TY - JOUR
T1 - Hierarchical vector auto-regressive models and their applications to multi-subject effective connectivity
AU - Gorrostieta, Cristina
AU - Fiecas, Mark
AU - Ombao, Hernando
AU - Burke, Erin
AU - Cramer, Steven
PY - 2013/11/12
Y1 - 2013/11/12
N2 - Vector auto-regressive (VAR) models typically form the basis for constructing directed graphical models for investigating connectivity in a brain network with brain regions of interest (ROIs) as nodes. There are limitations in the standard VAR models. The number of parameters in the VAR model increases quadratically with the number of ROIs and linearly with the order of the model and thus due to the large number of parameters, the model could pose serious estimation problems. Moreover, when applied to imaging data, the standard VAR model does not account for variability in the connectivity structure across all subjects. In this paper, we develop a novel generalization of the VAR model that overcomes these limitations. To deal with the high dimensionality of the parameter space, we propose a Bayesian hierarchical framework for the VAR model that will account for both temporal correlation within a subject and between subject variation. Our approach uses prior distributions that give rise to estimates that correspond to penalized least squares criterion with the elastic net penalty. We apply the proposed model to investigate differences in effective connectivity during a hand grasp experiment between healthy controls and patients with residual motor deficit following a stroke.
AB - Vector auto-regressive (VAR) models typically form the basis for constructing directed graphical models for investigating connectivity in a brain network with brain regions of interest (ROIs) as nodes. There are limitations in the standard VAR models. The number of parameters in the VAR model increases quadratically with the number of ROIs and linearly with the order of the model and thus due to the large number of parameters, the model could pose serious estimation problems. Moreover, when applied to imaging data, the standard VAR model does not account for variability in the connectivity structure across all subjects. In this paper, we develop a novel generalization of the VAR model that overcomes these limitations. To deal with the high dimensionality of the parameter space, we propose a Bayesian hierarchical framework for the VAR model that will account for both temporal correlation within a subject and between subject variation. Our approach uses prior distributions that give rise to estimates that correspond to penalized least squares criterion with the elastic net penalty. We apply the proposed model to investigate differences in effective connectivity during a hand grasp experiment between healthy controls and patients with residual motor deficit following a stroke.
KW - Brain effective connectivity
KW - Elastic net
KW - Functional magnetic resonance imaging
KW - Hierarchical models
KW - Multivariate time series
KW - Stroke
KW - Vector auto-regressive model
UR - http://www.scopus.com/inward/record.url?scp=84887886445&partnerID=8YFLogxK
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U2 - 10.3389/fncom.2013.00159
DO - 10.3389/fncom.2013.00159
M3 - Article
AN - SCOPUS:84887886445
SN - 1662-5188
JO - Frontiers in Computational Neuroscience
JF - Frontiers in Computational Neuroscience
IS - NOV
M1 - 159
ER -