Brain blood volume rises but neuronal ATP drops during REM sleep

REM sleep, often described as “paradoxical sleep,” is a stage in which the body remains largely immobile while the brain exhibits heightened activity and vivid dreaming. A new study published in *Communications Biology* has uncovered a further paradox within this stage: while overall brain blood volume rises, the amount of adenosine triphosphate (ATP) available inside neurons actually falls.

Using advanced imaging and metabolic assays, the researchers measured cerebral blood flow and intracellular ATP levels in human subjects during REM sleep. They found that the surge in blood volume, which typically supplies oxygen and nutrients, coincides with a measurable reduction in neuronal ATP concentrations. This suggests that the brain’s energy demands during REM may outpace the supply provided by increased blood flow, or that ATP is being rapidly consumed for processes such as memory consolidation or synaptic remodeling.

The findings add a new layer to our understanding of REM sleep’s physiological role, highlighting a mismatch between vascular supply and cellular energy status. Further research will be needed to determine whether this ATP depletion is a normal aspect of REM function or a marker of underlying metabolic stress, and how it might influence cognitive processes that occur during dreaming.