Design and Psychophysical Validation of a Slip Induction Device for Sensorimotor Evaluation of Prehensile Grip

The purpose of this study was to investigate the psychophysical understanding of a slip stimulus applied at the fingertips. We hypothesized that the perception of slip and its characteristics, such as slip distance and slip speed depends on the interaction between slip direction, slip distance, and slip speed. We developed a novel slip induction device to simulate the artificial sense of slip for prehensile grasps. We conducted a psychophysical experiment on eight healthy subjects. The experiment was designed to evaluate the effect of slip direction on slip perception as well as on the perception of slip distance and slip speed. A series of psychophysical questions were asked at the end of the slip stimulus to record the subjective responses of the participants. The average perceptual accuracy (PA) (%) was used to quantify the subject responses. We showed that the perception of slip during a prehensile grasp is independent of slip direction, but slip direction significantly modulates the perception of slip distance and slip speed. We also observed that a significant interaction exists between slip distance and slip speed in the upward slip direction. It was also observed that the average PA was significantly different for various combinations of slip distance and slip speed in the upward slip direction. This study clearly establishes an interaction between the slip direction, slip distance, and slip speed for prehensile grasps. Our findings may have a direct impact on grip function assessment and rehabilitation for individuals with sensorimotor deficits.