Navigation Links
Blind mice can 'see' thanks to special retinal cells
Date:7/14/2010

It would make the perfect question for the popular television show "Are You Smarter than a 5th Grader:" What parts of the eye allow us to see?

The conventional wisdom: rods and cones. The human retina contains about 120 million rods, which detect light and darkness, shape and movement, and about 7 million cones, which in addition detect color. Without them, or so we are taught, our eyesight simply would not exist.

But that might not be true, according to a study -- published July 15 in the journal Neuron -- that provides new hope to people who have severe vision impairments or who are blind.

A team led by biologist Samer Hattar of The Johns Hopkins University's Krieger School of Arts and Sciences found that mice that didn't have any rods and cones function could still see -- and not just light, but also patterns and images -- courtesy of special photosensitive cells in the rodents' retinas. Until now, it was presumed that those cells, called intrinsically photosensitive Retinal Ganglion Cells, (or ipRGCs), didn't play a role in image formation, but instead served other functions, such as dictating when the animals went to sleep or woke up. (All mammals, including humans, have ipRGCs, as well as rods and cones.)

"Up until now, it was assumed that rods and cones were the only cells capable of detecting light to allow us to form images," said Hattar, who as an assistant professor in the Department of Biology, studies mammals' sleep-wake cycles, also called "circadian rhythms." "But our study shows that even mice which were blind could form low-acuity yet measurable images, using ipRGCs. The exciting thing is that, in theory at least, this means that a blind person could be trained to use his or her ipRGCs to perform simple tasks that require low visual acuity."

"Visual acuity" refers to the sharpness or clarity of a person's (or animal's) vision. Someone with so-called "20/20 vision" can see clearly at a distance of 20 feet what the "average" human being can see at that distance. In contrast, a person with "20/100" vision would have to stand 20 feet away from, for instance, an eye chart that the average person could read from 100 feet away. People with very low visual acuity (worse than "20/100" with corrective lenses) are considered "legally blind."

In addition to providing hope for people with serious vision problems, Hattar's findings hint that, in the past, mammals may have used their ipRGCs for sight/image formation, but during the course of evolution, that function was somehow taken over by rods and cones.

The study also concludes that, far from being homogenous, ipRGCs come in five different subtypes, with the possibility that each may have different light-detecting physiological functions.

To conduct the study, the team used a special system to genetically label cells and then "trace" them to the rodents' brains before subjecting the mice to a number of vision tests. In one, mice followed the movements of a rotating drum, a test that assessed the animals' ability to track moving objects. In another, the rodents were placed within a "Y"-shaped maze and challenged to escape by selecting the lever that would let them out. That lever was associated with a certain visual pattern. The mice that were blind -- they lacked rods, cones and ipRGCs -- couldn't find that lever. But those with only ipRGCs could.

"These studies are extremely exciting to me, because they show that even a simple light-detecting system like ipRGCs has incredible diversity and may support low-acuity vision, allowing us to peer into evolution to understand how simple vision may have originally evolved before the introduction of the fancy photoreceptors rods and cones," Hattar said.


'/>"/>

Contact: Lisa DeNike
Lde@jhu.edu
443-287-9960
Johns Hopkins University
Source:Eurekalert  

Related biology news :

1. Genetic finding implicates innate immune system in major cause of blindness
2. ORNL, Southern Cal set sights on preventing blindness
3. Researchers develop flow sensors based on hair structures of blind cavefish
4. Work in mice will contribute to the study of hereditary diseases that lead to blindness
5. MSU researcher identifies cell mechanism leading to diabetic blindness
6. Caltech scientists create robot surrogate for blind persons in testing visual prostheses
7. Bat researchers no longer flying blind on echolocation
8. Experimental treatments restore partial vision to blind people
9. Discovery points toward anti-inflammation treatment for blinding disease
10. Visual assistance for cosmic blind spots
11. Scripps research team reveals how an old drug could have a new use for treating river blindness
Post Your Comments:
*Name:
*Comment:
*Email:
Related Image:
Blind mice can 'see' thanks to special retinal cells
(Date:3/31/2016)... -- Genomics firm Nabsys has completed a financial  restructuring under ... M.D., who returned to the company in October 2015. ... including Chief Technology Officer, John Oliver , Ph.D., ... Vice President of Software and Informatics, Michael Kaiser ... Bready served as CEO of Nabsys from 2005-2014 and ...
(Date:3/23/2016)... 23, 2016 ... Gesichts- und Stimmerkennung mit Passwörtern     ... MESG ), ein führender Anbieter digitaler ... mit SpeechPro zusammenarbeitet, um erstmals dessen Biometrietechnologie ... die Möglichkeit angeboten, im Rahmen mobiler Apps ...
(Date:3/22/2016)... OTTAWA, Ontario , PROVO ... 2016 Newborn Screening Ontario (NSO), which operates ... for molecular testing, and Tute Genomics and ... process management technology respectively, today announced the launch of ... new next-generation sequencing (NGS) testing panel. ...
Breaking Biology News(10 mins):
(Date:4/29/2016)... , April 29, 2016 Elekta ... latest update to its industry-leading treatment planning software, is ... Monaco version 5.11 provides significant ... attain calculation speeds up to four times faster than ... With the industry,s gold standard Monte Carlo ...
(Date:4/28/2016)... (PRWEB) , ... April 28, 2016 , ... ... and ongoing support for Connecticut's innovative, growing companies, today announced the launch of ... and financial technology (fintech) companies. , “VentureClash looks to attract the ...
(Date:4/28/2016)... ... 28, 2016 , ... Morris Midwest ( http://www.morrismidwest.com ), a ... at its Maple Grove, Minnesota technical center, May 11-12. The event will ... Almost 20 leading suppliers of tooling, accessories, software and other related technology will ...
(Date:4/27/2016)... ... 27, 2016 , ... The Pittcon Organizing Committee is pleased to announce that ... volunteer member of Committee since 1987. Since then, he has served in a number ... was chairman for both the program and exposition committees. In his professional career, Dr. ...
Breaking Biology Technology: