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:1/4/2017)... LAS VEGAS , Jan. 4, 2017  For the thousands of ... , a global leader in connected health and biometric measurement devices and ... pressure monitors. On display in A&D Medical,s special CES ... monitors represent the ongoing expansion of the company,s WellnessConnected product ... ...
(Date:12/20/2016)... , Dec. 20, 2016 The ... sharing, rental and leasing is stoking significant interest ... radio frequency technology, Bluetooth low energy (BLE), biometrics ... as the next wave of wireless technologies in ... access system to advanced access systems opens the ...
(Date:12/16/2016)... 2016 The global wearable medical device market, in terms ... from USD 5.31 billion in 2016, at a CAGR of 18.0% ... ... advancements in medical devices, launch of a growing number of smartphone-based ... among healthcare providers, and increasing focus on physical fitness. ...
Breaking Biology News(10 mins):
(Date:1/19/2017)... PUNE, India , Jan. 19, 2017  Market Research Future ... The Global Market for Liquid Biopsy is growing rapidly and expected ... period. Market Highlights ... The Global Liquid Biopsy Market has been assessed as ... high growth figures and boom in the coming future. There has ...
(Date:1/19/2017)... Berkeley, CA (PRWEB) , ... January 19, 2017 ... ... the delivery of product vigilance software to leading biopharmaceutical and medical device manufacturers ... Mail is a fully 21 CFR Part 11-compliant email client designed to provide ...
(Date:1/19/2017)... ... January 18, 2017 , ... LabRoots ... scientists from around the world, was today awarded the "Best Science & Technology ... entirely on merit and decided upon by a dedicated team of researchers and ...
(Date:1/19/2017)... N.Y. , Jan. 18, 2017 Acupath ... services, announces the formation of an Executive Committee that ... and beyond. John Cucci , a ... promoted from Director of Business Development to Chief ... 2015, Mr. Cucci served in senior sales leadership roles ...
Breaking Biology Technology: