A unified framework for group independent component analysis for multi-subject fMRI data

• Type of Material: Article
• Authors: Ying Guo, Emory University; Giuseppe Pagnoni, Emory University
• Language: English
• Date: 2008-09-01
• Publisher: Elsevier
• Publication Version: Author Accepted Manuscript (After Peer Review)
• Copyright Statement: © 2008 Elsevier Inc. All rights reserved.
• License: Creative Commons Attribution-NonCommerical-NoDerivs 3.0 Unported
• Final Published Version (URL): http://dx.doi.org/10.1016/j.neuroimage.2008.05.008
• Title of Journal or Parent Work: NeuroImage
• ISSN: 1053-8119
• Volume: 42
• Issue: 3
• Start Page: 1078
• End Page: 1093
• Grant/Funding Information: Y.G. was partially supported by the National Institute of Mental Health (NIH grant R01-MH079251).; The imaging data were collected as part of a pilot study awarded to G.P. by the Emory Center for Research on Complementary and Alternative Medicine in Neurodegenerative Diseases (NIH grant P30-AT00609)
• Keywords: Independent component analysis; Functional magnetic resonance imaging (fMRI); Maximum likelihood estimation; Multi-subject data; EM algorithm; Group comparison; Likelihood ratio test
• Research Categories: Biology, Biostatistics

Abstract

Independent component analysis (ICA) is becoming increasingly popular for analyzing functional magnetic resonance imaging (fMRI) data. While ICA has been successfully applied to single-subject analysis, the extension of ICA to group inferences is not straightforward and remains an active topic of research. Current group ICA models, such as the GIFT (Calhoun et al., 2001) and tensor PICA (Beckmann and Smith, 2005), make different assumptions about the underlying structure of the group spatio-temporal processes and are thus estimated using algorithms tailored for the assumed structure, potentially leading to diverging results. To our knowledge, there are currently no methods for assessing the validity of different model structures in real fMRI data and selecting the most appropriate one among various choices. In this paper, we propose a unified framework for estimating and comparing group ICA models with varying spatio-temporal structures. We consider a class of group ICA models that can accommodate different group structures and include existing models, such as the GIFT and tensor PICA, as special cases. We propose a maximum likelihood (ML) approach with a modified Expectation-Maximization (EM) algorithm for the estimation of the proposed class of models. Likelihood ratio tests (LRT) are presented to compare between different group ICA models. The LRT can be used to perform model comparison and selection, to assess the goodness-of-fit of a model in a particular data set, and to test group differences in the fMRI signal time courses between subject subgroups. Simulation studies are conducted to evaluate the performance of the proposed method under varying structures of group spatio-temporal processes. We illustrate our group ICA method using data from an fMRI study that investigates changes in neural processing associated with the regular practice of Zen meditation.