Dear SPMers,
II have a block design experiment to measure the functional activation related to the processing of food pictures. The experimental is made up of 2 runs. Each session has 36 blocks. Each block (Each block lasts for 20 seconds) consisted of 2s of food visual stimuli, followed by a 18s resting baseline. In addition, participants were asked to press a button for rating the picture (how much they liked the food in pictures 1-8). Therefore I have a behavior data for each trial. I'm interested about how the behavior across the trials related to the brain activity. To do that I am using a parametric modulation and now this my questions:
1- I used a second order of PM. And if I understand it correctly this paper (http://www.sciencedirect.com/science/article/pii/S1053811998903512) , they put the most important column of interest in as the first. Is it possible to change the order of the columns in a design matrix in SPM12? I would like to make a first column of the design matrix reflected the second order of PM.
2- I would like to put the reaction time as a PM in the design matrix to make the GLM model more robust and explain everything in my data, is that make sense?
3- In some trails the participants did not rating the picture, Can I put 0 for the missing value in rating or reaction time?
Thanks in advance,
Arkan
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