Hi,
Computing individual fMRI analysis (several runs) and looking at the design matrix (X.mat), I saw that only one regressor represents each condition. I was expecting that the number of regressors concerning a condition would be the number of runs (as SPM). There are "inter-run effect" regressors but is this better if I affect a different value for each of run and each condition (see examples below). Other question concerning design matrix : only 3 movement parameters included in the design matrix. Why 3 rather than the 6 computed during movement correction? Concerning inter-run effects and movement parameters, is there any advantage of reducing the number of regressors but having a less ideal model?
1 condition = 1regressor
0 = rest 1=conditionA 2=conditionB
Pardagim files : RUN#1 RUN#2 RUN#3 0 0 0 0 0 0 3 0 3 0 3 0 6 0 6 0 6 0 9 0 9 0 9 0 12 0 12 0 12 0 15 1 15 1 15 1 18 1 18 1 18 1 21 1 21 1 21 1 24 1 24 1 24 1 27 1 27 1 27 1 30 0 30 0 30 0 33 0 33 0 33 0 36 0 36 0 36 0 39 0 39 0 39 0 42 2 42 2 42 2 45 2 45 2 45 2 48 2 48 2 48 2 51 2 51 2 51 2 54 2 54 2 54 2 57 0 57 0 57 0
1 condition = 1regressor / run
0=rest 1=conditionA run#1 2=conditionB run#1 3=conditionA run#2 4=conditionB run#2 5=conditionA run#3 6=conditionB run#3
Pardagim files : RUN#1 RUN#2 RUN#3 0 0 0 0 0 0 3 0 3 0 3 0 6 0 6 0 6 0 9 0 9 0 9 0 12 0 12 0 12 0 15 1 15 3 15 5 18 1 18 3 18 5 21 1 21 3 21 5 24 1 24 3 24 5 27 1 27 3 27 5 30 0 30 0 30 0 33 0 33 0 33 0 36 0 36 0 36 0 39 0 39 0 39 0 42 2 42 4 42 6 45 2 45 4 45 6 48 2 48 4 48 6 51 2 51 4 51 6 54 2 54 4 54 6 57 0 57 0 57 0
Frédéric ANDERSSON.