Functional MRI

Brain motion interferes with functional magnetic resonance imaging (fMRI) by causing a variety of signal artifacts whose characteristics depend on the kind of motion, the pulse sequence used, and when and how the motion occurred. In task fMRI, motion artifact uncorrelated with the task design degrades statistical power by introducing noise, causing false negatives. If motion correlates with task design, it can lead to false positives. In task-free (i.e., resting state) fMRI, head motion artifacts introduce a colored distance-dependent noise such that covariance is higher between nearby brain regions due to shared proximal artifacts. Methods to ameliorate head motion's effects include prevention, retrospective attempts to correct data, and attempts to correct for head motion “online” prospectively during acquisition. However, there are remaining challenges to correcting motion specific to fMRI. Head motion, and its artifacts, are collinear with factors including age, clinical diagnosis, body weight, and with physiological processes like breathing.