(condA-condAcontrol)>(condB-condBcontrol) is actually just a simple contrast where you are looking for (condA-condAcontrol)-(condB-condBcontrol)>0, which works out to (condA-condAcontrol-condB+condBcontrol) which works out to the -a 1 -c 2 -c 3 -a 4 contrast we first discussed
On 1/26/2021 11:46 AM, Paula Maldonado wrote:
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I want to find which regions are specifically activated for condA after subtracting out the activity for condB, after subtracting out the activity for their respective control tasks (condAControl and condBcontrol).
(condA-condAcontrol)>(condB-condBcontrol)
I’d like to do the analysis showed in figure 6 in: Bugden S, Woldorff MG, Brannon EM. Shared and distinct neural circuitry for nonsymbolic and symbolic double-digit addition. Hum Brain Mapp. 2019;40:1328–1343. *MailScanner has detected a possible fraud attempt from "secure-web.cisco.com" claiming to be* https://doi.org/10.1002/hbm.24452 https://secure-web.cisco.com/16EgUgo-O6ZgU2AnR7aI9rJDim8n78Dicw7nBRrgmyXoWokJw0p5qP-oWEI8fM48K9iLV-KUhzq2NlFmy_Pyu0MlW8_38Ukm8GE_u1N46VKCziDLHw4yV9Q8KFrZ5X4M_gRbVePSHe_Kbc9xJGW_LzmdDmO94_yoNiuzFeGr9kERDDUS__aN6owP4rjN-BTeiZ4jlTKrsZ7gT2t0hIMK20nk7lk4BI5ouKt_27d4uI8tc7hgxDoBW45sIcjSAgLB7usKrD72ih0RHk1iR8bXZjg/https%3A%2F%2Fdoi.org%2F10.1002%2Fhbm.24452
Thanks,
Paula
Il giorno 26 gen 2021, alle ore 16:18, Douglas N. Greve <dgreve@mgh.harvard.edu mailto:dgreve@mgh.harvard.edu> ha scritto:
They way you have specified your contrast is a conjunction of individual contrasts, ie, cA>cAc AND cB>cBc. If that what you want? Originally, you were just asking about the interaction
On 1/26/2021 5:17 AM, Paula Maldonado wrote:
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Thanks for your reply, However I have now a doubt regarding one aspect that I had not noticed before.
What I wanted to do is to perform the contrast (condA>condAcontrol)>(condB>condBcontrol) with the order of my condition being condA, condAcontrol, condB, condBcontrol
You said that to do so I should use -a 1 -c 2 -c 3 -a 4, but I don’t understand why condition 3 is -c and condition 4 is -a. To my understanding a is assigning a positive weight to my predictors, while c is assigning a negative one. So if I run -a 1 -c 2 -c 3 -a 4, am I not testing the contrast (condA>condAcontrol)>(condBcontrol>condB) ?
In addition, if now I want to obtain: (condA>condB)>(condAcontrol>condBcontrol) should I run mkcontrast-sess -analysis analysis -contrast contrastname -a 1 -c 3 -c 2 -a 4, or -a 1 -c 3 -a 2 -c 4?
Thanks,
Paula
Il giorno 27 ott 2020, alle ore 22:50, Douglas N. Greve <dgreve@mgh.harvard.edu mailto:dgreve@mgh.harvard.edu> ha scritto:
You would just run mkcontrast-sess, eg, if your four conditions are ordered condA, condAcontrol, condB, condBcont, then mkcontrast-sess -analysis analysis -contrast contrastname -a 1 -c 2 -c 3 -a 4 If you want it reversed, then just reverse the a's and c's
On 10/23/2020 4:39 AM, Paula Maldonado wrote:
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Dear experts, I am running an fMRI experiment in which I have four conditions: two main conditions (condition A and condition B) and two respective control conditions (condition Acontrol and condition Bcontrol). I would like to create a map showing significantly greater activity for condition A relative to condition B, after subtracting out the activity for the respective control conditions. In other words, I would like to perform the following contrast: (condition A - condition A control) - (condition B - condition B control) Then I would like to have a map that shows the reverse contrast too:(condition B - condition B control) - (condition A - condition A control).
How do I do that?To obtain the first map: (condition A - condition A control) - (condition B - condition B control) I have tried with the mergecontrasts-sess function with the -conjunction flag and the OR option as detailed below: mergecontrasts-sess -mergedcontrast conjres -conjunction or -analysis analysisname -map sig -space sph -isxavg fixed -contrast Contrast1 2 pos 0 -contrast Contrast 2 pos 0 -s sessionsfMRI/Sub01/bold -hemi lh
where Contrast1= (condition A - condition A control) and Contrast2= (condition B - condition B control) however the map I get is exactly the same as (condition A - condition A control), as if subtracting out Contrast 2 had no impact on the map.
Thanks,
Paula
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