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Math Medicine Science

Dead Salmon's "Brain Activity" Cautions fMRI Researchers 287

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).
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Dead Salmon's "Brain Activity" Cautions fMRI Researchers

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  • by Anonymous Coward on Sunday September 20, 2009 @04:18PM (#29484691)

    Fuck, if the thing is dead anyway, why not throw a human brain in there and get way better results.

  • Re:spoooooky (Score:4, Interesting)

    by Kartoffel ( 30238 ) on Sunday September 20, 2009 @04:41PM (#29484871)

    "It's OK to eat fish cause they don't have any feelings."
    -- K. Cobain

  • by ciroknight ( 601098 ) on Sunday September 20, 2009 @04:43PM (#29484885)
    Even vegetables put into an MRI machine for a functional scan can show some 'brain activity', simply because the fMRI doesn't actually show 'brain activity', it (in its typical configuration) shows blood oxygenation concentration levels in various places in the brain. The real problem is translating increasing or decreasing levels of oxygenation into brain activity. That's precisely what this study is showing: even a dead fish has changing brain-blood oxygenation levels. You need to remember to do the science and the math part of the problem, and make sure that the statistics are really showing meaningful relations.

    The question remains as to what functionality is required to call a person "alive" or "brain dead". If you want to be as absolutely conservative as possible, anyone with a beating heart and working brain stem (corneal reflexes, heart-beat signal, breathing stimuli, etc) and can be considered alive, even if their entire frontal lobe has been entirely caved in removing any wisp of humanity and they aren't even capable of controlling their bowels or bladder or many other autonomic or homeostatic functions. Whether you think it's cruel to pull the plug on someone in this state is entirely up to personal beliefs and/or religious convictions. Medicine tries not to tread too deeply into this water, simply because it's not worth it to rehash the ethical dilemmas with no new science to change anyone's opinion. We leave it up to the individuals (through advanced directives, living wills, etc) and their families to choose.

    Just don't be fooled into thinking that scattered activity in a bundle of nerves we happen to call a brain necessarily means she's "alive".
  • by Anonymous Coward on Sunday September 20, 2009 @04:44PM (#29484887)

    fMRI is a blunt instrument compared to what ultra high resolution spectroscopic MRI will show us in the future.

    Current MRI is tuned to the proton nmr signal (and variations of it). As magnet technology advances and ginourmous gradients are achieved, it will be possible to obtain full spectroscopic data (chemical shift) in addition to positional data. Not only for the proton but for other isotopes that produce an NMR signal (of which all the CHONPS elements have at least one). As aquisition electronics speed increases it should eventually be possible to show this data in real time (molecules in motion). Of course it will be a trade-off between positional data resolution and spectroscopic data resolution, but this will be a very powerful technique. fMRI is just the tip of the iceberg and only a first step toward spectroscopic MRI proper.

    That said (and without RTFA of course), I wonder how long the salmon was dead? What temperature was it stored at? The animal need not necessarily be alive for a stimulus to produce an effect. (Thinking of batteries and frog legs...) As long as the bulk of the cellular machinery is intact...

    OK, I broke down and read the pdf. This report is coming from a psyhchology department! (I expected biology) I'd wait until the chemists and physicists weigh in to make any conclusions about this observation.

  • by Eudial ( 590661 ) on Sunday September 20, 2009 @05:12PM (#29485081)

    Well, maybe what they saw wasn't a false positive? Maybe there is residual functionality of the brain some time after death, the same way you can electrically stimulate the muscles of a dead body to make them twitch. Is it that unthinkable that visual impulses have some effect on the brain, that death instantly renders every single braincell inoperable?

  • by oldhack ( 1037484 ) on Sunday September 20, 2009 @05:18PM (#29485115)
    Yep. What little I remember of stats is that it is an extraordinarily delicate tool, every little theorem is couched in uber cautious qualifications. All the more reasons to be cautious of stat-based findings of math-impaired social scientists, and medicine isn't all that far ahead in terms math literacy.
  • by Renraku ( 518261 ) on Sunday September 20, 2009 @05:34PM (#29485223) Homepage

    The brain can still function when 'brain dead.' Think about it. Your entire brain doesn't die once you don't get enough oxygen for a few minutes, you just can't maintain the feedback loop called consciousness. Just because of that, doesn't mean the cells aren't still functioning. Since you're unconscious, though, you may as well be dead if you can never recover from it.

    Consciousness is a rather circular loop in the brain. Minor damage to part of that loop can ensure that you never wake up, unless a path around that damage is formed, which may or may not happen. We've seen people wake up from comas after years, because their brain has formed pathways around the damage.

