Neural Signatures of Engagement and Event Segmentation during Story Listening in Background Noise

Speech in everyday life is often masked by background noise, making comprehension effortful. Characterizing brain activity patterns when individuals listen to masked speech can help clarify the mechanisms underlying such effort. In the current study, we used functional magnetic resonance imaging (fMRI) in humans of either sex to investigate how neural signatures of story listening change in the presence of masking noise. We show that, as speech masking increases, spatial and temporal activation patterns in auditory regions become more idiosyncratic to each listener. In contrast, spatial activity patterns in brain networks linked to effort (e.g., cingulo-opercular network) are more similar across listeners when speech is highly masked and less intelligible, suggesting shared neural processes. Moreover, at times during stories when one meaningful event ended and another began, neural activation increased in frontal, parietal, and medial cortices. This event-boundary response appeared little affected by background noise, suggesting that listeners process meaningful units and, in turn, the gist of naturalistic, continuous speech even when it is masked somewhat by background noise. The current data may indicate that people stay engaged and cognitive processes associated with naturalistic speech processing remain intact under moderate levels of noise, whereas auditory processing becomes more idiosyncratic to each listener.