title: Temporal relation between the ADC and DC potential responses to transient focal ischemia in the rat: a Markov chain Monte Carlo simulation analysis.
abstract: Markov chain Monte Carlo simulation was used in a reanalysis of the longitudinal data obtained by Harris et al. (J Cereb Blood Flow Metab 20:28-36) in a study of the direct current (DC) potential and apparent diffusion coefficient (ADC) responses to focal ischemia. The main purpose was to provide a formal analysis of the temporal relationship between the ADC and DC responses, to explore the possible involvement of a common latent (driving) process. A Bayesian nonlinear hierarchical random coefficients model was adopted. DC and ADC transition parameter posterior probability distributions were generated using three parallel Markov chains created using the Metropolis algorithm. Particular attention was paid to the within-subject differences between the DC and ADC time course characteristics. The results show that the DC response is biphasic, whereas the ADC exhibits monophasic behavior, and that the two DC components are each distinguishable from the ADC response in their time dependencies. The DC and ADC changes are not, therefore, driven by a common latent process. This work demonstrates a general analytical approach to the multivariate, longitudinal data-processing problem that commonly arises in stroke and other biomedical research.
authors.affiliation: RCS Unit of Biophysics, Institute of Child Health, University College, London, UK. M.King@inc.ucl.ac.uk
authors.forename: Martin D
authors.initials: MD
authors.lastname: King
authors.forename: Martin J
authors.initials: MJ
authors.lastname: Crowder
authors.forename: David J
authors.initials: DJ
authors.lastname: Hand
authors.forename: Neil G
authors.initials: NG
authors.lastname: Harris
authors.forename: Stephen R
authors.initials: SR
authors.lastname: Williams
authors.forename: Tihomir P
authors.initials: TP
authors.lastname: Obrenovitch
authors.forename: David G
authors.initials: DG
authors.lastname: Gadian
mesh_terms: D000818:Animals; D002560:Cerebrovascular Circulation / Q000502:physiology*; D003198:Computer Simulation; D002546:Ischemic Attack, Transient / Q000503:physiopathology*; D008137:Longitudinal Studies; D008390:Markov Chains; D008955:Models, Cardiovascular; D051381:Rats