This thesis mainly focuses on the technology development of electrophysiological recording devices and optical stimulation devices for studying the information. How along the neural network in the brain. Specifically, it concentrates on the penetrating microelectrode array and the micro-sized light emitting diode (µLED) coupled glass optrode array for electrophysiological recordings and optogenetic applications respectively. Since a neuron is an electrically excitable cell which is the basic building block of human brain, its electrical activities (spikes) are responsible for functions such as vision, speech, hearing, learning and memory. Therefore, neural recording is one of the efficient ways to understand the relationship between neural activities and brain functions. Devices like microelectrode arrays have been developed to extract the spikes from brain tissue to a read-out electronic system for analysing. In order to identify and sort out spikes generated by a single neuron, the electrode density of the penetrating microelectrode array in this project is about 350 electrodes/mm2. With the 200-µm long needles, the microelectrode array can penetrate the outer layer of sliced brain tissue and contact to the healthy cells underneath. Low impedance electrodes (450 kΩ at 1 kHz) makes the device able to record the small (hundreds of microvolts) extra cellular signals. On the other hand, neuronal modulation is another strategy to investigate the information flows in neural networks. Compared to the electrical stimulation, optogenetics provides an optical modulation to the neurons with high selectivity and spatio temporal resolution.In this project, a µLED array is designed and fabricated as a light source for a coupled optrode array. In terms of the design, the optrode array is able to provide an optical irradiance of about 80 mW/mm2 at the needle tip which is enough to optically excite up to 5500 neurons in the sub-cortical structures. Moreover, the optrode array can provide both deep brain stimulation and superficial illumination of the brain cortex. Besides, multi-site stimulation could also be achieved by lighting up one or more LED elements. During the stimulation, the temperature change can be kept below 1 °C which will not affect neuronal signalling in the cortex.
|Date of Award||28 Aug 2019|
- University Of Strathclyde
|Supervisor||Keith Mathieson (Supervisor) & Ian Watson (Supervisor)|