Naturalistic spoken language comprehension is supported by alpha and beta oscillations.

Brain oscillations are prevalent in all species and are involved in numerous perceptual operations. Alpha oscillations are thought to facilitate processing through the inhibition of task-irrelevant networks, while beta oscillations are linked to the putative reactivation of content representations. Can the proposed functional role of alpha and beta oscillations be generalized from low-level operations to higher-level cognitive processes? Here we address this question focusing on naturalistic spoken language comprehension. Twenty-two (18 female) Dutch native speakers listened to stories in Dutch and French while magnetoencephalography (MEG) was recorded. We used dependency parsing to identify three dependency states at each word: the number of (1) newly opened dependencies, (2) dependencies that remained open, and (3) resolved dependencies. We then constructed forward models to predict alpha and beta power from the dependency features. Results showed that dependency features predict alpha and beta power in language-related regions beyond low-level linguistic features. Left temporal, fundamental language regions are involved in language comprehension in alpha, while frontal and parietal, higher-order language regions, and motor regions are involved in beta. Critically, alpha- and beta-band dynamics seem to subserve language comprehension tapping into syntactic structure building and semantic composition by providing low-level mechanistic operations for inhibition and reactivation processes. Due to the temporal similarity of the alpha-beta responses, their potential functional dissociation remains to be elucidated. Overall, this study sheds light on the role of alpha and beta oscillations during naturalistic spoken language comprehension, providing evidence for the generalizability of these dynamics from perceptual to complex linguistic processes. SIGNIFICANCE STATEMENT: It remains unclear whether the proposed functional role of alpha and beta oscillations in perceptual and motor function is generalizable to higher-level cognitive processes, such as spoken language comprehension. We found that syntactic features predict alpha and beta power in language-related regions beyond low-level linguistic features when listening to naturalistic speech in a known language. We offer experimental findings that integrate a neuroscientific framework on the role of brain oscillations as "building blocks" with spoken language comprehension. This supports the view of a domain-general role of oscillations across the hierarchy of cognitive functions, from low-level sensory operations to abstract linguistic processes.