Dear all,
I have a task-bases fMRI experiment composed of 6 scans per session, for two sessions.
During each scan, subjects performed 10 blocks of a task alternated by fixation cross periods of the same duration.
During the two sessions they received a stimulation during the task either real or control (the same within each session) in a crossover design.
I now want to analyse regions modulated by task accuracy and how this is affected by the stimulation.
Still, during one of the scans, one of the subject reached 100% of accuracy during the whole scan, meaning that for that scan, the modulator has the same value for each block.
In that case, I think after the mean centering, the modulator becomes flat and hence I cannot define a contrast.
I am now then thinking in that case to use the standard block design column in which the signal is convolved with the simple block (same as modulating with a constant 1).
What do you think? Is this a possible solution?
Thank you very much in advance,
Elena
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