Cardiac responses to auditory irregularities reveal hierarchical information processing during sleep

Our ability to process environmental stimuli varies during sleep. Although much research focused on neural processing, emerging evidence shows that bodily signals may play a key role in understanding high-level sensory processing during sleep. Here, we tested how cardiac responses to the local-global paradigm, a typical oddball task probing the processing of simple (local) and complex (global) sensory irregularities. To do so, we analyzed electrocardiography (ECG) signals in a total of 56 participants from two existing datasets which contained cerebral responses to local auditory irregularities, but which did not analyze the ECG data before. We found that cardiac activity slowed down after global, but not local, auditory irregularities, revealing the presence of global deviance effect in Rapid Eye Movement (REM) sleep. In contrast, cardiac activity was faster after local, but not global, deviants in Non-Rapid Eye Movement (NREM) sleep. Overall, our results demonstrate that cardiac responses to auditory irregularities inform about hierarchical information processing and its variations during sleep beyond cerebral activity. They highlight the embodiment of cognitive function and the value of cardiac signals to understand the variations of sensory processing during sleep.