A Versatile Robotic Haptic Stimulator to Study the Influence of Pain on Human Motor Control and Learning.

This paper presents an inexpensive, versatile and easy-to-install robotic haptic stimulator, capable of delivering computer-controlled innocuous and noxious mechanical stimuli. The system can be coupled with robotic interfaces typically employed to investigate human motor control and learning, and synchronized with the acquisition of relevant physiological measures. The design is based on a modified commercial rotative servomotor that actuates a 1-DOF parallel guiding mechanism connected to an end-effector that applies forces against a subject's target body area. The position of the end-effector and the interaction force with the skin, as well as sensor readings of the subject's movements, can be used by a microcontroller to control the stimulator. The results of experiments to test the stimulator's control and subjects' psychophysical responses show that the device provides robust and consistent mechanical stimulation, which elicits perceptual ratings compatible with previous relevant psychophysical studies. The presented system is the first to allow investigating the effects of painful versus innocuous stimulation on human motor control and learning.