Predictions of bimanual self-touch determine the temporal tuning of somatosensory perception

Abstract

We effortlessly distinguish between touching ourselves with our hands and being touched by other people or objects. Motor control theories posit that this distinction is made possible by the brain predicting the somatosensory consequences of our voluntary movements based on an efference copy, and attenuating our responses to the predicted self-touch. However, it remains unclear how these predictions impact somatosensory perception at times other than during self- touch: for example, as our hand reaches to touch our body or moves away from it. Here participants discriminated forces applied on their left index finger by a motor. The forces were applied during the reaching movement of their right hand towards the left hand, including the time the reaching ended by simulating self-touch between the hands, or after the reaching movement. We observed that the forces on the left hand felt progressively weaker during the reaching phase, reached their minimum perceived intensity at the time of self-touch, and quickly recovered after the end of the reaching. All effects were replicated with a new cohort of participants that further demonstrated that this gradual attenuation of the perceived magnitude of touch vanished during similar right hand reaching movements that did not produce expectations for self-touch between the two hands. Together, our results indicate a temporal tuning of somatosensory perception during movements to self-touch and underscore the role of sensorimotor context in forming predictions that attenuate the intensity of self- generated touch.