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Activity Number: 631
Type: Topic Contributed
Date/Time: Thursday, August 7, 2014 : 10:30 AM to 12:20 PM
Sponsor: Biopharmaceutical Section
Abstract #312983
Title: Multiple Comparisons, fMRI Imaging, and One Brave (But Dead) Atlantic Salmon
Author(s): Jeffrey Blume*+ and Hakmook Kang
Companies: Vanderbilt University and Vanderbilt University
Keywords: Multiple comparisons ; fMRI imaging ; Likelihood ; Statistical Evidence
Abstract:

The attribution of "activation" to brain regions in fMRI images involves the analysis of data from thousands of voxels (3D pixels), raising concerns about multiple comparisons. A study by Bennett (2009) revealed brain activity a (dead) Atlantic salmon and Bennett (2009) argued that the results demonstrated the need for rigorous multiple comparison adjustments in fMRI studies. But Bennett's argument is problematic. Findings of a similar magnitude in, say, a (dead) Minnow, would not have been vanquished by the adjustments (fewer voxels in a Minnow's image). The problem is not that there are a large number of comparisons, but rather that the strength of statistical evidence is not well described by p-values. An alternative approach that better characterizes "activated" voxels uses likelihood ratios to represent the strength of statistical evidence, obviating the need for multiple comparison adjustments. While this approach requires forethought about the magnitude of brain activation, it is preferable to using p-values which conflate the magnitude of brain activation with the magnitude of evidence against the null hypothesis (this is why dead fish sometimes appear deep in thought).


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