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Simulation of the Self-organized Critical Models on the
Human’s Brain Network

Shokouhi, Fatemeh | 2017

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 49936 (04)
  4. University: Sharif University of Technology
  5. Department: Physics
  6. Advisor(s): Moghimi Araghi, Saman
  7. Abstract:
  8. Self-organized critical phenomena are interesting phenomena which are ubiquitous in nature. Examples include mountain ranges , coastlines and also activities in the hu-man's brain. In these processes, without fine-tuning of any external parameter such as the temperature, the system exhibits critical behavior. In other words, the dynamics of the system, drives it towards an state in which long range correlations in space and scaling behaviors can be seen.The first successful model which could characterize such systems was BTW model, introduced by Bak , Tang and Wiesenfeld in 1987. This model, later named Abelian sandpile model, was very simple and because of this simplicity, a large amount of ana- lytical and numerical work has been done on it. One of the interesting systems which seems to exhibit scaling behaviors is the brains system. Beggs and Plenz has shown that the brain's activities exhibit scaling behaviors and concluded that the brain is in a critical state. On the other hand, numerous work has been done to obtain a simplified version of actual network of human brain. In the Connectome project, the human's brain is divided into about 1000 regions. Using fMRI technique, the connections between these regions were obtained. In other words, they have extracted the adjacency matrix of the different regions of the brain. In this research, we have simulated some variations of the sandpile models on the brain's network to investigate its critical behavior. Because the network of connectome is a small one and has only 1000 nodes, investigation of critical properties is hard. Therefore we have constructed large networks which are in many aspects similar to connectome : they are hierarchichal networks with high efficiency. We studied the sandpile models on these networks and found that the avalanche size distribution fol-lows a power law with an exponent 1.8 which could be in agreement with the Beggs and Plenzs experimental results of the criticality of the human's brain
  9. Keywords:
  10. Brain ; Sand Pile Model ; Hierarchical Structure ; Self Organized Criticality ; Connectome Network

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