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: > External Email - Use Caution > > 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 >> <dgr...@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: >>> External Email - Use Caution >>> >>> 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 >>> >>> >>> >>> _______________________________________________ >>> Freesurfer mailing list >>> Freesurfer@nmr.mgh.harvard.edu >>> https://secure-web.cisco.com/17Vis7CsewfzKVGLwUV1wLKkghjPfiDm9VeIZ6t9CHXifdcWEg0Z6PdDLO-bFcp-Ie-E_CNaHQm97ldOW3j0GgaivIZZogL1rmUpS07_zswoVI7F_x8z4aL9RkBExxoEMbJjuSwOQiY-xoGtoLQF6kQVRq4Z8YJ64IlUuxvRM0j1FALZF5_BxMy_IxGa0P5vezrjvpHsK9T76iLBmck0BFNQKuOxWjhK1p-dQGxmCPkdVOP_18BUraanTnU6tG93o_F4dSSNY678vxXeomHj0sQ/https%3A%2F%2Fmail.nmr.mgh.harvard.edu%2Fmailman%2Flistinfo%2Ffreesurfer >> _______________________________________________ >> Freesurfer mailing list >> Freesurfer@nmr.mgh.harvard.edu >> https://secure-web.cisco.com/17Vis7CsewfzKVGLwUV1wLKkghjPfiDm9VeIZ6t9CHXifdcWEg0Z6PdDLO-bFcp-Ie-E_CNaHQm97ldOW3j0GgaivIZZogL1rmUpS07_zswoVI7F_x8z4aL9RkBExxoEMbJjuSwOQiY-xoGtoLQF6kQVRq4Z8YJ64IlUuxvRM0j1FALZF5_BxMy_IxGa0P5vezrjvpHsK9T76iLBmck0BFNQKuOxWjhK1p-dQGxmCPkdVOP_18BUraanTnU6tG93o_F4dSSNY678vxXeomHj0sQ/https%3A%2F%2Fmail.nmr.mgh.harvard.edu%2Fmailman%2Flistinfo%2Ffreesurfer > > _______________________________________________ > Freesurfer mailing list > Freesurfer@nmr.mgh.harvard.edu > https://mail.nmr.mgh.harvard.edu/mailman/listinfo/freesurfer _______________________________________________ Freesurfer mailing list Freesurfer@nmr.mgh.harvard.edu https://mail.nmr.mgh.harvard.edu/mailman/listinfo/freesurfer
