Specialeforsvar af Jessica Y. Zhou – Niels Bohr Institute - University of Copenhagen

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Specialeforsvar af Jessica Y. Zhou

In this thesis, a theoretical, computer-simulated model of neural networks in the spinal cord is studied.

The network described in the model is inhomogeneous, with random connectivity and single-neuron parameters distributed around their central values. Both excitatory and inhibitory neurons are contained in the network, which also receives input neurons from external environments. All these neurons are connected to each other via synapses, modelled as synaptic conductances. To make the model more biologically realistic, the neurons are divided into two compartments - soma and dendrite.

The neurons fire during network activity. We measure population firing rates and membrane potentials of single neurons selected randomly. Because the neuronal parameters in the inhomogeneous network can be spread to large or small extents by a so-called ``spread factor" - denoting varying degrees of inhomogeneity, firings are investigated for different values of the spread factor, and the value for which the firing pattern is most like experimental observations is determined. We also explore the cases where the sodium and potassium conductances are knocked out in some neurons. The results are compared with corresponding cases in the so-called BRK model for a single neuron. Furthermore, correlations and power spectra of firing rates and membrane potentials are computed. Finally, the mechanism responsible for the generation of irregular spiking in the 20-Hz frequency range is analysed."