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

Purpose Listeners shift their listening strategies to prioritize lower-level acoustic information and higher-level semantic information in challenging listening conditions. However, the neural mechanisms underlying different strategies are unclear. The current study examined the extent to which encoding of lower-level acoustic cues is modulated by task demand and relationships with the higher-level semantic processing. Method Electroencephalography (EEG) was acquired while participants listened to sentences in noise 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 (TRFs). Results Task difficulty did not affect cortical tracking of temporal envelope of speech under challenging listening conditions. No correlations were observed between the cortical tracking of temporal envelope of speech and semantic processes, even after controlling for the effect of individualized signal-to-noise ratios. Conclusions Cortical tracking of 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 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.