{
  "id": 47992,
  "title": "When more blood does not mean more neuronal energy during REM sleep",
  "url": "https://urgent.news/2026/08/02/when-more-blood-does-not-mean-more-neuronal-energy-during-rem-sleep",
  "topic": "science",
  "section": "Science",
  "published": "2026-08-02T15:00:04.000Z",
  "source": {
    "name": "Medical Xpress",
    "slug": "medical-xpress",
    "url": "https://medicalxpress.com/news/2026-07-blood-neuronal-energy-rem.html"
  },
  "original_language": "en",
  "account": "A recent study published in Communications Biology has uncovered a surprising paradox during REM sleep: despite an increase in brain blood volume, the amount of ATP available to neurons actually decreased. This finding challenges the common belief that more blood automatically equates to more neuronal energy.\n\nThe research team began by asking how the sleeping brain adjusts its energy supply to match changing patterns of information processing. They focused on three key signals: brain blood volume, astrocytic pyruvate, and neuronal ATP. Observing the cerebral cortex of living mice through their native skull coated with a transparent resin, they recorded these signals throughout various sleep stages.\n\nDuring non-REM sleep, fluctuations in theta-band brain activity were found to predict changes in brain blood volume approximately four to five seconds later. This suggests that blood-volume changes are not merely passive but are actively adjusted to ongoing neuronal activity. Spatial patterns were also observed, with blood-volume waves propagating from anterior to posterior cortical regions at a relatively fast pace.\n\nAs the transition into REM sleep approached, brain blood volume began to rise about 50 seconds before the conventional identification of REM sleep from brain and muscle recordings. This indicates that the brain starts preparing for REM sleep even before the usual electrical signs are fully established.\n\nUpon expecting neuronal ATP to rise alongside the vascular signal, the researchers encountered a surprising result. Astrocytic pyruvate increased during REM sleep, particularly in posterior cortical regions, while neuronal ATP showed a decrease. This dissociation between vascular delivery, astrocytic metabolism, and neuronal energy availability prompted further investigation into the underlying mechanisms.\n\nPossible explanations for the decreased neuronal ATP during REM sleep include rapid ATP consumption by neurons for synaptic reorganization and communication, changes in the transfer of metabolic substrates from astrocytes to neurons, or temporary inefficiency in mitochondrial ATP production. However, the exact reasons remain unclear.\n\nThese findings also call into question the interpretation of hemodynamic brain imaging techniques, such as functional MRI, which rely on changes in blood flow, volume, and oxygenation to infer brain activity. The study highlights that these vascular signals do not fully capture the metabolic story, as seen in the case of REM sleep where increased blood flow coincided with decreased neuronal ATP.\n\nThe concept of brain energy regulation during REM sleep is now viewed as a complex, multilayered process. Blood vessels adjust oxygen and glucose delivery, astrocytes process, store, and redistribute metabolic substrates, and neurons utilize ATP for information processing. The brain achieves remarkable energy efficiency not by supplying uniform resources to every cell but by reallocating limited resources based on its current computational state.\n\nWhile the study did not directly address human fatigue, it provides valuable insights into the biological phenomenon of REM sleep. The experiment demonstrates that neuronal ATP can fall even when brain blood volume rises, shedding light on the intricate relationship among vessels, astrocytes, and neurons during this paradoxical stage of sleep. Understanding this dynamic may contribute to our knowledge of sleep, memory, and the principles underlying biological intelligence's energy efficiency.",
  "summary": "REM sleep is already called \"paradoxical sleep.\" The body is largely still, yet the brain is highly active. In humans, this is also the stage most closely associated with vivid dreaming. Our study, published in Communications Biology, has revealed another paradox hidden within REM sleep: Brain blood volume increased, but the ATP available inside neurons decreased.",
  "key_points": [
    "Brain blood volume rises before REM sleep onset",
    "Neuronal ATP decreases despite increased blood flow",
    "Astrocytic pyruvate increases in REM sleep regions"
  ],
  "editors_take": null,
  "illustration": null,
  "coverage": {
    "outlets": 1,
    "also_reported_by": []
  },
  "ai_generated": true,
  "disclaimer": "Summaries, key points and the editor’s take are written by software from other outlets’ reporting and may contain errors — always check the linked original."
}