title: Spurious group differences due to head motion in a diffusion MRI study.
abstract: Diffusion-weighted MRI (DW-MRI) has become a popular imaging modality for probing the microstructural properties of white matter and comparing them between populations in vivo. However, the contrast in DW-MRI arises from the microscopic random motion of water molecules in brain tissues, which makes it particularly sensitive to macroscopic head motion. Although this has been known since the introduction of DW-MRI, most studies that use this modality for group comparisons do not report measures of head motion for each group and rely on registration-based correction methods that cannot eliminate the full effects of head motion on the DW-MRI contrast. In this work we use data from children with autism and typically developing children to investigate the effects of head motion on differences in anisotropy and diffusivity measures between groups. We show that group differences in head motion can induce group differences in DW-MRI measures, and that this is the case even when comparing groups that include control subjects only, where no anisotropy or diffusivity differences are expected. We also show that such effects can be more prominent in some white-matter pathways than others, and that they can be ameliorated by including motion as a nuisance regressor in the analyses. Our results demonstrate the importance of taking head motion into account in any population study where one group might exhibit more head motion than the other.
authors.affiliation: Athinoula A. Martinos Center for Biomedical Imaging, Department of Radiology, Massachusetts General Hospital, Harvard Medical School, Boston, MA, USA. Electronic address: ayendiki@nmr.mgh.harvard.edu.
authors.forename: Anastasia
authors.initials: A
authors.lastname: Yendiki
authors.affiliation: Department of Brain and Cognitive Sciences, Massachusetts Institute of Technology, Cambridge, MA, USA.
authors.forename: Kami
authors.initials: K
authors.lastname: Koldewyn
authors.affiliation: Athinoula A. Martinos Center for Biomedical Imaging, Department of Radiology, Massachusetts General Hospital, Harvard Medical School, Boston, MA, USA.
authors.forename: Sita
authors.initials: S
authors.lastname: Kakunoori
authors.affiliation: Department of Brain and Cognitive Sciences, Massachusetts Institute of Technology, Cambridge, MA, USA.
authors.forename: Nancy
authors.initials: N
authors.lastname: Kanwisher
authors.affiliation: Athinoula A. Martinos Center for Biomedical Imaging, Department of Radiology, Massachusetts General Hospital, Harvard Medical School, Boston, MA, USA; Computer Science and Artificial Intelligence Laboratory, Massachusetts Institute of Technology, Cambridge, MA, USA.
authors.forename: Bruce
authors.initials: B
authors.lastname: Fischl
mesh_terms: D016477:Artifacts; D000067877:Autism Spectrum Disorder / Q000000981:diagnostic imaging*; D001921:Brain / Q000000981:diagnostic imaging*; D002648:Child; D002675:Child, Preschool; D038524:Diffusion Magnetic Resonance Imaging / Q000592:standards*; D056324:Diffusion Tensor Imaging / Q000592:standards*; D006257:Head; D006801:Humans; D009038:Motion
keywords: Autism; Diffusion MRI; Motion; Tractography