz) and beta (16-20) frequency ranges have been related to the prediction of upcoming sensory input. It remains still debated whether these frequency bands relate to language prediction as well. In this magnetoencephalography study, we recorded alpha/beta oscillatory activity while participants listened to sentences whose ending had varying degree of predictability based on past linguistic information. Our results show that alpha/beta power modulations were non-monotonically related to the degree of linguistic predictability: the strongest modulation of alpha/beta power was observed for intermediate levels of linguistic predictability during sentence reading. Together, the results emphasize that alpha/beta oscillations cannot directly be linked to predictability in language, but potentially relate to attention or control operations during language processing.

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Listening to speech is difficult in noisy environments, and is even harder when the interfering noise consists of intelligible speech as compared to non-intelligible sounds. This suggests that the ignored speech is not fully ignored, and that competing linguistic information interferes with the neural processing of target speech. We tested this hypothesis using magnetoencephalography (MEG) while participants listened to target clear speech in the presence of distracting noisevocoded signals. Crucially, the noise vocoded distractors were initially unintelligible but were perceived as intelligible speech after a small training session. We compared participants' performance in the speech-in-noise task before and after training, and neural entrainment to both target and distracting speech. The comprehension of the target clear speech was reduced in the presence of intelligible distractors as compared to when they were unintelligible. The neural entrainment to target speech in the delta range (1-4 Hz) reduced in strength in the presence of an intelligible distractor. In contrast, neural entrainment to distracting signals was not significantly modulated by intelligibility. These results support and extend previous findings, showing, first, that the masking effects of distracting speech originate from the degradation of the linguistic representation of target speech, and second, that delta entrainment reflects linguistic processing of speech.

Words are not processed in isolation, instead they are commonly embedded in phrases and sentences. The sentential context influences the perception and processing of a word. However, how this is achieved by brain processes and whether predictive mechanisms underlie this process remains a debated topic. To this end we employed an experimental paradigm in which we orthogonalized sentence context constraints and predictive validity, which was defined as the ratio of congruent to incongruent sentence endings within the experiment. While recording electroencephalography, participants read sentences with three levels of sentential context constraints (high, medium and low). Participants were also separated into two groups, which differed in their ratio of valid congruent to incongruent target words that could be predicted from the sentential context. For both groups we investigated modulations of alpha power before, and N400 amplitude modulations after target word onset. The results reveal that the N400 amplitude gradually decreases with higher context constraints. Contrary, alpha power is non-monotonically influenced, displaying the strongest decrease for high context constraints over frontal electrode sites, while alpha power between medium and low context constraints does not differ. This indicates that both neural correlates are influenced by the degree of context constraint but are not affected by changes in predictive validity. The results therefore suggest that both N400 and alpha power are not unequivocally linked to the predictability of a target word based on larger contextual information.