Study: Tactile feedback creates ‘muscle sense’ in prosthetic hand

Tactile feedback on the skin allowed blindfolded participants to determine the size of objects gripped with a prosthetic hand, according to researchers from Rice University, the University of Pisa and the Italian Institute of Technology.

“Humans have an innate sense of how the parts of their bodies are positioned, even if they cannot see them,” Marcia O’Malley, PhD, MS, professor of mechanical engineering at Rice University, said in a press release. “This muscle sense is what allows people to type on a keyboard, hold a cup, throw a ball, use a brake pedal and do countless other daily tasks.”

The researchers recruited 18 participants to test Rice’s Haptic Rocker in partnership with the Soft Hand, developed by researchers at Pisa and the Italian Institute of Technology (IIT). The goal of the study was to determine whether participants could better determine the size of objects with a prosthetic hand after they received haptic feedback from a simple skin-stretch device on the upper arm,

The Rice Haptic Rocker uses a rotating arm that brushes a soft rubber pad over the skin of the arm, according to the release. When the prosthesis is fully open, the rubber arm does not touch the skin. However, as the hand closes, the arm rotates. The harder the hand closes, the greater the skin is stretched, the release noted. In addition, researchers at Pisa and IIT designed the Soft Hand to mimic the control synergy of a natural hand.

Participants in the size-determination study were blindfolded and asked to grip two objects. They were then asked which object was larger. Those without haptic feedback chose correctly 33% of the time, while those using the Rice Haptic Rocker chose correctly 70% of the time, according to the release.

The researchers are now studying to determine if amputees using the Soft Hand experience a similar benefit with the haptic rocker, according to the release. They will present their findings June 7 at the World Haptics 2017 conference in Germany.


Disclosure: The researchers report no relevant financial disclosures.

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