Hi Emily
>
> 1) I have tried running Melodic on one session, with the appropriate
> FEAT design (3 column format
> for custom timing), but since the full model fit covers ALL the
> copes (is that right),
No, the total model fit combines all EVs, it does not consider copes
at all.
> I have no idea
> how to pick the relevant component out of the 183 it gives me.
>
If you specify the design.mat as the model _and_ the design.con as
the set of contrasts in the melodic GUI then the GLM table underneath
the plot should contain significance for each one of the individual
contrasts (rightmost column). Given that ICA time courses might be
inverted it always makes sense to include each contrast in it's
positive and negative form (or look for p<0.01 _and_ p>0.99 to see if
a particular contrast is significantly related to the IC time course)
> 2) I then ran ONLY one contrast (2 EV), with same problem
> 3) I have no run only one Contrast with one EV, to see if I can
> find the timecourses in Melodic that
> look like the timecourse from FEAT for that EV. I am assuming that
> is how I identify what
> components are related to that contrast in ICA?
>
They might not, ICA will attempt to show you what's in the data.
Imagine a finger tapping experiment where you ask subjects to use
their index finger in condition A and perform random finger tapping in
condition B. In the GLM the canonical way of modelling this is to have
2 EVs, one for conditionA and one for condition B (assuming that you
also have rest in between). In ICA, however, the associated time
course should be one which shows both active conditions in the same
time course (at different levels, hopefully). Therefore, the ICA time
course will not look like any one single EV but instead be a linear
combination of the two. The full model fit does show you if it is task
related.
> 4) If the full model fit is all the inputs, why does it change
> between components?
Because the data changes (i.e. the tested time courses change).
>
>
> 5) Is the IC ## time course supposed to fit that full model line
> really closely? NONE of ours do, but
> our data is from a self paced task, and the timecourse is not
> blocked predictably-
The data is never wrong, the ICA time courses might be poorly
estimated and/or your design might be badly wrong
> is that why it
> doesn't?
>
maybe
> 6) Is it possible to run that many COPES in ICA and have any
> meaningful data come out, or should
> I be running 1 EV at a time, or just one contrast at a time?
The number of contrasts does not matter. In fact, compared to a GLM
you might actually want to add more contrasts to e.g. ook at de-
activations or at signifcace of nuisance regressors that you'd
typically not include in your COPEs for a standard GLM
hth
Christian
|