• Homological scaffolds of brain functional networks

    October 29, 2014 • Publication

    Homological scaffolds of brain functional networks

    Topdrim partners G. Petri, and F. Vacarino from ISI published a new paper with colleagues from the Kings College London and Imperial College London entitled Homological scaffolds of brain functional networks. The paper appeared in the Journal of the Royal Society Interface and is available as open access.


    Networks, as efficient representations of complex systems, have appealed to scientists for a long time and now permeate many areas of science, including neuroimaging (Bullmore and Sporns 2009 Nat. Rev. Neurosci. 10, 186–198. (doi:10.1038/nrn2618)). Traditionally, the structure of complex networks has been studied through their statistical properties and metrics concerned with node and link properties, e.g. degree-distribution, node centrality and modularity. Here, we study the characteristics of functional brain networks at the mesoscopic level from a novel perspective that highlights the role of inhomogeneities in the fabric of functional connections. This can be done by focusing on the features of a set of topological objects—homological cycles—associated with the weighted functional network. We leverage the detected topological information to define the homological scaffolds, a new set of objects designed to represent compactly the homological features of the correlation network and simultaneously make their homological properties amenable to networks theoretical methods. As a proof of principle, we apply these tools to compare resting- state functional brain activity in 15 healthy volunteers after intravenous infusion of placebo and psilocybin—the main psychoactive component of magic mush- rooms. The results show that the homological structure of the brain’s functional patterns undergoes a dramatic change post-psilocybin, characterised by the appearance of many transient structures of low stability and of a small number of persistent ones that are not observed in the case of placebo.

    The paper can be accessed at:

    Petri G, Expert P, Turkheimer F, Carhart-Harris R, Nutt D, Hellyer PJ, Vaccarino F. 2014 Homological scaffolds of brain functional networks. J. R. Soc. Interface 11: 20140873. http://dx.doi.org/10.1098/rsif.2014.0873

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