A troublesome source of physiological noise in functional magnetic resonance imaging (fMRI) is due to the spatio-temporal modulation of the magnetic field in the brain caused by normal subject respiration. fMRI data acquired using echo-planar imaging are very sensitive to these respiratory-induced frequency offsets, which cause significant geometric distortions in images.
But this does not mean do expert roundups. Expert roundups are a lazy, terrible excuse for good content. Get a single person to write the definitive guide to the topic. Please do not pollute the Internet with more expert roundups.