Cardio-audio synchronization elicits prediction in auditory sequences during human wakefulness and sleep

The human brain can infer temporal regularities across cardiac and auditory inputs. Here, we investigated whether cardio-audio regularity processing occurs during sleep, when the balance between bodily and environmental stimulus processing may be altered. Using electroencephalography and electrocardiography in healthy volunteers (N=26) during wakefulness and sleep, we measured the response to unexpected sound omissions within three regularity conditions: synchronous, where sound and heartbeat are temporally coupled, isochronous, with fixed sound-to-sound intervals, and a third control condition without specific regularity. The synchronous and isochronous sequences induced a modulation of the omission-evoked neural response in wakefulness and N2 sleep, the latter accompanied by a reorganization of the background oscillatory activity. Cardio-audio regularity encoding was further demonstrated by a heartbeat deceleration upon omissions in all vigilance states, higher in the synchronous compared to the other regularity types. The human brain processes cardio-audio temporal relationships to predict future auditory events across distinct vigilance stages. ### Competing Interest Statement The authors have declared no competing interest.