Brain Turns Hearing Inward During REM Sleep

During REM sleep, the brain selectively suppresses external auditory processing while amplifying internal heartbeat-evoked neural signals. Marzia De Lucia said the brain turns its listening inward. The study, published in Current Biology on August 3, 2026, found that as responsiveness to external sounds weakens during REM sleep transitions, the brain's processing of internal cardiac signals systematically intensifies. Researchers developed an audio-cardio index to quantify this neural pivot, offering a novel physiological marker for assessing altered states of consciousness.