Dear all,

I am interested in head motion under anesthesia. As we all know, subjects exhibit variability in head motion when lying awake in the scanner.
Under anesthesia, all subjects of a dataset that I am working on show the same kind of small but ongoing, rapid, and "spike-like" head motion.

Since we can only estimate head motion in fMRI, my question is if the time-series of the motion parameters approximately reflect real head motion, or if this "white noise like head motion" is rather an artifact by AFNI’s head motion estimation (when there is probably little or almost no head motion in anesthesia)?

I attach an paradigmatic image of AFNIs QC for one subject below.

Thanks,
Philipp