title: Genetics of Path Lengths in Brain Connectivity Networks: HARDI-Based Maps in 457 Adults.
abstract: Brain connectivity analyses are increasingly popular for investigating organization. Many connectivity measures including path lengths are generally defined as the number of nodes traversed to connect a node in a graph to the others. Despite its name, path length is purely topological, and does not take into account the physical length of the connections. The distance of the trajectory may also be highly relevant, but is typically overlooked in connectivity analyses. Here we combined genotyping, anatomical MRI and HARDI to understand how our genes influence the cortical connections, using whole-brain tractography. We defined a new measure, based on Dijkstra's algorithm, to compute path lengths for tracts connecting pairs of cortical regions. We compiled these measures into matrices where elements represent the physical distance traveled along tracts. We then analyzed a large cohort of healthy twins and show that our path length measure is reliable, heritable, and influenced even in young adults by the Alzheimer's risk gene,CLU.
authors.affiliation: Imaging Genetics Center - Laboratory of Neuro Imaging, Department of Neurology, UCLA School of Medicine, Los Angeles, CA.
authors.forename: Neda
authors.initials: N
authors.lastname: Jahanshad
authors.affiliation: University of Queensland, Centre for Advanced Imaging, Brisbane, Australia.
authors.forename: Gautam
authors.initials: G
authors.lastname: Prasad
authors.affiliation: University of Queensland, School of Psychology, Brisbane, Australia.
authors.forename: Arthur W
authors.initials: AW
authors.lastname: Toga
authors.affiliation: Queensland Institute of Medical Research, Brisbane, Australia.
authors.forename: Katie L
authors.initials: KL
authors.lastname: McMahon
authors.forename: Greig I
authors.initials: GI
authors.lastname: de Zubicaray
authors.forename: Nicholas G
authors.initials: NG
authors.lastname: Martin
authors.forename: Margaret J
authors.initials: MJ
authors.lastname: Wright
authors.forename: Paul M
authors.initials: PM
authors.lastname: Thompson
keywords: Dijkstra’s algorithm; HARDI tractography; Structural connectivity; neuroimaging genetics; path length