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Abstract #5345

Inflated false positive rates in fMRI depend on the voxel size of normalized images

Karsten Mueller1, Jöran Lepsien1, Harald E. Möller1, and Gabriele Lohmann2,3

1Max Planck Institute for Human Cognitive and Brain Sciences, Leipzig, Germany, 2Department of Biomedical Magnetic Resonance, University Hospital Tübingen, Tübingen, Germany, 3Magnetic Resonance Center, Max Planck Institute for Biological Cybernetics, Tübingen, Germany

Recently, Eklund et al published a manuscript discussing the issue of false positive results in functional MRI (fMRI) using the most common software packages. In their analysis, image upscaling was performed in fMRI preprocessing after registering images into a standard space (normalization). We show that the degree of image upscaling used for normalization impacts the statistical results when using the Gaussian Random field approach. A higher upscaling generally leads to smaller p-values increasing the number of false positive clusters. This result is quite troubling because statistical inference should not depend on a preprocessing parameter which can be chosen ad libitum.

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