title: Motion correction algorithms may create spurious brain activations in the absence of subject motion.
abstract: This paper describes several experiments that prove that standard motion correction methods may induce spurious activations in some motion-free fMRI studies. This artifact stems from the fact that activated areas behave like biasing outliers for the difference of square-based measures usually driving such registration methods. This effect is demonstrated first using a motion-free simulated time series including artificial activation-like signal changes. Several additional simulations explore the influence of activation amplitude and extent. The effect is finally highlighted on an actual time series obtained from a 3-T magnet. All the experiments are performed using four different realignment methods, which allows us to show that the problem may be overcome by methods based on a robust similarity measure like mutual information.
authors.affiliation: Service Hospitalier Frédéric Joliot, CEA, 91401 Orsay, France.
authors.forename: L
authors.initials: L
authors.lastname: Freire
authors.forename: J F
authors.initials: JF
authors.lastname: Mangin
mesh_terms: D000465:Algorithms; D016477:Artifacts; D001921:Brain / Q000502:physiology*; D001931:Brain Mapping / Q000379:methods*; D003198:Computer Simulation; D006801:Humans; D008279:Magnetic Resonance Imaging; D008959:Models, Neurological; D009038:Motion