David Chik Department of Applied Mathematics, University of New South Wales Global Coherent Activities in Inhibitory Neural Systems Wednesday 5th April 14:05-14:55pm, Carslaw Building Room 373. This talk introduces my PhD research work. It consists of 5 parts: Part One is a brief introduction on the biological background. Part two and three would be a theoretical study on the conditions when the electrical discharges of a large number of neurons are either synchronised or grouped into a few clusters. These phenomena have been observed in the brains of both human beings and animals, and are suggested to function as information binding during various cognitive processes. We pay speical attention on the case of inhibitory coupling. In Part Two we consider a particular firing rate model that admits to an exact analysis. The existence regions for cluster states as a function of the strength and duration of synaptic couplings are explicitly calculated. In Part Three we consider a more biologically realistic model called Hodgkin-Huxley (HH) model. Using reduction techniques and a geometric analysis on the phase plane, we again obtain expressions for the stability of different cluster states. A comparison is made against Part Two. In Part Four and Five, we numerically observe the stochastic synchronies of a population of globally coupled HH neurons. The synchronies are induced through the coherence resonance mechanism, using either noise or chaos. Bell-shaped curves are found in both case, that a maximal synchrony can be achieved in an optimal range of parameter values. In the case of noise, that parameter would be the noise variance (noise intensity); but in the case of chaos, the physical meaning of that parameter is an interesting question.