ORCID Profile
0000-0002-5357-4062
Current Organisations
University of Cape Town
,
KU Leuven
,
University of South Australia
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Publisher: Elsevier BV
Date: 02-2021
Publisher: Public Library of Science (PLoS)
Date: 14-10-2020
Publisher: Oxford University Press (OUP)
Date: 14-12-2016
DOI: 10.1093/PM/PNV044
Abstract: Clinical scenarios of repeated pain usually involve both nociceptive and non-nociceptive input. It is likely that associations between these stimuli are learned over time. Such learning may underlie subsequent lification of pain, or evocation of pain in the absence of nociception. We undertook a systematic review and meta-analysis to evaluate the evidence that allodynia or hyperalgesia can be a classically conditioned response. A sensitive search of the literature covered Medline, Embase, CINAHL, AMED, PubMed, Scopus, PsycArticles, PsycINFO, Cochrane Library, and Web of Science. Additional studies were identified by contacting experts and searching published reviews. Two reviewers independently assessed studies for inclusion, evaluated risk of bias, and extracted data. Studies were included if they aimed to elicit or lify pain using a classical conditioning procedure in healthy, adult humans. Studies were excluded if they did not distinguish between classical conditioning and explicit verbal suggestion as learning sources, or did not use experiential learning. Thirteen studies, with varying risk of bias, were included. Ten studies evaluated classically conditioned hyperalgesia: nine found hyperalgesia one did not. Pooled effects (n = 8 with full data) showed a significant pain increase after conditioning (mean difference of 7.40 [95%CI: 4.00-10.80] on a 0-100 pain scale). Three studies evaluated conditioned allodynia and found conflicting results. The existing literature suggests that classical conditioning can lify pain. No conclusions can be drawn about whether or not classical conditioning can elicit pain. Rigorous experimental conditioning studies with nociceptive unconditioned stimuli are needed to fill this gap in knowledge.
Publisher: AOSIS
Date: 24-02-2020
Publisher: Elsevier BV
Date: 08-2019
Publisher: AOSIS
Date: 19-02-2009
Abstract: Background: The goals of a chronic pain management clinic includeincreasing patient knowledge about pain, developing pain management skillsand increasing patients’ confidence in their pain management abilities.A Chronic Pain Management Programme (CPMP) based on evidence basedguidelines was developed at a chronic pain management clinic to facilitatepatient discharge to a primary healthcare level. Aim: The aim of this study was to explore patient satisfaction with, acceptability of and the perceived success which could be due to the CPMP developed at the Chronic Pain Management Clinic of Groote Schuur Hospital,Cape Town.Methods: Patients (n=14) were referred to the pilot study from the Chronic Pain Management Clinic. A s a pilot, four courses were run over a period ofone year. In order to reach the research aim, an eleven-question, structuredopen-ended interview was conducted with all participants. Results: Fourteen patients enrolled in the CPMP. Responses were favourable with participants emphasising the roleof increased knowledge about pain, the role of exercise and of stress management techniques. Participants also recog-nised a positive change in behaviours and attitudes following participation in the CPMP.Conclusions: Findings suggest that participants found the format of the course acceptable as regards course content,structure and delivery. Participant responses suggest that the course was acceptable and perceived as useful. However,future courses would benefit from refresher courses or structured support groups.
Publisher: Elsevier BV
Date: 06-2021
DOI: 10.1016/J.JPAIN.2021.01.004
Abstract: We tested the hypotheses that rendering sensory input about hand location imprecise increases a classically conditioned pain expectancy effect, increases generalization of the effect to novel locations and reduces extinction of the effect. Forty healthy volunteers performed movements with their right hand along predefined paths. Each path passed through 2 locations that were defined as either i) the conditioned stimulus (CS+ paired with a painful unconditioned stimulus), or ii) unpaired (CS-). During acquisition phase, participants watched their hand as they moved it. Participants were randomly allocated to an Imprecise group, for whom visual feedback of the hand was offset 30 to 50 mm from its true location, or a Precise group, for whom vision was not disrupted. In the test phase, participants moved their hands to 5 locations-the CS+, CS-, and 3 locations that lay between the 2 ("generalization stimuli"). Our primary hypothesis was supported-pain expectancy was greater at the CS+ location in the Imprecise group than in the Precise group (6.9 [SD = 1.9] vs 5.4 [SD = 2.5], P= .02). Pain expectancies generalized to novel locations similarly in both groups and there was no difference in extinction between groups. Our primary hypothesis was supported but our subsequent hypotheses were not. PERSPECTIVE: We conditioned pain expectancy at a certain location of one hand, even though most participants were unaware of the contingency. Conditioned pain expectancy was greater when sensory information about location was less precise. This adds support to the possibility that associative learning may play a role in the progression of an acute pain episode to a more generalized pain disorder.
