High-frequency neural activity predicts word parsing in ambiguous speech streams

Abstract

Kösem A, Basirat A, Azizi L, van Wassenhove V. High-frequency neural activity predicts word parsing in ambiguous speech streams. J Neurophysiol 116: 2497-2512, 2016. First published September 7, 2016 doi:10.1152/jn.00074.2016.-During speech listening, the brain parses a continuous acoustic stream of information into computational units (e.g., syllables or words) necessary for speech comprehension. Recent neuroscientific hypotheses have proposed that neural oscillations contribute to speech parsing, but whether they do so on the basis of acoustic cues (bottom-up acoustic parsing) or as a function of available linguistic representations (top-down linguistic parsing) is unknown. In this magnetoencephalography study, we contrasted acoustic and linguistic parsing using bistable speech sequences. While listening to the speech sequences, participants were asked to maintain one of the two possible speech percepts through volitional control. We predicted that the tracking of speech dynamics by neural oscillations would not only follow the acoustic properties but also shift in time according to the participant's conscious speech percept. Our results show that the latency of high-frequency activity (specifically, beta and gamma bands) varied as a function of the perceptual report. In contrast, the phase of low-frequency oscillations was not strongly affected by top-down control. Whereas changes in low-frequency neural oscillations were compatible with the encoding of prelexical segmentation cues, high-frequency activity specifically informed on an individual's conscious speech percept.

Low-frequency Neural Activity Reflects Rule-based Chunking during Speech Listening

“…After the chunk structure is parsed, the listener could synchronize their attention and predictions to the sequence. Previous studies have suggested that entrained neural oscillations may reflect both sequence parsing (Ding et al, 2016;Kösem et al, 2016;Meyer et al, 2016;Wang et al, 2017;Meyer and Gumbert, 2018) and temporal attention/prediction (Morillon and Baillet, 2017;Jin et al, 2018;Rimmele et al, 2018), and could causally modulate speech perception (Kösem et al, 2018;Riecke et al, 2018;Zoefel et al, 2018). The current results cannot distinguish which chunk-related process drives the chunk-rate response.…”

Phase−amplitude coupling between theta and gamma oscillations adapts to speech rate

“…The envelope of the audio signals was estimated by using a filter bank that models the passage of the signal through the cochlea . − Coherence between the speech envelope and neural activity in each voxel of both ROIs was obtained in the 0.5−10 Hz frequency band with 0.5 Hz frequency resolution . The average coherence value of all voxels in LAC and RAC was calculated for each participant, condition, and frequency bin.…”

Distracting Linguistic Information Impairs Neural Tracking of Attended Speech

“…Broadly speaking, this could be either acoustic features or higher-level language information (20,21). Recent work suggests that the different neural oscillatory markers link to distinct aspects of speech perception: theta entrainment underlies speech sound analysis (22)(23)(24) while delta oscillations reflect higher-level linguistic processing, such as semantic and syntactic processing (15,25).…”