retinal ganglion cells

Our First and Last (Ch. 8)

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Ch. 11 | Ch. 12 (Final)

  • Pairings: Jeon Jungkook x Reader (MAIN) | Park Jimin x Kim Taehyung | Jung Hoseok x Min Yoongi | Kim Namjoon x Kim Seokjin
  • Genre: angst and fluff, soulmate au, scifi
  • Words: 3,706
  • Description: It was an illustration of a view from a balcony, a scene of another city moments after a thunderstorm. The entire piece of artwork had a cool-toned tinge to it and although it was strange, it gave you a familiar feeling you couldn’t quite explain.

“Y/N! I got the job!” Hoseok shouts as he checks his email on his phone while the two of you were sitting on the couch of your living room on a lazy Sunday afternoon.

“At the hospital?!”

“Yup!”

“Is that where you ran off to the other day?” You narrow your eyes as you remember spending over twenty minutes scouring the lab looking for him, only to get weird looks from the other researchers.

“Oh you mean the day you met Dr. Jeon?”

“Yeah.”

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Making artificial vision look more natural

In laboratory tests, researchers have used electrical stimulation of retinal cells to produce the same patterns of activity that occur when the retina sees a moving object. Although more work remains, this is a step toward restoring natural, high-fidelity vision to blind people, the researchers say. The work was funded in part by the National Institutes of Health.

(Image caption: Chichilnisky and colleagues used an electrode array to record activity from retinal ganglion cells (yellow and blue) and feed it back to them, reproducing the cells’ responses to visual stimulation. Credit: E.J. Chichilnisky, Stanford.)

Just 20 years ago, bionic vision was more a science fiction cliché than a realistic medical goal. But in the past few years, the first artificial vision technology has come on the market in the United States and Western Europe, allowing people who’ve been blinded by retinitis pigmentosa to regain some of their sight. While remarkable, the technology has its limits. It has enabled people to navigate through a door and even read headline-sized letters, but not to drive, jog down the street, or see a loved one’s face.

A team based at Stanford University in California is working to improve the technology by targeting specific cells in the retina—the neural tissue at the back of the eye that converts light into electrical activity.

“We’ve found that we can reproduce natural patterns of activity in the retina with exquisite precision,” said E.J. Chichilnisky, Ph.D., a professor of neurosurgery at Stanford’s School of Medicine and Hansen Experimental Physics Laboratory. The study was published in Neuron, and was funded in part by NIH’s National Eye Institute (NEI) and National Institute of Biomedical Imaging and Bioengineering (NIBIB).

The retina contains several cell layers. The first layer contains photoreceptor cells, which detect light and convert it into electrical signals. Retinitis pigmentosa and several other blinding diseases are caused by a loss of these cells. The strategy behind many bionic retinas, or retinal prosthetics, is to bypass the need for photoreceptors and stimulate the retinal ganglion cell layer, the last stop in the retina before visual signals are sent to the brain.

Several types of retinal prostheses are under development. The Argus II, which was developed by Second Sight Therapeutics with more than $25 million in support from NEI, is the best known of these devices. In the United States, it was approved for treating retinitis pigmentosa in 2013, and it’s now available at a limited number of medical centers throughout the country. It consists of a camera, mounted on a pair of goggles, which transmits wireless signals to a grid of electrodes implanted on the retina. The electrodes stimulate retinal ganglion cells and give the person a rough sense of what the camera sees, including changes in light and contrast, edges, and rough shapes.

“It’s very exciting for someone who may not have seen anything for 20-30 years. It’s a big deal. On the other hand, it’s a long way from natural vision,” said Dr. Chichilnisky, who was not involved in development of the Argus II.

Current technology does not have enough specificity or precision to reproduce natural vision, he said. Although much of visual processing occurs within the brain, some processing is accomplished by retinal ganglion cells. There are 1 to 1.5 million retinal ganglion cells inside the retina, in at least 20 varieties. Natural vision—including the ability to see details in shape, color, depth and motion—requires activating the right cells at the right time.

