Professor Sheila Nirenberg of Weill Medical College in Cornell University has been breaking new ground in the field of merging neural coding with mathematical equations in order to develop a prosthetic device that improves by leaps and bounds the severely impaired vision of people who have been diagnosed with retinitis pigmentosa or macular degeneration.
"Fundus of patient with retinitis pigmentosa, mid stage" by Christian Hamel - Retinitis pigmentosa by Christian Hamel. Licensed under CC BY 2.0 via Wikimedia Commons
Retinitis pigmentosa is an inherited condition that appears as darker pigmentation found in the epithelium of the retina, causing tunnel vision initially and eventually leading to blindness. The degeneration of light-sensitive photo-receptor cells is irreversible in both retinitis pigmentosa and macular degeneration.
The remarkable research that Dr. Nirenberg and her colleague Dr. Chethan Pandarinath (an electrical engineer now at the Neural Prosthetics Laboratory at Stanford University) have done is to view the process of vision this way:
(Image from TEDMED talk by Dr. Nirenberg; http://www.ted.com/talks/sheila_nirenberg_a_prosthetic_eye_to_treat_blindness?language=en#t-135375)
The highlighted front end cells or photoreceptors of the retina respond to the image that we see in the form of a code. Then the output cells (orange balls) interpret the code and create numerous signals or action potentials that eventually travel to the brain which processes them into the image we see.
In a degenerative eye disease like retinitis pigmentosa, the front end cells are lost. So no visual encoding occurs. The solution proposed by Nirenberg and Pandarinath is to create a microchip that can mathematically encode the image ("encoder"):
(Image from TEDMED talk by Dr. Nirenberg; http://www.ted.com/talks/sheila_nirenberg_a_prosthetic_eye_to_treat_blindness?language=en#t-135375)
The transducer is a light-sensitive protein that fires the action potential signals. Currently, there is no prosthetic device superior to the visual enablement of this technology, and Dr. Nirenberg has plans to submit her research by the end of this year to the FDA for approval. If all goes well, a small clinical trial will begin in early 2016, implementing a prosthetic device (glasses) that requires little invasive surgery:
(Image from TEDMED talk by Dr. Nirenberg; http://www.ted.com/talks/sheila_nirenberg_a_prosthetic_eye_to_treat_blindness?language=en#t-135375)
Here, the glasses contain the microchip encoder that will mathematically interpret the images and send the code to the light-sensitive transducer cells or channel rhodopsin.
The transducer is known as channel rhodopsin, a protein that can form a channel when activated by light:
Rhodopsin itself is composed of 2 components: opsin and retinal. Let's take a look at this latter molecule which has some interesting structural characteristics.
I highlighted the purple double bond to point out that retinal exhibits geometrical isomerism, a feature many alkene molecules have where they show differences in spatial arrangement around a carbon-carbon double bond. Upon exposure to visible light (the part of the electromagnetic spectrum we can see), the molecule changes from the trans to cis isomer. This reaction is important in the function of channel rhodopsin as it allows the protein to create a larger opening (by ~6 angstroms) and enables ions to travel through the channel and generate an action potential.
Fortunately for people with macular degeneration or retinitis pigmentosa, vision remains a possibility as long as trans- to cis-retinal isomerization can occur in this light-activated channel opening of rhodopsin.
For this innovative work, Dr. Nirenberg was awarded the MacArthur "Genius" Award.
Resources
*Nirenberg Lab, Department of Physiology and Biophysics, Weill Medical College of Cornell University
*Retinal prosthetic strategy with the capacity to restore normal vision; S. Nirenberg and C. Pandarinath; Proceedings of the National Academy of Sciences (PNAS); vol. 109, no. 37, pp 15012-15017.
*"A Prosthetic Eye to Treat Blindness" (TEDMED 2011 talk by Dr. Nirenberg; October 2011)
*MacArthur Fellows/Meet the Class of 2013/Sheila Nirenberg
*Method of the Year 2010: Optogenetics - by Nature
Rhodopsin itself is composed of 2 components: opsin and retinal. Let's take a look at this latter molecule which has some interesting structural characteristics.
(Image from http://www.biophys.mpg.de/de/bamberg.html)
The YFP stands for yellow fluorescent protein which is found in green algae.
Fortunately for people with macular degeneration or retinitis pigmentosa, vision remains a possibility as long as trans- to cis-retinal isomerization can occur in this light-activated channel opening of rhodopsin.
For this innovative work, Dr. Nirenberg was awarded the MacArthur "Genius" Award.
Resources
*Nirenberg Lab, Department of Physiology and Biophysics, Weill Medical College of Cornell University
*Retinal prosthetic strategy with the capacity to restore normal vision; S. Nirenberg and C. Pandarinath; Proceedings of the National Academy of Sciences (PNAS); vol. 109, no. 37, pp 15012-15017.
*"A Prosthetic Eye to Treat Blindness" (TEDMED 2011 talk by Dr. Nirenberg; October 2011)
*MacArthur Fellows/Meet the Class of 2013/Sheila Nirenberg
*Method of the Year 2010: Optogenetics - by Nature
Department
of Physiology and Biophysics and a member of the Institute for
Computational Biomedicine at Weill Medical College of Cornell University
- See more at:
http://www.macfound.org/fellows/899/#sthash.fXVHrHd7.dpuf
