The brain’s ability to integrate internal body signals with external stimuli is essential for survival. A recent study led by Marzia De Lucia in the Department of Clinical Neurosciences at CHUV reveals that this mechanism persists even in coma
Our body and brain are in constant interaction. This dialogue is crucial not only for reacting to signals from our organs, but also for interpreting stimuli from our environment. But how does this vital connection work, and how is it maintained in the absence of consciousness? These questions remain unanswered. New research shows that heartbeats play a key role: they guide the brains of comatose people as they process sounds from the outside world. The study, published on May 12, 2025 in the journal Proceedings of the Natural Academy of Sciences (PNAS), was led by Marzia De Lucia of the CHUV’s Department of Clinical Neurosciences and the Centre d’biomedical Imaging Center, MER and Associate Professor at the University of Lausanne’s Faculty of Biology and Medicine, in collaboration with several Swiss hospitals and the University of Geneva.
Using electroencephalography (EEG), the scientists recorded the brain responses of comatose patients exposed to sequences of simple sounds - beeps. These sounds were either synchronized with the heartbeat, or delivered independently. The results: even without consciousness, the brain continues to rely on the heartbeat to better process external sounds. "Heartbeats act as a kind of internal clock, helping the brain to anticipate auditory sensory information", explains Marzia De Lucia. This integration of signals thus helps the brain to interpret sounds emanating from the environment; it is essential for identifying potential dangers. "It’s an integrated surveillance system, capable of detecting changes and threats, even in the absence of consciousness."
What’s more, synchronization between heart and brain could predict the chances of recovery for people in a state of unconsciousness: the stronger the connection between heartbeat and sound processing, the higher the chances of waking up. "Our results not only improve our understanding of consciousness and perception, they also open up new avenues for diagnosing and treating comatose patients", enthuses the researcher
Reference
Cardiac signals inform auditory regularity processing in the absence of consciousness, Andria Pelentritou, Christian Pfeiffer, Manuela Iten and Marzia De Lucia, PNAS, May 12, 2025, 122 (20) e2505454122, doi.org/10.1073/pnas.2505454122
