ORCID Identifier(s)

0000-0001-7809-2994

Graduation Semester and Year

2016

Language

English

Document Type

Dissertation

Degree Name

Doctor of Philosophy in Biomedical Engineering

Department

Bioengineering

First Advisor

Hanli Liu

Abstract

Neural representations of chronic pain are complex and are least understood. Numerous magnetic resonance imaging (MRI) studies have revealed structural and functional abnormalities in several cortical and sub-cortical regions in subjects with chronic low-back pain (CLBP). A more recent MRI study has reported that structural and functional brain abnormalities in pain-treated patients with CLBP are reversible, demonstrating that an appropriate treatment of chronic pain can restore normal brain functions for the patients. Due to high cost, non-portability, and other restrictions of MRI, the development of a complementary brain imaging tool is therefore crucial in order to improve the understanding of neural representations of CLBP and to assess potential brain plasticity resulting from physical or pharmacological treatment of CLBP. Functional near-infrared spectroscopy (fNIRS) has been extensively used more than 20 years to investigate functional brain activities in subjects with and/or without neurological disorders. To date, however, fNIRS has not been utilized to study neural correlates of either chronic pain or CLBP. Therefore, the goal of my dissertation was (1) to examine whether or not noxious and innocuous thermal pain can be objectively measured and discriminated by fNIRS taken in the frontal cortical regions of healthy subjects, and (2) to utilize fNIRS as an objective imaging modality to explore pain-induced hemodynamic activities and resting-state brain functional connectivity in all cortical regions of normal subjects and subjects with CLBP, as well as to reveal any characteristic distinctions in such hemodynamic signals between the two groups. In my dissertation, for Aim 1, I demonstrated the feasibility of fNIRS for mapping neural correlates of selective attention and interference in the prefrontal cortex of subjects with post-traumatic stress disorder, using the linear general model. For Aim 2, I quantified, analyzed and discriminated frontal cortical hemodynamic signals in response to two levels of thermal pain, so the feasibility of using fNIRS to study neural correlates of acute thermal pain in healthy participants was reported. For Aim 3, I quantified robust temporal and spatial characteristics of hemodynamic responses in the prefrontal cortex during noxious thermal pain, induced by thermal-stimulations over three different body regions. For Aim 4, by utilizing a 133-channel fNIRS brain imager, I mapped and characterized pain-induced neural correlates in the whole cortex of normal older adults and age- and gender-matched CLBP patients, and I also observed restoration of normal brain functions in CLBP subjects after a four-week exercise treatment. For the last aim, I applied the group-level independent component analysis to the 133-channel fNIRS hemodynamic signals taken at resting state over control and CLBP subjects and successfully identified four resting-state functional networks, consistently among the pre-exercise CLBP and healthy subjects. The conclusion was that the connectivity of default mode network of subjects with CLBP is compromised due to chronic pain.

Keywords

Chronic low back pain, Functional near-infrared spectroscopy, Independent component analysis, Resting-state functional networks, Exercise treatment

Disciplines

Biomedical Engineering and Bioengineering | Engineering

Comments

Degree granted by The University of Texas at Arlington

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