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Spatial Summation of Localized Pressure for Haptic Sensory Prostheses

Sreela Kodali, Cihualpilli Camino Cruz, Thomas C. Bulea, Kevin S. Rao Diana Bharucha-Goebel, Alexander T. Chesler, Carsten G. Bonnemann, Allison M. Okamura

TL;DR

The study tackles sensory loss by proposing a forearm-based haptic sensory prosthesis that uses localized pressure and spatial summation to expand perceptual range without occluding the hand. It presents a modular, two-point pressure stimulation device with force sensing and position-controlled actuators, capable of independent control and multiple stimulators. In a preliminary perceptual experiment, the just noticeable difference decreases when using two simultaneous stimuli compared with a single stimulus, and participants can reliably rank mixed stimuli along a perceptual continuum. These findings support spatial summation as a viable strategy to enhance the resolution and dynamic range of arm-mounted haptic feedback devices for sensory substitution.

Abstract

A host of medical conditions, including amputations, diabetes, stroke, and genetic disease, result in loss of touch sensation. Because most types of sensory loss have no pharmacological treatment or rehabilitative therapy, we propose a haptic sensory prosthesis that provides substitutive feedback. The wrist and forearm are compelling locations for feedback due to available skin area and not occluding the hands, but have reduced mechanoreceptor density compared to the fingertips. Focusing on localized pressure as the feedback modality, we hypothesize that we can improve on prior devices by invoking a wider range of stimulus intensity using multiple points of pressure to evoke spatial summation, which is the cumulative perceptual experience from multiple points of stimuli. We conducted a preliminary perceptual test to investigate this idea and found that just noticeable difference is reduced with two points of pressure compared to one, motivating future work using spatial summation in sensory prostheses.

Spatial Summation of Localized Pressure for Haptic Sensory Prostheses

TL;DR

The study tackles sensory loss by proposing a forearm-based haptic sensory prosthesis that uses localized pressure and spatial summation to expand perceptual range without occluding the hand. It presents a modular, two-point pressure stimulation device with force sensing and position-controlled actuators, capable of independent control and multiple stimulators. In a preliminary perceptual experiment, the just noticeable difference decreases when using two simultaneous stimuli compared with a single stimulus, and participants can reliably rank mixed stimuli along a perceptual continuum. These findings support spatial summation as a viable strategy to enhance the resolution and dynamic range of arm-mounted haptic feedback devices for sensory substitution.

Abstract

A host of medical conditions, including amputations, diabetes, stroke, and genetic disease, result in loss of touch sensation. Because most types of sensory loss have no pharmacological treatment or rehabilitative therapy, we propose a haptic sensory prosthesis that provides substitutive feedback. The wrist and forearm are compelling locations for feedback due to available skin area and not occluding the hands, but have reduced mechanoreceptor density compared to the fingertips. Focusing on localized pressure as the feedback modality, we hypothesize that we can improve on prior devices by invoking a wider range of stimulus intensity using multiple points of pressure to evoke spatial summation, which is the cumulative perceptual experience from multiple points of stimuli. We conducted a preliminary perceptual test to investigate this idea and found that just noticeable difference is reduced with two points of pressure compared to one, motivating future work using spatial summation in sensory prostheses.
Paper Structure (5 sections, 2 figures)

This paper contains 5 sections, 2 figures.

Table of Contents

  1. Introduction
  2. Device Design
  3. Preliminary Tests and Results
  4. Just Noticeable Difference: One vs. Two Contacts
  5. Ordering Pairs of Stimuli

Figures (2)

  • Figure 1: The wearable device is comprised of modular pressure stimulators, a linear actuator in a rigid enclosure (a). Two pressure stimulators can be adjacent so their tactors are only 6 mm apart (b) and can be worn with its supporting electronics on the forearm (c).
  • Figure 2: (a) Results of a 2-down, 1-up staircase for a single stimulus and two stimuli, yielding JNDs of 12.3 ± 0.5 mm and 10.7 ± 0.5 mm, respectively. (b) A participant's results from ordering pairs of stimuli. Stimuli A (MIN, MIN) and stimuli I (MAX, MAX) are positioned at ends of continuum.