Hey AFNI gurus,

I am looking at some data with two runs of a task, one right after another. They are processed together in the same afni_proc.py call. At the moment, I am curious about how much motion happen, on average, over all runs, in addition to the max displacement. In examining the out_ss_review text file (or generated table), the average looks good but max displacement is a bit confusing.

For max displacement, it appears to be calculated from the concatenation of the motion parameters, ignoring run seperation. To me, this seems to cause an issue when the subject moves between runs. If they do that, then the max displacement reflects that shift - not max displacement during data collection.

For example, in my two runs of data the subject moves ~0.1mm during each run, but between them they shifted by 4mm, and thus, 4mm is reported as max displacement even though that did not occur while the scanner was running.

For my purposes, I am more curious about the max displacement during a run - rather than how much they shifted. Is this the intended behavior or perhaps I am misunderstanding something?