A +1 t contrast with the age regressor will give you voxels in which
there is a positive relationship between age and tissue; a -1 t
contrast voxels where there is a negative relationship. You can
verify this by plotting the values in each voxel as a function of age
(e.g., after you've run results: plot > fitted responses > age >
adjusted responses, and then you can plot against an explanatory
variable, namely, age; alternatively you can extract the values
outside of SPM and plot as a function of age).
Hope this helps,
On Sun, Jul 26, 2009 at 10:50 PM, Adnan Virani<[log in to unmask]> wrote:
> SPM Community,
> I am performing a VBM study to look at age-related volumetric changes in the
> rhesus monkey brain. I performed a simple regression test, where I inserted
> all the images from young to old and their respective ages as a co-variate.
> The results showed 9 white matter areas of statistical significance.
> However, after overlaying the Wisconsin group T1 template, which was also
> used for normalization and segmentation, I do not know how to identify if
> the areas of statistical significance are positively or negatively
> correlated with age?
> Thank you.
> Adnan Virani
> [log in to unmask]