Dear SPM experts:
I am trying to use SPM 99 to do a group analysis of some fMRI data
concerning cigarette smoking. Subjects are initially at rest in the
scanner (e.g. for 15 images), and then begin inhaling smoke (eg. for 85
images). We would like to know which areas of the brain increase their
activity as nicotine blood levels rise. Since we don't yet have a
catheter in place to directly measure blood levels, we will approximate it
as a linear increase from the time of first inhalation.
How should I ask SPM to do a linear regression of this kind?
Some more specific questions that have arisen from reading other
messages:
Is this considered a session x condition interaction, such that
scans from all subjects need to be entered as one session?
If I omitted the resting images, focusing only on the smoking period,
would I be able to use the 'time' option in the parametric modulation
choices?
Should I treat the smoking period as an epoch, and if so what type of
response should I assign it?
Thank you in advance for your help!
Warm regards,
Tavis
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