Sensorimotor incongruence and body perception: An experimental investigation

Objectives: Several studies have shown that mirrored arm or leg movements can induce altered body sensations. This includes the alleviation of chronic pain using congruent mirror feedback and the induction of abnormal sensation in healthy participants using incongruent mirror feedback. Prior research has identified neuronal and conceptual mechanisms of these phenomena. With the rising application of behavior-based methods for pain relief, a structured investigation of these reported effects seems necessary. Methods: We investigated a mirror setup that included congruent and incongruent hand and arm movements in 113 healthy participants and assessed the occurrence and intensity of unusual physical experiences such as pain, the sensation of missing or additional limbs, or changes in weight or temperature. A wooden surface instead of a mirror condition served as control. Results: As reported earlier, mirrored movements led to a variety of subjective reactions in both the congruent an incongruent movement condition, with the sensation of possessing a third limb being significantly more intense and frequent in the incongruent mirror condition. Reports of illusory pain were not more frequent during mirrored than during non-mirrored movements. Conclusions: These results suggest that, while all mirrored hand movements induce abnormal body perceptions, the experience of an extra limb is most pronounced in the incongruent mirror movement condition. The frequent sensation of having a third arm may be related to brain processes designed to integrate input from several senses in a meaningful manner. Painful sensations are not more frequent or intense when a mirror is present. © 2013 Foell, Bekrater-bodmann, Mccabe and Flor

Sensory disturbances, but not motor disturbances, induced by sensorimotor conflicts are increased in the presence of acute pain

© 2017 Brun, Gagné, McCabe and Mercier. Incongruence between our motor intention and the sensory feedback of the action (sensorimotor conflict) induces abnormalities in sensory perception in various chronic pain populations, and to a lesser extent in pain-free individuals. The aim of this study was to simultaneously investigate sensory and motor disturbances evoked by sensorimotor conflicts, as well as to assess how they are influenced by the presence of acute pain. It was hypothesized that both sensory and motor disturbances would be increased in presence of pain, which would suggest that pain makes body representations less robust. Thirty healthy participants realized cyclic asymmetric movements of flexion-extension with both upper limbs in a robotized system combined to a 2D virtual environment. The virtual environment provided a visual feedback (VF) about movements that was either congruent or incongruent, while the robotized system precisely measured motor performance (characterized by bilateral amplitude asymmetry and medio-lateral drift). Changes in sensory perception were assessed with a questionnaire after each trial. The effect of pain (induced with capsaicin) was compared to three control conditions (no somatosensory stimulation, tactile distraction and proprioceptive masking). Results showed that while both sensory and motor disturbances were induced by sensorimotor conflicts, only sensory disturbances were enhanced during pain condition comparatively to the three control conditions. This increase did not statistically differ across VF conditions (congruent or incongruent). Interestingly however, the types of sensations evoked by the conflict in the presence of pain (changes in intensity of pain or discomfort, changes in temperature or impression of a missing limb) were different than those evoked by the conflict alone (loss of control, peculiarity and the perception of having an extra limb). Finally, results showed no relationship between the amount of motor and sensory disturbances evoked in a given individual. Contrary to what was hypothesized, acute pain does not appear to make people more sensitive to the conflict itself, but rather impacts on the type and amount of sensory disturbances that they experienced in response to that conflict.Moreover, the results suggest that some sensorimotor integration processes remain intact in presence of acute pain, allowing us to maintain adaptive motor behavior

The contribution of motor commands to the perturbations induced by sensorimotor conflicts in fibromyalgia

