Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Researchers measure the basis of color vision

07.09.2017

Dr. Wolf M. Harmening from University Eye Hospital Bonn, together with American colleagues, studied color vision by probing individual sensory cells – photoreceptors – in the human eye. The results confirm that the photoreceptor cells of the retina are especially sensitive to colors corresponding to their visual pigments, even when stimulated in isolation. A new observation is that proximity effects play a key role: sensitivity of tested photoreceptors varied depending on which cell classes were located in their immediate neighborhood. The results have now been published in advance online and will soon be published in the Journal of Neuroscience.

It is a constant ‘aha’ effect: when the light is switched on in a dark room, color vision sets in. “This not only makes the world more colorful,” says Dr. Wolf M. Harmening, who heads an Emmy Noether research group at Bonn University Eye Hospital.


At the Adaptive Optics Scanning Laser Ophthalmoscope: Dr. Wolf M. Harmening (left) from University Eye Hospital Bonn and Dr. William S. Tuten (right) from the University of California, Berkeley.

© Photo: Rolf Müller/Ukom-UKB


The mosaic of photoreceptor cells in the human retina conveys our rich sense of color.

© William S. Tuten/Wolf M. Harmening

“Color also allows spatial detail to become apparent that has proven vital for survival over the course of evolution.” Some predator camouflage can only be identified through color. Poisonous animals and plants also provide warning signals through color. That human color vision emerges from three independent channels within the retina is well established in the vision science literature.

By stimulating individual photoreceptor cells in living subjects, the lead authors Dr. Wolf M. Harmening from University Eye Hospital Bonn and Dr. William S. Tuten from the University of California, Berkeley, together with colleagues from the US universities in Seattle, Washington and Birmingham, Alabama, have now shown on a cellular scale how the human retina conveys color signals.

To do this, the researchers used an ophthalmoscope that can examine and stimulate the human retina non-invasively. The novel method – Adaptive Optics Scanning Laser Ophthalmoscopy – employs a combination of a laser and a very high-resolution microscope, which can even map individual sensory cells in the retina.

The research team has now used this ophthalmoscope to study vision in the retinas of two human subjects. According to common theory, all color stimuli can be formed by mixing the primary colors red, green, and blue. While rod photoreceptors are specialized for seeing in the dark, cone photoreceptors convey color vision. They carry light sensitive pigments specialized to absorb wavelengths near the primary colors, the basis of trichromatic vision.

Mapping of the retina

The researchers initially mapped the cone mosaic on the subjects’ retinas by measuring light absorption for certain wavelengths in each photoreceptor. In this way, they were able to determine the sensory cells’ identity, or class, within the framework of trichromacy. By reducing the intensity of the stimulation light, the researchers were then able to determine a detection threshold in each cone, at which light was just barely seen by the subjects. “This is important because we could use the sensitivity of each cell to determine how overall perception is governed by the contribution of individual cones,” reports Harmening.

Most notably, the sensitivity of single cells also depended on the immediate neighboring cells. “If a cone sensitive to red light is surrounded by cells that are more sensitive to green, this cone is more likely to behave like a green cone,” summarizes Harmening. Studying visual processing of color is complex, in part because the brain does not receive raw data from individual photoreceptors but rather an already preprocessed retinal signal. Harmening: “Spatial and color information of individual cones is modulated in the complex network of the retina, with lateral information spreading through what are known as horizontal cells.”

Their finding supports previous assumptions about color vision. “What’s new is that we can now study vision on the most elementary level, cell-by-cell,” says the scientist. Conventional tests of vision use stimuli that necessarily activate hundreds to thousands photoreceptor cells at the same time. Harmening emphasizes that cellular-scale retinal computation such as the proximity effect has important implications, for basic and clinical research. “When the basis of vision is understood better, we open avenues for new diagnoses and treatments in case of retinal disease,” says Harmening. The novel single cell approach offers access to new findings in ophthalmology.

Publication: William S. Tuten, Wolf M. Harmening, Ramkumar Sabesan, Austin Roorda, Lawrence C. Sincich: Spatiochromatic interactions between individual cone photoreceptors in the human retina, The Journal of Neuroscience, DOI: 10.1523/JNEUROSCI.0529-17.2017

Media contact:

Dr. Wolf M. Harmening
University Eye Hospital Bonn
Tel. ++49-228-28715882
E-mail: wolf.harmening@ukbonn.de

Johannes Seiler | idw - Informationsdienst Wissenschaft
Further information:
http://www.uni-bonn.de/

More articles from Health and Medicine:

nachricht Purdue cancer identity technology makes it easier to find a tumor's 'address'
16.11.2018 | Purdue University

nachricht Microgel powder fights infection and helps wounds heal
14.11.2018 | Michigan Technological University

All articles from Health and Medicine >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: UNH scientists help provide first-ever views of elusive energy explosion

Researchers at the University of New Hampshire have captured a difficult-to-view singular event involving "magnetic reconnection"--the process by which sparse particles and energy around Earth collide producing a quick but mighty explosion--in the Earth's magnetotail, the magnetic environment that trails behind the planet.

Magnetic reconnection has remained a bit of a mystery to scientists. They know it exists and have documented the effects that the energy explosions can...

Im Focus: A Chip with Blood Vessels

Biochips have been developed at TU Wien (Vienna), on which tissue can be produced and examined. This allows supplying the tissue with different substances in a very controlled way.

Cultivating human cells in the Petri dish is not a big challenge today. Producing artificial tissue, however, permeated by fine blood vessels, is a much more...

Im Focus: A Leap Into Quantum Technology

Faster and secure data communication: This is the goal of a new joint project involving physicists from the University of Würzburg. The German Federal Ministry of Education and Research funds the project with 14.8 million euro.

In our digital world data security and secure communication are becoming more and more important. Quantum communication is a promising approach to achieve...

Im Focus: Research icebreaker Polarstern begins the Antarctic season

What does it look like below the ice shelf of the calved massive iceberg A68?

On Saturday, 10 November 2018, the research icebreaker Polarstern will leave its homeport of Bremerhaven, bound for Cape Town, South Africa.

Im Focus: Penn engineers develop ultrathin, ultralight 'nanocardboard'

When choosing materials to make something, trade-offs need to be made between a host of properties, such as thickness, stiffness and weight. Depending on the application in question, finding just the right balance is the difference between success and failure

Now, a team of Penn Engineers has demonstrated a new material they call "nanocardboard," an ultrathin equivalent of corrugated paper cardboard. A square...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

VideoLinks
Industry & Economy
Event News

“3rd Conference on Laser Polishing – LaP 2018” Attracts International Experts and Users

09.11.2018 | Event News

On the brain’s ability to find the right direction

06.11.2018 | Event News

European Space Talks: Weltraumschrott – eine Gefahr für die Gesellschaft?

23.10.2018 | Event News

 
Latest News

Purdue cancer identity technology makes it easier to find a tumor's 'address'

16.11.2018 | Health and Medicine

Good preparation is half the digestion

16.11.2018 | Life Sciences

Microscope measures muscle weakness

16.11.2018 | Life Sciences

VideoLinks
Science & Research
Overview of more VideoLinks >>>