Residual effects of head movement in fMRI

Relatively large (>3 mm) and stimulus-correlated head movement during blood oxygen level dependent (BOLD) ´functional magnetic resonance imaging (MRI) is known to produce regions of false activation. We investigated a possible difference in brain activation with weakly correlated through-plane and in-plane head movement in fourteen healthy volunteers. fMRI was performed on a 4 Tesla whole-body MRI scanner, using gradient-echo single-shot EPI. Regions of false activation occurred despite small movements (<1-mm-translations and <1°-rotations) and motion correction. False activation was also observed when the motion was weakly correlated with the stimulus. Investigation of the extent of the residual effects of head movement and stimulus-correlated motion are required to increase the confidence that results reflect genuine activation rather than motion in film studies.