Publisher: Informa UK Limited
Date: 22-03-2021
DOI: 10.1080/09540121.2021.1902936
Abstract: Chronic pain is a common comorbidity in people with HIV (PWH), with prevalence estimates of 25-85%. Research in this area is growing, but significant gaps remain. A Global Task Force of HIV experts was organized to brainstorm a scientific agenda and identify measurement domains critical to advancing research in this field. Experts were identified through literature searches and snowball s ling. Two online questionnaires were developed by Task Force members. Questionnaire 1 asked participants to identify knowledge gaps in the field of HIV and chronic pain and identify measurement domains in studies of chronic pain in PWH. Responses were ranked in order of importance in Questionnaire 2, which was followed by a group discussion. 29 experts completed Questionnaire 1, 25 completed Questionnaire 2, and 21 participated in the group. Many important clinical and research priorities emerged, including the need to examine etiologies of chronic pain in PWH. Pain-related measurement domains were discussed, with a primary focus on domains that could be assessed in a standardized manner across various cohorts that include PWH in different countries. We collaboratively identified clinical and research priorities, as well as gaps in standardization of measurement domains, that can be used to move the field forward.
Publisher: PeerJ
Date: 20-06-2022
DOI: 10.7717/PEERJ.13512
Abstract: Pain is thought to be influenced by the threat value of the particular context in which it occurs. However, the mechanisms by which a threat achieves this influence on pain are unclear. Here, we explore how threat influences experimentally-induced secondary hyperalgesia, which is thought to be a manifestation of central sensitization. We developed an experimental study to investigate the effect of a manipulation of threat on experimentally-induced secondary hyperalgesia in 26 healthy human adults (16 identifying as female 10 as male). We induced secondary hyperalgesia at both forearms using high-frequency electrical stimulation. Prior to the induction, we used a previously successful method to manipulate threat of tissue damage at one forearm (threat site). The effect of the threat manipulation was determined by comparing participant-rated anxiety, perceived threat, and pain during the experimental induction of secondary hyperalgesia, between the threat and control sites. We hypothesized that the threat site would show greater secondary hyperalgesia (primary outcome) and greater surface area (secondary outcome) of induced secondary hyperalgesia than the control site. Despite a thorough piloting procedure to test the threat manipulation, our data showed no main effect of site on pain, anxiety, or threat ratings during high-frequency electrical stimulation. In the light of no difference in threat between sites, the primary and secondary hypotheses cannot be tested. We discuss reasons why we were unable to replicate the efficacy of this established threat manipulation in our s le, including: (1) competition between threats, (2) generalization of learned threat value, (3) safety cues, (4) trust, and requirements for participant safety, (5) s ling bias, (6) s le-specific habituation to threat, and (7) implausibility of (sham) skin examination and report. Better strategies to manipulate threat are required for further research on the mechanisms by which threat influences pain.
Publisher: Elsevier BV
Date: 10-2017
DOI: 10.1016/J.JPAIN.2017.04.011
Abstract: A growing body of research has identified fear of visceral sensations as a potential mechanism in the development and maintenance of visceral pain disorders. However, the extent to which such learned fear affects visceroception remains unclear. To address this question, we used a differential fear conditioning paradigm with nonpainful esophageal balloon distensions of 2 different intensities as conditioning stimuli (CSs). The experiment comprised of preacquisition, acquisition, and postacquisition phases during which participants categorized the CSs with respect to their intensity. The CS+ was always followed by a painful electrical stimulus (unconditioned stimulus) during the acquisition phase and in 60% of the trials during postacquisition. The second stimulus (CS-) was never associated with pain. Analyses of galvanic skin and startle eyeblink responses as physiological markers of successful conditioning showed increased fear responses to the CS+ compared with the CS-, but only in the group with the low-intensity stimulus as CS+. Computational modeling of response times and response accuracies revealed that differential fear learning affected perceptual decision-making about the intensities of visceral sensations such that sensations were more likely to be categorized as more intense. These results suggest that associative learning might indeed contribute to visceral hypersensitivity in functional gastrointestinal disorders. This study shows that associative fear learning biases intensity judgements of visceral sensations toward perceiving such sensations as more intense. Learning-induced alterations in visceroception might therefore contribute to the development or maintenance of visceral pain.
Publisher: Cold Spring Harbor Laboratory
Date: 09-09-2023
Publisher: European Medical Group
Date: 27-10-2020
DOI: 10.33590/EMJRESPIR/20-00167
Abstract: A dynamic and intricately connected tissue-resident immune cell network continuously monitors the lungs, which are incessantly subjected to external environmental insults. The lungs are protected by the respiratory epithelium, which not only serves as a physical barrier through mucociliary mechanisms, but also a reactive one that can release cytokines, chemokines, and other defence proteins in response to danger signals. In the maintenance of pulmonary homeostasis in health, the lung-resident immune cell network instructs tolerance to innocuous particulates and can rapidly and efficiently drive immunity and memory to pathogenic antigens. This review examines the spatiotemporal dynamics that underlie the exquisite network of highly specialised immune cells and their mediators in the support of pulmonary tissue homeostasis and effective lung immunity in health. In particular, this review examines the specialised immune cells that reside in distinct populations within the erse compartments of the lung, and the molecular signals that retain and recruit lung-resident immune cells, to further our understanding of how these can be targeted therapeutically to return inflamed or diseased lungs to homeostasis.
