Dear Rick,

Thank you for your answers.
But, I could not understand some of your explanations.

1. The 'step()' function will not end up multiplying by 0.3333, say, at the
edges of the mask.

-> In this part, then is this command incorrect? do I have to change the command?

2. So at this point you are satisfied with the precuneus beta values, yes?

-> As I mentioned, my problem was that the beta values of the precuneus are much smaller comparing with other beta values of the ACC.
Then, the beta values of the precuneus are absolutely comparable with the beta values of the ACC?
Or, as the beta values are relative, the beta values of the precuneus can be multiplied by some constant number.
I thought that multiplying some constant is similar to the scaling to a mean of 100.
Is it correct?

Sorry about keeping asking.
But, I think that my understanding is not perfect.
Thanks.

Woogul Lee