Dear Fan,
What Colin is describing can be defined using an SPM's two-sample t-test
model where you add one covariate and select "interaction with factor
1". You would then test for a group by skill interaction with a contrast
[0 0 1 -1]. For the centering options, have a look at this summary from
Jeanette Mumford:
http://mumford.fmripower.org/mean_centering/
Best regards,
Guillaume.
On 14/12/16 20:03, Colin Hawco wrote:
> Use a multiple regression to enter your behavioral covariates. Then,
> contrast (1 -1) the columns in the design matrix related to those
> covariates.
>
>
>
> For comparing between groups, mean center the variable across all
> subjects. They split it into two columns, one for each group, with zeros
> for other groups in those columns. Again, do a 1 -1 contrast. This tests
> if the slope of the regression of the variable on the contrast map is
> the same in each group.
>
>
>
> Good luck,
>
>
>
> Colin Hawco, PhD
>
> Neuranalysis Consulting
>
> Neuroimaging analysis and consultation
>
> www.neuranalysis.com <http://www.neuranalysis.com>
>
> [log in to unmask]
>
>
>
>
>
>
>
> *From:*SPM (Statistical Parametric Mapping) [mailto:[log in to unmask]]
> *On Behalf Of *Fan Cao
> *Sent:* December-14-16 11:16 AM
> *To:* [log in to unmask]
> *Subject:* [SPM] how to compare correlations in SPM
>
>
>
> Dear SPM experts,
>
>
>
> I want to find out which part of the brain activation is more correlated
> with a behavioral skill in group A than group B.
>
> I also want to find out which part of the brain activation is more
> correlated with a skill in task A than task B for the same subjects.
>
> Currently I don't know any method to run these comparisons in SPM. Any
> suggestions or ideas from this group of experts? Thanks so much!
>
>
>
> Best,
>
> Fan
>
--
Guillaume Flandin, PhD
Wellcome Trust Centre for Neuroimaging
University College London
12 Queen Square
London WC1N 3BG
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