title: Lagged and instantaneous dynamical influences related to brain structural connectivity.
abstract: Contemporary neuroimaging methods can shed light on the basis of human neural and cognitive specializations, with important implications for neuroscience and medicine. Indeed, different MRI acquisitions provide different brain networks at the macroscale; whilst diffusion-weighted MRI (dMRI) provides a structural connectivity (SC) coincident with the bundles of parallel fibers between brain areas, functional MRI (fMRI) accounts for the variations in the blood-oxygenation-level-dependent T2(*) signal, providing functional connectivity (FC). Understanding the precise relation between FC and SC, that is, between brain dynamics and structure, is still a challenge for neuroscience. To investigate this problem, we acquired data at rest and built the corresponding SC (with matrix elements corresponding to the fiber number between brain areas) to be compared with FC connectivity matrices obtained by three different methods: directed dependencies by an exploratory version of structural equation modeling (eSEM), linear correlations (C) and partial correlations (PC). We also considered the possibility of using lagged correlations in time series; in particular, we compared a lagged version of eSEM and Granger causality (GC). Our results were two-fold: firstly, eSEM performance in correlating with SC was comparable to those obtained from C and PC, but eSEM (not C, nor PC) provides information about directionality of the functional interactions. Second, interactions on a time scale much smaller than the sampling time, captured by instantaneous connectivity methods, are much more related to SC than slow directed influences captured by the lagged analysis. Indeed the performance in correlating with SC was much worse for GC and for the lagged version of eSEM. We expect these results to supply further insights to the interplay between SC and functional patterns, an important issue in the study of brain physiology and function.
authors.affiliation: Basque Center for Applied Mathematics Bilbao, Spain.
authors.forename: Carmen
authors.initials: C
authors.lastname: Alonso-Montes
authors.affiliation: Biocruces Health Research Institute, Cruces University Hospital Barakaldo, Spain.
authors.forename: Ibai
authors.initials: I
authors.lastname: Diez
authors.affiliation: Basque Center for Applied Mathematics Bilbao, Spain.
authors.forename: Lakhdar
authors.initials: L
authors.lastname: Remaki
authors.affiliation: Biocruces Health Research Institute, Cruces University Hospital Barakaldo, Spain ; Radiology Service, Cruces University Hospital Barakaldo, Spain.
authors.forename: Iñaki
authors.initials: I
authors.lastname: Escudero
authors.affiliation: Biocruces Health Research Institute, Cruces University Hospital Barakaldo, Spain ; Radiology Service, Cruces University Hospital Barakaldo, Spain.
authors.forename: Beatriz
authors.initials: B
authors.lastname: Mateos
authors.affiliation: Department of Data Analysis, Faculty of Psychological and Pedagogical Sciences, Ghent University Ghent, Belgium.
authors.forename: Yves
authors.initials: Y
authors.lastname: Rosseel
authors.affiliation: Department of Data Analysis, Faculty of Psychological and Pedagogical Sciences, Ghent University Ghent, Belgium.
authors.forename: Daniele
authors.initials: D
authors.lastname: Marinazzo
authors.affiliation: Basque Center for Applied Mathematics Bilbao, Spain ; Dipartimento di Fisica, Universitá degli Studi di Bari and INFN Bari, Italy.
authors.forename: Sebastiano
authors.initials: S
authors.lastname: Stramaglia
authors.affiliation: Biocruces Health Research Institute, Cruces University Hospital Barakaldo, Spain ; Ikerbasque, The Basque Foundation for Science Bilbao, Spain ; Department of Cell Biology and Histology, University of the Basque Country Leioa, Spain.
authors.forename: Jesus M
authors.initials: JM
authors.lastname: Cortes
keywords: functional connectivity; functional magnetic resonance imaging; resting state; structural connectivity; structural equation modeling; tensor diffusion imaging