During sending the two previous message the contrast matrix was altered so I
try to re-submit my mail re-writing the contrast matrix in another manner.
Can you help me with the hypothesis interpretation connected with my
contrast?
2x2 factorial event-related fMRI (A1 vs. A2) x (B1 vs. B2), 1 regressor of
non-interest always I set zeros, six movement parameters (from realignment),
one session, one subject (first-level analysis), canonical hrf and time and
dispersion derivatives. So my matrix has the 22 columns ordered in the
following manner:
A1_B1_canonical, time, dispersion
A1_B2_canonical, time, dispersion
A2_B1_canonical, time, dispersion
A2_B2_canonical, time, dispersion
1 regressor of non-interest_canonical, time, dispersion
6 movement parameters (from realignment)
intercept
Which is the statistical hypothesis for each following contrast(how are
betas combined?) or which are the voxels I see in the spm map after running
each contrast?
I try to give a name to the contrasts but I want to understand deeply what
each contrast means so you think that I know nothing about them.
F contrast:
1) Effects of interest
1, 21 zeros;
1 zero, 1, 20 zeros;
2 zeros, 1, 19, zeros;
3 zeros, 1, 18 zeros;
4 zeros, 1, 17 zeros;
5 zeros, 1, 16 zeros;
6 zeros, 1, 15 zeros;
7 zeros, 1, 14 zeros;
8 zeros, 1, 13 zeros;
9 zeros, 1, 12 zeros;
10 zeros, 1, 11 zeros;
11 zeros, 1, 10 zeros;
12 zeros, 1, 9 zeros;
13 zeros, 1, 8 zeros;
14 zeros, 1, 7 zeros;
15 zeros, 1, 6 zeros;
16 zeros, 1, 5 zeros;
17 zeros, 1, 4 zeros;
18 zeros, 1, 3 zeros;
19 zeros, 1, 2 zeros;
20 zeros, 1, 1 zeros.
2) Canonical hrf
1, 21 zeros;
3 zeros, 1, 18 zeros;
6 zeros, 1, 15 zeros;
9 zeros, 1, 12 zeros.
3) Time derivative
1 zero, 1, 20 zeros;
4 zeros, 1, 17 zeros;
7 zeros, 1, 14 zeros;
10 zeros, 1, 11 zeros.
4) Dispersion derivative
2 zeros, 1, 19 zeros;
5 zeros, 1, 16 zeros;
8 zeros, 1, 13 zeros;
11 zeros, 1, 10 zeros.
5) F-contrast for A1B1 condition?
1, 21 zeros;
1 zero, 1, 20 zeros;
2 zeros, 1, 19 zeros.
6) Movement parameters
15 zeros, 1, 6 zeros;
16 zeros, 1, 5 zeros;
17 zeros, 1, 4 zeros;
18 zeros, 1, 3 zeros;
19 zeros, 1, 2 zero;
20 zeros, 1, 1 zero.
7) Canonical hrf + derivatives for main effect of factor A?
1, 2 zeros, 1, 2 zeros, -1, 2 zeros, -1, 2 zeros, 10 zeros;
1 zero, 1, 2 zeros, 1, 2 zeros, -1, 2 zeros, -1, 2 zeros, 9 zeros;
2 zeros, 1, 2 zeros, 1, 2 zeros, -1, 2 zeros, -1, 2 zeros, 8 zeros.
8) Canonical hrf for main effect of factor A?
1, 2 zeros, 1, 2 zeros, -1, 2 zeros, -1, 2 zeros, 10 zeros.
T contrast:
9) ?
1, 2 zeros, 1, 2 zeros, 1, 2 zeros, 1, 2 zeros, 10 zeros.
10) ?
-1, 2 zeros, -1, 2 zeros, -1, 2 zeros, -1, 2 zeros, 10 zeros.
11) ?
1 zero, 1, 2 zeros, 1, 2 zeros, -1, 2 zeros, -1, 2 zeros, 9 zeros.
A last question:
Which contrast shall I use at first-level analysis if I want to do a
second-level analysis with one-way ANOVA(no costant term)as suggested by Rik
Henson? (I want consider canonical hrf and two derivatives and I dont't want
to set the derivatives as confounds that is zeros).
Thank you.
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