Medical Device Daily
Paralyzed patients being able to move objects with the power of their mind might not be such a foreign concept for much longer. A new study from the University of Chicago found that the performance of a brain-machine interface application designed to help paralyzed subjects move objects with their thoughts is improved with the addition of a robotic arm providing sensory feedback.
Researchers published their study findings in The Journal of Neuroscience.
“We saw 40% improvement in the monkeys using the robotic arm as opposed to just using visual feedback,“ Aaron Suminski, an author of the study, told Medical Device Daily. “This really is a first for us.“
According to Suminski, monkeys used in the experiment controlled a cursor without actively moving their arm. Movement of the cursor occurred via a sleeve like device that translated activity in the primary motor cortex of their brain into cursor motion. Researchers found that when wearing the sleeve-like exoskeleton in tandem with the cursor, the monkey's control increased.
“Essentially, in the experiment, the monkey is making a plan that he wants to move his arm,“ Suminski said.
Typically when a person moves their arm or hand, they use sensory feedback called proprioception to control that motion. For example, if one reaches out to grab a pencil or a pair of keys, sensory neurons in the arm and hand send information back to the brain about where one's limbs are positioned and moving. Proprioception tells a person where their arm is positioned, even if their eyes are closed.
But in patients with conditions where sensory neurons die out, executing basic motor tasks such as buttoning a shirt or even walking becomes exceptionally difficult. Paraplegic subjects in the early clinical trials of brain-machine interfaces faced similar difficulty in attempting to move a computer cursor or robot arm using only visual cues.
Researchers added that in the early days they didn't even think about sensory feedback as an important part of the system. They added that they simply thought of it as signals coming from the brain and then out to take control of the limb, adding that it was only until fairly recently that there is a loop with feedback coming back.
Looking at this loop, the researchers on the new study also observed changes in the brain activity recorded from the monkeys when sensory feedback was added to the set-up.
With proprioception feedback, the information in the cell firing patterns of the primary motor cortex contained more information than in trials with only visual feedback.
The improvement seen from adding proprioception feedback could lead to a broader creation of the next generation of brain-machine interface devices. Already, scientists are developing different types of “wearable robots“ to augment a person's natural abilities. Combining a decoder of cortical activity with a robotic exoskeleton for the arm or hand can serve a dual purpose: allowing a paralyzed subject to move the limb, while also providing sensory feedback.
For patients without both motor and sensory function, direct stimulation of sensory cortex may be able to simulate the sensation of limb movement. But Suminski cautioned that it was way to early to expect to see these study results applied to technology and that some gains needed to be made before this could be come a viable treatment for patients.
“From our findings we can imagine this [eventually] being beneficial to someone with some sort of residual sensory information from the limbs,“ he said. “But to make these study findings clinical realities there still need to be some gains in technology that need to occur.“
Researchers have been working on this particular project for a little more than four years now according to Suminski.
“We never really hit a road block,“ he told MDD. “There was lots of trial and error and adjustments, but we never hit a dead end.“
While this phase of the research looks to be finished, that doesn't mean that team won't do further research in this field in the future.
“I don't think by any stretch that we're done with this work,“ Suminski said.
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