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Hi. I am hoping someone out there can give me some advice on an analysis I'd like to try with our Freesurfer data.
We have data (1 mm isotropic MPRAGE at 3T) on healthy older individuals, and have run them through the Freesurfer pipeline, generating cortical volume and thickness measurements. We are interested in studying the moderating effects of cortical atrophy on functional measures taken outside of the MRI. Our hypothesis is that the difference between two different functional measures is moderated by cortical volume/thickness. Thus it is really the interaction term = GM volume/thickness * task (binary 0/1) which we are after.
So, we have fixed effects = GM volume/thickness, task, GM*task, age, .... Other covariates Random effects = subject. Repeated measure = task
We have already run these analyses using mean cortical volume and thickness, as well as regional cortical volume and thickness in the PFC, and found very significant interaction effects. We would now like to refine these analyses with VBM/SBA analysis.
I am hoping that someone can provide some guidance for us in terms of setting up such a model?
(This is different from the standard LME analyses in which the imaging measure is the dependent variable. Here our dependent variable is our functional measure taken outside of the scanner, while the imaging measure - e.g. cortical thickness - is a moderating effect on the RHS of the equation. I'm not sure why this couldn't be done on a voxel-wise or vertex-wise basis, but hopefully someone can enlighten me if I'm being overly naive).
Thanks in advance for the advice!
Mark ____________________ Mark Wagshul, PhD Associate Professor Gruss Magnetic Resonance Research Center Albert Einstein College of Medicine Bronx, NY 10461
Ph: 718-430-4011 FAX: 718-430-3399 Email: mark.wagshul@einstein.yu.edumailto:mark.wagshul@einstein.yu.edu
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