title: Restricted Boltzmann machines for neuroimaging: an application in identifying intrinsic networks.
abstract: Matrix factorization models are the current dominant approach for resolving meaningful data-driven features in neuroimaging data. Among them, independent component analysis (ICA) is arguably the most widely used for identifying functional networks, and its success has led to a number of versatile extensions to group and multimodal data. However there are indications that ICA may have reached a limit in flexibility and representational capacity, as the majority of such extensions are case-driven, custom-made solutions that are still contained within the class of mixture models. In this work, we seek out a principled and naturally extensible approach and consider a probabilistic model known as a restricted Boltzmann machine (RBM). An RBM separates linear factors from functional brain imaging data by fitting a probability distribution model to the data. Importantly, the solution can be used as a building block for more complex (deep) models, making it naturally suitable for hierarchical and multimodal extensions that are not easily captured when using linear factorizations alone. We investigate the capability of RBMs to identify intrinsic networks and compare its performance to that of well-known linear mixture models, in particular ICA. Using synthetic and real task fMRI data, we show that RBMs can be used to identify networks and their temporal activations with accuracy that is equal or greater than that of factorization models. The demonstrated effectiveness of RBMs supports its use as a building block for deeper models, a significant prospect for future neuroimaging research.
authors.affiliation: Mind Research Network, Albuquerque, NM 87106, USA; Department of Computer Science, University of New Mexico, Albuquerque, NM 87131, USA.
authors.forename: R Devon
authors.initials: RD
authors.lastname: Hjelm
authors.affiliation: Mind Research Network, Albuquerque, NM 87106, USA; Department of Computer Science, University of New Mexico, Albuquerque, NM 87131, USA. Electronic address: vcalhoun@mrn.org.
authors.forename: Vince D
authors.initials: VD
authors.lastname: Calhoun
authors.affiliation: Department of Computer Science, University of Toronto, Toronto, ON M5S 2J7, Canada.
authors.forename: Ruslan
authors.initials: R
authors.lastname: Salakhutdinov
authors.affiliation: Mind Research Network, Albuquerque, NM 87106, USA; Department of Biological and Medical Psychology, University of Bergen 5009, Norway.
authors.forename: Elena A
authors.initials: EA
authors.lastname: Allen
authors.affiliation: University of Maryland Baltimore County, Baltimore, MD 21250, USA.
authors.forename: Tulay
authors.initials: T
authors.lastname: Adali
authors.affiliation: Mind Research Network, Albuquerque, NM 87106, USA.
authors.forename: Sergey M
authors.initials: SM
authors.lastname: Plis
mesh_terms: D001921:Brain / Q000502:physiology*; D001931:Brain Mapping / Q000379:methods*; D003627:Data Interpretation, Statistical; D005260:Female; D006801:Humans; D007090:Image Interpretation, Computer-Assisted / Q000379:methods*; D008279:Magnetic Resonance Imaging / Q000379:methods; D009415:Nerve Net / Q000502:physiology*; D016571:Neural Networks, Computer; D010363:Pattern Recognition, Automated / Q000379:methods*; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D013269:Stochastic Processes; D055815:Young Adult
keywords: DBN; ICA; Intrinsic networks; RBM; fMRI