Saturday, 13 April 2019

Scientists Have Created an Artificial Retina Implant That Could Restore Vision to Millions

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Scientists have developed a retinal implant that can restore lost vision in rats, and are planning to trial the procedure in humans later this year.
The implant, which converts light into an electrical signal that stimulates retinal neurons, could give hope to millions who experience retinal degeneration – including retinitis pigmentosa – in which photoreceptor cells in the eye begin to break down, leading to blindness.

The retina is located at the back of the eye, and is made up of millions of these light-sensitive photoreceptors. But mutations in any one of the 240 identified genes can lead to retinal degeneration, where these photoreceptor cells die off, even while the retinal neurons around them are unaffected.
Because the retinal nerves remain intact and functional, previous research has looked at treating retinitis pigmentosa with bionic eye devices that stimulate the neurons with lights, while other scientists have investigated using CRISPR gene editing to repair the mutations that cause blindness.
Now, a team led by the Italian Institute of Technology has developed a new approach, with a prosthesis implanted into the eye that serves as a working replacement for a damaged retina.
The implant is made from a thin layer of conductive polymer, placed on a silk-based substrate and covered with a semiconducting polymer.
The semiconducting polymer acts as a photovoltaic material, absorbing photons when light enters the lens of the eye. When this happens, electricity stimulates retinal neurons, filling in the gap left by the eye's natural but damaged photoreceptors.
To test the device, the researchers implanted the artificial retina into the eyes of rats bred to develop a rodent model of retinal degeneration – called Royal College of Surgeons (RCS) rats.
After the rats had healed from the operation 30 days later, the researchers tested how sensitive they were to light – called the pupillary reflex – compared to healthy rats and untreated RCS rats.
At the low intensity of 1 lux – a bit brighter than the light from a full moon – the treated rats weren't much more responsive than untreated RCS rats.
But as the light increased to around 4–5 lux – about the same as a dark twilight sky – the pupillary response of treated rats was largely indistinguishable from healthy animals.
When they retested the rats at six and 10 months after surgery, the implant was still effective in the rats – although all the rats in the tests (including the treated rats, the healthy animals, and the RCS controls) had suffered minor vision impairment due to being older.
Using positron emission tomography (PET) to monitor the rats' brain activity during the light sensitivity tests, the researchers saw an increase in the activity of the primary visual cortex, which processes visual information.

Based on the results, the team concludes that the implant directly activates "residual neuronal circuitries in the degenerate retina", but further research will be required to explain exactly how the stimulation works on a biological level.
"[T]he detailed principle of operation of the prosthesis remains uncertain," they explain in their paper.
While there are no guarantees that the results seen in rats will translate to people, the team is hopeful that it will – and from the sounds of things, it won't be too long until we find out.
"We hope to replicate in humans the excellent results obtained in animal models," says one of the researchers, ophthalmologist Grazia Pertile from the Sacred Heart Don Calabria in Negrar, Italy.
"We plan to carry out the first human trials in the second half of this year and gather preliminary results during 2018. This [implant] could be a turning point in the treatment of extremely debilitating retinal diseases."
The findings are reported in Nature Materials.


Tuesday, 9 April 2019

Scientists build a machine to generate quantum superposition of possible futures

Unlike classical particles, quantum particles can travel in a quantum superposition of different directions. Mile Gu, together with researchers from Griffith harnessed this phenomena to design quantum devices that can generate a quantum superposition of all possible futures. Credit: NTU, Singapore.
In the 2018 movie Avengers: Infinity War, a scene featured Dr. Strange looking into 14 million possible futures to search for a single timeline in which the heroes would be victorious. Perhaps he would have had an easier time with help from a quantum computer. A team of researchers from Nanyang Technological University, Singapore (NTU Singapore) and Griffith University in Australia have constructed a prototype quantum device that can generate all possible futures in a simultaneous quantum superposition.
"When we think about the future, we are confronted by a vast array of possibilities," explains Assistant Professor Mile Gu of NTU Singapore, who led development of the  algorithm that underpins the prototype "These possibilities grow exponentially as we go deeper into the future. For instance, even if we have only two possibilities to choose from each minute, in less than half an hour there are 14 million possible futures. In less than a day, the number exceeds the number of atoms in the universe." What he and his research group realised, however, was that a quantum computer can examine all possible futures by placing them in a  – similar to Schrödinger's famous cat, which is simultaneously alive and dead.
To realise this scheme, they joined forces with the experimental group led by Professor Geoff Pryde at Griffith University. Together, the team implemented a specially devised photonic quantum information processor in which the potential future outcomes of a decision process are represented by the locations of photons – quantum  of light. They then demonstrated that the state of the quantum device was a superposition of multiple potential futures, weighted by their probability of occurrence.

Singapore and Australian Scientists Build a Machine to See all Possible Futures
A picture of the Experimental Device used for the experiment. Credit: Griffith’s University
"The functioning of this device is inspired by the Nobel Laureate Richard Feynman," says Dr. Jayne Thompson, a member of the Singapore team. "When Feynman started studying quantum physics, he realized that when a particle travels from point A to point B, it does not necessarily follow a single path. Instead, it simultaneously transverses all possible paths connecting the points. Our work extends this phenomenon and harnesses it for modelling statistical futures."
The machine has already demonstrated one application—measuring how much our bias towards a specific choice in the present impacts the future. "Our approach is to synthesise a quantum superposition of all possible futures for each bias." explains Farzad Ghafari, a member of the experimental team, "By interfering these superpositions with each other, we can completely avoid looking at each possible future individually. In fact, many current artificial intelligence (AI) algorithms learn by seeing how  in their behaviour can lead to different future outcomes, so our techniques may enable quantum enhanced AIs to learn the effect of their actions much more efficiently."
The team notes while their present prototype simulates at most 16 futures simultaneously, the underlying quantum algorithm can in principle scale without bound. "This is what makes the field so exciting," says Pryde. "It is very much reminiscent of classical computers in the 1960s. Just as few could imagine the many uses of classical computers in the 1960s, we are still very much in the dark about what quantum computers can do. Each discovery of a new application provides further impetus for their technological development."
The work is featured in a forthcoming paper in the journal Nature Communications.
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