Hello,
I had a question about the way the model peak-to-peak height was
computed for a second level analysis of which input were cope images
rather than feat directories, and about running featquery on it. I had
forgotten to mention that I am interested in percent signal change for
contrasts (condition vs. modeled rest), which explains why I'm looking
at the ppheight values in design.lcon. Also, I'm looking at contrasts
that have been set at the first level already, then I have ppheight
values for each of those and for each first level run.
Can anybody tell me whether I'm doing the right thing here?
Thanks a lot,
Stephane
Stephane Jacobs wrote:
> Hello,
>
> I would like to run featquery on a second level analysis (cross session -
> within subject level) to compute percent change of COPEs within a given ROI.
> I understand that featquery is using the average ppheight found in the
> design.lcon file in the copeX.feat directory as a scale factor to compute
> percent change.
> However, I am wondering whether this is still correct to do so in my case.
> Indeed, I have fed cope images into my second level analysis, instead of
> .feat directories, as I needed to contrast EVs coming from different runs.
> Then, I end up with one single cope1.feat directory at the output of my
> second level analysis, which contains as many cope images as I have set
> contrasts at the 2nd level (4), rather than getting cope1.feat..cope4.feat
> as when you feed feat directories containing all the same EVs.
>
> Therefore, it seems that the value contained in design.lcon is the average
> of the ppheight across all my contrasts. I wonder if I rather should compute
> an average ppheight for each of my 2nd level contrast separately, to be more
> accurate?
>
> Thanks in advance for all your thoughts and advice,
>
> Best,
>
> Stephane
>
>
>
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