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
