December 16, 2025
Dead salmon, live drama
40 percent of MRI signals do not correspond to actual brain activity
It’s fMRI, not your hospital MRI—crowd calls ‘old news’ and dead salmon vibes
TLDR: A new study says fMRI’s blood-oxygen signal can mislead about brain activity in roughly 40% of cases. Commenters blast the headline as confusing MRI with fMRI, call it “old news,” summon the dead salmon meme, and push for better, energy-based measures to avoid misreading brain research.
A splashy Nature Neuroscience study says the brain’s popular blood‑oxygen signal (the thing behind functional MRI, or fMRI) mismatches real activity in about 40% of cases. Translation: sometimes a stronger “glow” on the scan means less actual brain action, and vice versa. The authors urge adding direct oxygen‑use measurements to stop guessing and start measuring energy. But the community didn’t quietly nod—they pounced. The loudest chorus: the headline is misleading. Multiple commenters stressed this is about fMRI’s blood‑oxygen proxy, not your hospital MRI for bumps and broken bones. One user begged to change the title so scrollers don’t panic, another rolled eyes with the classic dead salmon meme—yes, a famous prank scan once “found activity” in a fish.
Cue the hot takes: a lab veteran claimed this was “not news even thirty years ago,” and others shrugged, saying this just confirms fMRI’s BOLD signal is an imperfect stand‑in for neurons. Meanwhile, skeptics tossed spice—“you’re telling me the results were likely bs?” with a link. Still, beneath the drama, folks agreed the stakes are big: rethinking studies on aging, depression, Alzheimer’s, and more. The vibe? Calm down, correct the headline, upgrade the tools—and leave the salmon out of it.
Key Points
- •Study in Nature Neuroscience finds no universal coupling between MRI-measured oxygen content and neuronal activity.
- •About 40% of cases showed increased fMRI signals paired with reduced brain activity; decreased signals also appeared in active regions.
- •Researchers tested over 40 healthy participants performing tasks while simultaneously measuring oxygen consumption with quantitative MRI.
- •In some regions, higher energy demand was met by increased oxygen extraction from unchanged blood flow, not by increased perfusion.
- •Authors recommend complementing conventional MRI with quantitative measurements and building energy-based brain models to improve interpretation, especially in populations with vascular changes.