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The relationship between pain and arousal: The modulation of noxious sensation by the brain’s alerting network

English, Amber (2017) The relationship between pain and arousal: The modulation of noxious sensation by the brain’s alerting network. Honours thesis, Murdoch University.

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The literature indicates that pain is decreased by arousal in healthy individuals. Conversely, arousal has been observed to increase pain in those with chronic pain. The present study explored the relationship between psychological arousal and pain in healthy adults (N=30). To elucidate this interaction, this study utilised an acoustic startle stimulus and electrically-induced pain, while also manipulating stimulus timing. The acoustic startle was presented prior to electrical stimulation, to act as the arousal induction. The reverse stimulus timing, the acoustic startle presented after electrical stimulation, acted as the experimental control. Using a repeated-measures design, timing effects were evaluated according to physiological responses and subjective self-ratings. The main hypothesis was that the presentation of the acoustic startle before electrical stimulation would result in significantly lower pain ratings, in comparison to electrical stimulation alone. Not only was this inhibitory effect supported but it extended to both pain and sharpness ratings, in comparison to the reverse stimulus timing. In line with predictions, pupillary responses supported that there was adequate physiological arousal in all conditions. Contradictory to predictions, stimulus timing did not significantly alter pupillary responses or spinal nociceptive reflexes. These physiological outcomes were inconsistent with the interaction found between stimulus timing and participant ratings. Additionally, Pain Catastrophizing did not correlate with the other pain measures and thus was not included in the other analyses. Together, these findings suggest that prior activation of arousal significantly inhibits the experience of pain in healthy individuals’, at a purely supra-spinal level.

Keywords: pain, nociception, arousal, descending inhibition, spinal reflex, pupillometry

Item Type: Thesis (Honours)
Murdoch Affiliation(s): School of Psychology and Exercise Science
Supervisor(s): Drummond, Peter
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