Dear Tim,
> I have three regions of interest ('A','B','C'). Two regions ('A' and
> 'B') show increased activation during my contrast of interest and one
> region ('C') shows decreased activation. I would like to put all
> three into a DCM analysis but need to extract the timeseries for each
> using the same contrast. If all were activated during the contrast
> then I would normally extract for the T-contrast and adjust for the
> F-contrast (but this will not work for the deactivated region 'C').
>
> So, for 'A' and 'B', can I simply extract for the F-contrast and
> adjust for the T-contrast for A and B. Then extract for the
> F-contrast and adjust for the negative T-contrast for C?
You could either construct a -1 T contrast that would show C, or perhaps
use an F contrast (of [1] over your condition of interest) which would
show both activations and deactivations. In a normal analysis this F
contrast would be somewhat more difficult to interpret (as you wouldn't
know if the regions showed positive or negative activity), but for your
purposes of simply identifying task-relevant regions it should work just
fine.
Hope this helps!
Best regards,
Jonathan
--
Dr. Jonathan Peelle
Center for Cognitive Neuroscience and
Department of Neurology
University of Pennsylvania
3 West Gates
3400 Spruce Street
Philadelphia, PA 19104
USA
http://jonathanpeelle.net/
