Fig. 3.

a: Standard deviation maps (σ-maps) generated from the same in-plane (row 1) and through-plane (row 2) scans as used in Fig. 2. For ease of reference, the same layout is used as in Fig. 2. Reference EPI images (column 1) are shown alongside σ-maps generated from time-series acquired with prospective correction ON (column 2) and OFF (columns 3,4); column 3 images remained completely unprocessed, while column 4 images were retrospectively realigned using SPM before generating the σ-maps. The σ-maps provide spatial information of image stability, with perfect correction reducing standard deviations to baseline resting levels of brain activation ~ 2 %. b: Comparison of image stability between correction methods using metric σ̄. For each of the three motions tested, each column represents the average σ̄ over the relevant volunteer scans, while error bars are standard deviations between scans. N = 7, 9, 9 for resting, in-plane, and through-plane motions, respectively; one resting scan was removed due to significant subject movement, while analysis for deliberate motions include all 8 smooth + 1 abrupt motion scans. Prospective correction provides the greatest decrease σ̄ in for both deliberate motions, returning image stability closest to resting levels.