Can a Dead Fish Prove that Modern Brain Studies Are Bunk?

By Brett Israel | September 21, 2009 5:00 pm

salmon_webScientists have a neat little tool they use to read your mind. It’s called fMRI (functional Magnetic Resonance Imaging for those not in the know) and it seems to be everywhere these days. Scientists are using it for everything from looking at your dreams to studying the brains of jazz musicians to IDing the part of the brain that is activated when we get grossed out.

But not everyone believes fMRI studies are all that useful. In fact, one group recently set out to show how the studies, if not done carefully, can be downright misleading. And to do this, they used dead fish.

Scientists  scanned the brains of deceased Atlantic salmon with fMRI to teach their colleagues a lesson in data analysis. The Great Beyond, a Nature blog, has the details:

The salmon was presented with a series of photographs, and then asked to determine what emotion the individual in each picture was experiencing. The team then analyzed tiny areas in the brain (voxels – like pixels but for volume) using basic methods for controlling for error. Surprisingly, report the team, “several active voxels were discovered in a cluster located within the salmon’s brain cavity.”

Of course the salmon were dead, so there shouln’t have been any activity detected. The point was to highlight the false-positive rate inherent in fMRI studies. More from TGB:

They are making a serious point about the dangers of not taking account of false positives. When you image the brain using fMRI, you’re basically asking whether there is activation in each of thousands of voxels. Because there are so many voxels (130,000 in a typical fMRI scan), “the probability of a false positive is almost certain,” writes Bennett [the study's lead author] in the introduction.

The research team says some studies do not do enough to rule out the false positives. Their results were presented at the 2009 Human Brain Mapping Conference in San Francisco.

More on what should be done to correct the problem at Neuroskeptic and Neurolaw.

Related Content:
Discoblog: Jazz Musicians Lose Control
Discoblog: Digusting Things are Just as Gross Whether They’re Real or Imagined
DISCOVER: The Pugnacious Paper That Aims to Turn Neuroscience on Its Head

Image: flickr / denn

  • http://prefrontal.org Craig Bennett

    The title and content of this article are both somewhat misleading. The point of our poster/paper is not that modern brain studies are bunk, but rather that we have to be very careful regarding how we compute and report our results. Also, for the record, we believe that fMRI is an enormously useful for investigating brain function. We use it every day as part of our research and think that it holds enormous promise in helping us understand human cognition.

    The issue at hand is one of controlling for false positives (a result that isn’t really a result) while still having enough ability to detect real signals. It is a kid of zero sum game. You can set your thresholds so high that you get no false positives, but then you would not observe any real results either. on the flip side you can set your thresholds so low that you detect all of the real results, but then you will have an overabundance of false positives as well. Where do you draw the line? In our commentary we argue that we need to set a stricter threshold than many neuroimaging papers might typically use.

    I will keep an eye on the comments if anyone has questions. One thing I do have to say about this article is that it has the best photo associated with it of any weblog post yet!

  • http://discovermagazine.com Brett Israel

    Hi Craig – Thanks for stopping by to comment and we’d love to open up the conversation between you and our readers!

  • jp

    Interesting article. In market research there it is now de rigueur to use fMRI to test advertising effectiveness… the flaws inherent in that methodology go beyond the false positives, but Mr. Bennett does bring up a good point.

    As for the misleading title… well, let’s be honest… its hard not to read an article whose title refers to debunking studies with a dead fish, so I guess Brett accomplished his goal and we informed ourselves in the process.

  • Pingback: Can a Dead Fish Prove that Modern Brain Studies Are Bunk? « Wisdom Beat

  • Ivan

    I will never feel the same about eating lox again. I thought that that fish was giving me the evil eye, now I guess I was correct. Salmon have been underestimated for years. Is this proof of life after death?

  • Kyle

    so you respond to craig but don’t change the title?

    come on, brett. The title of the article is either intentionally misleading to garner readers or simply ignorant… either way you’d be better off changing it.

    interesting enough finding but intellectual dishonesty is a no go. change the title.

  • Vasco H

    Already said but: you really cannot shoot shock titles like this that have nothing to do with the article. Is this Ananova or what?

  • Frank Powers

    Come on now, Brett – change that bloody title already. It’s still misleading, regardless of the article’s informational value.

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