Publisher: Elsevier BV
Date: 04-2019
DOI: 10.1016/J.JPAIN.2018.10.006
Abstract: In experiments on pain, participants are frequently exposed to nonpainful and painful stimuli however, the conventional pain-rating scales lack a nonpainful range and a clear point of transition from nonpainful to painful events. The Sensation and Pain Rating Scale (SPARS) assesses the full stimulus intensity range, extending from no sensation (rating: -50) to worst pain imaginable (rating: +50), and it explicitly identifies pain threshold (rating: 0). Here, we tested the SPARS in 2 experiments by using laser heat stimuli to establish its stimulus-response characteristics (Experiment 1, N = 19, 13 stimulus intensities applied 26 times each across a 1-4 J range), and compared it to 0 to 100 scales that assess nonpainful (0: no sensation, 100: pain) and painful (0: no pain, 100: worst pain imaginable) events (Experiment 2, N = 7, 9 stimulus intensities applied 36 times each across a 1.5-4.5 J range). Despite high inter- and intrain idual variations, we found a reasonably consistent curvilinear stimulus-response relationship (the curve flattens around pain threshold), with stable response characteristics across the range of the scale. The SPARS ratings transformed to a 0 to 100 range tended to be lower than the 0 to 100 pain rating scale in the noxious stimulus intensity range and greater than the 0 to 100 nonpainful sensation scale in the non-noxious stimulus range, likely reflecting differences in scale dimensionality. The SPARS overcomes limitations in scale range inherent to conventional pain rating scales. As such, it is well suited to experimental studies that must quantify a wider range of perceptual intensity or distinguish between painful and nonpainful events. PERSPECTIVE: This article presents the stimulus-response characteristics of a new scale designed to allow participants to rate a range of nonpainful and painful stimuli. The scale could be useful for research that involves exposing participants to a range of stimulation intensities or requires a clear distinction between nonpainful and painful events.
Publisher: Springer Science and Business Media LLC
Date: 11-02-2022
DOI: 10.1007/S00221-021-06285-4
Abstract: Innocuous cues that become associated with pain can enhance pain. This is termed classically conditioned hyperalgesia. The size of this effect varies under different conditions. We aimed to test whether the sensitising effect of pain-associated cues depends on the intensity of the paired test stimulus. To do this, two virtual reality environments were paired with either painful or non-painful vibrotactile stimuli in a counterbalanced fashion. The differential effect of the two environments was evaluated using pain intensity ratings of paired electrocutaneous test stimuli at three different intensity levels. Forty healthy participants were included in the study 30 participants experienced sufficient pain during the learning phase and were included in the main analysis. An effect of environment ( p = 0.014) and interaction between environment and test stimulus intensity was found ( p = 0.046). Only the most intense test stimulus was modulated by environment. While the effect was small, the results are consistent with the proposition that pain-associated cues may induce hyperalgesia to some degree, under certain conditions. In particular, results highlight the potential relevance of stimulus intensity during and after the initial painful experience. Further attention is needed to comprehensively understand the variables that impact classically conditioned hyperalgesia.
Publisher: Oxford University Press (OUP)
Date: 13-07-2023
Abstract: Knee osteoarthritis is one of the primary causes of chronic pain among older adults and because of the aging population, the number of total knee arthroplasties (TKAs) performed is exponentially increasing. While pain reduction is a goal of TKA, movement-evoked pain is rarely assessed pre- and post-TKA. We characterized the distributions of change in pain, function, and situational catastrophizing in patients from pre-surgery to 3 months post-surgery and explored associations among these pre-post changes. This prospective study longitudinally assessed movement-evoked pain, function, and situational catastrophizing in patients with knee osteoarthritis (N=92) using in-person performance-based tests (6-minute walk test [6MWT], stair-climb test [SCT]) prior to and 3-months after TKA. Patients also completed the Western Ontario McMaster Universities Scales (WOMAC) pain and function subscales, and Pain Catastrophizing Scale (PCS), pre-surgery and 3- and 6-months post-surgery. Movement-evoked pain and function on performance tests significantly improved from pre- to post-TKA. Improved SCT function was associated with reduced SCT pain and catastrophizing. Similarly, reduced pain during the SCT was associated with reduced catastrophizing during the SCT. However, 6MWT function was not associated with 6MWT pain or catastrophizing yet reduced pain during the 6MWT was associated with reduced catastrophizing during the 6MWT. Reduced movement-evoked pain during both performance tests was consistently associated with improved WOMAC function and pain, whereas improved function on performance tests was inconsistently associated with WOMAC function and pain. Notably, greater movement-evoked pain on both performance tests at 3-months post-TKA was associated with worse WOMAC function and pain at 6 months, whereas better function on performance tests at 3-months was associated with better WOMAC function, but not related to WOMAC pain at 6 months. Findings highlight the importance of situation-specific and in-vivo assessments of pain and catastrophizing during physical activity.
Publisher: PeerJ
Date: 14-01-2016
DOI: 10.7717/PEERJ.1577
Abstract: Background. Nd:YAP laser is widely used to investigate the nociceptive and pain systems, generating perpetual and laser-evoked neurophysiological responses. A major procedural concern for the use of Nd:YAP laser stimuli in experimental research is the risk of skin damage. The absorption of Nd:YAP laser stimuli is greater in darker skin, or in pale skin that has been darkened with ink, prompting some ethics boards to refuse approval to experimenters wishing to track stimulus location by marking the skin with ink. Some research questions, however, require laser stimuli to be delivered at particular locations or within particular zones, a requirement that is very difficult to achieve if marking the skin is not possible. We thoroughly searched the literature for experimental evidence and protocol recommendations for safe delivery of Nd:YAP laser stimuli over marked skin, but found nothing. Methods. We designed an experimental protocol to define safe parameters for the use of Nd:YAP laser stimuli over skin that has been marked with black dots, and used thermal imaging to assess the safety of the procedure at the forearm and the back. Results. Using thermal imaging and repeated laser stimulation to ink-marked skin, we demonstrated that skin temperature did not increase progressively across the course of the experiment, and that the small change in temperature seen at the forearm was reversed during the rest periods between blocks. Furthermore, no participant experienced skin damage due to the procedure. Conclusion. This protocol offers parameters for safe, confident and effective experimentation using repeated Nd:YAP laser on skin marked with ink, thus paving the way for investigations that depend on it.