Individuals with pain report higher sensory disturbances during sensorimotor conflicts compared to pain-free individuals. In the pain field, it is frequently assumed that disturbances arise from a discordance between sensory and efference copies (defined as sensory-motor conflict), while in the sensorimotor control field they are considered to result from the incongruence between sensory modalities (defined as sensory-sensory conflict). The general aim of this study was to disentangle the relative contribution of motor efferences and sensory afferences to the increased sensitivity to sensorimotor conflicts in individual with fibromyalgia (n = 20) compared to controls (n = 20). We assessed sensory and motor disturbances during sensory-sensory and sensory-motor conflicts using a robotized exoskeleton interfaced with a 2D virtual environment. There was a significant interaction between the group and the type of conflict (p = 0.03). Moreover, the increase in conflict sensitivity from sensory-sensory to sensory-motor conflicts in fibromyalgia was related to conflict-induced motor disturbances (r = 0.57; p < 0.01), but did not result from a poorer proprioception (r = 0.12; p = 0.61). Therefore, it appears that higher conflict sensitivity in fibromyalgia is mainly explained by a sensory-motor conflict rather by a sensory-sensory conflict. We suggest this arises due to a deficit in updating predicted sensory feedback rather than in selecting appropriate motor commands

Virtual reality-induced sensorimotor conflict evokes limb-specific sensory disturbances in complex regional pain syndrome

Sensory disturbances are frequently observed in complex regional pain syndrome (CRPS). They are characterized by changes in the perception of limb weight and temperature, a distorted mental image of the affected limb, feeling the limb as a foreign body part, etc. However, the origin of such disturbances remains unclear. It has been hypothesized that such disturbances are due to attentional effects and/or sensorimotor integration deficits. If sensory disturbances are explained by sensorimotor integration deficits rather than by attentional factors (as hypervigilance toward pain and pain-related sensations), they would be expected to be specific in terms of the type of sensation evoked and in terms of localization.Objectives: The first objective was to test whether sensory disturbances evoked by a unilateral sensorimotor conflict are specific to the painful limb and differ according to the type of sensory disturbances in individuals with a unilateral CRPS compared to healthy controls (HC). The second objective was to assess the association between clinical characteristics and sensory disturbances evoked by a unilateral sensorimotor conflict. The third objective was to assess motor disturbances induced by a unilateral sensorimotor conflict.Methods: Ten adults with upper limb (UL) CRPS and 23 HC were recruited. Sensorimotor conflict was elicited with a KINARM robotized exoskeleton interfaced with a 2D virtual environment allowing the projection of a virtual UL that was moving in either a congruent or incongruent manner relative to the actual UL movement. Participants were required to rate the sensory disturbances evoked from 0 (no change) to 3 (high change) on a questionnaire (8 items). According to a previous study, items were categorized in two Types (Type 1: pain, discomfort, the feeling of losing a limb, change in weight and temperature; Type 2: feelings of peculiarity, the impression of gaining a limb and losing control). Motor disturbances were quantified as mediolateral drift and changes in amplitude of UL movement. Recorded clinical characteristics included the intensity and duration of pain, proprioception deficits, and body perception disturbances.Results and conclusion: CRPS participants report higher Type 1 than Type 2 disturbances for the Affected limb (while the reverse was observed for HC and for the Unaffected limb). In addition, no difference was observed between the Unaffected limb in CRPS and the Dominant limb in HC for Type 2 disturbances, while higher conflict sensitivity was observed for Type 1 disturbances. Conflict sensitivity was related to higher pain (but not to other clinical characteristics) only for Type 1 disturbances in the Affected limb. Finally, no difference in motor disturbances was observed between CRPS and HC. While this does not completely rule out the attentional hypothesis, these results are in line with the hypothesis that sensory disturbances in CRPS are due to deficits in sensorimotor integration

Motor and sensory disturbances induced by sensorimotor conflicts during passive and active movements in healthy participants

