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

DiscoblogBy Brett IsraelSeptember 22, 2009 2:00 AM


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Scientists 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

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