    Then we get into the whole debate of 'what is death?' True brain death would mean that the entire brain is dead, and can never recover from it. Little pockets of cells can survive for a period of time, but they will always die in the end if they aren't getting the oxygen/energy/minerals they need. So, unconscious is dead? No, it's just unconscious. We can distinguish between coma, sleep, death, etc. Terry Schiavo should have been considered dead, since +90% of her brain was dead, but because she showed some basic brainstem functions, people said she was alive. In reality, she was less alive and less able to be revived than someone who hasn't had a pulse in ten minutes!

  • by horigath ( 649078 ) on Sunday September 20, 2009 @06:26PM (#29485559) Homepage
    No, west-coast farmed Atlantic salmon is a cheap substitute that is sometimes dyed red to disguise it as wild pacific salmon. Fortunately, Atlantic salmon exists outside of fish-farms and is a perfectly good fish in its own right.
  • by jd ( 1658 ) <> on Sunday September 20, 2009 @06:42PM (#29485673) Homepage Journal

    If they're zombies, wouldn't that be psychotic therapist?

  • by pla ( 258480 ) on Sunday September 20, 2009 @06:51PM (#29485737) Journal
    Dark matter and dark energy aren't just theories that a bunch of arrogant pricks pulled out of their asses.

    Ummm, actually...

    We have absolutely no direct evidence of either.

    We have numerous alternative theories that explain, without resorting to saying the universe consists of 96% invisible voodoo, various anomalies such as gravitational rotation and the implied anisotropy of the CMB.

    Keep in mind that until last week, we had no direct evidence of something so basic to modern physics as the Bohr model; before that, we had "hooked" atoms dating back to (at least) Epicurus. Theories come and go, and without reproducible, experimental evidence, we have at best a model that fits the data - NOT, as far too many people seem to believe, a necessarily accurate description of objective reality.

    I find it amazing that people who haven't even bothered to study the data or the reason for hypotheses like dark matter feel the need to make ass backwards comments about people who've literally dedicated their lives to it.

    The GP said no such thing. He merely hypothesized, and not without some basis in fact, that a dead fish may well still have neural activity. Keep in mind, for several hours after death-of-the-whole (depending on the cause, of course), the vast majority of cells in the body still work just fine.

    Now, if he had said something like "how do we know gravel doesn't have neural impulses", I would agree with your position; but we so poorly understand "death" that your ridicule reflects worse on you than on your target.
  • Re:Peer review (Score:5, Interesting)

    by benntop ( 449447 ) <craigo@g[ ] ['mai' in gap]> on Sunday September 20, 2009 @08:04PM (#29486149) Homepage Journal

    AC - The paper has been rejected once so far. I won't mention the journal, but it was rejected on an editorial basis before it reached the peer review stage. I can only conjecture regarding why the editor decided to pass on the paper, but it was not (to my knowledge) rejected for any methodological deficiencies. We are currently in the review stage at a second journal and the reviewers had no trouble with our methods, only how we argue for multiple comparisons correction without stepping on too many toes.

    As an interesting aside, the poster was also rejected at first. All the peer reviewers thought is was a joke and voted to exclude it from the conference. Once it went before the program committee they realized that, even though we had an odd approach, the conclusions of our data were sound and that we had a very good point to make.

  • by Ardeaem ( 625311 ) on Monday September 21, 2009 @03:28AM (#29488451)
    The need for multiple comparison corrections is standard knowledge among cognitive neuroscientists. It is actually common practice for manufacturers of MRI machines to image inanimate objects as a test of the machine. You could easily get that data, rather than imaging a dead fish. Once you know the amount of noise, it would be easier to just simulate within a statistical program to determine the effects of not correcting. If the authors of the poster weren't aware of the value of multiple comparison corrections BEFORE they stuck a fish in the magnet, at least they learned a lesson everyone else gets in second year stat.
  • by Anonymous Coward on Monday September 21, 2009 @02:38PM (#29494545)

    Neuroscience IS my field, well neurobiology to be specific. And no, these problems aren't always corrected for.

    The trouble is, most scientists are not mathematicians, and have no good theoretical understanding of statistics. Most people pushing buttons in SPSS or SAS (or what have you) are just doing "cargo cult" mathematics. Ask them to justify why their "very conservative" confidence interval for a given test is appropriate when dealing with eleventy billion variables, or why a particular post-hoc test is the proper one to use, and they'll look at you like you just asked them to prove that the sky is blue.

    Some of the software just makes matters worse. SPSS (I think it's SPSS) will on some tests give you the smallest p-value for which your data pass the test. Let's say for example you're testing whether a bunch of different drugs can cure headaches. When SPSS tells you that drug #1's test rejects null hypothesis with p=0.05, and drug #2 with p=0.0001, it's VERY tempting (and people fall for it all the time) to say there is "stronger evidence" for drug #2, or worse, that drug #2 itself is stronger. This is NOT correct. You set your confidence interval, run the tests, and either the null hypothesis is rejected or it isn't. Period, end of statement.

There's no such thing as a free lunch. -- Milton Friendman