 |
 |
Dear SPM'ers, to complement Marco question, I would propose an alternative way, but I am not sure if it is fully correct : 1) at 1st level, compute separately every individual contrasts lets say A : [Cond1 vs Cond2] AND B : [Cond3 vs Cond4] 2) forward the resulting A and B *con*.img at the 2nd level using Basic models -- multiple regression without the constant term design 3) estimate the effect of A inclusively or exclusively masked by B Practically, it works (SPM propose the masking option) , but theoretically ? Did the SPM experts agree with the procedure ? Philippe Peigneux -----Original Message----- From: SPM (Statistical Parametric Mapping) [mailto:[log in to unmask]]On Behalf Of Marco Tettamanti Sent: Wednesday, May 16, 2001 5:20 PM To: [log in to unmask] Subject: masking and RFX analysis Dear SPMers, there have been a couple of similar questions on this topic a while ago: http://www.jiscmail.ac.uk/cgi-bin/wa.exe?A2=ind0005&L=spm&P=R1286&D=0 http://www.jiscmail.ac.uk/cgi-bin/wa.exe?A2=ind0006&L=spm&P=R7873&D=0 but I couldn't find no clear answers to them. I also would like to perform some masking of contrasts at a second level RFX analysis. Could someone please specifiy whether the following procedure is correct: 1) At the first level, compute for every single subject the statistical map of say contrast x (Condition 1 vs Condition 2) masked with contrast y (Conditions 3 vs Condition 4). 2) Write filtered the maps obtained by step 1. 3) Perform a second level RFX analysis (e.g. one-sample t-test) on the images obtained by step 2. Thank you a lot for your help! Best wishes, Marco Tettamanti Istituto Scientifico San Raffaele Medicina Nucleare Via Olgettina 60 I-20131 Milano Italia tel. 0039 - 02 - 26 42 34 60 fax. 0039 - 02 - 21 71 75 58 email:[log in to unmask]