Search

Refereed/Peer-reviewed

Background: Burning mouth syndrome (BMS) is a chronic pain disorder affecting the oral cavity. Previous work has shown promising analgesic results of bodily illusions in other chronic pain conditions. The aim of this proof‐of‐concept, pilot study was to investigate whether bodily illusions reduce pain in BMS patients. Methods: Nine participants diagnosed with BMS underwent bodily illusions using a MIRAGE‐mediated reality system. All participants completed 4 conditions and performed standardised movements of the tongue. First, a baseline condition was performed while the tongue was viewed at normal size and colour. Then, three conditions were performed in random order: resizing shrink, colour‐based (blue tongue), and incongruent movement illusions. During each condition, participants rated overall pain intensity as well as the intensity of burning pain/sensation on the tongue. Results: There was no difference in overall pain intensity ratings between conditions. However, a significant effect of condition was found for burning pain/sensation of the tongue. The colour illusion significantly reduced burning pain compared with baseline (MD = ‐12.8, 95% CI ‐20.7 to ‐4.8), corresponding to an average pain reduction of 32%. Exploratory analyses showed the colour illusion also significantly reduced pain compared with the shrink illusion (MD = ‐11.7, 95% CI ‐22.2 to ‐1.1). Conclusion: Using visual illusions to change tongue colour to blue resulted in significant reductions in burning pain/sensations in BMS patients for the duration of the illusion. This proof‐of‐concept study suggests that BMS patients may benefit from bodily illusions, and supports additional research using larger samples and more comprehensive control conditions. Refereed/Peer-reviewed

The capacity to regulate one’s attention in accordance with fluctuating task demands and environmental contexts is an essential feature of adaptive behavior. Although the electrophysiological correlates of attentional processing have been extensively studied in the laboratory, relatively little is known about the way they unfold under more variable, ecologically-valid conditions. Accordingly, this study employed a ‘real-world’ EEG design to investigate how attentional processing varies under increasing cognitive, motor, and environmental demands. Forty-four participants were exposed to an auditory oddball task while (1) sitting in a quiet room inside the lab, (2) walking around a sports field, and (3) wayfinding across a university campus. In each condition, participants were instructed to either count or ignore oddball stimuli. While behavioral performance was similar across the lab and field conditions, oddball count accuracy was significantly reduced in the campus condition. Moreover, event-related potential components (mismatch negativity and P3) elicited in both ‘real-world’ settings differed significantly from those obtained under laboratory conditions. These findings demonstrate the impact of environmental factors on attentional processing during simultaneously-performed motor and cognitive tasks, highlighting the value of incorporating dynamic and unpredictable contexts within naturalistic designs.

Background Anecdotally, people living with Complex Regional Pain Syndrome (CRPS) often report difficulties in localising their own affected limb when it is out of view. Experimental attempts to investigate this report have used explicit tasks and yielded varied results. Methods Here we used a limb localisation task that interrogates implicit mechanisms because we first induce a compelling illusion called the Disappearing Hand Trick (DHT). In the DHT, participants judge their hands to be close together when, in fact, they are far apart. Sixteen volunteers with unilateral upper limb CRPS (mean age 39 ± 12 years, four males), 15 volunteers with non-CRPS persistent hand pain (‘pain controls’; mean age 58 ± 13 years, two males) and 29 pain-free volunteers (‘pain-free controls’; mean age 36 ± 19 years, 10 males) performed a hand-localisation task after each of three conditions: the DHT illusion and two control conditions in which no illusion was performed. The conditions were repeated twice (one for each hand). We hypothesised that (1) participants with CRPS would perform worse at hand self-localisation than both the control samples; (2) participants with non-CRPS persistent hand pain would perform worse than pain-free controls; (3) participants in both persistent pain groups would perform worse with their affected hand than with their unaffected hand. Results Our first two hypotheses were not supported. Our third hypothesis was supported —when visually and proprioceptively encoded positions of the hands were incongruent (i.e. after the DHT), relocalisation performance was worse with the affected hand than it was with the unaffected hand. The similar results in hand localisation in the control and pain groups might suggest that, when implicit processes are required, people with CRPS’ ability to localise their limb is preserved.

