Davidsen, JörnKorchinski, Daniel James2019-05-082019-05-082019-05-02Korchinski, D. J. (2019). The Universal Critical Dynamics of Noisy Neurons (Master's thesis, University of Calgary, Calgary, Canada). Retrieved from https://prism.ucalgary.ca.http://hdl.handle.net/1880/110325The criticality hypothesis posits that the brain operates near a critical point. Typically, critical neurons are assumed to spread activity like a simple branching process and thus fall into the universality class of directed percolation. The branching process describes activity spreading from a single initiation site, an assumption that can be violated in real neurons where external drivers and noise can initiate multiple concurrent and independent cascades. In this thesis, I use the network structure of neurons to disentangle independent cascades of activity. Using a combination of numerical simulations and mathematical modelling, I show that criticality can exist in noisy neurons but that the presence of noise changes the underlying universality class from directed to undirected percolation. Directed percolation describes only small scale distributions of activity, on larger scales cascades can merge together and undirected percolation is the appropriate description.engUniversity of Calgary graduate students retain copyright ownership and moral rights for their thesis. You may use this material in any way that is permitted by the Copyright Act or through licensing that has been assigned to the document. For uses that are not allowable under copyright legislation or licensing, you are required to seek permission.PercolationBranching processNoiseSpontaneous ActivityNeuronsCriticalityCritical phenomenacritical phenomenonCriticality hypothesisBrainPhase transitionDirected percolationScalingFinite sizeNetworksEducation--MathematicsNeuroscienceBiophysicsPhysicsmaster thesis10.11575/PRISM/36501