title: Motion correction and the use of motion covariates in multiple-subject fMRI analysis.
abstract: The impact of using motion estimates as covariates of no interest was examined in general linear modeling (GLM) of both block design and rapid event-related functional magnetic resonance imaging (fMRI) data. The purpose of motion correction is to identify and eliminate artifacts caused by task-correlated motion while maximizing sensitivity to true activations. To optimize this process, a combination of motion correction approaches was applied to data from 33 subjects performing both a block-design and an event-related fMRI experiment, including analysis: (1) without motion correction; (2) with motion correction alone; (3) with motion-corrected data and motion covariates included in the GLM; and (4) with non-motion-corrected data and motion covariates included in the GLM. Inclusion of covariates was found to be generally useful for increasing the sensitivity of GLM results in the analysis of event-related data. When motion parameters were included in the GLM for event-related data, it made little difference if motion correction was actually applied to the data. For the block design, inclusion of motion covariates had a deleterious impact on GLM sensitivity when even moderate correlation existed between motion and the experimental design. Based on these results, we present a general strategy for block designs, event-related designs, and hybrid designs to identify and eliminate probable motion artifacts while maximizing sensitivity to true activations.
authors.affiliation: Waisman Laboratory for Brain Imaging and Behavior, University of Wisconsin-Madison, Madison, Wisconsin 53705, USA. itjohnstone@wisc.edu
authors.forename: Tom
authors.initials: T
authors.lastname: Johnstone
authors.forename: Kathleen S
authors.initials: KS
authors.lastname: Ores Walsh
authors.forename: Larry L
authors.initials: LL
authors.lastname: Greischar
authors.forename: Andrew L
authors.initials: AL
authors.lastname: Alexander
authors.forename: Andrew S
authors.initials: AS
authors.lastname: Fox
authors.forename: Richard J
authors.initials: RJ
authors.lastname: Davidson
authors.forename: Terrence R
authors.initials: TR
authors.lastname: Oakes
mesh_terms: D000293:Adolescent; D000328:Adult; D016477:Artifacts; D001921:Brain / Q000502:physiology*; D001931:Brain Mapping; D005260:Female; D006801:Humans; D007091:Image Processing, Computer-Assisted / Q000379:methods*; D008279:Magnetic Resonance Imaging; D008297:Male; D008875:Middle Aged; D008962:Models, Theoretical; D009068:Movement; D012680:Sensitivity and Specificity