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Yawning reorganizes brain fluid flow in unexpected ways

Source: newscientist.com

TL;DR

MRI scans show yawning reorganizes cerebrospinal fluid flow out of the brain differently from deep breathing.
During yawns, CSF and venous blood move together toward the spinal column, boosting carotid arterial inflow by over a third.
This reveals yawning as a distinct process that may aid brain fluid regulation, though its exact benefits remain unclear.

The story at a glance

MRI scans of 22 healthy adults reveal that yawning triggers a unique flow of cerebrospinal fluid (CSF) and venous blood away from the brain toward the spinal column, unlike deep breathing. Researchers led by Adam Martinac at Neuroscience Research Australia conducted the study, published as a preprint on bioRxiv in December 2025 and covered in New Scientist on 30 January 2026. The work is reported now to highlight yawning's unexpected role in neurofluid dynamics beyond common theories like oxygenation or cooling.

Key points

Yawning couples CSF and venous blood flows directionally, moving both out of the brain, while deep breathing shows opposing flows (venous blood out, CSF in).
Carotid arterial inflow increases by 34% during yawning compared to deep breathing, likely due to space created by the combined outflow.
Each participant showed a unique "yawning signature" in tongue movement patterns.
Study involved MRI scans during normal breathing, yawning (induced by yawn videos), yawn suppression, and forceful deep breaths.
Estimated CSF movement per yawn is a few millilitres; exact mechanism unclear but may involve neck muscles, tongue, and throat.
Yawning remains evolutionarily conserved across vertebrates, with theories including brain fluid circulation and cortisol management.

Details and context

The study challenges the idea that yawning is just an intensified deep breath. Researchers expected similar CSF outflow in both but found yawns reorganize neurofluids in a novel way, potentially pulling waste or aiding solute transport down the spinal column.[[1]](https://www.newscientist.com/article/2513692-yawning-has-an-unexpected-influence-on-the-fluid-inside-your-brain/)[[2]](https://www.biorxiv.org/content/10.64898/2025.12.17.695005v1)

Experts note limitations: the research used contagious yawns (shorter than spontaneous ones averaging 6 seconds), so effects may be stronger naturally. Possible benefits like thermoregulation or waste clearance are speculated but unproven; one expert suggests flushing adenosine to boost alertness.[[1]](https://www.newscientist.com/article/2513692-yawning-has-an-unexpected-influence-on-the-fluid-inside-your-brain/)

Key quotes

“But the yawn was triggering a movement of the CSF in the opposite direction than during a deep breath... And we’re just sitting there like, whoa, we definitely didn’t expect that.” – Adam Martinac, Neuroscience Research Australia[[1]](https://www.newscientist.com/article/2513692-yawning-has-an-unexpected-influence-on-the-fluid-inside-your-brain/)
“The fact that internal carotid arterial flow increased by 34 per cent during… yawning is a really important finding that seems to be overlooked.” – Andrew Gallup, Johns Hopkins University[[1]](https://www.newscientist.com/article/2513692-yawning-has-an-unexpected-influence-on-the-fluid-inside-your-brain/)

Why it matters

Yawning's role in directing CSF could link to brain health functions like waste removal or nutrient delivery, conserved across vertebrates for subtle cumulative benefits. For everyday people, it suggests the behaviour supports brain maintenance beyond signaling tiredness, potentially influencing alertness or cooling. Watch for follow-up studies quantifying CSF volume shifted and testing spontaneous yawns or mechanisms like muscle coordination.[[1]](https://www.newscientist.com/article/2513692-yawning-has-an-unexpected-influence-on-the-fluid-inside-your-brain/)