To understand pain processing requires the assessment of an individual’s perception of pain with temporal stimulation over different periods. Offset analgesia (OA), a phenomenon widely studied, refers to a disproportionate decrease in pain experience following a small reduction in temperature during noxious thermal stimulation. OA leads to skin desensitization, causing brief pain inhibition at the stimulation site and leading to adaptation and a decrease in pain scores. To avoid sensitization and habituation during thermal pain procedures, previous studies have utilized protocols in which the thermal stimulation is applied to different areas of the skin (e.g., upper forearm versus lower forearm). The reliability of this thermal pain calibration procedure in producing a nonadaptive effect has been previously tested using pain rating scales. The utilization of neuroimaging to further elucidate these relationships has not been widely studied, but it is likely an important tool to investigate these constructs. Functional near-infrared spectroscopy (fNIRS) is a noninvasive optical imaging technique that measures changes in hemoglobin (Hb) concentrations within the brain using the characteristic absorption spectra of Hb in the near-infrared range. This thesis investigated whether adaptation exists across four conditions of the OA paradigm using fNIRS. Introducing fNIRS to define significant differences in brain metrics (e.g., activated regions of interest) in participants who have undergone surgery and are experiencing chronic pain as well as healthy, pain-free controls could have implications for more accurate measures of OA and more reliable pain treatment options. In this study, noxious thermal stimulation was given to 19 participants on the forearm of the nondominant hand through a commonly used three-temperature OA paradigm with offset, constant, and control trials. Each OA paradigm consisted of four conditions (A, B, C, and D) with a pseudorandom sequence design of three trials. OA was implemented with the participant while real-time fNIRS data were obtained on the subject’s prefrontal and somatosensory cortices, regions known to be involved in pain processing. Hemoglobin responses during the four OA trials were evaluated and compared within experimental conditions. Repeated measures ANOVA was used to analyze the significant differences among conditions. Results showed no significant differences among the four OA trials. The findings of this thesis study indicated that brain response from the prefrontal and somatosensory cortices is not affected within the four OA trials. The consistent brain activation across multiple trials of stimulation suggests an absence of adaptive responses. In line with previous findings, these results imply the reliability of such thermal pain calibration procedures by fNIRS brain imaging. Further investigation with a larger sample size is likely for the verification of the findings from this study. / 2026-02-14T00:00:00Z
| Identifer | oai:union.ndltd.org:bu.edu/oai:open.bu.edu:2144/48112 |
| Date | 15 February 2024 |
| Creators | Campos, Ana Isabel |
| Contributors | Spencer, Jean L., Seiberg, Christine |
| Source Sets | Boston University |
| Language | en_US |
| Detected Language | English |
| Type | Thesis/Dissertation |
| Rights | Attribution 4.0 International, http://creativecommons.org/licenses/by/4.0/ |
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