The Influence of Motor Task on Tactile Suppression During Action

Movement of a limb substantially decreases the intensity and sensitivity with which tactile stimuli on that limb are perceived. This movement-related tactile suppression likely interferes with performance in motor tasks that require the precise evaluation of tactile feedback, such as the adjustment of grip forces during grasping. Therefore, we hypothesise that suppression might be stronger for stimuli that are irrelevant to successful performance in a given motor task. To test this hypothesis, we measured participants’ perception of tactile intensity while performing different motor tasks. We investigated perception of both supra-threshold stimuli (Exp. 1: intensity discrimination) and of stimuli close to the detection threshold (Exp. 2: detection). We compared tactile perception between two grasping conditions (active, tactile inputs relevant), a condition where participants pointed in the air (active, tactile inputs irrelevant) and a static condition (baseline). In both experiments, we observed tactile suppression in all three movement conditions but not the predicted attenuation of tactile suppression in the grasp conditions. Contrary to our hypothesis, there was even an amplification of tactile suppression in the grasping conditions of Exp. 1, which might be related to the movement velocity. In conclusion, we did not find evidence that motor tasks modulate the strength of tactile suppression. Our results further suggest that it is important to control for possibly confounding variables, such as movement velocity and laterality, in this line of research.