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The effect of proximity to pain on protective blink reflexes in individuals with induced hyperalgesia

Macri, Gabriella (2016) The effect of proximity to pain on protective blink reflexes in individuals with induced hyperalgesia. Honours thesis, Murdoch University.

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Abstract

The present study explored the notion that proximity to pain increases protective blink reflexes, and that individuals with chronic pain experience an exacerbation of this effect. Chronic pain sufferers experience a heightened sensitivity to pain (hyperalgesia) and body-space perceptual disturbances. Thus, this study predicted that healthy individuals induced with similar symptoms would have stronger blink reflexes when the stimulated wrist was closer to the face. Adopting a between-subjects design, half of the participants (N = 14) received high-frequency electrical stimulation (HFS) to induce hyperalgesia while the other half of the participants (N = 14) did not. Firstly, participants underwent psychophysical testing on the wrists and forehead to discern baseline sensitivity to stimuli. The HFS condition then completed an electrical detection threshold test to determine the stimulus intensity of the HFS procedure. Following HFS of the wrist, psychophysical testing was repeated to discern changes in sensitivity. Lastly, all twenty-eight participants completed the blink reflex procedure, consisting of a sequence of sixty electrical stimuli applied to the head and the wrist. Independent variables included the position of the wrist (close vs. far), and the site stimulated (head alone, wrist alone, vs. head + wrist together). Dependent variables included pain and sharpness ratings of each stimulus, in addition to the magnitude of the blinks. Results revealed that blink reflexes increased when the wrist was close to the face, confirming the findings of previous literature on proximity to pain. Although the HFS group gave higher sharpness ratings for close stimuli, there was no difference between groups for pain ratings and blinks. Thus, the central premise was not substantiated. Additionally, simultaneous stimulation of the head and the wrist increased all dependent variables; however, this effect did not interact with the proximity effect. Further research should collect a larger sample for more meaningful comparisons between groups.

Publication Type: Thesis (Honours)
Murdoch Affiliation: School of Psychology and Exercise Science
Supervisor: Drummond, Peter
URI: http://researchrepository.murdoch.edu.au/id/eprint/40613
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