Dear SPM users,
I plan to do PPI analysis. What I want to see is the change of the
functional connectivity before and after practice. Could anyone give me
advice whether my way of analysis is correct or not?
Before and after practice, subjects repeated task (T) and rest (R)
conditions 4 times in a simple block design (TRTRTRTR). For each before-
and after-practice condition, I made a design-matrix using three regressors
(Here, PPI.ppi is box-car function of task*neural signal convolved with
HRF, PPI.P is box-car function of task (10101010) and PPI.Y is a BOLD time
series data of my ROI). In group level analysis, I compared the contract
images using paired t-test to detect the change of functional
connectivity. Does the way of analysis make sense?
If it is correct, my concern is that the orthogonality between PPI.P and
PPI.Y is high (.57). Is it a serious problem?
Thanks a lot in advance.
Satoshi TANAKA Ph.D.
Human Cortical Physiology Section
National Institute of Neurological Disorders and Stroke
NIH, Building 10, Room 5S208
Bethesda, MD 20817 USA
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