Dance involves exemplary sensory-motor control, which is subserved by sophisticated neural processing at the spinal cord and brain level. Such neural processing is altered in the presence of nociception and pain, and the adaptations within the central nervous system that are known to occur with persistent nociception or pain have clear implications for movement and, indeed, risk of further injury. Recent rapid advances in our understanding of the brain's representation of the body and the role of cortical representations, or "neurotags," in bodily protection and regulation have given rise to new strategies that are gaining traction in sports medicine. Those strategies are built on the principles that govern the operation of neurotags and focus on minimizing the impact of pain, injury, and immobilization on movement control and optimal performance. Here we apply empirical evidence from the chronic pain clinical neurosciences to introduce new opportunities for rehabilitation after dance injury. Refereed/Peer-reviewed

The ability to know where our own body and body parts are in space is often taken for granted, yet it is of fundamental importance for the majority of our everyday activities, let alone high performance activities such as dancing. This review focuses on the concept of self-localization, the monitoring of the space surrounding one's body, and the disruptions that occur in the presence of pain. A conceptual model is presented of the cortical body matrix with which to consider self-localization; also provided are its historical context, underlying assumptions, and current limitations. Issues described include the neurophysiological and behavioral background to the cortical body matrix model, its application to pain and performance, and the rapidly growing use of bodily illusions to investigate how it is that we know where we are, that we exist in a given location, and that we can interact with the space that surrounds us. Recent insights are drawn on from behavioral, clinical, neuroimaging, and physiological research. Spatial performance is discussed in people with and without pain and its relevance for prevention of injuries, the role of pain during performance, and pain education for dancers and their teachers. Refereed/Peer-reviewed

Background Bodily self-consciousness depends on the coherent integration of sensory information. In addition to visual and somatosensory information processing, vestibular contributions have been proposed and investigated. Vestibular information seems especially important for self-location, but remains difficult to study. Methods This randomised controlled experiment used the MIRAGE multisensory illusion box to induce a conflict between the visually- and proprioceptively-encoded position of one hand. Over time, the perceived location of the hand slowly shifts, due to the fact that proprioceptive input is progressively weighted more heavily than the visual input. We hypothesised that left cold caloric vestibular stimulation (CVS) augments this shift in hand localisation. Results The results from 24 healthy participants do not support our hypothesis: CVS had no effect on the estimations with which the perceived position of the hand shifted from the visually- to the proprioceptively-encoded position. Participants were more likely to report that their hand was ‘no longer there’ after CVS. Taken together, neither the physical nor the subjective data provide evidence for vestibular enhanced self-location.

BackgroundThe 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.MethodsWe 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.ResultsWe found that the width of the zone of uncertainty varied notably between individuals and that the zone was non-continuous for most participants. Plots of group-level data concealed the inter-individual variability apparent in the individual 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.ConclusionsThe 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 sample that is required for adequate statistical powering of experiments, and provides rationale for the use of statistical approaches that account for individual 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.

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 intraindividual 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.

When vision and proprioception are rendered incongruent during a hand localisation task, vision is initially weighted more than proprioception in determining location, and proprioception gains more weighting over time. However, it is not known whether, under these incongruency conditions, particular areas of space are also weighted more heavily than others, nor whether explicit knowledge of the sensory incongruence (i.e. disconfirming the perceived location of the hand) modulates the effect. Here, we hypothesised that both non-informative inputs coming from one side of space and explicit knowledge of sensory incongruence would modulate perceived location of the limb. Specifically, we expected spatial weighting to shift hand localisation towards the weighted area of space, and we expected greater weighting of proprioceptive input once perceived location was demonstrated to be inaccurate. We manipulated spatial weighting using an established auditory cueing paradigm (Experiment 1, n = 18) and sensory incongruence using the ‘disappearing hand trick’ (Experiment 2, n = 9). Our first hypothesis was not supported—spatial weighting did not modulate hand localisation. Our second hypothesis was only partially supported—disconfirmation of hand position did lead to more accurate localisations, even if participants were still unaware of their hand position. This raised the possibility that rather than disconfirmation, a simple movement of the hand in view could update the sensory–motor system, by immediately increasing the weighting of proprioceptive input relative to visual input. This third hypothesis was then confirmed (Experiment 3, n = 9). These results suggest that hand localisation is robust in the face of differential weighting of space, but open to modulation in a modality-specific manner, when one sense (vision) is rendered inaccurate. Refereed/Peer-reviewed

