University Researchers Reveal Brain Prioritizes Internal Signals During REM Sleep

A study by researchers at the University of Lausanne and the University of Geneva found that as humans enter rapid eye movement (REM) sleep, the brain reduces processing of external sounds while amplifying responses to internal cardiac signals. Using high‑density EEG, the team quantified this shift with an audio‑cardio index, suggesting a new biomarker for assessing consciousness levels in clinical settings.

In a separate mouse study at Tohoku University, scientists observed that during REM sleep the brain’s blood volume and astrocytic fuel stores increase, yet neuronal ATP levels fall, indicating a temporary energy shortfall. The findings highlight a metabolic paradox in dreaming, where heightened neural activity outpaces energy replenishment. Both studies deepen understanding of REM sleep’s unique sensory and metabolic dynamics.