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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, Am Neuen Palais, Universitaet Potsdam


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.

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