Hi,
I encounter an analysis question and hope someone could help. In my group analysis, I first do a linear regression analysis using a Visual (V) behavioral parameter of each subject as a covariate, and I found that the brain region A is correlated with V. I also do a second group analysis in another model using a Spatial (S) behavioral parameter of each subject as a covariate, and I found that brain region B is correlated with S.
Since I've separately identified brain regions associated with V and S, my question is how can I make a direct statistical assessment of this difference? In other words, I want to prove that activity in region A is associated with / predicted by V, whereas that in B is associated with / predicted by S.
I have two ideas to solve this issue but not sure if my thinking is correct.
Solution (1).
Extract the BOLD signal changes in region A, plot the data with V and S parameters respectively. Prove that BOLD signals in A is correlated with V and not correlated with S. Compare the slopes of the two lines and, if both slopes are significantly different, I can say that activity in region A is associated with / predicted by V. Repeat the same process for region B.
Solution (2).
Construct another linear regression model (actually a multiple linear regression one) and enter V and S as the two covariates. Perform small-volume correction (SVC) analyses in regions A and B. Considering SVC in region A, if the contrast (1 0) shows that region A is significantly predicted by V after regressing out the effect of S, and contrast (0 1) shows that it is not correlated with S after regressing out the effect of V, I can conclude that activity in region A is associated with V. On the other hand, considering SVC in region B, if the contrast (0 1) shows that its activity is significantly predicted by S after regressing out the effect of V, and contrast (1 0) shows that it is not significantly predicted by V after regressing out the effect of S, I can conclude that activity in region B is associated with / predicted by S.
Can I use either one of them? Thanks a lot.
Mike
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