voxel-wise covariate in 3dMVM

AFNI Message Board
1

Hi there,

I included the the SPM/VBM grey matter output as a voxel-wise covariate in the ANOVA (3dMVM). After I ran the anova with the covariate, I didn’t see any differences in the output relative to when no covariate was included. Below is the code I used. There were no error messages. Does this code look correct?

Thank you very much.

Code:

3dMVM -prefix Choice_VBM -jobs 4
-bsVars group
-wsVars "phasereinf"
-vVars VBM
-SS_type 3
-num_glt 19
-gltLabel 1 3way_inter -gltCode 1 'group : 1pat -1ctrl phase : 1acq -1rev reinf : 1corr -1incor’
-gltLabel 2 group_phase -gltCode 2 'group : 1pat -1ctrl phase : 1acq -1rev’
-gltLabel 3 group_reinf -gltCode 3 'group : 1pat -1ctrl reinf : 1corr -1incor’
-gltLabel 4 phase_reinf -gltCode 4 'phase : 1acq -1rev reinf : 1corr -1incor’
-gltLabel 5 group -gltCode 5 'group : 1pat -1ctrl’
-gltLabel 6 phase -gltCode 6 'phase : 1acq -1rev’
-gltLabel 7 reinf -gltCode 7 'reinf : 1corr -1incor’
-gltLabel 8 acq_group -gltCode 8 'phase : 1acq group : 1pat -1ctrl’
-gltLabel 9 rev_group -gltCode 9 ‘phase : 1rev group : 1pat -1ctrl’
-gltLabel 10 corr_group -gltCode 10 'reinf : 1corr group : 1pat -1ctrl’
-gltLabel 11 incor_group -gltCode 11 ‘reinf : 1incor group : 1pat -1ctrl’
-gltLabel 12 acq_reinf -gltCode 12 'phase : 1acq reinf : 1corr -1incor’
-gltLabel 13 rev_reinf -gltCode 13 ‘phase : 1rev reinf : 1corr -1incor’
-gltLabel 14 corr_phase -gltCode 14 'reinf : 1corr phase: 1acq -1rev’
-gltLabel 15 incor_phase -gltCode 15 ‘reinf : 1incor phase : 1acq -1rev’
-gltLabel 16 group_acq_corr -gltCode 16 'group : 1pat -1ctrl phase : 1acq reinf : 1corr’
-gltLabel 17 group_acq_incor -gltCode 17 'group : 1pat -1ctrl phase : 1acq reinf : 1incor’
-gltLabel 18 group_rev_corr -gltCode 18 'group : 1pat -1ctrl phase : 1rev reinf : 1corr’
-gltLabel 19 group_rev_incor -gltCode 19 'group : 1pat -1ctrl phase : 1rev reinf : 1*incor’
-dataTable
Subj group phase reinf VBM InputFile
6292 pat acq corr 6292/VBM_6292+tlrc 6292/Proc_FIRST_3RUNS_6292_April2019.results/6292_RevP_acq_corr+tlrc
6292 pat acq incor 6292/VBM_6292+tlrc 6292/Proc_FIRST_3RUNS_6292_April2019.results/6292_RevP_acq_incor+tlrc
6292 pat rev corr 6292/VBM_6292+tlrc 6292/Proc_FIRST_3RUNS_6292_April2019.results/6292_RevP_rev_corr+tlrc
6292 pat rev incor 6292/VBM_6292+tlrc 6292/Proc_FIRST_3RUNS_6292_April2019.results/6292_RevP_rev_incor+tlrc
8225 pat acq corr 8225/VBM_8225+tlrc 8225/Proc_FIRST_8225_April2019.results/8225_RevP_acq_corr+tlrc
8225 pat acq incor 8225/VBM_8225+tlrc 8225/Proc_FIRST_8225_April2019.results/8225_RevP_acq_incor+tlrc
8225 pat rev corr 8225/VBM_8225+tlrc 8225/Proc_FIRST_8225_April2019.results/8225_RevP_rev_corr+tlrc \

2

It’s no surprise that you didn’t see any differences because you didn’t incorporate the voxel-wise variable into the model. With the assumption that the VBM values do not vary within subject, you probably want to try

-bsVars “group+VBM” \

or

-bsVars “group*VBM” \

3

Thank you very much!

When I now try to run the code, it keeps telling me “3dMVM: No match” . This code had worked previouslty. Do you know why this error keeps coming up?

Thank you,
Tamara

4

Tamara, what changes did you make? Could you post the script as much as the one in your OP?

5

Hi Gang,

Sorry, I was able to figure out the issue just now. Thank you again for your help.

In your previous message, you had suggested that I include the VBM in the between subject line in the model with the assumption that the VBM values do not vary within subject. I just want to clarify whether it would be appropriate it include the VBM values in the bsVars line or the Wsvars line.

The VBM covariate is a nifti image from SPM that has GM volumes per voxel. Each participant has only one VBM nifti file (one time point). The values at each voxel for each participant do vary (because there are different GM values at each voxel). The values also differ by groups (patients show less GM volumes vs. controls). My goal is to control for the GM volumes for my fMRI analysis as there are differences in GM between the groups that could potentially be causing the fMRI results.

Thank you again.

6

Each participant has only one VBM nifti file

Since the VBM value does not vary within subject at each voxel, it is a between-subject variable. Depending on your prior knowledge (not your research interest), go with

-bsVars "group+VBM" \

or

-bsVars "group*VBM" \

7

Thank you very much!! I really appreciate all your help.