Navigation Links
JHU biologists identify new neural pathway in eyes that aids in vision
Date:5/21/2014

A type of retina cell plays a more critical role in vision than previously known, a team led by Johns Hopkins University researchers has discovered.

Working with mice, the scientists found that the ipRGCs an atypical type of photoreceptor in the retina help detect contrast between light and dark, a crucial element in the formation of visual images. The key to the discovery is the fact that the cells express melanopsin, a type of photopigment that undergoes a chemical change when it absorbs light.

"We are quite excited that melanopsin signaling contributes to vision even in the presence of functional rods and cones," postdoctoral fellow Tiffany M. Schmidt said. Schmidt is lead author of a recently published study in the journal Neuron. The senior author is Samer Hattar, associate professor of biology in the university's Krieger School of Arts and Sciences. Their findings have implications for future studies of blindness or impaired vision.

Rods and cones are the most well-known photoreceptors in the retina, activating in different light environments. Rods, of which there are about 120 million in the human eye, are highly sensitive to light and turn on in dim or low-light environments. Meanwhile the 6 million to 7 million cones in the eye are less sensitive to light; they drive vision in brighter light conditions and are essential for color detection.

Rods and cones were thought to be the only light-sensing photoreceptors in the retina until about a decade ago when scientists discovered a third type of retinal photoreceptor the ipRGC, or intrinsically photosensitive retinal ganglion cell that contains melanopsin. Those cells were thought to be needed exclusively for detecting light for non-image-dependent functions, for example, to control synchronization of our internal biological clocks to daytime and the constriction of our pupils in response to light.

"Rods and cones were thought to mediate vision and ipRGCs were thought to mediate these simple light-detecting functions that happen outside of conscious perception," Schmidt said. "But our experiments revealed that ipRGCs influence a greater diversity of behaviors than was previously known and actually contribute to an important aspect of image-forming vision, namely contrast detection."

The Johns Hopkins team along with other scientists conducted several experiments with mice and found that when melanopin was present in the retinal ganglion cells, the mice were better able to see contrast in a Y-shaped maze, known as the visual water task test. In the test, mice are trained to associate a pattern with a hidden platform that allows them to escape the water. Mice that had the melanopsin gene intact had higher contrast sensitivity than mice that lack the gene.

"Melanopsin signaling is essential for full contrast sensitivity in mouse visual functions," said Hattar. "The ipRGCs and melanopsin determine the threshold for detecting edges in the visual scene, which means that visual functions that were thought to be solely mediated by rods and cones are now influenced by this system. The next step is to determine if melanopsin plays a similar role in the human retina for image-forming visual functions."


'/>"/>
Contact: Latarsha Gatlin
lgatlin1@jhu.edu
443-997-9909
Johns Hopkins University
Source:Eurekalert

Related biology news :

1. IU biologists offer clearer picture of how protein machine systems tweak gene expression
2. Microbiologists can now measure extremely slow life
3. American Society of Plant Biologists honors early career women scientists
4. Penn biologists identify a key enzyme involved in protecting nerves from degeneration
5. University of Toronto biologists predict extinction for organisms with poor quality genes
6. Biologists turn back the clock to understand evolution of sex differences
7. Double the pain: RUB biologists find the cause of pain in the treatment of fair skin cancer
8. UCLA biologists reveal potential fatal flaw in iconic sexual selection study
9. New book on stereology by Mark West is essential reading for neurobiologists
10. SF State biologists tag zombees to track their flight
11. Biologists unlocking the secrets of plant defenses, 1 piece at a time
Post Your Comments:
*Name:
*Comment:
*Email:
(Date:3/29/2017)... 2017  higi, the health IT company that operates ... America , today announced a Series B investment ... EveryMove. The new investment and acquisition accelerates higi,s strategy ... transform population health activities through the collection and workflow ... higi collects and secures data today on behalf of ...
(Date:3/27/2017)... , March 27, 2017  Catholic Health ... and Management Systems Society (HIMSS) Analytics for achieving ... Adoption Model sm . In addition, CHS previously ... U.S. hospitals using an electronic medical record (EMR). ... its high level of EMR usage in an ...
(Date:3/24/2017)... , Mar 24, 2017 Research and ... Access System Market Analysis & Trends - Industry Forecast to 2025" ... ... to grow at a CAGR of around 15.1% over the next ... This industry report analyzes the market estimates and forecasts for all ...
Breaking Biology News(10 mins):
(Date:10/11/2017)... ... October 11, 2017 , ... ComplianceOnline’s Medical Device Summit is back for its ... 2018 in San Francisco, CA. The Summit brings together current and former FDA office ... directors and government officials from around the world to address key issues in device ...
(Date:10/11/2017)... TX (PRWEB) , ... October 11, 2017 , ... ... August compared the implantation and pregnancy rates in frozen and fresh in ... contribution of progesterone and maternal age to IVF success. , After comparing the ...
(Date:10/10/2017)... ... October 10, 2017 , ... Dr. Bob Harman, founder and CEO ... Diego Rotary Club. The event entitled “Stem Cells and Their Regenerative ... attendees. Dr. Harman, DVM, MPVM was joined by two human doctors: Peter B. ...
(Date:10/9/2017)... DIEGO , Oct. 9, 2017  BioTech ... biological mechanism by which its ProCell stem cell ... critical limb ischemia.  The Company, demonstrated that treatment ... amount of limbs saved as compared to standard ... the molecule HGF resulted in reduction of therapeutic ...
Breaking Biology Technology: