The role of grasping demands on tactile suppression

Tactile perception is impaired in a limb that is moving compared to when it is static. A possible mechanism that explains this phenomenon is an internal forward model that estimates future sensory states of the moving limb and suppresses associated feedback signals arising from that limb. Because sensorimotor estimations are based on an interplay of efferent and afferent feedback signals, the strength of tactile suppression may also depend on the relative utilization of sensory feedback from the moving limb. To test how the need to process somatosensory feedback influences movement-induced tactile suppression, we asked participants to perform reach-to-grasp movement of different demands: the target object was covered with materials of different frictional properties and the task was performed both with and without vision. As expected, participants performed the grasping movement more carefully when interacting with objects of low than high friction surfaces and when performing the task without vision. This denotes a greater need for somatosensory guidance of the digits to appropriately position the digits on the object. Accordingly, tactile suppression was weaker when grasping low than high friction objects, but only when grasping without vision. This suggests that movement-induced tactile suppression is modulated by grasping demands. Tactile suppression is downregulated when the need to process somatosensory feedback signals from that moving limb increases, like in situations when somatosensory input about the digit's state is the sole source of sensory information and when this information is particularly important for the task at hand.