I have a question abt. how to do group effects analyses with parametric
modulation.
I ran a gambling study lately. Participants make a decision, see the
outcome, and then on the next screen, they are asked to rate their
feelings abt. "how much i wish i chose a different gamble" (5 pt.
scale). There are 4 different types of outcome conditions; one of them
is regret. For regret trials, i want to see what areas of regret are
modulated by this rating.
In SPM2, for each subject, what I did is that I ran a model with 11
regressors (including baseline), and for the regret condition, I added
the ratings as its parametric modulator, yielding 12 regressors in the
model.
My question would be what should I do next? Do I use the contrast images
of the regret rating regressor for the random effects? Do I create a
different contrast test? Or do use the beta images for regret modulated
with the ratings in the random effects model?
Do I run a 1-sample t-test in the random effects model?
Once I see the results, how can I see how the ratings modulated the
regret areas, e.g., higher ratings are correlated with which areas for
the regret condition?
If you can reply to this message, or give me references on where to look
it up, that'll be EXTREMELY helpful.
Thanks, Hannah
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