Publisher: Ovid Technologies (Wolters Kluwer Health)
Date: 11-2019
DOI: 10.1097/PR9.0000000000000783
Abstract: Pain affects over half of the people living with HIV/AIDS (LWHA), and pharmacological treatment has limited efficacy. Preliminary evidence supports nonpharmacological interventions. We previously piloted a multimodal intervention in amaXhosa women LWHA and chronic pain in South Africa with improvements seen in all outcomes, in both intervention and control groups. A multicentre, single-blind randomised controlled trial with 160 participants recruited was conducted to determine whether the multimodal peer-led intervention reduced pain in different populations of both male and female South Africans LWHA. Participants were followed up at weeks 4, 8, 12, 24, and 48 to evaluate effects on the primary outcome of pain, and on depression, self-efficacy, and health-related quality of life. We were unable to assess the efficacy of the intervention due to a 58% loss to follow-up (LTFU). Secondary analysis of the LTFU found that sociocultural factors were not predictive of LTFU. Depression, however, did associate with LTFU, with greater severity of depressive symptoms predicting LTFU at week 8 ( P = 0.01). We were unable to evaluate the effectiveness of the intervention due to the high LTFU and the risk of retention bias. The different sociocultural context in South Africa may warrant a different approach to interventions for pain in HIV compared with resource-rich countries, including a concurrent strategy to address barriers to health care service delivery. We suggest that assessment of pain and depression need to occur simultaneously in those with pain in HIV. We suggest investigation of the effect of social inclusion on pain and depression.
Publisher: Elsevier BV
Date: 07-2019
Publisher: Wiley
Date: 2020
DOI: 10.1111/ANAE.14934
Abstract: Deaths following surgery are the third largest contributor to deaths globally, and in Africa are twice the global average. There is a need for a peri-operative research agenda to ensure co-ordinated, collaborative research efforts across Africa in order to decrease peri-operative mortality. The objective was to determine the top 10 research priorities for peri-operative research in Africa. A Delphi technique was used to establish consensus on the top research priorities. The top 10 research priorities identified were (1) Develop training standards for peri-operative healthcare providers (surgical, anaesthesia and nursing) in Africa (2) Develop minimum provision of care standards for peri-operative healthcare providers (surgical, anaesthesia and nursing) in Africa (3) Early identification and management of mothers at risk from peripartum haemorrhage in the peri-operative period (4) The role of communication and teamwork between surgical, anaesthetic, nursing and other teams involved in peri-operative care (5) A facility audit/African World Health Organization situational analysis tool audit to assess emergency and essential surgical care, which includes anaesthetic equipment available and level of training and knowledge of peri-operative healthcare providers (surgeons, anaesthetists and nurses) (6) Establishing evidence-based practice guidelines for peri-operative physicians in Africa (7) Economic analysis of strategies to finance access to surgery in Africa (8) Establishment of a minimum dataset surgical registry (9) A quality improvement programme to improve implementation of the surgical safety checklist and (10) Peri-operative outcomes associated with emergency surgery. These peri-operative research priorities provide the structure for an intermediate-term research agenda to improve peri-operative outcomes across Africa.
Publisher: BMJ
Date: 06-2022
DOI: 10.1136/BMJOPEN-2021-059723
Abstract: Many people with HIV report both distress and pain. The relationship between distress and pain is bidirectional, but the mechanisms by which distress exacerbates pain are unclear. The inflammatory response to challenge (inflammatory reactivity, IR) may be a partial mediator, given that neuroimmune interactions provide a substrate for IR to also influence neurological reactivity and, thus, pain-related neural signalling. This prospective, observational, case–control study will characterise the relationships between distress, IR, pain-related signalling as captured by induced secondary hyperalgesia (SH), and pain, in people with HIV who report persistent pain (PP) (cases) or no pain (controls). One hundred people with suppressed HIV, reporting either PP or no pain, will be assessed two or four times over 6 months. The primary outcomes are distress (Hopkins 25-item symptom checklist), IR (multiplex assay after LPS challenge), and PP (Brief Pain Inventory), assessed at the baseline timepoint, although each will also be assessed at follow-up time points. Induced SH will be assessed in a subs le of 60 participants (baseline timepoint only). To test the hypothesis that IR partly mediates the relationship between distress and pain, mediation analysis will use the baseline data from the PP group to estimate direct and indirect contributions of distress and IR to pain. To test the hypothesis that IR is positively associated with SH, data from the subs le will be analysed with generalised mixed effects models to estimate the association between IR and group membership, with SH as the dependent variable. Information obtained from this study will be published in peer-reviewed journals and presented at scientific meetings. The study has been approved by the Human Research Ethics Committee of the University of Cape Town (approval number: 764/2019) and the City of Cape Town (ref: 24699). NCT04757987 .
