Dear SPMers,
I wonder if you can help soving a puzzle.
I have 6 fmri acquisition, two for conditions A versus rest, two for B
versus rest, two for C versus rest.
The order of the acquisitions is: B C A A C B
A = only hand movement
B = only speech production
C = hand mov + speech prod
I did only t-tests, not F-tests.
If as basis set for the SPM analysis I consider only the hrf I have the
following.
When I consider the contrast [0 0 1 1 0 0] I see a huge activation in the
motor cortex, while with [0 0 -1 -1 0 0] there is little or no
(de)activation
When I consider [1 0 0 0 0 1] or [0 1 0 0 1 0], I see little activation in
some parts of the brain, while with [-1 0 0 0 0 -1] or [0 -1 0 0 -1 0] I see
large (de)activation almost everywhere in the brain.
If as basis set for the SPM analysis I consider only the hrf+time
derivatives I have the following.
When I consider the contrast [0 0 1 1 0 0] I see much less activation in the
motor cortex, while with [0 0 -1 -1 0 0] there is maybe more (de)activation
When I consider [1 0 0 0 0 1] or [0 1 0 0 1 0], I see much more activation
in some parts of the brain, and with [-1 0 0 0 0 -1] or [0 -1 0 0 -1 0] I
see less (de)activation.
I am quite puzzled. Has anybody find something similar?
Is it more likely that there was a problem during the acquisition or the
analysis of the data, or that it is a real behaviour of the brain?
Many thanks,
Laura
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