interesting paper

http://www.pnas.org/content/pnas/early/2016/06/27/1602413113.abstract.html?… Functional MRI (fMRI) is 25 years old, yet surprisingly its most common statistical methods have not been validated using real data. Here, we used resting-state fMRI data from 499 healthy controls to conduct 3 million task group analyses. Using this null data with different experimental designs, we estimate the incidence of significant results. In theory, we should find 5% false positives (for a significance threshold of 5%), but instead we found that the most common software packages for fMRI analysis (SPM, FSL, AFNI) can result in false-positive rates of up to 70%. These results question the validity of some 40,000 fMRI studies and may have a large impact on the interpretation of neuroimaging results. They state "Our principal finding is that the parametric statistical methods work well, if conservatively, for voxelwise inference, but not for clusterwise inference. We note that other authors have found RFT clusterwise inference to be invalid in certain settings under stationarity (21, 30) and nonstationarity (13, 33). This present work, however, is the most comprehensive to explore the typical parameters used in task fMRI for a variety of software tools. Our results are also corroborated by similar experiments for structural brain analysis (VBM) (11–13, 39, 40), showing that cluster-based P values are more sensitive to the statistical assumptions. For voxelwise inference, our results are consistent with a previous comparison between parametric and nonparametric methods for fMRI, showing that a nonparametric permutation test can result in more lenient statistical thresholds while offering precise control of false positives (13, 41). " Would be worth discussing at a ynic seminar later in the summer Gary -- --------------- Gary Green York Neuroimaging Centre & Centre for Hyperpolarisation in Magnetic Resonance The Biocentre York Science Park Innovation Way Heslington York YO10 5NY tel +44 (0) 1904 435349 fax +44 (0) 1904 435356 mobile +44 (0) 788 191 3004 http://www.ynic.york.ac.uk http://www.york.ac.uk/chym/ https://www.ynic.york.ac.uk/about-us/people/ggrg