© 2018 Brun et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. Sensorimotor conflict induces both sensory and motor disturbances, but the specific factors playing a role in conflict-induced disturbances are still misunderstood. For example, we still do not know the role played by motor intention (vs. a purely visuo-proprioceptive conflict) or the influence of specific types of incongruent visual feedback. The objective of this study was threefold: 1- to compare the effect of passive and active movement during sensorimotor conflict on sensory disturbances measured with a questionnaire; 2- to compare the effect of three incongruent visual feedback conditions on sensory and motor (mediolateral drift and movement amplitude) disturbances; 3- to test whether conflict-induced sensory and motor disturbances were stable over time. 20 healthy participants realized active or passive cyclic upper limb movements while viewing either congruent or incongruent visual feedback about their movement using a robotized exoskeleton combined with 2D virtual reality interface. First, results showed that in condition of conflict, participants reported higher sensory disturbances during active movements compared to passive movements (p = 0.034), suggesting that the efference copy reinforces the conflict between vision and proprioception. Second, the three conditions of incongruence in the active condition induced similar sensory (all p>0.45) and motor disturbances (medio-lateral drift: all p>0.59 and amplitude: all p>0.25), suggesting that conflict induced motor disturbances could be related more to the observation of another movement rather than to a detection of conflict between motor intention and sensory feedback. Finally, both sensory and motor disturbances were stable over time (all ICCs between 0.76 and 0.87), demonstrating low variability within participants. Overall, our results suggest that the efference copy is more involved in sensory disturbances than in motor disturbances, suggesting that they might rely on independent processes

Visual illusions modulate body perception disturbance and pain in Complex Regional Pain Syndrome: A randomized trial

Background: Effective treatment of longstanding Complex Regional Pain Syndrome (CRPS) is a challenge, as causal mechanisms remain elusive. People with CRPS frequently report distorted subjective perceptions of their affected limb. Evidence of pain reduction when the affected limb is visually altered in size suggests that visual illusions used to target central processing could restore coherence of this disrupted limb representation. We hypothesized that using virtual reality that alters hand image to match the patient's desired hand appearance would improve body perception disturbance and pain. Also, repeated exposure would maintain any therapeutic effect. Methods: A blinded randomized controlled trial of 45 participants with refractory upper-limb CRPS and body perception disturbance (BPD) viewed a digital image of their affected hand for 1min. The image was digitally altered according to the patient's description of how they desired their hand to look in the experimental group and unaltered in the control group. BPD and pain were measured pre- and post-intervention. A subgroup was followed up 2weeks after a course of repeated interventions. Results: BPD (mean-6, ±SD 7.9, p=0.036, effect size [ES]=0.6) and pain intensity (mean-0.43, ±SD 1.3, p=0.047, ES=0.5) reduced in 23 participants after single exposure compared to controls (n=22). At follow-up, the subgroup (experimental n=21; control n=18) showed sustained pain reduction only (p=0.037, ±SD 1.9, ES=0.7), with an overall 1.2 decrease on an 11-point scale. Conclusions: Visually changing the CRPS hand to a desired appearance modulates BPD and pain suggesting therapeutic potential for those with refractory CRPS. Further research to optimize this therapeutic effect is required. Significance: Visual bodily illusions that change the shape and appearance of the painful CRPS hand to that desired by the patient result in a rapid amelioration of pain and body perception disturbance in people with longstanding CRPS. These findings highlight the future potential of this drug-free approach in the treatment of refractory CRPS

Measurement properties of the SF-MPQ-2 neuropathic qualities subscale in persons with CRPs: Validity, responsiveness, and Rasch analysis

© 2018 American Academy of Pain Medicine. All rights reserved. Objectives. The purpose of this study was to conduct classical psychometric evaluation and Rasch analysis on the Neuropathic Qualities subscale of the Short-Form McGill Pain Questionnaire-2 utilizing scores from persons with complex regional pain syndrome to consider reliability and person separation, validity (including unidimensionality), and responsiveness in this population. Methods. Secondary analysis of longitudinal data from persons with acute complex regional pain syndrome was utilized for analysis of the psychometric properties and fit to the Rasch model of the Neuropathic Qualities subscale. We followed an iterative process of Rasch analysis to evaluate and address data fitting challenges. Results. Repeated measures from 59 persons meeting the Budapest criteria were used for analysis. Both item-total correlations and unidimensionality analyses supported theoretical construct validity; all convergent construct validity hypotheses were also supported. Responsiveness was demonstrated comparing baseline and one-year data at d ¼ 0.92, with a standardized response mean of 0.97. Data were able to fit the Rasch model, but all Neuropathic Qualities items had disordered thresholds that required rescoring. Additionally, local dependency and differential item function were addressed by “bundling,” suggesting that no further item reduction would be possible. Conclusions. This study provided preliminary support for the validity and responsiveness of the Neuropathic Qualities subscale in persons with complex regional pain syndrome. Rasch analysis further endorses use of the Neuropathic Qualities subscale as a “stand-alone” measure for neuropathic features, but with substantial background data transformations. Replication with larger samples is recommended to increase confidence in these findings

