A recent study conducted by researchers from the GIGA – Centre of Research Cyclotron at the University of Liege has illuminated the dynamics between the brain and the heart during sleep. Their findings suggest that the body remains responsive to external stimuli while asleep, potentially influencing sleep quality.
Collaborating with the University of Fribourg in Switzerland, the researchers investigated whether the body truly disconnects from the external environment during sleep. Their focus was on how different words heard during sleep affect heart rate variability.
The study revealed that hearing relaxing words led to a decrease in cardiac activity, indicative of deeper sleep, compared to neutral words that did not elicit such a response. These findings, published in the Journal of Sleep Research, offer fresh insights into the interactions between the brain and the heart during sleep.
Previously, researchers from the GIGA Cyclotron Research Center at ULiege, including Matthieu Koroma, Christina Schmidt, and Athena Demertzi, had conducted a study analyzing brain data (electroencephalogram), which showed that relaxing words increased the duration of deep sleep and improved sleep quality. This suggested the potential for positively influencing sleep through meaningful auditory stimuli.
Building on this hypothesis, the researchers investigated whether the brain’s interpretation of sensory information during sleep could induce relaxation. Analyzing cardiac activity (electrocardiogram), they discovered that the heart’s activity slowed down only in response to relaxing words, not control words.
Comparing markers of both cardiac and brain activity, the researchers sought to understand the extent to which each contributed to the modulation of sleep by auditory stimuli. While previous evidence suggested that cardiac activity influences perception during wakefulness, this study demonstrated its role during sleep as well.
These findings underscore the significance of considering bodily reactions alongside brain activity for a comprehensive understanding of sleep processes. Christina Schmidt emphasized the importance of including bodily activity in sleep research, highlighting the interconnectedness of the brain and body even during unconscious states.
Athena Demertzi further emphasized the need to integrate both brain and body information for a holistic understanding of cognitive processes, including sleep.
Dr. Koroma advocated for open science principles, sharing their methodology freely to inspire further research into the role of the heart in various sleep functions.