When they got around to analyzing the voxel (think: 3-D or 'volumetric' pixel) 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.
Of course, the salmon wasn't actually responding to pictures illustrating human emotions. But the data manipulation commonly used in brain studies caused apparently significant patterns to appear by chance. More from the Wired article: 'The result is completely nuts — but that's actually exactly the point. Bennett, who is now a post-doc at the University of California, Santa Barbara, 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."
The study demonstrates the potential for misinterpretation and misuse of data in brain studies, particularly as data manipulation becomes more and more complex. 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.'
So far the paper has been rejected for publication a number of times, but there is a poster available that was employed in a conference presentation. Recently it has been making the rounds informally in the neuroscience community."
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