Tohoku mouse study finds ATP falls in REM sleep despite more blood and fuel

A Tohoku University mouse study covered by SciTechDaily reports an energy imbalance during rapid eye movement sleep. As the brain entered REM, blood volume increased across the cortex and astrocytes accumulated more metabolic fuel, yet ATP, the molecule neurons use as an immediate energy source, declined. The findings were published in Communications Biology. The write-up says the result challenges the simple assumption that delivering more fuel to the brain should immediately increase its usable energy. Instead, REM sleep may place such intense or unusual demands on neural circuits that energy consumption briefly outpaces production, even as the brain prepares additional resources. Professor Ko Matsui of Tohoku University is quoted noting that sleep may appear peaceful while the brain is highly active, especially when dreaming, and that the team wanted to look into the scientific basis behind why dreaming is somehow tiring. During REM, astrocytic pyruvate levels increased along with local brain blood volume, according to the article. The paper is listed as "Energy paradox in REM sleep: balancing supply and consumption in brain metabolism" by Yusuke Takahashi, Yoko Ikoma, and Ko Matsui, 27 July 2026 (DOI: 10.1038/s42003-026-10646-6). Sleep-metabolism researchers gain a concrete ATP-versus-supply mismatch to test; models that equate higher fuel delivery with higher usable energy lose a clean fit for REM.