Markov models for fMRI correlation structure: is brain functional connectivity small world, or decomposable into networks?

Abstract : Correlations in the signal observed via functional Magnetic Resonance Imaging (fMRI), are expected to reveal the interactions in the underlying neural populations through hemodynamic response. In particular, they highlight distributed set of mutually correlated regions that correspond to brain networks related to different cognitive functions. Yet graph-theoretical studies of neural connections give a different picture: that of a highly integrated system with small-world properties: local clustering but with short pathways across the complete structure. We examine the conditional independence properties of the fMRI signal, i.e. its Markov structure, to find realistic assumptions on the connectivity structure that are required to explain the observed functional connectivity. In particular we seek a decomposition of the Markov structure into segregated functional networks using decomposable graphs: a set of strongly-connected and partially overlapping cliques. We introduce a new method to efficiently extract such cliques on a large, strongly-connected graph. We compare methods learning different graph structures from functional connectivity by testing the goodness of fit of the model they learn on new data. We find that summarizing the structure as strongly-connected networks can give a good description only for very large and overlapping networks. These results highlight that Markov models are good tools to identify the structure of brain connectivity from fMRI signals, but for this purpose they must reflect the small-world properties of the underlying neural systems.
Complete list of metadatas

Cited literature [77 references]  Display  Hide  Download

https://hal.inria.fr/hal-00665340
Contributor : Gaël Varoquaux <>
Submitted on : Friday, February 3, 2012 - 5:35:30 PM
Last modification on : Friday, July 26, 2019 - 1:12:03 PM
Long-term archiving on : Friday, May 4, 2012 - 3:05:17 AM

Files

paper.pdf
Files produced by the author(s)

Identifiers

Collections

Citation

Gaël Varoquaux, Alexandre Gramfort, Jean Baptiste Poline, Bertrand Thirion. Markov models for fMRI correlation structure: is brain functional connectivity small world, or decomposable into networks?. Journal of Physiology - Paris, Elsevier, 2012, 106, pp.212-221. ⟨10.1016/j.jphysparis.2012.01.001⟩. ⟨hal-00665340v2⟩

Share

Metrics

Record views

2551

Files downloads

806