Featured Research

from universities, journals, and other organizations

New neural pathway found in eyes that aids in vision

Date:
May 21, 2014
Source:
Johns Hopkins University
Summary:
A less-well-known type of retina cell plays a more critical role in vision than previously understood. 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.

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."


Story Source:

The above story is based on materials provided by Johns Hopkins University. Note: Materials may be edited for content and length.


Journal Reference:

  1. TiffanyM. Schmidt, NaziaM. Alam, Shan Chen, Paulo Kofuji, Wei Li, GlenT. Prusky, Samer Hattar. A Role for Melanopsin in Alpha Retinal Ganglion Cells and Contrast Detection. Neuron, 2014; 82 (4): 781 DOI: 10.1016/j.neuron.2014.03.022

Cite This Page:

Johns Hopkins University. "New neural pathway found in eyes that aids in vision." ScienceDaily. ScienceDaily, 21 May 2014. <www.sciencedaily.com/releases/2014/05/140521162707.htm>.
Johns Hopkins University. (2014, May 21). New neural pathway found in eyes that aids in vision. ScienceDaily. Retrieved October 20, 2014 from www.sciencedaily.com/releases/2014/05/140521162707.htm
Johns Hopkins University. "New neural pathway found in eyes that aids in vision." ScienceDaily. www.sciencedaily.com/releases/2014/05/140521162707.htm (accessed October 20, 2014).

Share This



More Health & Medicine News

Monday, October 20, 2014

Featured Research

from universities, journals, and other organizations


Featured Videos

from AP, Reuters, AFP, and other news services

Microneedle Patch Promises Painless Pricks

Microneedle Patch Promises Painless Pricks

Reuters - Innovations Video Online (Oct. 18, 2014) Researchers at The National University of Singapore have invented a new microneedle patch that could offer a faster and less painful delivery of drugs such as insulin and painkillers. Video provided by Reuters
Powered by NewsLook.com
Raw: Nurse Nina Pham Arrives in Maryland

Raw: Nurse Nina Pham Arrives in Maryland

AP (Oct. 17, 2014) The first nurse to be diagnosed with Ebola at a Dallas hospital walked down the stairs of an executive jet into an ambulance at an airport in Frederick, Maryland, on Thursday. Pham will be treated at the National Institutes of Health. (Oct. 16) Video provided by AP
Powered by NewsLook.com
Raw: Cruise Ship Returns to US Over Ebola Fears

Raw: Cruise Ship Returns to US Over Ebola Fears

AP (Oct. 17, 2014) A Caribbean cruise ship carrying a Dallas health care worker who is being monitored for signs of the Ebola virus is heading back to Texas, US, after being refused permission to dock in Cozumel, Mexico. (Oct. 17) Video provided by AP
Powered by NewsLook.com
Spanish Govt: Four Suspected Ebola Cases in Spain Test Negative

Spanish Govt: Four Suspected Ebola Cases in Spain Test Negative

AFP (Oct. 17, 2014) All four suspected Ebola cases admitted to hospitals in Spain on Thursday have tested negative for the deadly virus in a first round of tests, the government said Friday. Duration: 00:55 Video provided by AFP
Powered by NewsLook.com

Search ScienceDaily

Number of stories in archives: 140,361

Find with keyword(s):
Enter a keyword or phrase to search ScienceDaily for related topics and research stories.

Save/Print:
Share:

Breaking News:

Strange & Offbeat Stories


Health & Medicine

Mind & Brain

Living & Well

In Other News

... from NewsDaily.com

Science News

Health News

Environment News

Technology News



Save/Print:
Share:

Free Subscriptions


Get the latest science news with ScienceDaily's free email newsletters, updated daily and weekly. Or view hourly updated newsfeeds in your RSS reader:

Get Social & Mobile


Keep up to date with the latest news from ScienceDaily via social networks and mobile apps:

Have Feedback?


Tell us what you think of ScienceDaily -- we welcome both positive and negative comments. Have any problems using the site? Questions?
Mobile: iPhone Android Web
Follow: Facebook Twitter Google+
Subscribe: RSS Feeds Email Newsletters
Latest Headlines Health & Medicine Mind & Brain Space & Time Matter & Energy Computers & Math Plants & Animals Earth & Climate Fossils & Ruins