Thanks for your response. From this then, would it be sensible to say that you are only interested in the effects of one condition on the regional response and therefore place variance associated with the other condition in the null space?
Drew,
The point of adjusting is to remove the effect of the null-space effects from the data (e.g the effects of motion and constant term). If you are going to adjust, you want to use the same adjustment for all conditions. You want to use an F-contrast that
tests for the effect of any condition as the contrast to adjust for.