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Hi, This does happen with the refrms metric when there is a reasonable amount of motion present. The easiest way to avoid it is to switch to the dvars metric, which only evaluates differences to the next volume in the series. In that way it is not sensitive to the reference volume. All the best, Mark On 3 Jan 2013, at 14:09, Darren G <[log in to unmask]> wrote: > Steven / List > > Sorry. That was silly. I thought the original message had been copied in the reply. The issue is that fsl_motion_outliers seems to exclude the middle volume in the time series and often one of the ones next to it as showing a spike. > > First reported in this message. > > https://www.jiscmail.ac.uk/cgi-bin/webadmin?A2=FSL;734bff91.1004 > > Hello all, I've been using fsl_motion_outliers to remove motion peaks, and noticed that in most of my functional runs the reference functional volume is tagged as an outlier. My runs have 122 TRs, and TRs #61 and 62 are almost always being tagged as outliers, even for those runs that had minimal motion detected by McFLIRT (mean displacement peak of 0.3mm for absolute motion, for example). > > Is it ok for me to include the confound EVs matrix generated by fsl_motion_outliers for all functional runs despite minimal motion detected, or am I at risk of introducing bias as TRs #61 and 62 are almost always being "removed" from further analysis? > > Thanks for any insight. > > Estephan > > > Subsequent reports listed below. > https://www.jiscmail.ac.uk/cgi-bin/webadmin?A2=FSL;7add521f.1004 > > https://www.jiscmail.ac.uk/cgi-bin/webadmin?A2=FSL;c1c3da8e.1201 > > https://www.jiscmail.ac.uk/cgi-bin/webadmin?A2=FSL;5bfecea3.1201 > > https://www.jiscmail.ac.uk/cgi-bin/webadmin?A2=FSL;f1372fb0.1301 > > https://www.jiscmail.ac.uk/cgi-bin/webadmin?A2=FSL;1aa758dc.1301