Hi, I've read the handouts, but I am still confused about AM1 and AM2.

If the item-wise regressors is actually the main effect which is of interest, should I use AM1 instead of AM2? Say three critical conditions are differ in semantic distance, and I used GLT to test the difference between conditions in the past. And now I'd like to find the areas that activation is modulated by semantic distance, should AM1 be used? Should I just put the three conditions in ONE "stim_times_AM1"?

When the three conditions differ in semantic distance but semantic distance is not what we are interested in, is it better for us to use AM2 so that we can discriminate the areas which is sensitive and insensitive to semantic distance, especial those unmodulated? In this case, should I define each condition in a separate "stim_times_AM2"?

In stim_times_AM1, it is assumed that "the change in FMRI signal as ABI changes is linearly proportional to the changes in the ABI values", what about AM2?
If we assume that the changed is not lineal, say it is a lg relationship, can we "marry" the transfered semantic distance(i.e. new index of semantic distance = lg(old semantic distance)) to the onset time?

Does it matter if the semantic distance of some item is zero? When should we centered the semantic distance and when we don't have to?

Thank you very much!