Hi everybody,

 

I am very grateful for all the helpful information on the spm email discussion list as well as on the website of the Wellcome Trust Centre for Neuroimaging.

 

As I’m a full beginner in MRI analyses and in using Statistical Parametric Mapping, I am sorry if the asked questions are basic and will be very thankful for any advice you could give me. 

 

In fact, I have a 2 x 2 x 2 design regrouping 3 within-subject factors, with factor 1 consisting in two blocks (i.e. Block 1 vs. Block 2), factor 2 consisting in two levels of  speed (i.e. slow vs. fast) and factor 3 consisting in two levels of difficulty (i.e. low vs. high).

 

To test the contrasts of interest, I tried different way, the first one was to perform at the first-level analysis four one-sample t-tests on each subject (1) Block1_Slow in low difficulty>Fast in low difficulty, (2) Block2_Slow in low difficulty>Fast in low difficulty, (3) Block1_Slow in high difficulty>Fast in low difficulty, (4) Block2_Slow in high difficulty>Fast in low difficulty.

Then in the second-level analyses, (1) four one-sample t-tests with all subjects (the same as previously for each subject independtly) and (2) two paired-sample t-tests to test the differential activation between block 1 and block 2 for each level of difficulty.

 

However, I encountered a problem in the first stage of analyses (i.e. paired-sample t-tests). Indeed, Matlab displayed this error message :

 

Index exceeds matrix dimensions.

 

Error in spm_list (line 709)

        if  ~isempty(TabDat.dat{i,5}), fw = 'Bold'; else fw = 'Normal'; end

 

Error in spm_list (line 138)

    spm_list('Display',TabDat,hReg);

 

Error while evaluating uicontrol Callback

 

 

 

I have no idea how to manage this problem. Would you have any advice ?

 

So far, I envisaged a full factorial design to perform 2 x 2 x 2 within-subjects ANOVA in SPM12. However, I was stuck at the stage where it was needed to select the images for each cell. Indeed, I haven’t images regrouping all scans of each variable (i.e. cell) for all subjects. Would you have any recommendation how I could manage that ?

 

I thank you a lot for any advice and recommendation you could give me and wish you still all the best for the New Year.

 

Best regards,

 

Claudie