Hi Everyone
I've read through most of the posts related to whether or not to include movement parameters in the 1st level design matrix. We have an event-related episodic memory task which we have performed on 21 healthy young subjects. We estimated the 1st level models for all participants both with and without the movement parameters included in the design matrix.
The problem is that there are substantial differences between the SPM T-maps from the 1 sample t-tests when done with contrast images where motion parameters were included versus when the 1 sample t-tests were done with contrast images where motion parameters were not included
The most salient difference during encoding is that medial temporal lobe (MTL) activation is nonexistent even using a liberal p value of p = 0.01 with the motion parameter contrast images. Conversely, we observe pretty robust medial temporal lobe activation (p = 0.001) when the contrast images without motion parameters were used for the 1 sample t-test, which is consistent with the literature.
However I am a little apprehensive about that finding given our failure to demonstrate MTL activation when motion parameters were included. Obviously, the results seem to indicate that MTL activation correlated with motion.
I've read several papers and there appears to be no consensus about whether or not to include motion parameters in the 1st level design matrix. Even within the same lab, I've seen papers published both with and without movement parameters included in the design matrix.
I've searched through the listserv with no luck, it seems like most of the relevant posts end with some version of "you should include the movement parameters, except when your activation in key brain regions is correlated with motion." Unfortunately, that doesn't really help me.
I guess what I'm looking for is some guidance about how to proceed, how would I justify not including the movement parameters in the design? are there any alternatives to including the movement parameters in the design matrix? because I have not come across any on the listserv
Any help would be greatly appreciated!
Cheers
Mehul Trivedi, Ph.D.
Instructor
Department of Neurological Sciences
Rush University Medical Center
Chicago, IL
60622
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