Dear DCM experts,
few days ago I sought your assistance in the matter of coupling parameter in nonlinear DCM. Please see original message below. Is any information missing to solve the problem?
Kind regards, Lisa
Dear DCM experts,
I am a PhD student using DCM for the first time. In the current project, I am using nonlinear DCM to answer the question whether the connections between different areas in network A (consisting of 3 areas) are modulated by two experimental conditions and by the activity of network B (consisting of 2 areas).
I constructed 44 models, of which one was superior. I tested whether the coupling parameters for the B- and D- matrices are different from zero and found significant effects that are consistent with our hypotheses. But I am surprised by the small Hz values of the coupling parameters (ranging from .00002 to .0044). My first question is: Can I trust the significant effects despite the small values? Does anyone have an idea why these values are so small?
Also, our GLM analysis showed different activation peaks in network B for condition 1 vs. control than for condition 2 vs. control. One of the two areas of network B was only activated by condition 1, but not by condition 2. I used only the peaks from condition 1 in the DCM analysis but tested for modulatory effects of both conditions. Now my second question is: should I run two different DCM analyses to consider the varying peaks, i.e. run a separate analysis for each condition?
Many thanks in advance!
Best, Lisa
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