Dear FSL people,
I am having problems to understand a contrasting & design matrix question.
My experiment is basic: a block design with one active condition and
a baseline. I have run the GLM-analyses by having one EV (EV1, for the
active condition) and one contrast with value 1 for EV 1. So, the
resulting statistical maps show the regions where voxels time-courses
follow the model in the specified level of signifigance. These areas are
then considered "activated".
Iīve read articles where baseline > active condition contrast is
represented (in addition of active condition > baseline contrast), with
same kind of block design. How is this done?
I canīt feed in both EV 1 and baseline in the design matrix and have a 1 -1
contrast since the two EVs would be a linear combination of each other.
Could I use orthogonalizing of the contrasts? Or is this kind of
thinking at all sensible since I do not have a baseline for the
baseline?
And what would be represented if I ran the EV 1 contrast with value -1
instead of 1?
Sorry for these stupid questions...
And thanks for help the previous times.
Best wishes,
Johanna Pekkola
TKK/LCE
Espoo, Finland
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