REM sleep paradox: Dreaming may drain the brain’s energy even as fuel supply rises

The brain uses an extraordinary amount of energy compared with most other organs. Even so, it can continue processing information when energy is limited by adjusting how available resources are used. Scientists are still trying to understand how the brain manages this energy budget as it moves through different internal states.

Sleep offers a useful way to study that question. Although the body is resting, the brain remains active, especially during rapid eye movement (REM) sleep, which is closely associated with dreaming and memory processing. REM sleep is often described as "paradoxical sleep" because the body is mostly still while brain activity resembles wakefulness.

Researchers at Tohoku University have now identified another REM sleep paradox. During this stage, the apparent energy supply to the dreaming brain increases, yet levels of the energy molecule neurons directly use actually decline.

The findings were published in Communications Biology .