Volume 8 Supplement 2
Exploring sparse connectivity in the motor system using multivariate autoregression analysis
© Rodriguez-Rojas et al; licensee BioMed Central Ltd. 2007
Published: 6 July 2007
Multivariate autoregressive (MAR) models can be used in the identification of causal relations from functional MRI time series. Connectivity information is extracted from large neural networks combining graphical modeling methods and Granger causality. The aim of this paper is to demonstrate the feasibility of working with the MAR models to identify functional circuits in the human motor system, and demonstrates their application to data of motor performance in patients with Parkinson's disease (PD).
In this work we incorporate a family of linear methods called penalized linear regression that were designed to deal with problems having a large set of variables (i.e. brain structures) and a relatively small set of observations (i.e. fMRI time points). One parkinsonian patient with early stage akinetic PD was studied by fMRI during the "drug-off" state and after reaches the "drug-on" state (table 1).
Effects of L-Dopa treatment on strength of inter-regional path coefficients
ASC – PRE
TAL – PM
TAL – SMA
STR – TAL
TAL – SMA
In opposition to widely spread methods for connectivity analysis, the proposed algorithm does not rely on preconditioned connections between regions from anatomical models. The penalized regression techniques expand the basic idea of ordinary least squares by means of the addition of new terms to the minimization equation. Our results support that MAR models form a valuable and feasible approach to study functional circuits in the human motor system, in normal and disease condition.
This article is published under license to BioMed Central Ltd.