Sensory disturbances induced by sensorimotor conflicts are higher in complex regional pain syndrome and fibromyalgia compared to arthritis and healthy people, and positively relate to pain intensity

Background Sensorimotor conflicts are well known to induce sensory disturbances. However, explanations as to why patients with chronic pain are more sensitive to sensorimotor conflicts remain elusive. The main objectives of this study were (a) to assess and compare the sensory disturbances induced by sensorimotor conflict in complex regional pain syndrome (n = 38), fibromyalgia (n = 36), arthritis (n = 34) as well as in healthy volunteers (HV) (n = 32); (b) to assess whether these disturbances were related to the intensity and duration of pain, or to other clinical variables assessed using questionnaires (abnormalities in sensory perception, depression and anxiety); and (c) to categorize different subgroups of conflict-induced sensory disturbances. Methods One hundred and forty participants performed in phase or anti-phase movements with their arms while viewing a reflection of one arm in a mirror (and the other arm obscured). They were asked to report changes in sensory disturbances using a questionnaire. Results First, results showed that patients with complex regional pain syndrome and fibromyalgia were more prone to report sensory disturbances than arthritis patients and HV in response to conflicts (small effect size). Second, conflict-induced sensory disturbances were correlated with pain intensity (large effect size) and abnormalities in sensory perception (only in the CRPS group) but were not related to the duration of the disease or psychological factors. Finally, we identified two distinct subgroups of conflict-induced sensory disturbances. Conclusions Our results suggest that pain lowers the threshold for the detection of sensorimotor conflicts, a phenomenon that could contribute to the maintenance of pain in clinical populations. Significance Individuals with complex regional pain syndrome and fibromyalgia were more sensitive to sensorimotor conflicts than arthritis patients and controls. Moreover, conflict-induced sensory disturbances were specific to higher pain intensity and higher sensory abnormalities in all groups, suggesting that pain lowers the threshold for the detection of sensorimotor conflicts

Pain and other symptoms of CRPS can be increased by ambiguous visual stimuli - An exploratory study

Background: Visual disturbance, visuo-spatial difficulties, and exacerbations of pain associated with these, have been reported by some patients with Complex Regional Pain Syndrome (CRPS). Aims: We investigated the hypothesis that some visual stimuli (i.e. those which produce ambiguous perceptions) can induce pain and other somatic sensations in people with CRPS. Methods: Thirty patients with CRPS, 33 with rheumatology conditions and 45 healthy controls viewed two images: a bistable spatial image and a control image. For each image participants recorded the frequency of percept change in 1 min and reported any changes in somatosensation. Results: 73% of patients with CRPS reported increases in pain and/or sensory disturbances including changes in perception of the affected limb, temperature and weight changes and feelings of disorientation after viewing the bistable image. Additionally, 13% of the CRPS group responded with striking worsening of their symptoms which necessitated task cessation. Subjects in the control groups did not report pain increases or somatic sensations. Conclusions: It is possible to worsen the pain suffered in CRPS, and to produce other somatic sensations, by means of a visual stimulus alone. This is a newly described finding. As a clinical and research tool, the experimental method provides a means to generate and exacerbate somaesthetic disturbances, including pain, without moving the affected limb and causing nociceptive interference. This may be particularly useful for brain imaging studies. © 2010 Published by Elsevier Ltd. on behalf of European Federation of International Association for the Study of Pain Chapters