Publisher: Cold Spring Harbor Laboratory
Date: 17-01-2019
DOI: 10.1101/521302
Abstract: The pain threshold is traditionally conceptualised as a boundary that lies between painful and non-painful events, suggesting a reasonably stable relationship between stimulus and response. In two previous experiments, participants received laser stimuli of various intensities and rated each stimulus on the Sensation and Pain Rating Scale (SPARS), which includes ranges for rating painful and non-painful events and clearly defines the presumed boundary between them. In the second experiment, participants also provided ratings on the conventional 0-100 Numerical Rating Scale for pain (NRS) and a new rating scale for non-painful events. Those data showed the SPARS to have a curvilinear stimulus-response relationship, reflecting that several different intensities may be rated as painful and non-painful in different trials. This suggests that participants were uncertain about painfulness over a range of intensities and calls into question the idea of a boundary between non-painful and painful events. The current study aimed to determine the number of different stimulus intensities across which each participant provided ‘painful’ and ‘non-painful’ reports in different trials. We undertook novel exploratory analyses on data from the aforementioned two experiments (n = 19, 11 female, 18-31 years old n = 7, 5 female, 21-30 years old). We used the binomial test to formally determine the width of this ‘zone of uncertainty’ about painfulness, using ratings on the SPARS and the comparator scales, and data visualisation to assess whether trial-to-trial change in stimulus intensity influences ratings. We found that the width of the zone of uncertainty varied notably between in iduals and that the zone was non-continuous for most participants. Plots of group-level data concealed the inter-in idual variability apparent in the in idual plots, but still showed a wide zone of uncertainty on both the SPARS and the NRS, but a narrow zone on the scale for non-painful events. There was no evidence that trial-to-trial change in stimulus intensity influenced ratings. The variability revealed by this study has important design implications for experiments that include initial calibration of repeatedly delivered stimuli. The variability also stands to inflate the size of s le that is required for adequate statistical powering of experiments, and provides rationale for the use of statistical approaches that account for in idual variability in studies of pain. Finally, the high variability implies that, if experimental stimuli are to be used in clinical phenotyping, many trials may be required to obtain results that represent a single patient’s actual response profile.
Publisher: Oxford University Press (OUP)
Date: 28-09-2016
DOI: 10.1093/PM/PNW221
Abstract: Associative learning has been proposed as a mechanism behind the persistence of pain after tissue healing. The simultaneous occurrence of nociceptive and non-nociceptive input during acute injury mimics the pairings thought to drive classical conditioning effects. However, empirical evidence for classically conditioned allodynia is lacking. We aimed to manipulate pain thresholds with a classical conditioning procedure that used non-nociceptive somatosensory stimuli as conditioned stimuli (CS) and nociceptive stimuli as unconditioned stimuli. We also explored the influence of gender, depression, anxiety, negative affect, and pain catastrophizing on the main manipulation. Thirty-four healthy humans participated in a differential classical conditioning procedure that used vibrotactile stimulations at two different locations as CS. In an acquisition phase, CS+ was paired with painful thermal stimulation, and CS- with nonpainful thermal stimulation. Heat pain threshold was assessed during paired heat-CS trials before and after acquisition. A 2 (time: 1 and 2) x 2 (condition: CS+ and CS-) repeated-measures analysis of variance compared pain thresholds before and after acquisition. Exploratory analyses explored the influence of gender, depression, anxiety, negative affect, and pain catastrophizing. Postexperiment questions investigated participants' awareness of the contingencies employed. The classical conditioning procedure did not alter pain thresholds. Exploratory analyses did not reveal any influence of in idual differences. Thirty of the 34 participants were unaware of the contingencies between stimuli. The results of this study provide no evidence that allodynia can be induced in healthy humans using a classical conditioning procedure with simultaneous timing.
Publisher: PeerJ
Date: 08-03-2019
DOI: 10.7717/PEERJ.6486
Abstract: Classical conditioning has frequently been shown to be capable of evoking fear of pain and avoidance behavior in the context of chronic pain. However, whether pain itself can be conditioned has rarely been investigated and remains a matter of debate. Therefore, the present study investigated whether pain threshold ratings can be modified by the presence of conditioned non-nociceptive sensory stimuli in healthy participant. In 51 healthy volunteers, pain threshold to electrocutaneous stimuli was determined prior to participation in a simultaneous conditioning paradigm. Participants underwent an acquisition phase in which one non-painful vibrotactile stimulus (CS + ) was repeatedly paired with a painful electrocutaneous stimulus, whereas a second vibrotactile stimulus of the same quality and intensity (CS − ) was paired with a non-painful electrocutaneous stimulus. Stimulation was provided on the lower back with close proximity between the conditioned stimulus and the unconditioned stimulus. In the test phase, electrocutaneous stimuli at the in idually-set threshold intensity were simultaneously delivered together with either a CS + or CS − . Pain intensity ratings were obtained after each trial expectancy ratings were obtained after each block. The primary outcome was the percentage of test stimuli that were rated as painful. Test stimuli were more likely to be rated as painful when they were paired with the CS + than when they were paired with the CS − . This effect was not influenced by contingency awareness, nor by expectancies or mood states. The findings support the notion that the judgement of an event being painful or non-painful can be influenced by classical conditioning and corroborate the possible role of associative learning in the development and maintenance of chronic pain.
