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Dear Dandil, Did you try longer rest periods? 4 seconds seem too little to see a good the visual response with the duration of the stimulation you use. Other option is that the response itself is small. To enhance it you might try white and blue checkerboard. But the answer can be simpler: Why duration of your blue screen is 8 in the vector and 16 in the design drawing? The ISI also seem strange: 8 (blue)+4(rest)+16(white) +4(rest ) gives ISI of 32, not 20 as it is seen from your onset vectors. There must be a mistake, 200 scans X 2 sec gives 400 seonds while your last onset is 188... Sincerely yours, Vladimir ________________________________ From: dandil dNd <[log in to unmask]> To: [log in to unmask] Sent: Tuesday, October 1, 2013 11:15 AM Subject: [SPM] Problem with condition definition Hi dear all, I am running a 1st level fMRI analysis using "specify 1st level". The experiment block design has been attached. The task lasts for 400 second (10 trials, each one 40 second). There are 200 scans and intersection interval is 2 second. After deletion of 5 volumes, two conditions have been defined as: (1) for blue screen (onset=[1 18 38 58 78 98 118 138 158 178] , duration=[5 8 8 8 8 8 8 8 8 8 8]) and (2) for white screen (onset=[8 28 48 68 88 108 128 148 168 188] , duration=16). after model specification and contrast ([1,0], [0,1]) definition SMP gives a very very sparse activation map with very small clusters and there is not a good match between fitted response and experiment design. I don not know what is the problem. Can any one help me? Best regards, Dandil