Iotzov, I. | Search bioRxiv

bioRxiv2023

Pupil size and EEG speech tracking as independent measures of listening effort and speech intelligibility

Speech is hard to understand when there is background noise. Speech intelligibility and listening effort both affect our ability to understand speech, but the relative contribution of these subjective factors is hard to disentangle. Previous studies suggest that speech intelligibility could be assessed with EEG speech tracking and listening effort via pupil size. However, these measures may be confounded, because poor intelligibility may require a larger effort. To address this we developed a novel word-detection paradigm that allows for a rapid behavioral assessment of speech processing. In this paradigm words appear on the screen during continuous speech similar to closed captioning. In two listening experiments with a total of 51 participants we manipulated intelligibility with changing auditory noise levels and modulated effort by varying monetary reward. Increasing signal-to-noise ratio (SNR) improved detection performance along with EEG speech tracking, suggesting improved intelligibility. Additionally, we find larger pupil size with increased SNR, suggestive of increased effort. Surprisingly, when we modulated both reward and SNR, we found that reward modulated only pupil size, while SNR modulated only EEG speech tracking. We suggest that this new paradigm can be used to independently and objectively assess speech intelligibility and listening effort.

neuroscience↗

bioRxiv2017

Common neural responses to narrative speech indisorders of consciousness

ObjectiveClinical assessment of auditory attention in patients with disorders of consciousness is often limited by motor impairment. Here, we employ inter-subject correlations among electroencephalography responses to naturalistic speech in order to assay auditory attention among patients and healthy controls.\n\nMethodsElectroencephalographic data were recorded from 20 subjects with disorders of consciousness and 14 healthy controls during of two narrative audio stimuli, presented both forwards and time-reversed. Inter-subject correlation of evoked electroencephalography signals were calculated, comparing responses of both groups to those of the healthy control subjects. This analysis was performed blinded and subsequently compared to the diagnostic status of each patient based on the Coma Recovery Scale-Revised.\n\nResultsSubjects with disorders of consciousness exhibit significantly lower inter-subject correlation than healthy controls during narrative speech. Additionally, while healthy subjects had higher inter-subject correlation values in forward vs. backwards presentation, neural responses did not vary significantly with the direction of playback in subjects with disorders of consciousness. Increased inter-subject correlation values in the backward speech condition were noted with improving disorder of consciousness diagnosis, both in cross-sectional analysis and in a subset of patients with longitudinal data.\n\nInterpretationInter-subject correlation of neural responses to narrative speech audition differentiates healthy controls from patients and appears to index clinical diagnoses in disorders of consciousness.

neuroscience↗