Hello Afni Experts,

1) I was interested in finding out how to save out the residuals of my 3dMVM model. It this possible to do (similar to the -resid in 3dttest++)? I am performing a seed based resting state correlation analysis using age, gender, group and MOCA as between group covariates and do no have any within subject covariates. If it is not possible within 3dMVM, is there another model that is more appropriate for this analysis (ie 3dLME since 3dttest++ won't work in this situation)? Finally, if no residuals can be output by these models, what would be the best "noise" estimate for 3dFWHMx (ie the average of each individuals epits/errts.anaticor files even though it is technically not noise or something else)?

Ideally I want to use this noise/residual term from 3dMVM as an input to 3dFWHMx with the -acf option in order to properly estimate my smoothness, as underlying spatial stucture from 3dMVM output may incorrectly estimate my smoothness. This output would be fed into 3dClustSim in order to estimate the clusterwise extent for given P values.

2) I recently saw an article by Nichols and colleagues which evaluates the validity of clusterwise estimates in FMRI. The conclusion was that alpha <0.05 is not correctly assessed for any p>0.01. Due to limited number of subjects in a study, I could see where using a more liberal p<0.01 and larger cluster extent is appealing. Does the -acf option in 3dClustSim/3dFWHMx address issues raised in this article so that cluster extents calculated at p<0.01 are indeed accurate or do you recommend going to a p<0.005/0.001 in order to address these limitations for limited N (ie 20 per group).

Thanks,
Ajay