Dear SPM fMRI mavens,
I have fMRI data with 5 identical runs per subject. Each run includes
15 order-randomized presentations of three 15 sec stimuli, call them
A, B and C (5 trials each), with each stimulus preceded by a resting
baseline. In almost every subject, condition A produces highly
significant BOLD increases in some voxels of a small but
theoretically important structure, but equally strong decreases in
others. I want to contrast the functional connectivity of the peak
increases and decreases in response to stimulus A, but have to do
this separately for each subject, because these highly significant
effects spatially overlap across subjects and largely cancel each
other at the second level. I can identify the two voxels I'd like to
use as covariates for each subject, but don't know how to look at
their covariation with the rest of the brain only in response to
stimulus/condition A. I read the PPI paper but don't see how to
apply it to this design. Could anybody help?
Sincere Thanks,
Steven Berman, Ph.D.
UCLA Division of Digestive Diseases, Psychiatry and Brain
Research Institute
Center for Neurovisceral Sciences & Women's Health (CNSWH)
CURE: Digestive Diseases Research Center
Greater Los Angeles VA Healthcare System, Bldg. 115/CURE
11301 Wilshire Blvd., Los Angeles, CA 90073
Tel. (310) 478-3711 Ext.40696 Fax: 794-2864
http://ibs.med.ucla.edu
http://uclamindbody.org
http://www.bri.ucla.edu
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