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 threshold after being paired with painful nociceptive stimuli in healthy humans. We used a differential simultaneous conditioning paradigm in which one non-painful vibrotactile conditioned stimulus (CS+) was simultaneously paired with an unconditioned painful laser stimulus (US), while another vibrotactile stimulus (CS-) was paired with a non-painful 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 can not be anticipated. As such, it lays a critical foundation for further investigations of classical conditioning as a possible driver of persistent pain. publisher: Elsevier articletitle: Pain by Association? Experimental Modulation of Human Pain Thresholds Using Classical Conditioning journaltitle: The Journal of Pain articlelink: http://dx.doi.org/10.1016/j.jpain.2016.06.012 content_type: article copyright: © 2016 by the American Pain Society ispartof: The Journal of Pain vol:17 issue:10 pages:1105-1115 ispartof: location:United States status: published

Pain is a very relevant function for our survival and its alteration leads to important consequences for people's lives. In the last decades, researchers have started to investigate pain from a neurocognitive and neuropsychologic perspective, showing some important similarities and differences with other cognitive and perceptual functions. The complexity of pain perception, due to its multicomponential nature, has led to the need to interpret pain within a multisensory frame of reference. That is, this function and its neural foundation cannot be fully understood without taking into consideration the processing of other information that is concurrently presented together with noxious stimuli. The extant research in this field has shown that the parietal cortex plays a major role in pain perception, due to its involvement in the integration of information coming from different sources, to the support of body ownership, and to its role in sustaining spatial attention and awareness. It is likely that this neurocognitive knowledge will lead to better treatments of chronic and acute pain in the future.

Pain is a very relevant function for our survival and its alteration leads to important consequences for people's lives. In the last decades, researchers have started to investigate pain from a neurocognitive and neuropsychologic perspective, showing some important similarities and differences with other cognitive and perceptual functions. The complexity of pain perception, due to its multicomponential nature, has led to the need to interpret pain within a multisensory frame of reference. That is, this function and its neural foundation cannot be fully understood without taking into consideration the processing of other information that is concurrently presented together with noxious stimuli. The extant research in this field has shown that the parietal cortex plays a major role in pain perception, due to its involvement in the integration of information coming from different sources, to the support of body ownership, and to its role in sustaining spatial attention and awareness. It is likely that this neurocognitive knowledge will lead to better treatments of chronic and acute pain in the future.

Background Chronic orofacial pain patients often perceive the painful face area as ‘swollen’ without clinical signs, i.e., a perceptual distortion (PD). Local anesthetic (LA) injections in healthy participants are also associated with PD Objective The aim was to explore whether PD evoked by LA into the infraorbital region of could be modulated by adding mechanical stimulation (MS) to the affected area Methods MS was given with a brush and a 128 mN von Frey filament. First, sixty healthy participants were randomly divided into three groups: 1) LA control, 2) LA with MS, 3) Isotonic solution (ISO) with MS as an additional control condition. To further examine the role of a multisensory modulation an additional experiment was conducted. Twenty participants received LA with MS (filament) in addition to visual feedback of their distorted face. The results of the two experiments are presented together Results All three LA groups experienced PD, per contra PD was not reported in the ISO group. MS alone did not change the magnitude of PD: brush (p = 0.089), filament (p = 0.203). However, when the filament stimulation was combined with additional visual information of a distorted face there was observable decrease in PD (p = 0.002) Conclusion The findings indicate the importance of multisensory integration for PD, and represent a significant step forward in the understanding of the factors that may influence this common condition. Future studies are encouraged to investigate further the cortical processing for possible implications for PD in pain management. This article is protected by copyright. All rights reserved.

Neural representations, or neurotags, refer to the idea that networks of brain cells, distributed across multiple brain areas, work in synergy to produce outputs. The brain can be considered then, a complex array of neurotags, each influencing and being influenced by each other. The output of some neurotags act on other systems, for example, movement, or on consciousness, for example, pain. This concept of neurotags has sparked a new body of research into pain and rehabilitation. We draw on this research and the concept of a cortical body matrix - a network of representations that subserves the regulation and protection of the body and the space around it - to suggest important implications for rehabilitation of sports injury and for sports performance. Protective behaviours associated with pain have been reinterpreted in light of these conceptual models. With a particular focus on rehabilitation of the injured athlete, this review presents the theoretical underpinnings of the cortical body matrix and its application within the sporting context. Therapeutic approaches based on these ideas are discussed and the efficacy of the most tested approaches is addressed. By integrating current thought in pain and cognitive neuroscience related to sports rehabilitation, recommendations for clinical practice and future research are suggested. Refereed/Peer-reviewed

