Hello all!
This is a general question about DCM setup and interpretation that relates
to my data, but I hope will have relevance to many other users.
I have two regions of interest from an fMRI data set which I found to be
activated by interesting contrasts in a task, and are coupled to each other,
as determined by a PPI analysis (comparing condition 1 coupling to condition
2 coupling). What I would like to understand is how condition 1 vs condition
2 affects the region A to B path separate of the B to A path. This will
hopefully give some directionality to the PPI effect across the two
conditions. I am trying to set up a DCM model and have several questions.
Please tell me if any of the below are right or wrong:
1. For intrinsic connections I chose A to B and B to A.
2. For which conditions to include (out of 7) I chose conditions 1 and 2.
3. For effects of condition 1, I chose it to affect region A, region B, the
path from A to B and the path from B to A.
4. same as above for condition 2
from what I understand, the area of the results I should be looking at is:
DCM.A (intrinsic connectivity)
-1.0000 0.0252
-0.0193 -1.0000
DCM.B (effects of conditions 1 and 2) on A to B and B to A paths
ans(:,:,1) =
1.0e-004 *
0 0.2279
-0.0309 0
ans(:,:,2) =
0 0.0003
0.0016 0
DCM.C (input effects)
0.0007 -0.0684
0.0022 -0.0264
Questions:
1. What do the intrinsic connection values mean? and are they in relation to
the conditions in any way?
2. Am I right in interpreting the DCM.B results as saying that, relative to
condition 1, condition 2 led to a decrease in B to A path strength and an
increase in A to B path strength?
3. Am I right in saying that, relative to condition 1, condition 2 led to
less activation in regions A and B (values going from slightly positive to
negative)?
4. Should I include all 7 conditions? If so, how should I set up the model
if all I'm interested in is the effects of conditions 1 and 2 in A to B and
B to A paths.
5. Can I take the values for each of these items (once I understand them) to
the group level by a simple t-test approach?
6. What unit of measure do the numbers in DCM.A, .B, and .C refer to?
much thanks!
Amit
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