title: The contribution of geometry to the human connectome.
abstract: The human connectome is a topologically complex, spatially embedded network. While its topological properties have been richly characterized, the constraints imposed by its spatial embedding are poorly understood. By applying a novel resampling method to tractography data, we show that the brain's spatial embedding makes a major, but not definitive, contribution to the topology of the human connectome. We first identify where the brain's structural hubs would likely be located if geometry was the sole determinant of brain topology. Empirical networks show a widespread shift away from this geometric center toward more peripheral interconnected skeletons in each hemisphere, with discrete clusters around the anterior insula, and the anterior and posterior midline regions of the cortex. A relatively small number of strong inter-hemispheric connections assimilate these intra-hemispheric structures into a rich club, whose connections are locally more clustered but globally longer than predicted by geometry. We also quantify the extent to which the segregation, integration, and modularity of the human brain are passively inherited from its geometry. These analyses reveal novel insights into the influence of spatial geometry on the human connectome, highlighting specific topological features that likely confer functional advantages but carry an additional metabolic cost.
authors.affiliation: Systems Neuroscience Group, QIMR Berghofer Medical Research Institute, Herston, QLD 4006, Australia. Electronic address: james.roberts@qimrberghofer.edu.au.
authors.forename: James A
authors.initials: JA
authors.lastname: Roberts
authors.affiliation: Systems Neuroscience Group, QIMR Berghofer Medical Research Institute, Herston, QLD 4006, Australia; Centre for Healthy Brain Ageing (CHeBA), School of Psychiatry, University of New South Wales, Sydney, NSW, Australia; School of Psychiatry, University of New South Wales, Sydney, NSW 2052, Australia.
authors.forename: Alistair
authors.initials: A
authors.lastname: Perry
authors.affiliation: Systems Neuroscience Group, QIMR Berghofer Medical Research Institute, Herston, QLD 4006, Australia; Leibniz Institute for Neurobiology, Magdeburg, Germany.
authors.forename: Anton R
authors.initials: AR
authors.lastname: Lord
authors.affiliation: School of Psychiatry, University of New South Wales, Sydney, NSW 2052, Australia; Black Dog Institute, Prince of Wales Hospital, Hospital Road, Randwick, NSW 2031, Australia.
authors.forename: Gloria
authors.initials: G
authors.lastname: Roberts
authors.affiliation: School of Psychiatry, University of New South Wales, Sydney, NSW 2052, Australia; Black Dog Institute, Prince of Wales Hospital, Hospital Road, Randwick, NSW 2031, Australia.
authors.forename: Philip B
authors.initials: PB
authors.lastname: Mitchell
authors.affiliation: The Florey Institute of Neuroscience and Mental Health, Heidelberg, VIC, Australia.
authors.forename: Robert E
authors.initials: RE
authors.lastname: Smith
authors.affiliation: The Florey Institute of Neuroscience and Mental Health, Heidelberg, VIC, Australia; Department of Medicine, Austin Health and Northern Health, University of Melbourne, Melbourne, VIC, Australia; Florey Department of Neuroscience and Mental Health, University of Melbourne, Melbourne, VIC, Australia.
authors.forename: Fernando
authors.initials: F
authors.lastname: Calamante
authors.affiliation: Systems Neuroscience Group, QIMR Berghofer Medical Research Institute, Herston, QLD 4006, Australia; Metro North Mental Health Service, Royal Brisbane and Women's Hospital, Brisbane, QLD, Australia.
authors.forename: Michael
authors.initials: M
authors.lastname: Breakspear
mesh_terms: D000293:Adolescent; D000328:Adult; D000465:Algorithms; D001921:Brain / Q000033:anatomy & histology*; D063132:Connectome / Q000379:methods*; D003627:Data Interpretation, Statistical; D038524:Diffusion Magnetic Resonance Imaging / Q000379:methods; D005260:Female; D006801:Humans; D007091:Image Processing, Computer-Assisted / Q000379:methods; D008297:Male; D055641:Mathematical Concepts; D008959:Models, Neurological; D009434:Neural Pathways / Q000033:anatomy & histology; D055815:Young Adult