Hi Afni Experts,

We are attempting to run a covariate analysis looking at the impact of emotional ratings on BOLD response. We have used covariate files with 3dttest++ (covariate = behavioural rating for emotion) and are unsure what the output sub-brick refer to.

Sub-brick [0] is described as "difference of the means; covariate removed". Does this mean:
a) the difference of the means after controlling for the influence of the covariate
Or
b) the difference of the means without considering the covariate.

If the answer is 'A', does this sub-brick represent the BOLD signal after controlling for all covariate (we have 4 separate covariates)? If so, is it possible to control for the influence of each covariate independently?

If the answer is 'B', which sub-brick refers to difference of means after controlling for the influence of the covariate?

Also, we assume that sub-brick [2], described as "difference of slopes wrt covariate" shows us the areas that are correlated with the first covariate (i.e. an increase in the covariate is associated with an increase in the BOLD).

Thanks very much in advance for your help.