Dissertation

Growth and Guidance: A Study of Neuron Morphology and How It Is Modified by Fractal and Euclidean Electrodes In Vitro

Rowland, Conor Tye

2023

Overview

For well over a century, neuroscientists have been studying the inherent ties between neuronal morphology and functionality. Santiago Ramón y Cajal, in his work that ultimately awarded him a Nobel Prize in 1906, established that neurons function as the fundamental unit of the nervous system. Ramón y Cajal himself recognized the relationship between neuronal form and function by proposing the wiring economy principle, which states that the nervous system’s complex network of neurons is efficiently wired in a way that minimizes wiring length. The research within this dissertation works towards the goal of optimizing the design of the electrode-neuron interface of medical implants by building upon Ramón y Cajal’s foundational ideas and integrating them with the techniques of fractal analysis.The dissertation begins by addressing the question of how electrode geometry impacts the morphology of the networks of neurons and glia interfacing with the electrode. This was done by interacting dissociated mouse retinal cell cultures in vitro with vertically aligned carbon nanotube (VACNT) electrodes grown on a silicon dioxide (SiO2) substrate and patterned into Euclidean and fractal geometries. The VACNT-SiO2 material system was shown to perform exceptionally well at guiding neurons onto the VACNTs and glia onto the surrounding SiO2. Furthermore, the electrode geometries that performed the best at supporting a healthy network of neurons and glia were those that balanced providing a large VACNT electrode area with maintaining connectedness in the surrounding SiO2 surface and allowing it to interpenetrate the VACNT electrode.Following these in vitro experiments, three-dimensional models of pyramidal neurons from the CA1 region of the rat hippocampus were reconstructed using confocal microscopy. The fractal properties of the neurons and how these relate to their functionality were then analyzed. It was then demonstrated that the natural, fractal behavior of the neurons, though limited in its scaling range, was sufficient to provide the neurons with an optimal balance between connectivity and building and operating costs.The dissertation concludes by reviewing the results of these studies, providing directions for future work, and discussing the implications regarding electrode design.This dissertation includes previously published co-authored material.

• Publisher: ProQuest Dissertations & Theses
• Subject: Biophysics / Neurosciences / Physics
• ISBN: 9798379447465