Hi there,
Along those lines: how can we compute an F-Test for these two runs?
Thanks,
h.
-----Original Message-----
From: FSL - FMRIB's Software Library [mailto:[log in to unmask]] On
Behalf Of Stephen Smith
Sent: Wednesday, November 13, 2002 9:49 AM
To: [log in to unmask]
Subject: Re: [FSL] Single Subject multi session
Hi - you are right in saying that if you want to combine just two runs
as
if they had been one then this should be approached as a fixed-effects
analysis. In this case you want to use simple command-line combination
of
the cope and varcope images in the <featdir>/stats subdirectories; for
example:
avwmerge -t COPES <featdir1>/stats/cope1 <featdir2>/stats/cope1
avwmerge -t VARCOPES <featdir1>/stats/varcope1 <featdir2>/stats/varcope1
avwmaths VARCOPES -Tmin MASK
avwmaths VARCOPES -Tmean -div 2 -mas MASK VARCOPE
avwmaths COPES -Tmean COPE
ttoz -zout FIXEDZ VARCOPE COPE <DOF>
(where <DOF> is the sum of the values in the different stats/dof files
in
the different FEAT directories)
You can then do normal thresholding for example using easythresh.
Note - the above assumes that the two runs are registered to each other
-
which will not in general be exactly true for first-level analyses. The
easy thing to do if you have run FEAT registration is to first run
featregapply <featdir>
on each FEAT directory and then use the resulting
copes and varcopes from the <featdir>/reg_standard/stats subdirectories
instead of just the stats subdirectory.
Thanks, Steve.
On Wed, 13 Nov 2002, Thomas Stephan wrote:
> Dear FSL-List,
>
> how can I perform a fixed effects analysis of two fmri imaging runs
acquired
> from one subject
> in one day ? It is easy to do the analysis of one run using FEAT, but
I
> could not find out
> how to enter two runs at once.
>
> Thank you for your support
> Thomas Stephan
> ======================================================================
> Thomas Stephan Email: [log in to unmask]
> Klinikum Grosshadern
> Neurologisches Forschungshaus
> Marchioninistr. 23 Fon: +49 089 / 7095-4819
> 81377 Muenchen Fax: +49 089 / 7095-4801
> ======================================================================
>
Stephen M. Smith
Head of Image Analysis, FMRIB
Oxford University Centre for Functional MRI of the Brain
John Radcliffe Hospital, Headington, Oxford OX3 9DU, UK
+44 (0) 1865 222726 (fax 222717)
[log in to unmask] http://www.fmrib.ox.ac.uk/~steve
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