Journal Article

A comprehensive assessment of regional variation in the impact of head micromovements on functional connectomics

Craddock, R. Cameron, Di Martino, Adriana, Cheung, Brian, Castellanos, F. Xavier, Kelly, Clare, Zuo, Xi-Nian, Colcombe, Stan, Milham, Michael P., Yan, Chao-Gan, Li, Qingyang

2013

Overview

Functional connectomics is one of the most rapidly expanding areas of neuroimaging research. Yet, concerns remain regarding the use of resting-state fMRI (R-fMRI) to characterize inter-individual variation in the functional connectome. In particular, recent findings that “micro” head movements can introduce artifactual inter-individual and group-related differences in R-fMRI metrics have raised concerns. Here, we first build on prior demonstrations of regional variation in the magnitude of framewise displacements associated with a given head movement, by providing a comprehensive voxel-based examination of the impact of motion on the BOLD signal (i.e., motion–BOLD relationships). Positive motion–BOLD relationships were detected in primary and supplementary motor areas, particularly in low motion datasets. Negative motion–BOLD relationships were most prominent in prefrontal regions, and expanded throughout the brain in high motion datasets (e.g., children). Scrubbing of volumes with FD>0.2 effectively removed negative but not positive correlations; these findings suggest that positive relationships may reflect neural origins of motion while negative relationships are likely to originate from motion artifact. We also examined the ability of motion correction strategies to eliminate artifactual differences related to motion among individuals and between groups for a broad array of voxel-wise R-fMRI metrics. Residual relationships between motion and the examined R-fMRI metrics remained for all correction approaches, underscoring the need to covary motion effects at the group-level. Notably, global signal regression reduced relationships between motion and inter-individual differences in correlation-based R-fMRI metrics; Z-standardization (mean-centering and variance normalization) of subject-level maps for R-fMRI metrics prior to group-level analyses demonstrated similar advantages. Finally, our test–retest (TRT) analyses revealed significant motion effects on TRT reliability for R-fMRI metrics. Generally, motion compromised reliability of R-fMRI metrics, with the exception of those based on frequency characteristics — particularly, amplitude of low frequency fluctuations (ALFF). The implications of our findings for decision-making regarding the assessment and correction of motion are discussed, as are insights into potential differences among volume-based metrics of motion. •Positive but not negative motion-BOLD relationships appear to be neural in origin.•Motion should always be accounted for in group-level analyses.•Global signal regression and Z-standardization mitigate motion effects.•Motion compromises test-retest reliability, and correction strategies improve.

• Publisher: Elsevier Inc,Elsevier,Elsevier Limited
• Subject: Biological and medical sciences / Brain - physiology / Brain mapping / Brain Mapping - methods / Brain research / Connectome - methods / Fourier transforms / Functional connectomics / Fundamental and applied biological sciences. Psychology / Head motion correction / Head Movements / Humans / Image Processing, Computer-Assisted - methods / Motion / Neural Pathways - physiology / NMR / Nuclear magnetic resonance / Rest - physiology / Resting-state fMRI / Studies / Test–retest reliability / Vertebrates: nervous system and sense organs / Voxel-wise movement