Perception of Springs With Visual and Proprioceptive Motion Cues: Implications for Prosthetics

Abstract

Manipulating objects with an upper limb prosthesis requires significantly more visual attention than doing the same task with an intact limb. Prior work and comments from individuals lacking proprioception indicate that conveying prosthesis motion through a nonvisual sensory channel would reduce and possibly remove the need to watch the prosthesis. To motivate the design of suitable sensory substitution devices, this study investigates the difference between seeing a virtual prosthetic limb move and feeling one's real limb move. Fifteen intact subjects controlled a virtual prosthetic finger in a one-degree-of-freedom rotational spring discrimination task. A custom haptic device was used to measure both real finger position and applied finger force, and the resulting prosthetic finger movement was displayed visually (on a computer screen) and/or proprioceptively (by allowing the subject's real finger to move). Spring discrimination performance was tested for three experimental sensory conditions-visual motion, proprioceptive motion, and visual and proprioceptive motion-using the method of constant stimuli, with a reference stiffness of 290 N/m. During each trial, subjects sequentially pressed the right index finger on a pair of hard-surfaced virtual springs and decided which was stiffer. No significant performance differences were found between the three experimental sensory conditions, but subjects perceived proprioceptive motion to be significantly more useful than visual motion. These results imply that relaying proprioceptive information through a nonvisual channel could reduce visual attention during prosthesis control while maintaining task performance, thus improving the upper limb prosthesis experience.

Editorial IEEE Transactions on Human–Machine Systems: Year in Review for 2013

“…Gurari and colleagues [30] showed that one need not overload the visual channel to provide proprioceptive information. They describe a novel experimental apparatus that mimics the usage of a myoelectrically controlled upper limb prosthesis in a one-DOF rotational spring discrimination task.…”

Multisensory Softness

“…More details about the study can be found in Gurari et al (2013). The motivation for this work was to investigate whether the upper-limb prosthesis experience can be improved by reducing the demand on vision during arm control.…”

“…Tan et al (1992) showed that springs can be discriminated based on force cues, The mean WF and PSE values exclude Participants 5, 7, and 9, since a goodness-of-fit was not achieved for one sensory condition for each of these participants, as indicated by the asterisk (*). Adapted from Table 10.1 in Gurari et al (2013) © IEEE 2013 Across all trials in each testing condition during the exploration of a standard spring for a representative participant, the respective minimum, lower quartile, median, upper quartile, and maximum distance that the finger traveled is given. Adapted from Table IV in Gurari et al (2013) © IEEE 2013 not compliance cues, if the distance one's hand travels does not vary across testing trials, giving WFs close to 0.08.…”

“…Adapted from Table 10.1 in Gurari et al (2013) © IEEE 2013 Across all trials in each testing condition during the exploration of a standard spring for a representative participant, the respective minimum, lower quartile, median, upper quartile, and maximum distance that the finger traveled is given. Adapted from Table IV in Gurari et al (2013) © IEEE 2013 not compliance cues, if the distance one's hand travels does not vary across testing trials, giving WFs close to 0.08. The testing procedures used and data obtained in our study do not provide conclusive evidence as to whether participants were discriminating based on force or compliance.…”

An overview and comparison of upper limb prosthetics

“…The proprioceptive sense is significantly more useful than visual positioning when controlling a prosthetic arm. However, there are no current proprioceptive feedback devices commercially available for use in prosthetic arms [25].…”