Created a human brain implant to get tactile sensations from a mechanical arm

Touch - the feedback we get when using a hand. Thanks to the touch, you can manipulate objects without looking: grab them, iron them, beat them, etc. Feedback is necessary for the accurate handling of fragile items such as eggs. Touch gives critical information for instantaneous reflex response — so that a person keeps his mechanisms and organs intact.

In the end, thanks to the sense of touch, the brain receives information about certain properties of objects — such properties cannot be known otherwise. For example, softness / hardness, elasticity, stickiness, etc. Using these data, the brain calculates other properties of the object, which allows you to reliably predict the future, that is, predict the result of interaction with the object.

The importance of touch is undeniable. In this regard, it is very depressing that the designers of bioprostheses have not yet found a reliable way to transfer information from sensors of mechanical hands to the human brain.
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Until now, no commercially available prosthesis of the arms and legs is completed with touch sensors, because it is still impossible to transmit this information to a person in real time, that is, naturally: through the nerve endings to the brain.

Remember how Luke Skywalker felt pain when a needle pricked him into a newly installed bionic arm? Of course, I would like to make this technology available not only for the Sith, but also for ordinary people.

Engineers have long been trying to solve the problem. It is obvious that interaction with the human central nervous system is required, the protocol of which has not yet been fully decoded. We have to look for workarounds in order to combine living neural structures and mechanical structures. Now the applied science of neuroengineering is engaged in it. A group of neuro engineers from the University of Pittsburgh (USA) found a possible solution for transmitting tactile impulses from a mechanical arm.

Engineers tried to replace natural touch with artificial impulses in the hope that the brain would tune in to a new signal. Electrodes are mounted in the cerebral cortex, which stimulate certain areas in accordance with the indications of sensors on the mechanical arm. A person has a feeling that he seems to be touching something.

This phenomenon is described in several scientific papers. It seems that it was first seen in 1997 and described in a scientific paper in the journal Nature . Then the scientists noticed that stimulation of certain areas of the cerebral cortex causes animals to react as if their limbs are moving. But what exactly the animals feel during brain stimulation remains unknown. In subsequent years, such experiments were carried out on humans : the subjects confirmed that they felt certain feelings in the limbs.

At the University of Pittsburgh, they conducted a long six-month experiment on a 28-year-old patient, Nathan Copeland, with a long-standing spinal cord injury. The guy in 2004 got into an accident and broke his neck.

Two neuroimplants with a grid of 60 electrodes measuring 2.4 × 4 mm were implanted into Nathan’s brain. The wire from the brain goes outside the head and connects to an external metal module that serves as a connection.



The most difficult was to find a suitable place on the cerebral cortex for the introduction of implants. Scientists have long studied the functional map of the brain, trying to accurately determine the area of ​​the cortex in which the processing of tactile signals takes place. For this patient, who for 10 years did not touch anything with his hands, was forced to actively think about how he touched and felt with different fingers. At the same time, magnetic resonance imaging was taken.



In the end, scientists managed to make an approximate map of the areas of the somatosensory cortex associated with the processing of information from each of the three fingers (thumb, index finger, little finger) and palm.



The implants were inserted neatly next to the corresponding neurons, and the patient was connected to the microstimulation system, giving weak impulses to the electrodes and tracking the response. He said that he felt different combinations of vibrations, touches, pressure and tingling as if in the joints and under the skin of the arm. Interestingly, the sensation map has hardly changed in six months.

For the main scientific experiment, the implant connection module was connected to a mechanical prosthesis — and the sensations that arise in the patient during various actions of the mechanical arm were recorded. It turned out that he correctly recognizes pressing fingers in 84% of cases, and as workouts in 100% of cases.


The scientist presses the finger of the hand when the patient is blindfolded

Tactile interface for artificial limbs tried to create before. For example, in the framework of the DARPA HAPTIX program, a neural interface is being developed to transmit tactile signals from a prosthesis to the nervous system. The X-ray image below shows electrodes surgically implanted in the forearm and connected by wires to an external computer. Ideally, the sensory signals from the prosthesis enter through the tactile interface into the peripheral nervous system, and from there into the spinal cord.


Electrodes surgically implanted in the forearm and wired to an external computer

Scientists of the project HAPTIX managed to achieve a good result in creating a tactile interface. But he can not help people suffering from spinal cord injuries. But the development of neuro engineers from the University of Pittsburgh can help.

The value of the new method is that information is transmitted to the brain directly from the hand, bypassing the spinal cord, even though wirelessly. This gives hope to a huge number of people who live with spinal cord injuries. In the United States alone, between 243,000 and 347,000 people are estimated by the National Statistical Center for Spinal Cord Injuries. If approximated, there should be several million of them all over the world. Depending on the degree of damage to the nerve pathways, the effects vary in strength: from partial loss of sensation in the fingers to complete loss of the ability to control the entire limb.

It is for people with spinal cord injuries that implantation of a signal receiver in the brain is best suited. The only pity is that each person has a brain map that has its own characteristics, so that before implantation you will have to perform individual mapping of the somatosensory cortex, that is, several MRI sessions.

Brain tactile implant still needs some work. He doesn’t come close to a living hand, and instead of some tactile sensations, the patient feels a tingling sensation. Scientists have not managed to simulate the sense of touch from individual parts of the hand, for example, from the fingertips. Perhaps more accurate positioning of the electrodes in the somatosensory cortex is needed. Maybe the number of electrodes should be increased.

A scientific article describing an innovative implant will be published on October 19, 2016 in the journal Science Translational Medicine (doi: 10.1126 / scitranslmed.aaf8083).