Thursday, April 18, 2013

The Dead Salmon fMRI experiment

Have you ever heard about the dead salmon fMRI experiment? Me neither, until recently. The study may seem like a waste of money and expertise, but this study has actually open the eyes of the community about one important aspect of fMRI studies: multiple comparisons.

fmri-salmonImage from here.

The basic experiment was just to put a dead salmon inside the MRI scanner, perform an fMRI study and analyze results. Since in an fMRI experiment, you have a lot of voxels being compared, there are some voxels that will eventually show up as activated. In the dead salmon fMRI experiment, voxels in the brain and spine showed up as being activated (see image above). Some could say that even if the salmon is dead, there is activity in its brain, but the most likely (scientific) explanation is that those results just happened by chance. To avoid this problems, you should use a multiple comparison correction, which takes into account this problem. After this correction, of course, the dead salmon showed no activated voxels. Although scientifically based, this study stands out for being so funny. It actually won an IgNobel prize in 2012. The original poster is too good to be true:
Image from here.

Original poster:
And posts by the author in his blog:

Other Links:

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