How the retina works: Like a multi-layered jigsaw puzzle of receptive fields

Apr 07, 2009
Each neuron in the retina views the world through a small, irregularly shaped window. These regions fit together like pieces of a puzzle, preventing "blind spot" and excessive overlap that could blur our perception of the world. Credit: Image: Courtesy of Dr. Jeffrey Gauthier, Salk Institute for Biological Studies

About 1.25 million neurons in the retina -- each of which views the world only through a small jagged window called a receptive field -- collectively form the seamless picture we rely on to navigate our environment. Receptive fields fit together like pieces of a puzzle, preventing "blind spots" and excessive overlap that could blur our perception of the world, according to researchers at the Salk Institute for Biological Studies.

In the April 7 issue of the journal Public Library of Science, Biology, the scientists say their findings suggest that the nervous system operates with higher precision than previously appreciated and that apparent irregularities in individual may actually be coordinated and finely tuned to make the most of the world around us.

Previously, the observed irregularities of individual receptive fields suggested that the collective visual coverage might be uneven and irregular, potentially posing a problem for high-resolution vision. "The striking coordination we found when we examined a whole population indicated that neuronal circuits in the may sample the visual scene with high precision, perhaps in a manner that approaches the optimum for high-resolution vision," says senior author E.J. Chichilnisky, Ph.D., an associate professor in the Systems Neurobiology Laboratories.

All reaching the brain is transmitted by retinal ganglion cells. Each of the 20 or so distinct ganglion cell types is thought to transmit a complete visual image to the brain, because the receptive fields of each type form a regular lattice covering visual space. However, within each regular lattice, the individual cells' receptive fields have irregular and inconsistent shapes, which could potentially result in patchy coverage of the visual field.

To understand how the visual system overcomes this problem, postdoctoral researcher and first author Jeffrey L. Gauthier, Ph.D., used a microscopic electrode array to record the activity of ganglion cells in isolated patches of retina, the tissue lining the back of the eye.

After monitoring hundreds of ganglion cells over several hours, he distinguished between different cell types based on their light response properties. "Often people record from many cells simultaneously but they don't know which cell belongs to which type," says Gauthier. Without this information, he says, he wouldn't have been able to observe that the receptive fields of neighboring cells of a specific type interlock, complementing each others' irregular shapes.

"The receptive fields of all four cell types we examined were precisely coordinated," he says, "but we saw no coordination between cells of different types, emphasizing the importance of clearly distinguishing one cell type from another when studying sensory encoding by a population of neurons."

Source: Salk Institute (news : web)

Explore further: Growing a blood vessel in a week

add to favorites email to friend print save as pdf

Related Stories

How Much the Eye Tells the Brain

Jul 26, 2006

Researchers at the University of Pennsylvania School of Medicine estimate that the human retina can transmit visual input at about the same rate as an Ethernet connection, one of the most common local area ...

Discovery of retinal cell type ends 4-decade search

Oct 09, 2007

A research team combining high-energy physicists from the University of California, Santa Cruz, and neuroscientists from the Salk Institute in La Jolla, Calif., has discovered a type of retinal cell that may help monkeys, ...

Distinguishing between 2 birds of a feather

Aug 08, 2008

The bird enthusiast who chronicled the adventures of a flock of red-headed conures in his book "The Wild Parrots of Telegraph Hill" knows most of the parrots by name, yet most of us would be hard pressed to tell one bird ...

Recommended for you

Growing a blood vessel in a week

2 hours ago

The technology for creating new tissues from stem cells has taken a giant leap forward. Three tablespoons of blood are all that is needed to grow a brand new blood vessel in just seven days. This is shown ...

Testing time for stem cells

5 hours ago

DefiniGEN is one of the first commercial opportunities to arise from Cambridge's expertise in stem cell research. Here, we look at some of the fundamental research that enables it to supply liver and pancreatic ...

Team finds key signaling pathway in cause of preeclampsia

Oct 23, 2014

A team of researchers led by a Wayne State University School of Medicine associate professor of obstetrics and gynecology has published findings that provide novel insight into the cause of preeclampsia, the leading cause ...

Rapid test to diagnose severe sepsis

Oct 23, 2014

A new test, developed by University of British Columbia researchers, could help physicians predict within an hour if a patient will develop severe sepsis so they can begin treatment immediately.

User comments : 1

Adjust slider to filter visible comments by rank

Display comments: newest first

Stein
not rated yet Apr 07, 2009
Hello Dr Jefferey

Very Interesting!

Does that mean that the each different type or shape responds to a different light frequency?

What frequencies are associated with each type or shape.

Are the discs of each shape made from different chemical compositions?

If so what elements are present in the molecules of the receptor discs of a, b, c, d and e neurons?

Cheers Zwei Stein