Nishant Malik, Center for Dynamics of Complex Systems, University of Potsdam Title: Noise induced firing and synchronization in coupled type I neurons DFG Graduate School 1364 Time: September 10, 2008, 1:30 pm Place: Building 22.214.171.124, Am Neuen Palais, Universitaet Potsdam Abstract: A study of noise induced synchronization phenomena in neural firing activity of coupled Type-I spiking neurons is presented .The model used is a generic system of oscillators supporting saddle node bifurcation on an invariant circle called the theta neuron . Coupling is realized through a gating variable and a set of parameters describing its coupling strength and synapse type. The gating variables are governed by feedback equations which depend upon the output of the neurons they couple. We study both bidirectional and unidirectional coupling configurations with different combinations of synapses. Using various techniques of nonlinear dynamics, we study the rich dynamical structure of the emergent collective behaviour of the coupled neuronal system. We observe that introducing common white noise to this system induces synchronous activity in it. We have made use of Hilbert transforms and statistical interpretation of phase differences in the presence of noise to show phase synchronization in some of the cases where complete synchronization was found to be elusive. We have also found that noise can increase the rate of firing . We calculate Lyapunov exponents for the system in the presence of noise which gives us insights into the combinations of synaptic strengths and couplings required for the neurons to undergo complete synchronization. In a simulation of a neuronal ensemble containing 200 theta neurons with 150 excitatory and 50 inhibitory synapses and with all to all coupling, we have shown synchronous firing of all the neurons on introduction of weak white noise.