Previous studies showed that self-localisation ability involves both vision and proprioception, integrated into a single percept, with the tendency to rely more heavily on visual than proprioceptive cues. Despite the increasing evidence for the importance of vision in localising the hands, the time course of the interaction between vision and proprioception during visual occlusion remains unclear. In particular, we investigated how the brain weighs visual and proprioceptive information in hand localisation over time when the visual cues do not reflect the real position of the hand. We tested three hypotheses: Self-localisations are less accurate when vision and proprioception are incongruent; under the same conditions of incongruence, people first rely on vision and gradually revert to proprioception; if vision is removed immediately prior to hand localisation, accuracy increases. Sixteen participants viewed a video of their hands, under three conditions each undertaken with eyes open or closed: Incongruent conditions (right hand movement seen: inward, right hand real movement: outward), Congruent conditions (movement seen congruent to real movement). The right hand was then hidden from view and participants performed a localisation task whereby a moving vertical arrow was stopped when aligned with the felt position of their middle finger. A second experiment used identical methodology, but with the direction of the arrow switched. Our data showed that, in the Incongruent conditions (both with eyes open and closed), participants perceived their right hand close to its last seen position. Over time, the perceived position of the hand shifted towards the physical position. Closing the eyes before the localisation task increased the accuracy in the Incongruent condition. Crucially, Experiment 2 confirmed the findings and showed that the direction of arrow movement had no effect on hand localisation. Our hypotheses were supported: When vision and proprioception were incongruent, participants were less accurate and initially relied on vision and then proprioception over time. When vision was removed, this shift occurred more quickly. Our findings are relevant in understanding the normal and pathological processes underpinning self-localisation. Refereed/Peer-reviewed

The tendon vibration illusion has been extensively used to manipulate the perceived position of one's own body part. However, findings from previous research do not seem conclusive regarding the perceptual effect of the concurrent stimulation of both agonist and antagonist tendons over one joint. On the basis of recent data, it has been suggested that this paired stimulation generates an inconsistent signal about the limb position, which leads to a perceived shrinkage of the limb. However, this interesting effect has never been replicated. The aim of the present study was to clarify the effect of a simultaneous and equal vibration of the biceps and triceps tendons on the perceived location of the hand. Experiment 1 replicated and extended the previous findings. We compared a dual tendon stimulation condition with single tendon stimulation conditions and with a control condition ( no vibration) on both 'upward-downward' and 'towards-away from the elbow' planes. Our results show a mislocalisation towards the elbow of the position of the vibrated arm during dual vibration, in line with previous results; however, this did not clarify whether the effect was due to arm representation contraction (i.e., a 'telescoping' effect). Therefore, in Experiment 2 we investigated explicitly and implicitly the perceived arm length during the same conditions. Our results clearly suggest that in all the vibration conditions there was a mislocalisation of the entire arm (including the elbow), but no evidence of a contraction of the perceived arm length. Refereed/Peer-reviewed

Several studies have shown that watching one’s own body part improves tactile acuity and discrimination abilities for stimuli presented on that location. In a series of experiments we asked the participants to localize tactile stimuli presented on the left or right arm. In Experiment 1 the participants were not allowed to watch their body, but they could see another person’s left arm via a LCD display. This arm could be touched or not during the presentation of the stimuli. We found that when the participants saw the arm on the screen being touched, their responses to the tactile stimuli presented on the left and on the right arm were faster and more accurate than when the arm on the screen was approached but not touched. Critically, we did not find any illusion of ownership related to the hand seen on the screen. In Experiments 2 and 3 we varied the position of the screen with respect to the participant’s body midline and the image displayed on it (an arm or an object of equal size). The participants gave faster responses when an object rather than a hand was displayed on the screen. Moreover, the responses were slower when the hand on the screen was placed in front of the participants, as compared to any other position. Taken together the results of our experiments would seem to suggest that watching touch activates multisensory mechanisms responsible for alerting people regarding the possible presence of tactile stimuli on the body surface.