Caroline Beese

Alignment of alpha-band desynchronization with syntactic structure predicts successful sentence comprehension

&NA; Sentence comprehension requires the encoding of phrases and their relationships into working memory. To date, despite the importance of neural oscillations in language comprehension, the neural‐oscillatory dynamics of sentence encoding are only sparsely understood. Although oscillations in a wide range of frequency bands have been reported both for the encoding of unstructured word lists and for working‐memory intensive sentences, it is unclear to what extent these frequency bands subserve processes specific to the working‐memory component of sentence comprehension or to general verbal working memory. In our auditory electroencephalography study, we isolated the working‐memory component of sentence comprehension by adapting a subsequent memory paradigm to sentence comprehension and assessing oscillatory power changes during successful sentence encoding. Time–frequency analyses and source reconstruction revealed alpha‐power desynchronization in left‐hemispheric language‐relevant regions during successful sentence encoding. We further showed that sentence encoding was more successful when source‐level alpha‐band desynchronization aligned with computational measures of syntactic—compared to lexical‐semantic—difficulty. Our results are a preliminary indication of a domain‐general mechanism of cortical disinhibition via alpha‐band desynchronization superimposed onto the language‐relevant cortex, which is beneficial for encoding sentences into working memory. HighlightsAlpha‐band desynchronization is the EEG correlate of successful sentence encoding.Alpha‐band sources are likely located in the left‐hemispheric language network.Interaction of alpha‐band power and syntactic difficulty explains encoding success.

Temporally and spatially distinct theta oscillations dissociate a language-specific from a domain-general processing mechanism across the age trajectory

The cognitive functionality of neural oscillations is still highly debated, as different functions have been associated with identical frequency ranges. Theta band oscillations, for instance, were proposed to underlie both language comprehension and domain-general cognitive abilities. Here we show that the ageing brain can provide an answer to the open question whether it is one and the same theta oscillation underlying those functions, thereby resolving a long-standing paradox. While better cognitive functioning is predicted by low theta power in the brain at rest, resting state (RS) theta power declines with age, but sentence comprehension deteriorates in old age. We resolve this paradox showing that sentence comprehension declines due to changes in RS theta power within domain-general brain networks known to support successful sentence comprehension, while low RS theta power within the left-hemispheric dorso-frontal language network predicts intact sentence comprehension. The two RS theta networks were also found to functionally decouple relative to their independent internal coupling. Thus, both temporally and spatially distinct RS theta oscillations dissociate a language-specific from a domain-general processing mechanism.

Adult age differences in the benefit of syntactic and semantic constraints for sentence processing.

Verbal working memory-intensive sentence processing declines with age. This might reflect older adults’ difficulties with reducing the memory load by grouping single words into multiword chunks. Here we used a serial order task emphasizing syntactic and semantic relations. We evaluated the extent to which older compared with younger adults may differentially use linguistic constraints during sentence processing to cope with verbal working memory limitations. Probing syntactic–semantic interactions, age differences were hypothesized to be confined to the use of syntactic constraints and to be accompanied by an increased reliance on semantic information. Two experiments varying in verbal working memory demands were conducted: the sequence length was increased from eight items in Experiment 1 to 11 items in Experiment 2. We found the use of syntactic constraints to be compromised with aging, while the benefit of semantic information for sentence processing was comparable across age groups. Hence, we suggest that semantic information processing may become relatively more important for successful sentence processing with advancing adult age, possibly inducing a syntactic-to-semantic-processing strategy shift.