title: Topological characterization of neuronal arbor morphology via sequence representation: I--motif analysis.
abstract: BACKGROUND
  The morphology of neurons offers many insights into developmental processes and signal processing. Numerous reports have focused on metrics at the level of individual branches or whole arbors; however, no studies have attempted to quantify repeated morphological patterns within neuronal trees. We introduce a novel sequential encoding of neurite branching suitable to explore topological patterns.
  
  
  RESULTS
  Using all possible branching topologies for comparison we show that the relative abundance of short patterns of up to three bifurcations, together with overall tree size, effectively capture the local branching patterns of neurons. Dendrites and axons display broadly similar topological motifs (over-represented patterns) and anti-motifs (under-represented patterns), differing most in their proportions of bifurcations with one terminal branch and in select sub-sequences of three bifurcations. In addition, pyramidal apical dendrites reveal a distinct motif profile.
  
  
  CONCLUSIONS
  The quantitative characterization of topological motifs in neuronal arbors provides a thorough description of local features and detailed boundaries for growth mechanisms and hypothesized computational functions.
authors.affiliation: Department of Molecular Neuroscience, Center for Neural Informatics, Structures, and Plasticity, Krasnow Institute for Advanced Study (MS2A1), George Mason University, Fairfax, VA, USA. todd.gillette@gmail.com.
authors.forename: Todd A
authors.initials: TA
authors.lastname: Gillette
authors.affiliation: Department of Molecular Neuroscience, Center for Neural Informatics, Structures, and Plasticity, Krasnow Institute for Advanced Study (MS2A1), George Mason University, Fairfax, VA, USA. ascoli@gmu.edu.
authors.forename: Giorgio A
authors.initials: GA
authors.lastname: Ascoli
mesh_terms: D020816:Amino Acid Motifs / Q000235:genetics*; D000818:Animals; D001369:Axons / Q000502:physiology*; D001483:Base Sequence; D003712:Dendrites / Q000502:physiology*; D051379:Mice; D008969:Molecular Sequence Data; D016501:Neurites / Q000502:physiology*; D009474:Neurons / Q000166:cytology / Q000502:physiology*; D011712:Pyramidal Tracts / Q000166:cytology*