study which was conducted at the University of Chicago and the Case Western
Reserve University is published in the Science Translational
, explains how the nervous system encodes the intensity or
magnitude of sensation and how neuro-prosthetics
are the future of this
‘Neuro-prosthetics that are capable of producing a natural sensation of touch can be developed by using a combination of high-quality implantable devices that interfaces directly with the brain and machine-learning algorithms.’
The above research was a joint effort by Bensmaia
and Dustin Tyler, PhD, the Kent H. Smith Professor of Biomedical Engineering at
Case Western Reserve University.
nerve signals from our upper limb or the hand are carried to the brain via the
median, radial and ulnar nerves.
The new study describes how
interfacing with the brain is possible by implanting devices called neural
interfaces, which can be embedded into the nerves of the arm.
researchers used two male subjects who had lost an arm following traumatic
injuries. The research team stimulated the
nerves of the subjects through the interface.
then tested the subjects' ability to distinguish the magnitude
of the sensations evoked after
stimulation. The aspects of the signals, such as frequency and
intensity of each electrical pulse was
The strength or magnitude of sensation was
determined using the activation charge rate.
By changing the activation charge rate, the team could change
sensory magnitude in a highly predictable way.
"If you want to create a dexterous hand for use
in an amputee or a quadriplegic patient, you need to not only be able to move
it, but have sensory feedback from it," said Bensmaia, who is an associate
professor of organismal biology and anatomy at the University of Chicago. "To
do this, we first need to look at how the intact hand and the intact nervous
system encodes this information, and then, to the extent that we can, try to
mimic that in a neuro-prosthesis."
Earlier in October 2016, in a separate publication from Science Translational Medicine
Bensmaia and his team led by Robert Gaunt,
PhD, from the University of Pittsburgh had announced that
they were able to restore the
sense of touch in a quadriplegic patient using a robotic arm which was controlled by his brain.
In that study, after an array of electrodes
were implanted in the areas of the brain responsible for hand
movements and for touch via a surgical procedure, researchers
interfaced directly with the patient's brain.
This allowed the patient to both
move the robotic arm and feel objects through it.
Earlier research from Bensmaia's lab had
predicted that the population spike rate
or number of times certain nerve fibers fire in response to a
given stimulus, determines how the nervous
system discerns intensity of touch
for example, how hard an object is pressing against the skin.
The team then showed that the
activation charge rate was also closely related to the evoked population spike
Building neuro-prosthetics that approximate the
natural nervous system is the next step in achieving this objective.
Earlier this year in,
in a separate paper published in IEEE Transactions on Haptics,
Bensmaia and his team led by Benoit Delhaye and Erik Schluter, tested the sensory abilities
of a robotic fingertip equipped with touch sensors.
The team tested the finger's
ability to distinguish different touch locations, different pressure levels,
the direction and speed of surfaces moving across it and the identity of
textures scanned across it.
The robotic finger
with machine learning algorithms,
proved to be almost as good as a human at most of these
A similar combination of such
high-quality input with the algorithms and data,
neuro-prosthetics that approximate natural sensations of touch
can be developed.
Without realistic, natural-feeling sensations,
neuro-prosthetics will never come close to achieving the dexterity of our
"The idea is that if we can reproduce those
signals exactly, the amputee won't have to think about it, he can just interact
with objects naturally and automatically. Results from this study constitute a
first step towards conveying finely graded information about contact pressure,"
The study, The Neural Basis of Perceived
Intensity in Natural and Artificial Touch
, was supported
by the Defense Advanced Research Projects Agency (DARPA), the Department of
Veterans Affairs, the National Science Foundation and the National Institutes
of Health. Additional authors include Matthew Schiefer from the Louis-Stoke
Veterans Affairs Medical Center, and Hannes Saal and Benoit Delhaye from the
University of Chicago.
- In a first, brain computer interface helps
paralyzed man feel again - (https://www.eurekalert.org/pub_releases/2016-10/uops-iaf101216.php)