Does CRPS impair the perception of somatosensory and non-somatosensory stimuli?

Filbrich, Lieve [UCL] Alamia, Andrea [UCL] Verfaille, Charlotte [UCL] Barbier, Olivier [UCL] Libouton, Xavier [UCL] Fraselle, Virginie [UCL] Mouraux, Dominique [ULB] Berquin, Anne [UCL] Legrain, Valéry [UCL] et al.[show all]

Patients suffering from the complex regional pain syndrome (CRPS) are presumed to be affected by cognitive deficits altering their ability to represent and perceive their body (for a review see Legrain et al., PAIN, 2012). Up to now, it is however unclear whether these cognitive deficits only affect the perception of stimuli applied to the body surface, or also stimuli presented in external space, e.g. visual stimuli. If the latter is the case, it also remains unclear if these deficits in spatial perception are limited to the space proximal to the patients’ body or if they extend toward farther space. We investigated these questions using temporal order judgement (TOJ) tasks in upper-limb CRPS patients, with either tactile or visual stimuli. TOJ tasks are classically used to investigate mechanisms of spatial attention. In typical TOJ tasks, participants have to report which of two stimuli presented with various inter-stimulus time intervals has been perceived first. In the tactile TOJ task used in the present study, pairs of vibrotactile stimuli were presented, one applied to either hand. CRPS patients performed the task with their arms either in a crossed or an uncrossed posture. This manipulation of posture was aimed at clarifying whether the patients used an anatomical representation of the skin surface or a spatial representation of the body (i.e. based on the position of the limbs in external space) to perform the task. In the visual TOJ task, pairs of visual stimuli were presented, one in either side of space. Visual stimuli were presented either close or far from the patients’ hands. This manipulation intended to differentiate whether patients’ possible deficits affect the space immediately surrounding the body or external space in general. Results for the tactile TOJ task did not reveal systematic cognitive deficits in the ability to perceive the location of tactile stimuli, neither for the uncrossed nor the crossed arm posture. On the contrary, results in the visual TOJ task suggest that the patients paid more attention to the visual stimuli presented in the same side of space as the unaffected limb, independently of whether the visual stimuli were presented close or far from the hands. Our results extend previous studies, as they show that cognitive deficits in upper-limb CRPS patients can also affect the perception of the space external to the body. We did however not replicate previous findings which showed deficits in the processing of somatosensory information. These discrepant results could be explained by the duration of the CRPS.