Hi Anderson,

Thank you very much. I really appreciate your help. 

I have almost confidence about the steps which I've done on FSL. However, I did not regress out group membership before correlation.

Frankly, I did not have any idea why and how should I regress out group membership. So, I followed a discussion here:

https://stats.stackexchange.com/questions/117840/how-to-regress-out-some-variables

And applied the same method by regressing out the effect of age and gender on my data.

My data structure is: DATA=[Age Gender GMVoL Covariate]

So I first calculated correlation: [r,p] = corr(DATA)

And then did as mentioned in discussion:

%%

f1=r(:,1);

R1=f1*f1';

sub_R1=r-R1;

f2=sub_R1(:,2);

f21=f2/(sqrt(f2));

R21=f21*f21';

R12=sub_R1-R21;

%%

Finally I applied residuals matrix (R12) to my data: new_DATA=DATA*R12;

And run new correlation: [new_r,new_p] = corr(new_DATA);

After all, I got a significant correlation. Please see attached scatter plots before and after this action.

Could you please let me know whether I did right?

Thanks again for your support.

Sincerely,

Kavous

----------

PhD Candidate

Center for Human Engaged Computing

782-8502, Kochi University of Technology, Kami City, Japan

Skype: kavus.salehzadeh

On Wed, Aug 9, 2017 at 10:21 PM, Anderson M. Winkler <[log in to unmask]> wrote:

Hi Kavous,

TFCE benefits from voxels that may be outside the cluster, from the "support region", whereas just getting the data from within the cluster ignores that.

Even so, I'm surprised that there were no signs of correlation. Are you sure there were no missteps along the way? Are the results of the correlation completely off?

Also, remember you need to regress out group membership from X and Y before doing the correlation in Matlab.

All the best,

Anderson

On 6 August 2017 at 09:47, Kavous Salehzadeh Niksirat <[log in to unmask]> wrote:

Dear FSLers,

I used FSLVBM for a single-group average with a behavioral measure for over 600 subjects, exactly as explained here:

https://fsl.fmrib.ox.ac.uk/fsl/fslwiki/GLM#Single-Group_Average_with_Additional_Covariate

Fortunately, I got a significant result (FWE-corrected). I would like to report and visualize my results. As I read from the previous discussions, I used cluster to report it:
>> cluster -i tmp_tfce_corrp_tstat4 -t 0.95 --scalarname="1-p" --minclustersize --mm > my_cluster.txt

I found only one cluster. Later I masked my cluster as follows:
>> fslmaths tmp_tfce_corrp_tstat4 -thr 0.95 -bin mask_tmp_tfce_corrp_tstat4

and extracted its volume by this:
>> fslstats mask_tmp_tfce_corrp_tstat4 -V

I used fslmeants to extract mean GM volume for each subject and also eigen variates:
>> fslmeants -i GM_mod_merg_s3 -m mask_tmp_tfce_corrp_tstat4 -o mean_GM_volume.txt
>> fslmeants -i GM_mod_merg_s3 -m mask_tmp_tfce_corrp_tstat4 -o eig_GM_volume.txt --eig

I multiplied volume and each subject's GM_volume. However surprisingly when I tried to compute correlation in MATLAB between extracted GM results and my behavioral data, I could not see any significant correlation. I tried corr(X,Y) either between mean_GM and behavioral data or eig_GM and behavioral data. Both results showed no significant correlation.

Could you please help me to understand what I am doing wrong here?

Sincerely,
Kavous