The Interplay of Bottom-Up Arousal and Attentional Capture during Auditory Scene Analysis: Evidence from Ocular Dynamics

The auditory system plays a crucial role as the brain's early warning system. Previous work has shown that the brain automatically monitors unfolding auditory scenes and rapidly detects new events. Here, we focus on understanding how automatic change detection interfaces with the networks that regulate arousal and attention, measuring pupil dilation (PD) as an indicator of listener arousal and microsaccades (MS) as an index of attentional sampling. Naive participants (<i>N</i> = 36, both sexes) were exposed to artificial "scenes" comprising multiple concurrent streams of pure tones while their ocular activity was monitored. The scenes were categorized as REG or RND, featuring isochronous (regular) or random temporal structures in the tone streams. Previous work showed that listeners are sensitive to predictable scene structure and use this information to facilitate change processing. Scene changes were introduced by either adding or removing a single tone stream. Results revealed distinct patterns in the recruitment of arousal and attention during auditory scene analysis. Sustained PD was reduced in REG scenes compared with RND, indicating reduced arousal in predictable contexts. However, no differences in sustained MS activity were observed between scene types, suggesting no differences in attentional engagement. Scene changes, though task-irrelevant, elicited PD as well as MS suppression, consistent with automatic attentional capture and increased arousal. Notably, only MS responses were modulated by scene regularity. This suggests that changes within predictable environments more effectively recruit attentional resources. Together, these findings offer novel insights into how automatic auditory scene analysis interacts with neural systems governing arousal and attention.