The effects of astrocyte cell on the neuron dynamics

The glial cells, which are intertwined with approximately 100 billion neurons in the brain and are larger than the number of neurons, have hardly been mentioned in the scientific literature until the 1990s. Glia cells were thought to be support elements to function structurally as neurons. The focus of this study was on the recently reported studies of astrocytes in a subunit of glias, in which the astrocytes are highly in contact with the neurons with their star-like images and the structure surrounding the synaptic space. When astrocytes were stimulated with an external stimulus, instead of action potential, it was found to have a calcium response by producing a neurological information transmission study. Studies on the different aspects of the partner of these newly recognized neurons in the central nervous system are much needed. Simulation studies using computational models are a suitable approach because of technical difficulties of the laboratory investigation of neurological systems in the processing of astrocyte functions. Although it is completely impossible to create a complete mathematical model of the brain, it is quite valuable to support these studies with different structures. In this thesis study, the effects of the parameters controlling the astrocyte were first investigated in order to show the effects of astrocytes on information processing in neuronal systems. Then, the information processing performance of Hodgkin-Huxley neuron with astrocyte was investigated. For this purpose, the H-H neuron is stimulated by a weak signal, which is supposed to carry information, and its response to the noise level in the system is investigated. While this study was performed with and without astrocyte, the effects of astrocytes on information processing performance of neurons were found to be comparative. It has been found that the information processing performance of the neuron shows stochastic resonance effect depending on the noise density. Here, it has been observed that the neuron with astrocyte has significantly increased the information processing performance of the neuron compared to the neuron without astrocytes, in a suitable astrocyte-neuron coupling strength. The results also demonstrate the presence of an optimal weak signal frequency which provides the best detection performance. Finally, calcium and ion channel noise is included in the model. The results also show that the coupling strength that provides optimal information processing caused by the ion channels in astrocytes and ions such as sodium, potassium in the neuron are critically dependent on N-scaled calcium channel noise density.