 |
 |
Thanks Cyril. I was not sure to combining two sessions. Thanks again. Best Geon-Ho On 11/28/09, Cyril Pernet <[log in to unmask]> wrote: > > Dear Geon-Ho > > When you model 3 sessions at the 1st level, you notice that each session > has its own constant - i.e. you are only looking at variations around the > mean for each regressor of each session (the ,ean being what you called > baseline signal intensities). Drift and other stuffs should be ok as also > modelled. Contrasting session 1 vs. 2 should therefore be ok. In case you > have issues about heights of the estimates being different between sessions, > you can always choose the option to 'normalize' say to 100. > > Good luck > > Cyril > > > > > Dear SPM Expert > > > > I have the question regarding the comparison of tasks across separate > > sessions. I have run two sessions that one (session1) is with the > paradigm > > of (Base_Motor1)*4 times repeat for 100 scans and the other (session2) is > > with the same paradigm as the previous one, but replaced Motor1 task into > > Motor2 task. > > > > For the first level analysis, I would like to analyze two sessions > together > > (200 scans) to compare directly Motor1 and Motor2, rather than comparing > > those during the second level because of the third session (session3). > This > > is easy if baseline signal intensities are the same for the two sessions. > > However, if the baseline signal intensities are different because of coil > > loading or other system problems (e.g. baseline shift, etc), then I think > > the direct comparisons of Motor1 and Motor2 tasks using both the session1 > > and the session2 may have problems in the first level analysis. Please > > anyone comments this issue. If anyone knows how to solve this problem, > > please advise me and I will appreciate him/her. > > > > Session1: B_M1_B_M1_B_M1_B_M1 (100 scans) > > Session2: B_M2_B_M2_B_M2_B_M2 (100 scans) > > Session3: B_M1_B_M2_ B_M1_B_M2_ B_M1_B_M2_ B_M1_B_M2 (additional 200 > scans) > > Best regards > > Geon-Ho > > -- > > Geon-Ho Jahng,Ph.D. > > Department of Radiology > > East-West Neo Medical Center > > School of Medicine, Kyung-Hee University > > 149 Sangil-dong, Gangdong-gu, > > Seoul 134-727 South Korea > > TEL: 82-2-440-6187 > > Email: [log in to unmask] > > > > > <http://www.dcn.ed.ac.uk/bic/sinapse/sinapse.asp> > > > -- > The University of Edinburgh is a charitable body, registered in > Scotland, with registration number SC005336. > -- Geon-Ho Jahng,Ph.D. Department of Radiology East-West Neo Medical Center School of Medicine, Kyung-Hee University 149 Sangil-dong, Gangdong-gu, Seoul 134-727 South Korea TEL: 82-2-440-6187 Email: [log in to unmask]