With the overall goal of illuminating the relationship between neural dynamics and neural network
structure, this thesis presents a) a computer model of a network infrastructure capable of global broadcast
and competition, and b) a study of various convergence properties of spike-timing dependent plasticity
(STDP) in a recurrent neural network.
The first part of the thesis explores the parameter space of a possible Global Neuronal Workspace (GNW)
realised in a novel computational network model using stochastic connectivity. The structure of this
model is analysed in light of the characteristic dynamics of a GNW: broadcast, reverberation, and
competition. It is found even with careful consideration of the balance between excitation and inhibition,
the structural choices do not allow agreement with the GNW dynamics, and the implications of this are
addressed. An additional level of competition – access competition – is added, discussed, and found to be
more conducive to winner-takes-all competition.
The second part of the thesis investigates the formation of synaptic structure due to neural and synaptic
dynamics. From previous theoretical and modelling work, it is predicted that homogeneous stimulation in
a recurrent neural network with STDP will create a self-stabilising equilibrium amongst synaptic weights,
while heterogeneous stimulation will induce structured synaptic changes. A new factor in modulating the
synaptic weight equilibrium is suggested from the experimental evidence presented: anti-correlation due
to inhibitory neurons. It is observed that the synaptic equilibrium creates competition amongst synapses,
and those specifically stimulated during heterogeneous stimulation win out. Further investigation is
carried out in order to assess the effect that more complex STDP rules would have on synaptic dynamics,
varying parameters of a trace STDP model. There is little qualitative effect on synaptic dynamics under
low frequency (< 25Hz) conditions, justifying the use of simple STDP until further experimental or
theoretical evidence suggests otherwise.