AI News, Brain surface stimulation provides 'touch' feedback to direct movement
- On Saturday, June 16, 2018
- By Read More
Brain surface stimulation provides 'touch' feedback to direct movement
In the quest to restore movement to people with spinal cord injuries, researchers have focused on getting brain signals to disconnected nerves and muscles that no longer receive messages that would spur them to move.
Now, University of Washington researchers at the National Science Foundation Center for Sensorimotor Neural Engineering (CSNE) have used direct stimulation of the human brain surface to provide basic sensory feedback through artificial electrical signals, enabling a patient to control movement while performing a simple task: opening and closing his hand.
The team of bioengineers, computer scientists and medical researchers from the CSNE and UW's GRIDLab used electrical signals of different current intensities, dictated by the position of the patient's hand measured by a glove he wore, to stimulate the patient's brain that had been implanted with electrocorticographic (ECoG) electrodes.
They can test which parts of the brain are activated during different behaviors, what happens when a certain region of the brain's cortex is stimulated and even how to induce brain plasticity to promote rehabilitation and healing across damaged areas.
The potential to use ECoG electrodes implanted on the surface of the brain in future prosthetic or rehabilitative applications offers several advantages -- the signals are stronger and more accurate than sensors placed on the scalp, but less invasive than ones that penetrate the brain, as in a recent study by University of Pittsburgh researchers.
Performance dropped when the patient received random signals regardless of hand position, suggesting that the subject had been using the artificial sensory feedback to control hand movement.
Providing that artificial sensory feedback in a way that the brain can understand is key to developing prosthetics, implants or other neural devices that could restore a sense of position, touch or feeling in patients where that connection has been severed.
Brain Stimulation Allows Paralyzed Man to Feel His Hand Again
True neuroprosthetic limbs—artificial limbs that feel and behave like the real thing—may be in the distant future.
In the study, surgeons implanted electrode arrays in the brain of a 28-year-old man who was paralyzed from the neck down due to a spinal cord injury sustained 10 years earlier, specifically targeting the somatosensory cortex, the brain area responsible for the sensation of touch.
Prior to surgery, the researchers used magnetic resonance imaging (MRI) and magnetoencephalography (MEG) to determine where to place the electrodes by noting which areas in the somatosensory cortex were activated when the study participant imagined sensation in different parts of his right hand.
and after four weeks, the patient stopped perceiving them altogether.Around the same time, the intracortical microstimulation began to produce tactile sensations that the participant reported originating in his hand.* Collinger and her colleagues conducted two different types of trials, both involving intracortical microstimulation of the somatosensory cortex.
The participant reported primarily experiencing sensations in his upper palm and at the base of his four fingers, with sensation in a small area of his pinky as well as two-thirds of the way up his index finger as well.
And in 190 trials meant to determine the quality of the experienced sensations, he reported 67 percent of stimuli registering as pressure, 15 percent registering as warmth and another 15 percent as electrical stimulation.
In the second part of the experiment, the researchers mapped the output of torque sensors to specific fingers on a prosthetic hand, which were in turn mapped to the electrodes corresponding to each finger.
Collinger and Miller agreed that the next step is figuring out how to combine the existing discoveries in this field building on previous experiments showing that monkeys and humans can learn to feel virtual objects and control a robot arm with their minds.
(Re)Wiring The Brain: Brain Waves Can be Used to Move Robotic Limbs
While advances in medical technology already allow people with damaged limbs or robotic prostheses to communicate with those limbs, they haven’t yet gotten the limbs to properly talk back.
Patients were asked to move their hands into certain positions and would receive sensory feedback on the positioning in the form of electrical currents delivered directly to the brain through the ECoG electrodes.
Technology like this could make a huge difference in the lives of people with lost limbs or spinal cord injuries, as even the seemingly simplest tasks can be impossible without proper sensory feedback.
Thankfully, teams all across the globe are working on ways to improve haptic feedback, from socks that grant sensation to prosthetic feet to bionic hands fitted with force sensors.
Mind-controlled robot arm gives back sense of touch to paralysed man
A paralysed man has become the first to have a “natural” sense of touch restored, using a mind-controlled robotic arm.
Will it work in a person who has had an injury for a long time?” Previously the same team had allowed paralysis patients to control a prosthetic arm using thought alone, but the addition of sense of touch is seen as crucial.
We’re feeding back touch that the artificial hand encounters when it makes contact with an object.” In the trial, Copeland wore a neural implant for six months during which time he trained himself how to control the movement of the robotic arm.
When blindfolded, Copeland could tell which of the fingers on the prosthetic were being touched with 84% accuracy and he described 93% of the touch sensations he was given, such as pressing a cotton swab on the surface of the skin, as feeling “possibly natural.” Until now, it was not clear how natural the sensations delivered by this kind of prosthesis would feel.
I never really liked driving to begin with.” He tried to continue his studies, but health problems forced him to put his degree on hold and he kept busy by going to concerts and volunteering for the Pittsburgh Japanese Culture Society, which holds conventions on Japanese cartoons.
The electrodes read out electrical activity from one region - the motor area - to control the movement of the hand and electrically stimulated another region linked to sensation to induce a sense of touch.
Researchers Restore Elusive Sixth Sense to Lost Limbs
To be truly helpful, the researchers needed to combine the perception of hand movement with the intention of hand movement.
when the hand moved in response to a test subject's thoughts, it also triggered vibrations at their reinnervation sites, producing the kinesthetic illusion.
For instance, when the researchers linked the cylinder-grip signal to the movement of a virtual prosthesis, the feedback enabled patients to control their bionic hands a quarter, half, or three-quarters of the way—without looking at them.
Strapped on, the limb began to dissolve the boundaries between operation and embodiment—that is, the distinction between controlling an arm, and controlling your arm.
"It’s a real estate problem, because everything’s in the same place—you’re trying to provide feedback to the same skin you’re trying to record signals from,"
- On Sunday, August 18, 2019
The Mind-Controlled Bionic Arm With a Sense of Touch
In the first episode of Humans+, Motherboard dives into the world of future prosthetics, and the people working on closing the gap between man and machine.
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