The new study shows that patterned electrical stimulation can do just that in isolated retinal tissue. The lead author was Lauren Jepson, Ph.D., who was a postdoctoral fellow in Dr. Chichilnisky’s former lab at the Salk Institute in La Jolla, California. The pair collaborated with researchers at the University of California, San Diego, the Santa Cruz Institute for Particle Physics, and the AGH University of Science and Technology in Krakow, Poland.

They focused their efforts on a type of retinal ganglion cell called parasol cells. These cells are known to be important for detecting movement, and its direction and speed, within a visual scene. When a moving object passes through visual space, the cells are activated in waves across the retina.

The researchers placed patches of retina on a 61-electrode grid. Then they sent out pulses at each of the electrodes and listened for cells to respond, almost like sonar. This enabled them to identify parasol cells, which have distinct responses from other retinal ganglion cells. It also established the amount of stimulation required to activate each of the cells. Next, the researchers recorded the cells’ responses to a simple moving image—a white bar passing over a gray background. Finally, they electrically stimulated the cells in this same pattern, at the required strengths. They were able to reproduce the same waves of parasol cell activity that they observed with the moving image.

“There is a long way to go between these results and making a device that produces meaningful, patterned activity over a large region of the retina in a human patient,” Dr. Chichilnisky said. “But if we can handle the many technical hurdles ahead, we may be able to speak to the nervous system in its own language, and precisely reproduce its normal function.”

Such advances could help make artificial vision more natural, and could be applied to other types of prosthetic devices, too, such as those being studied to help paralyzed individuals regain movement. NEI supports many other projects geared toward retinal prosthetics.

“Retinal prosthetics hold great promise, but this research is a marathon, not a sprint,” said Thomas Greenwell, Ph.D., a program director in retinal neuroscience at NEI. “This important study helps illustrate the challenges of restoring high-quality vision, one group’s progress toward that goal, and the continued need to for the entire field to keep innovating.”

ATP production in mitochondria (purple) can lead to the formation of reactive oxygen species (ROS) that damage mitochondria. When an organelle is beyond repair, the cellular recycling system (green) kicks-in and targets them for mitophagy, a specialized form of mitochondrial degradation.

Image: A primary retinal ganglion cell expresses a red fluorescent protein targeted to mitochondria, a green fluorescent protein fused to the autophagosomal marker LC3, and a cyan fluorescent protein in the cytosol. This image reveals how autophagosomes (green) can contact individual mitochondria (purple), before their ingestion by mitophagy.

anonymous asked:

Hey! I love your Sherlolly Fanfictions and I can't get enough of them! I don't know if you're still taking requests, but I thought about what would happen if Molly and John were engaged and Sherlock needed to tell Molly he loved her before they get married. I can't get it out of my head and I'd LOVE to see it written out. And don't worry about the length, I like long stories! If you would be so kind as to write this, I'd really appreciate it!

Hi Nonny, I had to tweak your prompt a little bit because (a) love triangles are a genuinely difficult subject for me and (b) I cannot imagine John and Molly in a romantic way. And by John, I’m assuming you mean John Watson.

So I’ve twisted this to avoid the bumps that make me uncomfortable and hopefully the intrigue of it makes up for not following your prompt through. I have my boyfriend to thank for this brainwave of using another John (Helloooo, John H.) as opposed to John Watson. So thank you, boyfriend! 

Also this is insanely long and a little haphazard. In any case, I hope you’ll all enjoy it somehow. x

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Secrets & Rhythms

The change had been so subtle that even the great consulting detective had not noticed. Molly seemed to smile a little more to herself, particularly so when he was not in the room. He had only found this out when he walked past the morgue and peered into the circular perspex panels of its doors. There she was, smiling sweetly to herself as she made notes on her clipboard, carefully circling the grey body she examined. However, it was only when she started forbidding him to come to the lab at night, that he really pricked up his ears and took note. 

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