Simple Processes in Complex Places.

Adult Neurogenesis;Voter Model;Complex Networks;Glioblastoma;Physics;Science;Physics

Schneider-Mizell, Casey M.Zochowski, Michal R. ;

University of Michigan

关键词: Adult Neurogenesis;    Voter Model;    Complex Networks;    Glioblastoma;    Physics;    Science;    Physics;   

Others  :  https://deepblue.lib.umich.edu/bitstream/handle/2027.42/77828/caseysm_1.pdf?sequence=1&isAllowed=y

瑞士|英语

来源: The Illinois Digital Environment for Access to Learning and Scholarship

【 摘 要 】

Identical stochastic processes in different topologies can exhibit qualitatively distinct behavior. In complex environments, such as social or neuronal networks, rich structural details can lead to very different outcomes than occur in Euclidian lattices. In this dissertation, I use three relatively simple systems to explore the interaction between process and environment. First, I consider consensus times for two cases of the voter model, a non-equilibrium stochastic process with similarities to neutral spread of genes, opinions, and species. In one case, layers of states are coupled to one another. Long times scales emerge as a result of weak coupling. In the other case, I consider a generalization of the voter model that allows the role of network heterogeneity to be tuned. On power-law networks, the process contains three regimes as the high degree nodes become more important: one dominated by diffusive fluctuations, one dominated by exponential spread, and one in which local fluctuations in network structure induce long-lasting frustrated states. Next, I consider pattern formation of glioblastoma multiforme, a type of brain cancer characterized by its tendency to migrate into the brain and form secondary tumors. We use in vitro experiments to look at clustering on surfaces and invasion and migration in three dimensional collagen gels. We suggest that phenomenological changes in cell-cell adhesion can create clustering behavior in a manner similar to the Ising model. This effect, especially in three dimensional gels, is highly dependent on substrate adhesion and cell-induced reorganization. Finally, I study adult neurogenesis as a dynamical network. New cells are born into the adult mammalian hippocampus throughout life, and their integration and survival is promoted by firing activity in their local network. This creates a network with constant turnover of cells, thought to be organized to help memory and learning formation. We use a simple model to explore how the structure of the established network can influence the outcome of neurogenic reorganization. Small-world networks are better able to maintain functional specificity than either more global or local topologies.