Hi - to ask what are extrat first-level contrasts you will need to run
those contrasts at first level, before running group analysis.
You can put your extra rating EVs into the second-level analysis in the
manner shown at
http://www.fmrib.ox.ac.uk/fsl/feat5/detail.html#SingleGroupAveragewithAdditionalCovariate
Thanks, Steve.
On Fri, 25 Apr 2003, Darren Schreiber wrote:
>
> I succeeded in getting my first level analysis done, so thanks to all
> for your help. Now, I am trying to figure out how to do a second level
> analysis.
>
> To recap, I am running a 2x2 design with 18 subjects that are divided
> into three groups (R, D, N).
>
> Experimental Conditions:
>
> W B
> N WN BN
> P WP BP
>
>
> A sample subject run looked like this:
>
> (R=Rest)
>
> R R BN R WP R WN R BP R WN R WN R BN R BP R
>
>
> I ran the following contrasts:
>
> WN 1 0 0 0
> BN 0 1 0 0
> WP 0 0 1 0
> BP 0 0 0 1
> W>B 1 -1 1 -1
> B>W -1 1 -1 1
> P>N -1 -1 1 1
> N>P 1 1 -1 -1
> task>rest 1 1 1 1
>
> Now, in my second level analysis, I believe what I would want to do is
> create contrasts for the groups of subjects (R,D,N). Correct? Since I
> will have more statistical power. I will want to push harder on the
> data and I would like to test more relationships:
>
> WN
> BN
> WP
> BP
> W>B
> B>W
> P>N
> N>P
> task>rest
> WN>WP
> WN>BN
> WN>BP
> WP>WN
> WP>BN
> WP>BP
> BN>WN
> BN>WP
> BN>BP
> BP>WN
> BP>WP
> BP>BN
> task>rest
>
> How do I set this up? I looked at the higher level analysis part of
> the webpages, but wasn't sure which example is the closest analog to
> what I am doing.
>
> Also, I have data rating the subjects on two different scales that I
> believe might correlate to their activation under the different
> contrasts that I describe above. How do I incorporate that data into
> this design?
>
> Thanks very much for any assistance.
>
> Darren
>
>
Stephen M. Smith MA DPhil CEng MIEE
Associate Director, FMRIB and Analysis Research Coordinator
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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