UC Irvine

Our brain is made up of multiple levels of network activities that allow an individual to perceive, think, and react to the outside environment. These neuronal networks connect different regions of the brain and often activate synchronously to perform a complex mental activity such as memory formation. Despite such critical nature of the neural network, the fundamental understanding of how these mechanisms are not thoroughly understood. Multielectrode array (MEA) is one of the widely used methods for observing the in vitro neural network activity due to its ability to capture signals from multiple neurons at once. However, it has limited functionality for observing signal propagation from a specific group of stimulated neurons. Electrical stimuli that are given by the MEA are prone to crosstalk and is likely to introduce electrical artifact to the data. Using light to stimulate genetically modified neuron has shown a promising result in terms of spatial resolution as a light signal is relatively free from introducing an electric artifact that compromises the resolution. It also allows us to stimulate a specific group of cells in the same culture by modifying them to respond to a different wavelength. In this light, a device was conceived, designed, constructed, and initially tested that incorporated digital light processing (DLP) projector to MEA to combine the advantages of two different methods; i.e., stimulate neurons with high resolution and acquire data from multiple target sites at once. DLP projector utilizes Light Emitting Diodes (LED) and digital micromirror device (DMD) that can form specific patterns to deliver light to multiple regions simultaneously. The device propagate light reflected off of the DMD towards the cultured neurons, and the induced electrical signal are acquired via electrodes. As this device was designed to have better spatial resolution than systems that only use MEA and be able to induce stimulation on multiple neurons, it allows closer replication of neuron interaction in the brain and provides a deeper understanding of their function.

This thesis has been organized as follow:

Chapter 1 would provide background information by introducing neural network, highlight the neurodegenerative disease, and mention commonly used electrophysiological recording, including intracellular and extracellular methods. Chapter 1 also provide information on the evolution of optical technology in biological studies, development of optogenetics, and what makes it appealing as well as various methods by which light used in optogenetics can be delivered. Chapter 2 goes over the general design, building, and validation of the device as well as the experimental procedure that should be followed to conduct the experiment. Chapter 3 elaborates on the final design of the device as well as results of the light delivery validation and synchronization of the device between the projector and data acquisition device. Finally, Chapter 4 discusses the experiments that should be done to validate the device further as well as the limitation of the current design and the plan for animal testing. After that, it concludes the thesis by mentioning the future outlook on how the device could be implemented in a neural network study and what other question it could help answer.