An instance of tactile suppression: Active exploration impairs tactile sensitivity for the direction of lateral movement

Abstract

The phenomenon of a reduction in tactile sensitivity during voluntarily executed body movement we call “tactile suppression”. This is in analogy to saccadic suppression where the visual sensitivity is reduced during voluntarily executed eye movements [1]. Here we investigate tactile suppression using an integrated tactile/kinesthetic display – consisting of a tactile shear force device [2] mounted on a hyper redundant haptic display (ViSHaRD10 [3]). To quantify the tactile suppression effect we measured subject’s motion-direction discrimination performance for tactile stimuli moving laterally on the index finger under various active and passive exploration conditions. In the baseline condition (“static”) only tactile stimuli were provided using the shear-force device while the arm was held still. In the “active” condition subjects had to discriminate the direction of tactile motion while actively executing arm movements at the same time. Finally, in the “passive” condition the kinesthetic device pas\nsively moved the subjects’ arm, while the subject was performing the discrimination task. Compared to the “still” condition results indicate a significant decrease of tactile sensibility during active movements whereas passive movements seem to have a minor effect on tactile discrimination performance.