Motion and morphometry in clinical and nonclinical populations.

Introduction: The relationship between participant motion, demographic variables and MRI-derived morphometric estimates was investigated in autism spectrum disorder (ASD), attention deficit hyperactivity disorder (ADHD), schizophrenia and healthy controls. Participant motion was estimated using resting state fMRI and used as a proxy measure for motion during T1w MRI acquired in the same session. Analyses were carried out in scans qualitatively assessed as free from motion-related artifact.

Methods: Whole brain T1-weighted MRI and resting state fMRI acquisitions from the ABIDE, ADHD-200 and COBRE databases were included in our analyses. Motion was estimated using coregistration of sequential resting state volumes. We investigated if motion is related to diagnosis, age and gender, and scanning site. We further determined if there is a relationship between participant motion and cortical thickness, contrast, and volumetric estimates.

Results: 2141 participants were included in our analyses. Participant motion was higher in all clinical groups compared with healthy controls. Younger (age<20years) and older (age>40years) people move more than individuals aged 20-40years. Increased motion is associated with reduced average cortical thickness (-0.014mm thickness per mm motion, p=0.0014) and cortical contrast (0.77% contrast reduction per mm motion, p=2.16×10(-9)) in scans that have been qualitatively assessed as free from motion artifact. Volumetric estimates were also associated with motion, however the relationships were generally weaker than cortical thickness and contrast and were dependent on the segmentation method used.

Conclusions: Participant motion is increased in clinical groups and is systematically associated with morphometric estimates. These findings indicate that accounting for participant motion may be important for improving the statistical validity of morphometric studies.