Bernardeta Gómez sat at the table wearing a strange pair of glasses and slowly reached out his hand and pointed to the picture in front of him. Her fingers landed exactly where the black and white meet in the picture. This seemingly simple action is gomez's long-awaited "miracle".
It was hers, the real "give me three days of light".
Gomez, 57, a former biology teacher, permanently lost sight 16 years ago to toxic optic neuropathy. Today, she is involved as a volunteer in a clinical trial in which a "nail bed" is implanted in the visual cortex. The researchers hope that through this "nail bed," visual information will be transmitted directly into her brain.
By directly stimulating the cerebral cortex through electrodes, Gomez "saw" some simple signals such as points, lines, letters, etc., and could even play some simple games after training.
Shock the brain and see the "hallucination"
Directly stimulate the brain and make people "see" things – this magical technology appears in all kinds of science fiction works. In the movie The Matrix, the protagonist is the "brain in the vat" from the beginning, relying entirely on computer input to the brain to see the "real world".
In fact, science fiction has long been staged in reality. In 1929, when german neurologist Otfrid Foerster inserted an electrode into the patient's visual cortex and injected an electric current during surgery, the patient would see a bright spot out of thin air. This phenomenon is phosphene.
In some experiments, participants drew simulations of visual illusions in their left and right eyes丨 References[6]
For people with normal vision, light hallucinations are also common. When you close your eyes or rub your eyes, it's easy to see some bright spots or lines in the field of vision, even in situations where there is no light at all. This is because our visual cortex still has some spontaneous activity in the absence of external light input.
Blind people who are blind also have visual hallucinations. Many blind people who are blind are blind because the optic nerve that connects the retina and the brain is damaged, and conventional treatment cannot restore vision. In the matter of using visual illusions, scientists and science fiction writers have thought together: if the visual cortex is activated directly in the brain, can it be possible to bypass the eyes and let the blind see the world again?
In early experiments, scientists typically stuck electrodes to the surface of the brain. This electrode surgery is relatively simple, but the stimulation accuracy is insufficient, and often only a bright spot can be seen by the patient. There are also some risks associated with such experiments. The surface of the brain is some distance from the area where neurons are dense, and people often need to use a large current to cause light hallucinations. This can even induce epilepsy in patients.
Utah electrode array (although it looks painful, but the brain tissue does not feel pain)
In 2020, scientists are looking at the "nail bed". This is a Utah electrode array that scientists hope to use to improve the shortcomings of past electrodes. The team of Dutch neuroscientist Pieter R. Roelfsema implanted an array of Utah electrodes in the visual cortex of healthy macaques, which act like a small nail bed and puncture into the visual cortex to achieve more precise stimulation of deep locations. The monkeys in the experiment managed to see some of the finer visual hallucinations such as letters, and could even identify the shape and movement of the hallucinations. How do macaques do it? See "1024 electrodes implanted in the brain, how far we are from "virtual vision".
A year later, Gomez became the first human volunteer.
Learn how to "see"
The clinical trial, in which Gomez was involved, was led by Professor Eduardo Fernández of the University of Miguel Hernás de Elche in Spain. The research team implanted a small "nail bed" into her visual cortex. The size of this nail bed base is only 4mm*4mm, which is about half the size of the little thumb clip cover. It has a total of 100 1.5mm long "nails" arranged in a 10*10 grid, of which 96 are used as electrodes.
Implantation of "nail bed" in the brain 丨 References[1]
However, Gomez did not regain his sight immediately after the operation. She ran into a conundrum: how to distinguish between light hallucinations from electrode stimulation and spontaneously generated. To help Gomez define the timing of stimulation, the researchers would play a sound while the electrodes stimulated. After a period of training, Gomez gradually understood that the light hallucinations caused by the stimulation of a single "nail" were all small points of light, and these small points of light were always confined to the middle of the same area in the lower left of her field of vision.
After that, the researchers used Gomez's reliable reporting to optimize the parameters of the stimulus. The light hallucination produced by electrode stimulation is usually white. When the current is low, Gomez sees something very dim. As the stimulus increases in intensity, the hallucinations brighten and Gomez can pinpoint them. Continuous and repeated stimulation will keep the illusion stable in brightness and size.
Through the combined stimulation of different "nails", Gomez can see and distinguish several separated points, complete lines, and different letters. She also tried a game of judging the position of visual illusions left and right, and achieved a high rate of accuracy.
These 100 "nails" are like 100 blocks, and Gomez learned how to use them to build a new world in front of him.
Game for determining the orientation of visual illusion丨 References[1]
Gateway to the real world
At the end of the experimental period, the researchers put a pair of "bionic retina" glasses on Gomez. The glasses bring the real world to her eyes through the camera on the spectacle frame. Real-world images are filtered, leaving behind distinct visual features such as borders and corners. Together, they are encoded as electrical signals transmitted to the electrodes.
So we saw the opening scene. After training, Gomez can find the demarcation between the black and white patches in all tests, and can also find the location of a smaller white square (14*14cm) on the screen.
Although the "nail bed" is theoretically only 10*10 pixels, it can only show her some simple graphics. But this is still the first time after Gomez has been blind for 16 years that he can touch the world he "sees".
This "nail bed" did not remain in Gomez's mind forever. After 6 months, the researchers removed the electrodes. After a long period of implantation, scar tissue will form around the Utah electrode, which will lose its effectiveness. No one can currently determine how long the electrodes will continue to work without affecting the patient's brain. Fernandos hopes to extend the service life of the electrodes to decades through further research.
Gomez knew that he might not be able to fully restore his sight with this technology in his lifetime. Still, she told Fernandos that she could be a volunteer for his next research project at any time: after all, even a 10-by-10 pixel world is the hope of others regaining their light in the future.
bibliography
[1] Fernández, E., Alfaro, A., Soto-Sánchez, C., González-López, P., Ortega, A. M. L., Peña, S., … Chen, X. (2021). Visual percepts evoked with an intracortical 96-channel microelectrode array inserted in human occipital cortex. Journal of Clinical Investigation, 131(23).
[2] Beauchamp, M. S., Oswalt, D., Sun, P., Foster, B. L., Magnotti, J. F., Niketeghad, S., … Yoshor, D. (2020). Dynamic Stimulation of Visual Cortex Produces Form Vision in Sighted and Blind Humans. Cell, 181(4).
[3] Chen, X., Wang, F., Fernandez, E., & Roelfsema, P. R. (2020). Shape perception via a high-channel-count neuroprosthesis in monkey visual cortex. Science, 370(6521), 1191–1196.
[4] Spanish scientists help blind woman to see forms with brain implant. https://english.elpais.com/science-tech/2021-10-22/spanish-scientists-help-blind-woman-to-see-forms-with-brain-implant.html #
[5] A new implant for blind people jacks directly into the brain. https://www.technologyreview.com/2020/02/06/844908/a-new-implant-for-blind-people-jacks-directly-into-the-brain/#Echobox=1581003127
[6] T. Rajapakse, A. Kirton. (2016). Pediatric Brain Stimulation. Academic Press, 375-397(18).
By Insulindian
Edit: Owl, Window Knock rain
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