Publisher: Elsevier BV
Date: 10-2023
Publisher: SAGE Publications
Date: 17-02-2015
Abstract: Pain is a protective perceptual response shaped by contextual, psychological, and sensory inputs that suggest danger to the body. Sensory cues suggesting that a body part is moving toward a painful position may credibly signal the threat and thereby modulate pain. In this experiment, we used virtual reality to investigate whether manipulating visual proprioceptive cues could alter movement-evoked pain in 24 people with neck pain. We hypothesized that pain would occur at a lesser degree of head rotation when visual feedback overstated true rotation and at a greater degree of rotation when visual feedback understated true rotation. Our hypothesis was clearly supported: When vision overstated the amount of rotation, pain occurred at 7% less rotation than under conditions of accurate visual feedback, and when vision understated rotation, pain occurred at 6% greater rotation than under conditions of accurate visual feedback. We concluded that visual-proprioceptive information modulated the threshold for movement-evoked pain, which suggests that stimuli that become associated with pain can themselves trigger pain.
Publisher: Elsevier BV
Date: 10-2016
DOI: 10.1016/J.JPAIN.2016.06.012
Abstract: A classical conditioning framework is often used for clinical reasoning about pain that persists after tissue healing. However, experimental studies demonstrating classically conditioned pain in humans are lacking. The current study tested whether non-nociceptive somatosensory stimuli can come to modulate pain thresholds after being paired with painful nociceptive stimuli in healthy humans. We used a differential simultaneous conditioning paradigm in which one nonpainful vibrotactile conditioned stimulus (CS(+)) was simultaneously paired with an unconditioned painful laser stimulus, and another vibrotactile stimulus (CS(-)) was paired with a nonpainful laser stimulus. After acquisition, at-pain-threshold laser stimuli were delivered simultaneously with a CS(+) or CS(-) vibrotactile stimulus. The primary outcome was the percentage of at-threshold laser stimuli that were reported as painful. The results were as expected: after conditioning, at-threshold laser trials paired with the CS(+) were reported as painful more often, as more intense, and as more unpleasant than those paired with the CS(-). This study provides new evidence that pain thresholds can be modulated via classical conditioning, even when the stimulus used to test the threshold cannot be anticipated. As such, it lays a critical foundation for further investigations of classical conditioning as a possible driver of persistent pain. This study provides new evidence that human pain thresholds can be influenced by non-nociceptive somatosensory stimuli, via a classical conditioning effect. As such, it lays a critical foundation for further investigations of classical conditioning as a possible driver of persistent pain.
Publisher: Springer Science and Business Media LLC
Date: 19-08-2019
Publisher: Elsevier BV
Date: 07-2019
DOI: 10.1016/J.MSKSP.2019.04.015
Abstract: Perception is not simply a carbon copy of the real world, but is subject to distortions that may reflect protective drive. This study aimed to investigate whether people with chronic shoulder pain show perceptual distortions of space and body that may promote protective behavior. Eighty-four people with shoulder pain and 51 healthy controls participated. Participants estimated (1) distances to points on a cork-board within and outside reaching distance, and (2) the perceived length of their own arms. A novel measure of movement-related pain was also used to determine whether movement-related pain relates to perceptual distortion. Overall, distance and arm length estimates did not differ between groups, nor did participants perceive their arms to be of different length. However, a moderate correlation between movement-related pain and the index of distance perception was found within the pain group, specifically for distance estimates to points within reach. Our results suggest that distorted perception is not a typical consequence of chronic shoulder pain however, that it may occur in cases where pain is strongly linked to movement. Our findings have implications for understanding avoidance of movement in people with persistent pain.
Publisher: Future Medicine Ltd
Date: 07-2020
Abstract: Evidence indicates that over half of all people with HIV (PWH) will experience nonmalignant chronic pain throughout their lifetimes, with increasing prevalence as they age. Peripheral neuropathy resulting from the neurotoxic effects of HIV itself and the medications used to treat HIV were widely considered the primary cause of acute and chronic pain early on in the antiretroviral treatment era. However, recent studies suggest a predominance of non-neuropathic (e.g., musculoskeletal) pain in PWH with uncertain etiology. Chronic pain is often widespread in PWH, affecting multiple body locations. Additional research is needed to better understand contributors to chronic pain in PWH, which is likely to include biological (e.g., immune dysregulation), psychological (e.g., substance abuse) and social (e.g., stigma) factors.
