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Dead Salmon's "Brain Activity" Cautions fMRI Researchers
AthanasiusKircher sends in a Wired writeup on what should surely be a contender in the next Improbable Research competition: wiring a dead salmon into an fMRI machine and showing it pictures of humans designed to evoke various emotions. "When they got around to analyzing the voxel... data, the voxels representing the area where the salmon's tiny brain sat showed evidence of activity. In the fMRI scan, it looked like the dead salmon was actually thinking about the pictures it had been shown. ... The result is completely nuts — but that's actually exactly the point. [Neuroscientist Craig] Bennett... and his adviser, George Wolford, wrote up the work as a warning about the dangers of false positives in fMRI data. They wanted to call attention to ways the field could improve its statistical methods. ... Bennett notes: 'We could set our threshold [of significance] so high that we have no false positives, but we have no legitimate results.... We could also set it so low that we end up getting voxels in the fish's brain. It's the fine line that we walk.'" The research has been turned down by several publications, according to Wired, but a poster is available (PDF).
The point of the experiment was not to prove the type of fish.
Fish are capable of all sorts of feelings for humans.
[..] it looked like the dead salmon was actually thinking about the pictures it had been shown. ... The result is completely nuts -- [...] as a warning about the dangers of false positives [...]
Looks to me like the dark matter syndrome: "Our theories wrong? Our calculations off by an insane amount? Unpossible! That can never be. Nature must be lying!"
Has anyone even checked if a dead brain can still have flows of energy through its brain? I mean light patterns still reach the retinas, and can still trigger signals, depending on the state of the neurons there. How long was that salmon dead? I know that pigs can be frozen to be clinically dead for long times (90+ minutes), and still be revived without much damage.
I'd at least check if there are actual signals of current going trough the brain (with an OTHER (better) instrument, before dismissing it. Every unchecked assumption is a good chance for flaw in your study. You wouldn't want it to be dismissed by peer review, because of a faulty assumption.
Any sufficiently advanced intelligence is indistinguishable from stupidity.
No no he's not dead, he's, he's restin'! Remarkable fish, the salmon, idn'it, ay? Beautiful plumage!
It was probably a salmon of doubt.
The Tao of math: The numbers you can count are not the real numbers.
"That's precisely what this study is showing: even a dead fish has changing brain-blood oxygenation levels."
No, they're showing that the noise inherent in the scan can be taken for signal if you aren't careful with your stats. The dead fish is NOT exhibiting varying blood oxygenation levels.
Even the worst fMRI experiments that get published use a repetitive design, or equivalent. The simplest setup is to administer a stimulus or have the subject do something then stop, then do it again then stop, then do it again, etc. When you're done, you look for signals that vary in tandem with the stimulus.
A dead fish's brain does NOT have blood oxygenation levels that vary in that way. For the purposes of the experiment they're basically constant. However, if you look at enough different measurements, the noise superimposed on that static signal will correlate with the stimulus.
The fish is just for laughs. They could have easily done the same thing with a jar of agar.
Atlantic salmon is called Salmo salar in biology-speak. It is the model species of the entire order Salmoniformes. Salmon doesn't get any truer than that. Pacific species belong to the genus Oncorhynchus. They are true salmons too. "Trouts" belong to both Oncorhynchus and Salmo (and another 5 genera). Some of these trouts have anadromous forms (that is, go to the seas and return to the rivers to spawn), for instance, the rainbow trout (called steelhead in its anadromous form) is Oncorhynchus mykiss and the brown trout (sea trout) is Salmo trutta.
The mechanisms are the most important thing. What is fMRI actually measuring? It doesn't measure activity directly, since it's not built into the brain. Ergo, it measures activity indirectly by measuring something else entirely. But anything which also generates that something else will also be detected.
This is less a false positive than it is a complete confusion between direct and indirect observations. The falseness is not in the measurement but in the observer.
Sir Arthur Conan Doyle would have loved this finding, as he often has his most famous creation of Sherlock Holmes make snide remarks about the folly of poor observation and the absurdities that follow.
It's a small world and it smells funny; I'd buy another if it wasn't for the money; Take back what I paid (SoM)
you insensitive cod!
But this study showed that dead salmon can show just as much brain activity as Terri Schaivo...This study just shows that a "dead" organism with a brain that hasn't yet decomposed can still support some processes.
Bzzzt. Wrong. The entire point the write up was to warn about the danger of false positives. Your attributing of brain activity to random, natural noise is exactly the danger they want to avoid.