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On Mon, 4 Jan 2010 18:42:26 +0000, Amit Etkin <[log in to unmask]> wrote: >Hi all- > >This is a question that has come up periodically, and I've never seen a convincing answer >for....but why isn't something like AFNI's alphasim used more frequently with SPM analyses? >...it seems to be pretty intuitive, and an empirically-driven cluster-level correction, derived >from simulations that take into consideration voxel size, smoothness, etc. > >thanks and happy new year! (1) Heresy of using a competing neuroimaging software package (mostly kidding :-) ) (2) User must know enough to be able to glean what inputs to give alphasim from SPM My impression is that alphasim gives "better" results (i.e., the thresholds are more liberal) than the SPM cluster-level correction. It's possible that that's because alphasim uses a joint peak height-extent threshold, which is perhaps more powerful. On the other hand, alphasim makes certain assumptions which might not be correct; in particular, IIRC it uses a Gaussian random field. Some relevant posts to the SPM mailbase (perhaps somewhat redundant): https://www.jiscmail.ac.uk/cgi-bin/wa.exe? A2=SPM;MIgFGQ;20080218113511%2B0000 https://www.jiscmail.ac.uk/cgi-bin/wa.exe?A2=SPM;jqlr6w;20010203003210- 0500;ind01 https://www.jiscmail.ac.uk/cgi-bin/wa.exe? A2=SPM;MIgFGQ;20080218113511%2B0000 https://www.jiscmail.ac.uk/cgi-bin/wa.exe?A2=SPM;ITML2w;20051122081729- 0600;ind05 https://www.jiscmail.ac.uk/cgi-bin/wa.exe?A2=SPM;ITML2w;20051122081729- 0600;ind05 It's not clear to me how badly off the assumptions in alphasim are. >Amit