THESIS COMMITTEE:

Solomon Diamond, PhD  (Chair)

Brian Pogue, PhD

Erik Kobylarz, MD, PhD

Joseph Culver, PhD

ABSTRACT

This project focuses on the development of research tools and methods that are used to study the relationship between neural activity and subsequent hemodynamic responses in the human brain. This relationship, referred to as neurovascular coupling, involves complex interactions between neurons, glial cells and vascular endothelial cells. Noninvasive functional neuroimaging studies that combine multiple modalities can be used to study neurovascular coupling as a lumped input-output system and to map out its characteristics in various populations.

In the present work, we have developed a noninvasive head probe that combines near infrared spectroscopy (NIRS) and electroencephalography (EEG) to monitor and record neurovascular brain activity with whole head coverage. It is low cost, easy to use, fabricate, and assemble, and is de- signed and manufactured for compatibility with magnetic resonance imaging (MRI) and magnetoen- cephalography (MEG). In addition, we have devoted significant efforts towards design optimization of the components to maximize performance metrics, such as electrical and optical connectivity, and positioning accuracy and precision, and to minimize the problems that are usually present in these systems, such as mechanical stability or reusability. Specifically, we have designed and manufactured five distinct head probe prototypes and four EEG electrode prototypes. We have also developed simulation software to optimize NIRS optode design and probe design software to automatically compute the 3-dimensional coordinates of all electrode and optode positions on a surface mesh of a head from four fiducial positions. Finally, we completed an analysis of joint forward and inverse models for combined EEG and NIRS following the positions calculated with our software. The forward and inverse models contain the necessary data to perform tomographic reconstructions of measurement data recorded using the NIRS-EEG head probe. They also show the correspondence between the sensitivity of EEG and NIRS to the brain.

The research tools developed in this project provide an integrated human interface and software tools for the investigation of the fundamental questions regarding neurovascular coupling using multimodal EEG and NIRS.