Contact with Sliding over a Rotating Ridged Surface: the Turntable Illusion

The mechanical interaction between the skin and the environment is important in shaping our knowledge of object properties. In addition, the response of cutaneous mechanoreceptors also contributes to our sense of limb position and motion. In previous papers, we demonstrated a striking motor error during self-paced hand movements over a ridged stationary surface, with the hand out of sight, which depended on the orientation of the ridges. Tactile feedback, combined with muscular-skeletal proprioception and the forward model of hand motion, produced a bias in the perceived hand displacement, which triggers a corrective motion in a direction towards the long axis of the ridges. Here, we found a similar effect when participants are required to slide over a rotating surface with ridges. Instead, in a control condition where participants were required to slide over a rotating smooth plate, they tend to deviate toward the same direction of the plate rotation. This is in agreement with our previous results, and well-explained by the fact that the bias induced by tactile feedback increases in absolute angular value during task execution, due to ridge rotation. We propose a Kalman filter to model the dynamic integration of touch and proprioception for the estimation of the perceived hand displacement.