Cortical oscillations and entrainment in speech processing during working memory load

Abstract

Neuronal oscillations are thought to play an important role in working memory (WM) and speech processing. Listening to speech in real-life situations is often cognitively demanding but it is unknown whether WM load influences how auditory cortical activity synchronizes to speech features. Here, we developed an auditory n-back paradigm to investigate cortical entrainment to speech envelope fluctuations under different degrees of WM load. We measured the electroencephalogram, pupil dilations and behavioural performance from 22 subjects listening to continuous speech with an embedded n-back task. The speech stimuli consisted of long spoken number sequences created to match natural speech in terms of sentence intonation, syllabic rate and phonetic content. To burden different WM functions during speech processing, listeners performed an n-back task on the speech sequences in different levels of background noise. Increasing WM load at higher n-back levels was associated with a decrease in posterior alpha power as well as increased pupil dilations. Frontal theta power increased at the start of the trial and increased additionally with higher n-back level. The observed alpha-theta power changes are consistent with visual n-back paradigms suggesting general oscillatory correlates of WM processing load. Speech entrainment was measured as a linear mapping between the envelope of the speech signal and low-frequency cortical activity (< 13 Hz). We found that increases in both types of WM load (background noise and n-back level) decreased cortical speech envelope entrainment. Although entrainment persisted under high load, our results suggest a top-down influence of WM processing on cortical speech entrainment.

Stimulus-aware spatial filtering for single-trial neural response and temporal response function estimation in high-density EEG with applications in auditory research

“…One is the fronto-central region, and the other is the parietal-occipital region. This is in line with other related works that estimate spatial filters based on speech processing (Dmochowski et al, 2018) and those that shows the topography of speech processing in the brain Hjortkjaer et al, 2018;O'Sullivan et al, 2015). For the second component we did not find any significant clusters.…”

Neural representation of linguistic feature hierarchy reflects second-language proficiency

“…Interestingly, this result was obtained on a single-talker task with no competing noise. Therefore, the application of this same approach on a more cognitively demanding task 62,80 could help tease apart the effects of L2 proficiency and listening effort on the cortical encoding of acoustic features.…”

Pupillometry as an objective measure of sustained attention in young and older listeners

“…Pupil dilation has long been used as a measure of effort (Beatty, 1982;Bradshaw, 1968;Cabestrero et al, 2009;Granholm and Steinhauer, 2004;Hjortkjaer et al, 2018;Wel and Steenbergen, 2018) and is presently attracting considerable interest in the auditory modality because of evidence that pupil dilation can be used as an objective means with which to evaluate challenges to listening (McGarrigle et al, 2014;Peelle, 2018;Pichora-Fuller et al, 2016). The bulk of existing work has used pupillometry to evaluate listening effort associated with degraded speech (Koelewijn et al, 2012(Koelewijn et al, , 2014(Koelewijn et al, , 2015Kuchinsky et al, 2014;Naylor et al, 2018;Ohlenforst et al, 2017;Wang et al, 2017;Wendt et al, 2016Wendt et al, , 2017Winn et al, 2015Winn et al, , 2018Zekveld et al, 2010Zekveld et al, , 2011Zekveld et al, , 2018.…”

“…Indeed, most previous work has used coarse pupil measures (peak dilation) and over relatively short intervals (most investigations have focused on the first 5 seconds; but see Hjortkjaer et al, 2018). In contrast, we aim to measure instantaneous pupil diameter changes over a period of ~25 seconds.…”