• L Freire and J F Mangin.
• Service Hospitalier Frédéric Joliot, CEA, 91401 Orsay, France.
• Neuroimage. 2001 Sep 1; 14 (3): 709-22.

AbstractThis 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.Copyright 2001 Academic Press.

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