title: Motion or activity: their role in intra- and inter-subject variation in fMRI.
abstract: Functional MRI (fMRI) carries the potential for non-invasive measurements of brain activity. Typically, what are referred to as activation images are actually thresholded statistical parametric maps. These maps possess large inter-session variability. This is especially problematic when applying fMRI to pre-surgical planning because of a higher requirement for intra-subject precision. The purpose of this study was to investigate the impact of residual movement artefacts on intra-subject and inter-subject variability in the observed fMRI activation. Ten subjects were examined using three different word-generation tasks. Two of the subjects were examined 10 times on 10 different days using the same paradigms. We systematically investigated one approach of correcting for residual movement effects: the inclusion of regressors describing movement-related effects in the design matrix of a General Linear Model (GLM). The data were analysed with and without modeling the residual movement artefacts and the impact on inter-session variance was assessed using F-contrasts. Inclusion of motion parameters in the analysis significantly reduced both the intra-subject as well as the inter-subject-variance.
authors.affiliation: Danish Research Centre for MR, Copenhagen University Hospital, Kettegaard Allé 30, 2650 Hvidovre, Copenhagen, Denmark. torbenl@magnet.drcmr.dk
authors.forename: Torben E
authors.initials: TE
authors.lastname: Lund
authors.forename: Minna D
authors.initials: MD
authors.lastname: Nørgaard
authors.forename: Egill
authors.initials: E
authors.lastname: Rostrup
authors.forename: James B
authors.initials: JB
authors.lastname: Rowe
authors.forename: Olaf B
authors.initials: OB
authors.lastname: Paulson
mesh_terms: D000328:Adult; D016477:Artifacts; D001921:Brain / Q000502:physiology*; D001931:Brain Mapping / Q000379:methods*; D003627:Data Interpretation, Statistical; D006801:Humans; D016014:Linear Models; D008279:Magnetic Resonance Imaging / Q000706:statistics & numerical data*; D008959:Models, Neurological; D009068:Movement / Q000502:physiology*; D011597:Psychomotor Performance / Q000502:physiology; D015203:Reproducibility of Results; D013060:Speech / Q000502:physiology