BayesianGroupAna.py

AFNI Message Board
1

Hello Gang!

This might be a silly question, but I was intrigued when reading about BayesianGroupAna.py. Especially since you emphasise that the standard approach can be very over-penalizing. I just don’t know what part of our traditional analysis pipeline that could be replaced by this (for both resting state and task fmri). I don’t seem to see that you input any brain data into this function?

The example command I found was this:


BayesianGroupAna.py -dataTable my_roi_data.txt  \
                            -prefix dock_of_the_bayes   \
                            -y zscore -x some_x other_x \
                            -chains 4 -iterations 1000  \
                            -plot -more_plots rhat violin

Where the table could look like this


Subj  ROI   some_y  some_x other_x
        S001  roi1  0.12    0.056  0.356
        S001  roi2  0.65    0.232  0.231
        S002  roi1  0.14    0.456  0.856
        S002  roi2  0.64    0.432  0.431
        ...

Excuse my ignorance, but are the values in these ROIs (some_y, some_x) average beta-coefficients (or R-scores form seed based resting state) for a specific task regressor? And this makes the group analysis part (e.g. 3dMVM) obsolete? Or how do you compare these ROI-values between two groups of subjects? If this is the case, can you get the same information from this as MVM when it comes to group interactions and covariets and such?

Really sorry for a basic question but this function sound really good and something we would want to explore! I’m pretty tired of all these p-values =).

Thanks in advance!

2

Robin,

are the values in these ROIs (some_y, some_x) average beta-coefficients (or R-scores
form seed based resting state) for a specific task regressor?

It can be the average of the regression coefficient within each ROI. Or, you could average first the the voxel-wise time series within each ROI and then perform the regression analysis on the average time series.

And this makes the group analysis part (e.g. 3dMVM) obsolete?

Not necessarily. Currently the region-based approach is only performed on a list of regions, not at the voxel level.

Or how do you compare these ROI-values between two groups of subjects?

Treat the two groups as a between-subjects factor with two levels in the model.

If this is the case, can you get the same information from this as MVM when
it comes to group interactions and covariets and such?

Update your AFNI, and check out the help of RBA.