Head Motion Biases Brain Structural Scans

A regular theme here at Neuroskeptic is the worrying issue of head movement during brain scans. We've seen that motion can alter measures of functional and structural connectivity, and that common approaches to dealing with this problem may be inadequate. Now a new study reveals that even measures of the gross structure of the brain can be biased by excessive motion: Head motion during MRI acquisition reduces gray matter volume and thickness estimates. Harvard neurologists Martin Reuter and colleagues took twelve healthy people and told them to move their heads at certain points during a series of structural MRI scans. Reuter et al. measured the degree of movement using navigator scans throughout the experiment, allowing them to correlate the amount of motion with the measured brain structure. They found a strong correlation between the amount of movement and measures of brain cortical thickness and grey matter density (morphometry). The more someone moved, the less grey matter they seemed to have, and the size of this effect was pretty large: