Dear spm'ers
we thank Karl for the quick answer to our question regarding
the evaluation of an interaction between a contrast and a performance
variable in an fMRI study.
Now we would like to ask, whether an analysis applying a parametric
modulation would also be a way to go. Again here an outline of one
of our fMRI experiments:
a.) 2 conditions ABABABAB, of which we think that only one is modulated
with the performance variable.
b.) 6 scans per epoch, 9 subjects
We entered all 432 scans (9 subjects x 2 conditions x 4 repetitions x 6 scans)
as one session.
Then we specified 1 trial and chose the parametric modulation 'other',
entering 36 values (each value was entered 4 times since only 1 performance
variable exists per person but the trial was repeated 4 times).
We chose a 'linear' expansion and selected the F-contrast 'effects of interest'
in the results section.
Is this procedure OK? The results look good - but is it really appropriate to concatenate the scans
of different subjects in one session?
Thanks very much
Bruno
--
Bruno Weber
Neurologische Klinik
Abt. Neuropsychologie
Abt. EEG & Epileptologie
UniversitaetsSpital Zuerich
Frauenklinikstrasse 26
CH-8091 Zuerich
Tel.: ++41 1 255 55 79
Fax.: ++41 1 255 44 29
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