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Hi all, I'm trying to use the -bptf function in fslmaths to temporally filter some functional volumes. I have two questions: 1. I just want to check my understanding of how to specify sigma. If I want to retain frequencies between say .008 and .08 Hz, with a TR of 1.42 s, then the correct syntax would be: fslmaths input_4D.nii -bptf 44 4.4 output_4D.nii (e.g., .08 Hz = 1 cycle every 8.8 vols; sigma = 8.8/2 = 4.4) 2. When I run the above command on my data, where each 4D file contains 840 volumes, I get an out of memory error. Can anyone recommend a work around that does not involve changing the hardware? Thanks for your help, Alex