[VoxBo] Question about multiple contrasts in a glm

[David January]

Hello everyone,

I'm trying to find a linear trend among conditions in my data.  The
glm I have designed can be abstracted to be of the following kind,
with the conditions as column headings and the contrast covariates I
have included in the glm as the numbers below the column headings:

Rest CondA CondB CondC
0          1           1          1
0          -1           0         1
0          .5          -1        .5

This combination of covariates should allow me to detect any relation
among the conditions that I care about.

My question is this: if I want to which regions are showing the
pattern C > B > A, what do I enter in voxelsurfer (or vbview) to find
this?  I want B > rest, so I don't think I should just generate a
parametric map for covariate 2 alone; I should do both 1 and 2, right?
 But is just giving each of them a weight of 1 (and giving the 3rd a 0
weight) the correct thing to do?  Is there a problem with having the
weights I enter not even out to 0 (the way I would if I were directly
comparing A and B, for example)?  Also, when I do a random effects
analysis, should I set the contrast to include both covs 1 and 2?
would that cause any problems?

Sorry to be asking such a question, but my understanding of the
semantics of the commands is limited.

-- 
David January
Department of Psychology
University of Pennsylvania