> Does 3dMVM support within-subject covariates or is that still a 3dLME domain?
This is a very good question. Seriously!
3dMVM does not prevent one to run analysis with within-subject covariates. However, it is a delicate endeavor when dealing with within-subject covariates for the following two reasons:
1) How much does a within-subject covariate correlate with other variables, especially those within-subject factors? This involves a rarely discussed issue of centering.
2) Each subject may have a separate covariate effect.
Because of these complications, especially 2), 3dLME would be a better tool to handle within-subject covariates.
Gang