Hi Dorian,
Sounds like you have your answer, but if your analysis needs sensitivity to rotation and translation from SPM motion vectors, you might also be interested in the "Pythagorean Pythagorean Displacement and Motion Regressors" toolbox, on NITRC (http://www.nitrc.org/projects/pythagoras). It contains a single Matlab script that calculates head position and motion based on the rp*.txt motion summary generated during SPM-realignment, which keeps rotation and translation distinct for each vector. We've used those motion estimates to calculate subject differences in head motion similar to those suggested by Donald McLaren, although those were not built into the script per se.
Good luck!
Kenny Vaden
Kenny Vaden, Ph.D.
Hearing Research Program
Department of Otolaryngology
Medical University of South Carolina
[log in to unmask]
|