Ji Wei He

Graduation Semester and Year

2010

Language

English

Document Type

Dissertation

Degree Name

Doctor of Philosophy in Psychology

Department

Psychology

First Advisor

Yuan Bo Peng

Abstract

Neuroimaging technologies have been widely used to study brain functioning based on a tight correlation between neurons and neighboring vasculature during neural activation, called neurovascular coupling. However, many studies suggested some degree of uncoupling. Optical techniques are unique tools to directly measure tissue oxygen dynamics and other physiological parameters to reflect local metabolism. The objective of my dissertation was to seek for biomarkers of pain in the brain and spinal cord. Two distinct optical methods were used in an in vivo rat model, including a diffuse optical imager to monitor the whole brain-scaled hemodynamics and a fiber optic system to detect focal hemodynamics and light scattering alternation in the spinal cord and primary somatosensory cortex (SI). Results were summarized in four manuscripts, which were reorganized into four chapters in this report. In particular, Chapters 1 and 2 focused on hemodynamic signatures of formalin- and mechanical pinch-induced nociception (i.e. an objective description of pain perception) over a whole rat brain, respectively. Chapter 3 described a validation of the fiber optic system in a periphery inflammation model. Finally, Chapter 4 discussed functional significances of multiple physiological parameters collected by the fiber optical system. In conclusion, hemodynamic signatures of nociception tended to be stimulus- and brain region-dependent. A brief noxious stimulus tended to induce a regional hyperemia, whereas a decrease in regional oxygen saturation rate (i.e. the proportion of oxy-hemoglobin concentration in total-hemoglobin concentration) tended to be a reliable indicator of sustained nociception in the spinal cord and SI. Moreover, over a whole brain, a noxious stimulus tended to induce a different pattern of hemodynamics, from which was shown during innocuous somatosensory stimulation and reported by other studies with visual stimulation and motor tasks. As hemodynamic parameters reflect a balance of oxygen supply and consumption from different aspects, optical methods provide multiple reliable measures of local metabolism during neural activation, especially in pain processing; they will benefit our understanding of brain functioning.

Disciplines

Psychology | Social and Behavioral Sciences

Comments

Degree granted by The University of Texas at Arlington

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