title: Multivariate and repeated measures (MRM): A new toolbox for dependent and multimodal group-level neuroimaging data.
abstract: Repeated measurements and multimodal data are common in neuroimaging research. Despite this, conventional approaches to group level analysis ignore these repeated measurements in favour of multiple between-subject models using contrasts of interest. This approach has a number of drawbacks as certain designs and comparisons of interest are either not possible or complex to implement. Unfortunately, even when attempting to analyse group level data within a repeated-measures framework, the methods implemented in popular software packages make potentially unrealistic assumptions about the covariance structure across the brain. In this paper, we describe how this issue can be addressed in a simple and efficient manner using the multivariate form of the familiar general linear model (GLM), as implemented in a new MATLAB toolbox. This multivariate framework is discussed, paying particular attention to methods of inference by permutation. Comparisons with existing approaches and software packages for dependent group-level neuroimaging data are made. We also demonstrate how this method is easily adapted for dependency at the group level when multiple modalities of imaging are collected from the same individuals. Follow-up of these multimodal models using linear discriminant functions (LDA) is also discussed, with applications to future studies wishing to integrate multiple scanning techniques into investigating populations of interest.
authors.affiliation: Neuroscience & Psychiatry Unit, Stopford Building, The University of Manchester, Oxford Road, Manchester M13 9PL, UK. Electronic address: martyn.mcfarquhar@manchester.ac.uk.
authors.forename: Martyn
authors.initials: M
authors.lastname: McFarquhar
authors.affiliation: Neuroscience & Psychiatry Unit, Stopford Building, The University of Manchester, Oxford Road, Manchester M13 9PL, UK.
authors.forename: Shane
authors.initials: S
authors.lastname: McKie
authors.affiliation: Centre for Biostatistics, Jean McFarlane Building, The University of Manchester, Oxford Road, Manchester M13 9PL, UK.
authors.forename: Richard
authors.initials: R
authors.lastname: Emsley
authors.affiliation: Brain Mapping Unit, Herchel Smith Building for Brain and Mind Sciences, University of Cambridge, Robinson Way, Cambridge CB2 0SZ, UK.
authors.forename: John
authors.initials: J
authors.lastname: Suckling
authors.affiliation: Neuroscience & Psychiatry Unit, Stopford Building, The University of Manchester, Oxford Road, Manchester M13 9PL, UK.
authors.forename: Rebecca
authors.initials: R
authors.lastname: Elliott
authors.affiliation: Imaging Sciences, Stopford Building, The University of Manchester, Oxford Road, Manchester M13 9PL, UK.
authors.forename: Stephen
authors.initials: S
authors.lastname: Williams
mesh_terms: D001921:Brain / Q000502:physiology*; D001931:Brain Mapping / Q000379:methods*; D003198:Computer Simulation; D006801:Humans; D007091:Image Processing, Computer-Assisted; D016014:Linear Models; D015999:Multivariate Analysis; D059906:Neuroimaging / Q000379:methods*; D015203:Reproducibility of Results; D012815:Signal Processing, Computer-Assisted; D012984:Software
keywords: Discriminant functions; Multimodal; Multivariate GLM; Permutation; Repeated measures