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.
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