No abstract

The way in which humans represent their own bodies is critical in guiding their interactions with the environment. To achieve successful body-space interactions, the body representation is strictly connected with that of the space immediately surrounding it through efficient visuo-tactile crossmodal integration. Such a body-space integrated representation is not fixed, but can be dynamically modulated by the use of external tools. Our study aims to explore the effect of using a complex tool, namely a functional prosthesis, on crossmodal visuo-tactile spatial interactions in healthy participants. By using the crossmodal visuo-tactile congruency paradigm, we found that prolonged training with a mechanical hand capable of distal hand movements and providing sensory feedback induces a pattern of interference, which is not observed after a brief training, between visual stimuli close to the prosthesis and touches on the body. These results suggest that after extensive, but not short, training the functional prosthesis acquires a visuo-tactile crossmodal representation akin to real limbs. This finding adds to previous evidence for the embodiment of functional prostheses in amputees, and shows that their use may also improve the crossmodal combination of somatosensory feedback delivered by the prosthesis with visual stimuli in the space around it, thus effectively augmenting the patients' visuomotor abilities.

The human hand is one of the most complex structures in the body, being involved in dexterous manipulation and fine sensing. Traditional engineering approaches have mostly attempted to match such complexity in robotics without sufficiently stressing on the underlying mechanisms that its morphology encodes. In this work, we propose an artificial skin able to encode, through its morphology, the tactile sense of a robotic hand, characteristic to slippage events. The underlying layout consists of ridges and allows slippage detection and the quantification of slippage speed. Such encoding of slippage signal becomes suitable for relaying tactile feedback to users in prosthetic applications. This approach emphasizes the importance of exploiting morphology and mechanics in structures for the design of prosthetic interfaces. Artificial Ridged Skin for Slippage Speed Detection in Prosthetic Hand ApplicationsDana D. Damian, Harold Martinez, Konstantinos Dermitzakis, Alejandro Hernandez-Arieta and Rolf Pfeifer Abstract-The human hand is one of the most complex structures in the body, being involved in dexterous manipulation and fine sensing. Traditional engineering approaches have mostly attempted to match such complexity in robotics without sufficiently stressing on the underlying mechanisms that its morphology encodes. In this work, we propose an artificial skin able to encode, through its morphology, the tactile sense of a robotic hand, characteristic to slippage events. The underlying layout consists of ridges and allows slippage detection and the quantification of slippage speed. Such encoding of slippage signal becomes suitable for relaying tactile feedback to users in prosthetic applications. This approach emphasizes the importance of exploiting morphology and mechanics in structures for the design of prosthetic interfaces.

Aiming at the seamless integration of artificial limbs into the human body, sensory feedback plays an important role. There are two main methods of providing sensory feedback: invasive and non-invasive. One of the challenges of non-invasive methods is to identify the appropriate body location to transmit information through. In prosthetic applications it makes sense to target locations with low sensory loads. However, this presents new challenges to overcome due to the low mechanoreceptor density of these areas. In this study we aim to understand the limitations of using electrical stimulation for transmitting information to the body by targeting the lower back. We investigate the effects of (1) stimulation frequency and (2) electrode size on the stimulation parameters for sensation. Our results show an increased influence of stimulation frequency over the stimulation parameters with smaller electrodes. Larger electrodes reduced inter-individual diferences, however the stimulation range, that is the difference between the lower sensation threshold and the pain threshold, was considerably reduced. Our experiments show that the current required to achieve nerve depolarization was low (2mA to 10 mA).

No abstract