Hi Gang,
Thanks for the quick reply
>
> It seems to me that you need to better define the goal of your group analysis before laying out the model strategy at individual level.
>
I'll try to be clear in what I think the group analysis should be.


> It looks to me that you have four modulation effects, right?
>
> 1. sum(subjective values),
> 2. difference(subjective values),
> 3. delay(LL-choice), and
> 4. RT
>
> > -stim_times_AM2 3 ../stimuli/${subj}stimlist2.1D 'dmBLOCK' -stim_label 3 ALL \
>
> What modulation values did you put in the above line?
Yes, 4 modulation effects: globaltime*sum,diff,delay:RT
This models every event (whether or not they chose SS or LL)

The other two lines have one duration modulation:
-stim_times_AM1 1 ../stimuli/${subj}SS.1D 'dmBLOCK' -stim_label 1 SS \
-stim_times_AM1 2 ../stimuli/${subj}LL.1D 'dmBLOCK' -stim_label 2 LL \
globaltime:RT
SS models every event they made an SS choice.
LL models every event they made an LL choice.

> And why are you combining the two tasks?
I'm not sure what you mean - I probably was unclear in my earlier post. There is one task, every event they are presented with an SS and an LL choice. I'm splitting the task into two conditions: 1. Events when they chose the SS option, 2. Events when they chose the LL option. Let me know if you mean something different.

>
> > The comparison of interest is the SS vs LL
> trials - to see if there is different activation
> > between Patients and Controls, without the
> influence of differences in subjective value.
>
> By "without the influence of differences in
> subjective value" do you mean that you want to see
> the interaction between tasks and groups,
> comparing the two group in the difference of SS
> and LL, while controlling sum and difference of
> the subjective value at the group average? How
> about the other two modulation values: RT and
> delay?
Yes (if I interpret task correctly) - I am most interested the interaction between condition (SS or LL choice) and Group (Patient or Control), while controlling for subjective value. As some areas are sensitive to SV (sum or diff), I'd like to be sure that any differences in activation I see are not due to group differences in subjective value (behaviorally there is a non-significant difference).

As for delay, yes I want to control for delay, I don't imagine it will have a large effect, but what do I know.
For RT - I guess I wasn't thinking of duration modulation as way of controlling for differences in activation due to RT, but yes, that is what I'm doing, and I want to do it. Please let me know if that conclusion (and resulting self-confidence) is wrong!

That's all I have for now. I'll try splitting the regressors like I discussed in my first post. Perhaps the beta weights calculated will be similar enough, but I'm not sure how to check that. To be clear I would rewrite the 3dDeconvolve script to just have two stim lists:
-stim_times_AM2 1 ../stimuli/${subj}SS.1D 'dmBLOCK' -stim_label 1 SS \
-stim_times_AM2 2 ../stimuli/${subj}LL.1D 'dmBLOCK' -stim_label 2 LL \
with the following in each line of each stimfile:
globaltime*sum,diff,delay:RT
But I think I want the sum, diff, delay regressors of SS trials to be the same as LL trials.

Thanks, again.
Hugo