
What happens inside our brains when we sleep? To answer this question, French researchers have, for the first time, filmed the entire brain in sleeping rats, thanks to innovative ultrasound imaging technology. They were thus able to closely observe brain function in rodents, particularly during the REM sleep phase. These results were obtained in shared Inserm, ESPCI Paris, CNRS, and Sorbonne University laboratories. Published in Nature Communications, these findings allow this period to be redefined as a brain hypersynchronization phase, characterized by massive peaks in blood flow, particularly in the hippocampus. These new data, which question the role currently ascribed to REM sleep, have yet to be confirmed in humans.