A Dissertation submitted to the Faculty of Health Science, University of the Witwatersrand, Johannesburg, in fulfillment for the degree of Master of Science in Medicine. Johannesburg, 2014 / Differences in pain perception and beliefs have been demonstrated between races and sexes. Beliefs, social influence, psychological factors, and socioeconomic status have been attributed to these differences in pain. There currently are no data on whether sex and racial differences in pain perception and beliefs exist in the South African population. Therefore in this study I evaluated sex and racial differences in pain perception and pain beliefs within a cohort of black and white Southern African university students. Sixty-four black and 56 white female students and 44 black and 52 white male students were recruited from the University of Witwatersrand. Cold pain tolerance was assessed using the cold pressor test, and pressure-pain was assessed using a blunt pressure algometer. Pain intensity was measured after both pain tests and pain tolerance was recorded. Psychological variables and socioeconomic status were evaluated using the Pain Catastrophizing Scale; Hopkins Symptoms Checklist-25; Appropriate Pain Behaviour Questionnaire and the Assessment of Socioeconomic Status questionnaire. Univariate analyses were carried out for all variables, for the comparison of black males against black females; white males against white females; white females against black females, and white males against black males. Regression tree analyses were used to determine the correlates of experimental pain tolerance, pain intensity and pain beliefs, to the variables. Black males and females had a lower tolerance to cold pain (p = 0.01; p < 0.01) compared to white males and females, as well as greater depression (p < 0.01; p = 0.02) and pain catastrophizing (p = 0.03; p < 0.01). In general, females had a lower tolerance to pressure pain (p < 0.01; p < 0.01), as well as greater anxiety (p < 0.01; p < 0.01), depression (p < 0.01; p < 0.01), and pain catastrophizing in black females (p < 0.01). There were no differences in rating of pain intensity for the cold or pressure pain stimuli between the sexes and races, except for black females, who reported greater pain intensity during the cold pain test (p < 0.01). Males and females were more accepting of females expressing pain than men (p < 0.01; p = 0.04). In particular, black males felt men should not express pain (p < 0.01). Regression analyses revealed that pain beliefs on men; pain tolerance; and cold pain intensity were correlated with race and sex difference. In conclusion, pain tolerance and sensitivity to experimental pain were affected by both race and sex in this cohort of black and white South African students. Whilst these data need to be verified in patient cohorts, they have important implications for the assessment and management of pain in South Africa.

Nociception is the encoding and processing of noxious stimuli that is important as a protective mechanism to avoid potential or actual tissue damage. Previously, the neural basis of nociceptive processing was investigated by various neuroimaging techniques that measured neural activities in response to the experimental noxious stimuli. Such noxious stimuli can elicit sudden and short-lasting changes (event related potentials [ERPs], time-locked and phase-locked to the stimuli), and can trigger transient modulations of the ongoing oscillatory brain activity (appearing as event related desynchronization [ERD]/event related synchronization [ERS], time-locked but non-phase-locked to the stimuli). Most investigated pain-related ERPs have been shown to be correlated with subjective pain perception, reflecting the involuntary mechanism of attentional reorientation to a novel stimulus. In addition, pain induced α-ERD/ERS has been repeatedly associated with the administration of noxious stimuli, but their neural functions are still not fully understood. For a better understanding of the neural mechanism of α-ERD in pain perception, we comprehensively investigated changes in alpha oscillatory activities induced by transient and tonic experimental noxious stimuli. First, by applying oddball paradigms composed of auditory, visual, somatosensory, and pain modalities, we evaluated the characteristics of α-ERD and assessed the effective connectivity between P300 and α-ERD across the different sensory modalities. Second, we evaluated the specific neural functions of α-ERD in pain perception by comparing the temporal, spectral and spatial characteristics in response to frequent and infrequent painful stimuli. Third, we investigated changes in oscillatory activities induced by tonic heat by comparing the resting-state, innoxious-distracted, noxious-distracted, and noxious-attended conditions. We demonstrated that regardless of the sensory modalities, P300 and α-ERD were mainly generated from the posterior cingulate cortex and occipital lobe, respectively. The cortical information was consistently found to flow from α-ERD sources to P300 sources. This indicates that both α-ERD and the effective connectivity between the neural generators of P300 and α-ERD induced by the target stimuli were modality-independent, and that P300 was modulated by changes in α-ERD. These findings are useful for exploring the neural mechanism of cognitive information processing in the human brain. Moreover, α-ERD induced by painful stimuli reflected the summary effects of stimulus-related and task-related cortical processing, and could be greatly influenced by variations in the subject’s mental state. Our findings add to the understanding of the multiple neural functions of α-ERD, and could potentially help us more accurately interpret the possible modulation of physiological and/or psychological factors on α-ERD. Furthermore, the change of oscillatory activity in tonic heat pain perception was characterized by a stable and persistent decrease of contralateral-central alpha oscillation power and widespread increase of gamma oscillation power, which were significantly correlated with subjective pain intensity. The observed alpha suppression primarily reflected a top-down attention cognitive process, whereas the widespread gamma enhancement reflected the summary effects of bottom-up stimulus-related and top-down subject-driven cognitive processes. Finally, a theory model comprised of sensory, affective and cognitive modulations was proposed to explain the determinants of modulations of alpha oscillatory activity by pain. / published_or_final_version / Orthopaedics and Traumatology / Doctoral / Doctor of Philosophy

Thesis (MHSc--Health Science) -- Auckland University of Technology, 2003. / Also held in print (136 leaves, ill., 30 cm.) in Akoranga Theses Collection. (T 616.0472 MCC)

Thesis (Ph. D.)--Ohio State University, 2004. / Title from first page of PDF file. Document formatted into pages; contains xvi, 125 p.; also includes graphics. Includes bibliographical references (p. 116-125).

Thesis--University of Wisconsin--Madison. / Typescript. Vita. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references (leaves 134-140).

Thesis (Ph. D. in Psychology)--Washington State University. / Bibliography: leaves 82-86.

Thesis--University of Wisconsin--Madison. / Typescript. Vita. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references (leaves 177-184).

Thesis--Wisconsin. / Vita. Includes bibliographical references (leaves 131-134).

Thesis (M.S.)--University of Wisconsin--Madison. / Typescript. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references (leaves 45-47).

Thesis (M.S.)--University of Wisconsin--Madison, 1972. / eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references.