Publisher: Elsevier BV
Date: 12-2020
DOI: 10.1016/J.PHYSIO.2019.06.009
Abstract: To investigate whether graded motor imagery (GMI) is effective for reducing phantom limb pain (PLP) in people who have undergone limb utations. A single-blinded randomised, controlled trial. Physiotherapy out-patient departments in three secondary level hospitals in Cape Town, South Africa. Twenty-one adults (≥18 years) who had undergone unilateral upper or lower limb utations and had self-reported PLP persisting beyond three months. A 6-week GMI programme was compared to routine physiotherapy. The study outcomes were evaluated at baseline, 6 weeks, 3 months and 6 months. The pain severity scale of the Brief Pain Inventory (BPI) was used to assess the primary outcome - PLP. The pain interference scale of the BPI and the EuroQol EQ-5D-5L were used to assess the secondary outcomes - pain interference with function and health-related quality of life (HRQoL) respectively. The participants in the experimental group had significantly greater improvements in pain than the control group at 6 weeks and 6 months. Further, the participants in the experimental group had significantly greater improvements than the control group in pain interference at all follow-up points. There was no between-group difference in HRQoL. The results of the current study suggest that GMI is better than routine physiotherapy for reducing PLP. Based on the significant reduction in PLP and pain interference within the participants who received GMI, and the ease of application, GMI may be a viable treatment for treating PLP in people who have undergone limb utations. (PACTR201701001979279).
Publisher: Elsevier BV
Date: 04-2016
DOI: 10.1016/J.MATH.2015.12.003
Abstract: Anecdotally, clinical presentations in which pain seems to be elicited by non-noxious stimuli are often explained using a classical conditioning framework. We were primarily interested in whether (a) clinicians think that pain can be a classically conditioned response to a non-noxious stimulus, and (b) clinicians think that there is evidence to support that idea. Practising healthcare clinicians participated anonymously in an online survey. The information collected included descriptive demographics, clinical experience, personal experience of chronic pain, beliefs about pain, and beliefs about classical conditioning and pain. Responses to the pre-requisite question - whether pain can occur without nociception - were compared to a historical data set from 2004. 1090 people from 57 countries and eight distinct types of health profession completed the survey. 86% stated that pain can occur without nociception 96% of those believed that pain can be a classically conditioned response to a non-noxious stimulus 98% of those believed that there is evidence to support that statement. The 2004 data showed that 44% of participants distinguished between pain and nociception. This broad s le overwhelmingly endorsed the ideas that clinicians think that pain can be a classically conditioned response to a non-noxious stimulus and think that there is evidence to support that idea, revealing a discrepancy between beliefs in the clinical community and the scientific evidence. The distinction between nociception and pain has become more accepted by the clinical community over the last 10 years.
Publisher: JOTE Publishers
Date: 03-03-2022
DOI: 10.36850/E8
Abstract: Single-case experiments are increasingly popular in the behavioral sciences. Due to their flexibility, single-case designs can be customized to test a variety of experimental hypotheses. We were interested in using a single-case experimental approach to test whether pain thresholds can be influenced by Pavlovian classical conditioning. Following the ex le of earlier studies into this topic, we planned to measure whether participants would more frequently report specific electrocutaneous stimuli as painful when they were presented with specific vibrotactile stimuli that had previously been associated with painful electrocutaneous stimuli. First, we decided on a mean difference effect size measure derived from the Sensation and Pain Rating Scale ratings for the electrocutaneous stimuli provided by the participants. Next, we discussed several possible single-case designs and evaluated their benefits and shortcomings. Then, we ran pilot tests with a few participants based on the possible single-case designs. We also conducted a simulation study to estimate the power of a randomization test to test our hypothesis using different values for effect size, number of participants, and number of measurements. Finally, we decided on a sequentially replicated AB phase design with 30 participants based on the results from the pilot tests and the power study. We plan to implement this single-case design in a future experiment to test our hypothesis
Publisher: Walter de Gruyter GmbH
Date: 04-2016
DOI: 10.1016/J.SJPAIN.2015.09.007
Abstract: Non-nociceptive somatosensory input, such as tactile or proprioceptive information, alway precedes nociceptive input during a painful event. This relationship provides clear opportunities fo predictive associative learning, which may shape future painful experiences. In this differential classica conditioning study we tested whether pain-associated tactile cues (conditioned stimuli CS) could altei the perceived intensity of painful stimulation, and whether this depends on duration of the CS—seeing that CS duration might allow or prevent conscious expectation. Subjects underwent a classical differential conditioning task in which a tactile cue at locatior A (CS+) preceded painful electrical stimulation at location B (UShigh), whereas a tactile cue at location C (CS–) preceded non-painful electrical stimulation at location B (USlow). At test, we compared the pain evoked by a moderately painful stimulus (USmed) when preceded by either the CS+ or CS–. CS duration was manipulated between subjects. Participants were assigned to one of three groups: Long CS (4s, allowing conscious expectation), Short CS (110 ms) and CS-US indistinguishable (20 ms), preventing conscious expectation). We hypothesised that more pain would be evoked by the US when preceded by the CS+ relative to the CS-, and that the effect would be independent of CS duration. Fifty-four healthy participants (31 females, age = 26, SD = 9) were included in the analysis. The hypotheses were supported in that more intense pain was evoked by the USmed when paired with the tactile CS+, than when paired with the tactile CS- mean difference 3 mm on a 150 mm VAS (C 0.4-4.8 mm). CS duration did not moderate the effect. The effect was greater in those participants where calibration was optimal, as indicated by a relatively more painful UShigh. We conclude that pain-associated tactile cues can influence pain, and that this effect i: not dependent on stimulus duration. This suggests that explicit expectation is not a requirement for predictive cues to modulate pain. That the presence of the CS+ resulted in only a 5.3% higher intensity rating compared with the CS- may reflect a limitation of laboratory studies, where a limited number o trials, an artificial context and the use of experimental pain are likely to reveal only glimpses of what i: clinically possible. Pain-associated visual and auditory cues have been shown to enhance pain in laboratory and clinical scenarios, supposedly by influencing expectation of impending harm. We show that pain-associated somatosensory cues can also modulate pain and that this can occur independently of expectation. This points to a larger potential role for associative learning in the development and treatment of pain than has previously been considered. We suggest that research into associative mechanisms underpinning pain, as distinct from those that link pain to pain-related fear and avoidance, is worthwhile.
