Sensory Disturbances, but Not Motor Disturbances, Induced by Sensorimotor Conflicts Are Increased in the Presence of Acute Pain

Abstract

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.

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

“…This suggests that sensory disturbances are potentially related to two different processes, the corollary being that they should be considered separately. This result is consistent with recent findings showing that the presence of acute pain influences the nature of sensory disturbances evoked by sensorimotor conflicts (Brun et al., ). In the absence of acute pain, participants mainly reported conflict‐induced disturbances such as feelings of peculiarity, perception of an extra limb and perception of losing control, and these sensations were not influenced by the presence of acute pain.…”

“…First, visual conditions (Congruent VF and Incongruent VF) were presented in a fixed order, rather than randomized (confounder) and a convenience sample was used. However, the results of our study are in line with previous studies showing that Incongruent VF induced more sensory disturbances than Congruent VF (Brun et al., ; Daenen et al., ; Foell et al., ; Katayama et al., ; McCabe et al., , ; Roussel et al., ) suggesting that these potential methodological biases had a minimal impact on our results. Second, in order to provide an informed consent, participants were informed that the experimental manipulations might cause brief discomfort, and therefore, it could have an impact on the results.…”

“…However, the presence of pain appears to lower the threshold for the detection of sensorimotor conflicts. Indeed for the Subgroup 2 sensations, people with pain reported higher sensory disturbances even in the Congruent VF condition, suggesting that the Congruent VF can be interpreted as a sensorimotor conflict for individuals with pain, consistent with previous observations (Brun et al., ; McCabe et al., ). This inaccurate perception of a sensorimotor conflict might be explained by the fact that in the presence of acute (Gandevia & Phegan, ) and chronic pain (Bultitude & Rafal, ; Lewis, Kersten, McCabe, McPherson, & Blake, ; Valenzuela‐Moguillansky, ) alterations of body perception are frequently observed.…”

“…In the absence of acute pain, participants mainly reported conflict‐induced disturbances such as feelings of peculiarity, perception of an extra limb and perception of losing control, and these sensations were not influenced by the presence of acute pain. However, in the presence of acute pain, participants reported changes in pain, discomfort, temperature and a perceived lost limb (Brun et al., ). Interestingly, two EEG studies in pain‐free individuals (Katayama et al., ; Nishigami et al., ) also support the presence of two distinct mechanisms in response to sensorimotor conflicts.…”

“…We had previously observed that some sensory disturbance items seemed to be more frequent in response to visual incongruence than others, and some appeared to occur predominantly in the presence of pain in an acute pain model (Brun, Gagné, McCabe, & Mercier, 2017). A principal component analysis (PCA) was performed on the nine items of the sensory disturbances questionnaire measured during the Incongruent VF condition to determine whether it was possible to identify subgroups of related items.…”