oddly enough, this issue recently came up on the AFNI board in the
other direction...
http://afni.nimh.nih.gov/afni/community/board/read.php?f=1&i=32052&t=32052#reply_32052
JK
On Tue, Jan 5, 2010 at 2:18 PM, Stephen J. Fromm <[log in to unmask]> wrote:
> 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
>
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