A study conducted by researchers at the GIGA – Center of Research Cyclotron at the University of Liège, in collaboration with the University of Fribourg, Switzerland, has unveiled that the human body continues to interact with the external environment even during sleep, thereby influencing sleep quality based on sensory inputs. This groundbreaking research delves into the body’s response to auditory stimuli during sleep, mainly focusing on the effect of different types of words on the heart rate. The findings indicate that hearing calming words while asleep can reduce heart rate, signifying a state of more profound relaxation as opposed to neutral words that do not trigger a similar slowing of cardiac activity. Published in the Journal of Sleep Research, this study illuminates the intricate brain-heart dynamics during sleep.
The research team, including Matthieu Koroma (a postdoctoral researcher funded by the Fund for Scientific Research – FNRS), Christina Schmidt and Athena Demertzi (both research associates at the Fund for Scientific Research – FNRS) at the GIGA Cyclotron Research Center, University of Liège, along with colleagues from the University of Fribourg, expanded on previous work which analyzed brain data (via electroencephalograms). This prior study showed that calming words extended the duration of deep sleep and enhanced overall sleep quality, suggesting the potential of auditory stimuli to modulate sleep beneficially. It was hypothesized that the brain remains receptive to sensory information during sleep, leading to a relaxation of the body upon hearing soothing words. This latest study further explored this hypothesis by examining changes in cardiac activity (via electrocardiograms) after introducing relaxing versus neutral words, confirming that only relaxing words effectively reduce heart rate.
In comparing cardiac and brain activity markers, the researchers aimed to elucidate the extent to which each contributes to sleep modulation through auditory information. While previous assumptions were that cardiac activity’s influence on perception was limited to wakefulness, these new findings reveal its significance during sleep, offering a fresh perspective on the role of bodily responses in our understanding of sleep, in addition to brain activity.
Dr Schmidt noted the rarity of sleep research addressing bodily activities and highlighted the brain’s and body’s interconnectedness during sleep. This suggests a holistic approach is necessary to understand how humans process and react to environmental stimuli. Dr Demertzi added that considering brain and body responses is crucial for comprehensively understanding human interaction with the environment, even during sleep.
Furthermore, Dr. Koroma emphasized the team’s commitment to Open Science principles by sharing their methodology openly, hoping to inspire further research into the cardiac role in sleep functions.
This pioneering study proposes a broader framework for exploring how sensory information, particularly auditory stimuli, modulates sleep functions. Future research could investigate the body’s role in how sounds affect the emotional processing of memories during sleep, highlighting the potential for a more integrated approach to understanding sleep and its functions.
More information: Matthieu Koroma et al, Probing the embodiment of sleep functions: Insights from cardiac responses to word-induced relaxation during sleep, Journal of Sleep Research. DOI: 10.1111/jsr.14160
Journal information: Journal of Sleep Research Provided by University of Liège
