Isolated assessment of translation or rotation severely underestimates the effects of subject motion in fMRI data

• Published in: PloS one 2014-10, Vol.9 (10), p.e106498-e106498
• Main Author: Wilke, Marko
• Format: Article
• Language: English
• Subjects: Adolescent; Adult; Adults; Aged; Aged, 80 and over; Aging; Analysis; Artefacts; Biology and Life Sciences; Brain; Brain - diagnostic imaging; Brain Mapping; Child; Child, Preschool; Children; Corruption; Cortex; Datasets; Experiments; Female; Functional magnetic resonance imaging; Head; Head Movements; Humans; Image Processing, Computer-Assisted; Magnetic resonance imaging; Magnetic Resonance Imaging - methods; Male; Medical imaging; Medicine and Health Sciences; Middle Aged; NMR; Nuclear magnetic resonance; Parameters; Pediatrics; Quality control; Radiography; Repositories; Software; Trajectory analysis; Translations; Washing; Young Adult
• ISSN: 1932-6203; 1932-6203
• DOI: 10.1371/journal.pone.0106498

Subject motion has long since been known to be a major confound in functional MRI studies of the human brain. For resting-state functional MRI in particular, data corruption due to motion artefacts has been shown to be most relevant. However, despite 6 parameters (3 for translations and 3 for rotations) being required to fully describe the head's motion trajectory between timepoints, not all are routinely used to assess subject motion. Using structural (n = 964) as well as functional MRI (n = 200) data from public repositories, a series of experiments was performed to assess the impact of using a reduced parameter set (translationonly and rotationonly) versus using the complete parameter set. It could be shown that the usage of 65 mm as an indicator of the average cortical distance is a valid approximation in adults, although care must be taken when comparing children and adults using the same measure. The effect of using slightly smaller or larger values is minimal. Further, both translationonly and rotationonly severely underestimate the full extent of subject motion; consequently, both translationonly and rotationonly discard substantially fewer datapoints when used for quality control purposes ("motion scrubbing"). Finally, both translationonly and rotationonly severely underperform in predicting the full extent of the signal changes and the overall variance explained by motion in functional MRI data. These results suggest that a comprehensive measure, taking into account all available parameters, should be used to characterize subject motion in fMRI.