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.
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.
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.
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.
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.