Publisher: Springer Science and Business Media LLC
Date: 10-01-2019
Publisher: Academy of Science of South Africa
Date: 15-12-2014
DOI: 10.7196/SAJSM.535
Abstract: Background. Therapeutic ultrasound (US) is an electrophysical therapy that is commonly used by sports physiotherapists, but its mechanismof action is unclear. There is little evidence that US therapy is more effective than sham US therapy, and any clinical benefits may be dueto a placebo effect.Objective. To investigate whether US has a specific effect that renders it effective in its own right, or whether its effect is placebo driven.Methods. In a double-blind controlled trial, delayed-onset muscle soreness (DOMS) was experimentally induced in both bicep musclesof 15 females. Sham US was applied to one bicep (n=15 biceps) and pulsed active US to the other bicep (n=15 biceps) of each participant,48 and 72 h after induction of DOMS. Primary and secondary outcomes were pain reported on the McGill Pain Questionnaire (MPQ) andrange of movement (ROM) (elbow extension) measured by goniometry, respectively.Results. Results showed significant improvements in pain and ROM over the intervention periods, but there was no difference betweeninterventions.Conclusion. US and sham US therapy improve pain equally when treating DOMS of the biceps in the context of a therapeutic encounter.This analgesic effect is placebo driven. Clinicians can influence the analgesic effect of US by managing the therapeutic context. Managementof patients’ anxiety may also boost the analgesic effect of US.
Publisher: Ovid Technologies (Wolters Kluwer Health)
Date: 08-2016
DOI: 10.1097/AOG.0000000000001510
Abstract: To synthesize and critically evaluate all available evidence investigating whether localized, provoked vestibulodynia is associated with a specific inflammatory profile at both a local and a systemic level. Comprehensive electronic searches were performed in MEDLINE, EMBASE, Scopus, PubMed, Web of Science, Cumulative Index to Nursing and Allied Health Literature, the Cochrane Collaboration databases, and ClinicalTrials.gov. The search strategy was developed using MeSH terms related to localized, provoked vestibulodynia, and inflammatory markers. Two independent investigators screened titles and abstracts and performed data extraction and risk of bias assessments. Studies were included if they reported at least one baseline inflammatory marker in women with localized, provoked vestibulodynia and compared them with healthy women. Reference lists from published reviews on localized, provoked vestibulodynia were screened for additional studies. There were 1,619 studies identified. Eighteen studies met the inclusion criteria, including 400 women with localized, provoked vestibulodynia and 212 healthy women in a control group. Risk of bias assessment revealed that the methodologic quality was generally low. Fifteen studies investigated local inflammation and three studies investigated systemic inflammation. On a local level, the number of mast cells expressed in vestibular tissues was greater in women with localized, provoked vestibulodynia expressed than in women in the control group. Several studies reported undefined inflammatory infiltrate in vestibular tissues to a greater level in women with localized, provoked vestibulodynia than in women in the control group. Systemically, levels of natural killer cells were lower in women with localized, provoked vestibulodynia than in women in the control group. There were no systemic differences in systemic interferon-α and interferon-ϒ levels between groups. There is limited and contradictory evidence regarding the characteristics of local and systemic inflammation in women with localized, provoked vestibulodynia.
Publisher: Oxford University Press (OUP)
Date: 05-2016
DOI: 10.2522/PTJ.20150210
Abstract: Proprioceptive imprecision is believed to contribute to persistent pain. Detecting imprecision in order to study or treat it remains challenging given the limitations of current tests. The aim of this study was to determine whether proprioceptive imprecision could be detected in people with neck pain by testing their ability to identify incongruence between true head motion and a false visual reference using the Proprioception Incongruence Detection (PID) Test. A cross-sectional study was conducted. Twenty-four people with neck pain and 24 matched controls repeatedly rotated to specific markers within a virtual world and indicated if their true head rotation was more or less than the rotation suggested by the visual feedback. Visual feedback was manipulated at 6 corrections, ranging from 60% of true movement to 140% of true movement. A standard repositioning error (RPE) test as undertaken for comparison. Healthy controls were better able to detect incongruence between vision and true head rotation (X̅=75.6%, SD=8.5%) than people with neck pain were (X̅=69.6%, SD=12.7%). The RPE test scores were not different between groups. The PID Test score related to self-reported pain intensity but did not relate to RPE test score. Causality cannot be established from this cross-sectional study, and further work refining the PID Test is needed for it to offer clinical utility. Proprioceptive precision for neck movement appears worse in people with neck pain than in those without neck pain, and the extent of the deficit appears to be related to usual pain severity. The PID Test appears to be a more sensitive test than the RPE test and is likely to be useful for assessment of proprioceptive function in research and clinical settings.
No related grants have been discovered for Victoria Madden.