Bias in Resampling-Based Thresholding of Statistical Maps in fMRI

Selecting a threshold for the statistical parameter maps in functional MRI (fMRI) is a delicate matter. The use of advanced test statistics and/or the complex dependence structure of the noise may preclude parametric statistical methods for finding appropriate thresholds. Non-parametric statistical methodology has been presented as a feasible alternative. In this paper we discuss resampling-based methods for finding thresholds and show that proposed non-parametric approaches can lead to severely biased results.