Effects of Task Demands on Neural Correlates of Acoustic and Semantic Processing in Challenging Listening Conditions

Abstract

Purpose Listeners shift their listening strategies between lower level acoustic information and higher level semantic information to prioritize maximum speech intelligibility in challenging listening conditions. Although increasing task demands via acoustic degradation modulates lexical-semantic processing, the neural mechanisms underlying different listening strategies are unclear. The current study examined the extent to which encoding of lower level acoustic cues is modulated by task demand and associations with lexical-semantic processes. Method Electroencephalography was acquired while participants listened to sentences in the presence of four-talker babble that contained either higher or lower probability final words. Task difficulty was modulated by time available to process responses. Cortical tracking of speech—neural correlates of acoustic temporal envelope processing—were estimated using temporal response functions. Results Task difficulty did not affect cortical tracking of temporal envelope of speech under challenging listening conditions. Neural indices of lexical-semantic processing (N400 amplitudes) were larger with increased task difficulty. No correlations were observed between the cortical tracking of temporal envelope of speech and lexical-semantic processes, even after controlling for the effect of individualized signal-to-noise ratios. Conclusions Cortical tracking of the temporal envelope of speech and semantic processing are differentially influenced by task difficulty. While increased task demands modulated higher level semantic processing, cortical tracking of the temporal envelope of speech may be influenced by task difficulty primarily when the demand is manipulated in terms of acoustic properties of the stimulus, consistent with an emerging perspective in speech perception.

Prediction of Speech Intelligibility by Means of EEG Responses to Sentences in Noise

“…It seems possible that our findings relate primarily to investigation of the auditory pathway to a certain stage depending on electrode localization. Not all cognitive requirements for a complete understanding of speech can be investigated by these measurements (Decruy et al, 2020a ; Devaraju et al, 2021 ). Additionally, the chosen stimuli aim to imitate a matrix sentence test, resulting in periods between the single sentences, which only contain noise.…”

The Effects of Speech Masking on Neural Tracking of Acoustic and Semantic Features of Natural Speech

“…TRFs have also been used to investigate whether semantic features during continuous speech listening are encoded in the brain (Broderick et al, 2018; Gillis et al, 2021; Devaraju et al, 2021). In such studies, each word in a spoken story is represented by a high-dimensional numerical vector that captures semantic information.…”

The effects of speech masking on neural tracking of acoustic and semantic features of natural speech

“…TRFs have also been used to investigate whether semantic features during continuous speech listening are encoded in the brain (Broderick et al, 2018;Gillis et al, 2021;Devaraju et al, 2021). In such studies, each word in a spoken story is represented by a high-dimensional numerical vector that captures semantic information.…”