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MICROSCOPIC electronics will allow paralysed patients to use their thoughts to walk, thanks to a project to develop a “stentrode”.
The project is a close collaboration between 39 researchers from 16 departments across the University of Melbourne, the Royal Melbourne Hospital and the Florey Institute of Neuroscience and Mental Health.
The stentrode device would be implanted into a blood vessel next to the motor cortex in the brain, without requiring complex brain surgery. Once embedded, the device will pick up brain signals. The signals are decoded then passed wirelessly through the skin, allowing patients to effectively control a robotic exoskeleton attached to their limbs by simply thinking about it.
In pre-clinical animal trials of the three millimetre wide device, the researchers demonstrated the stentrode can pick up strong electrical frequencies emitted by the brain that are coded into a computer. The computer then sends a signal to an exoskeleton attached to the arms or legs, enabling movement.
In late 2017, a select group of paralysed patients from the Royal Melbourne and Austin Hospitals in Australia will be chosen for the trial, where they will be implanted with the stentrode. If the trial succeeds, the technology could become commercially available in as little as six years.
The stentrode could also benefit people with Parkinson’s disease, motor neurone disease, obsessive compulsive disorder and depression and could even predict and manage seizures in epileptic patients.
The stentrode, designed in Melbourne and crafted from a space-age alloy called nitinol, will be inserted into the blood vessel with a catheter fed up through the groin. The device is delivered through a small catheter, and when in position, the catheter is removed, deploying the stentrode.
The stentrode expands to press the electrodes against the vessel wall close to the brain where it can record neural information and translate these signals into commands that can be used to control an exoskeleton.
In trials of the technology in the brains of healthy living sheep, the sheep were unaffected by the painless, quick and simple operation, and were walking and eating within an hour.
As the device absorbed into the vein wall after nine or so days, the electrical signals continued to become clearer and stronger, up to 190 hertz, as strong as signals previously recorded with intricate invasive brain surgery.
The data between 70 to 200 hertz is the most useful for brain machine interfacing, as they are the signals that provoke intricate muscle movements. Interpreting them via software will allow the movement of an external skeleton.
Another challenge involved engineering the tiny net-like device which could be fitted with electrode receivers. This microscopic device had to be able to collapse to a tiny few millimetres in diameter and spring back into shape to act as a scaffold to maintain the flow of blood and permanently settle into the vein.
The nitinol device is fitted with tiny electrodes, which sit on the wall of the blood vessel, right next to the brain tissue.
The stentrode device went through hundreds of design changes before researchers were satisfied it met their requirements of being light, flexible, bio-compatible and small enough to be threaded into a one millimetre blood vessel.
Each electrode records electrical activity fired by some 10,000 neurons, which is delivered via delicate wires that run out of the brain, into the neck and emerge into the chest into a wireless transmission system.
In 2017, the stent will be implanted into carefully selected paraplegic or quadriplegic patients by surgeons at the Royal Melbourne Hospital. The long road to coding will begin at the Austin Hospital’s Spinal Cord Service.
The first patients will most likely be young people who have suffered a traumatic spinal cord injury around six months to a year earlier, who are suitable for exoskeleton legs. They will be chosen for their level of determination, their resolve and their physiology.
Possible other applications include the use of the stentrode to provide electrical stimulation, as well as receiving signals, which could be useful for the bionic eye.