>>If we don't use STC at all, then wouldn't it make more sense to set the microtime onset to the slice that represents t0, in your example (ascending interleaved), slice #2, which is the first slice being acquired? (so that it aligns with the event times).
>Well, if you don't go with STC at all, then most of the slices are slightly shifted in time. Assuming all the data of a volume to be acquired in the middle of the TR should lead to the least misalignment (- TR/2 for the first slice, ... + TR/2 for the last one, if you sum up the absolute values this is smaller than 0 for the first slice, ... + TR for the last one).
Sorry for the email onslaught. Has this changed in SPM12? In my case, I have 36 slices acquired in ascending order. I do NOT perform slice timing correction. Like the original poster, I thought that it was best for me to set microtime resolution = 36 and microtime onset = 1. After seeing this post, I re-ran with microtime resolution = 36, microtime onset = 18. However, the former analyses actually gives me substantially more signal.
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