REM Dreams Hint at a Hidden Brain Energy Paradox

A mouse study from Tohoku University shows that during REM sleep, blood flow and astrocyte-derived fuel rise, but neuronal ATP declines, suggesting energy delivery and usage are temporarily out of sync as dreaming triggers intense brain activity. This energy mismatch means more blood flow doesn’t automatically boost usable energy, and the brain may reorganize energy flow to support internal processing and memory, helping explain why dreaming can feel tiring and how sleep maintains neural efficiency.