What the mouse eye tells the mouse brain

January 7, 2016
The retina sends information to the brain via some 40 different channels. Credit: CIN/Tübingen University

Tübingen researchers have shown that image processing in the eye is more extensive than previously thought. They investigated the channels that transmit information from the eye to the brain. In the course of this investigation, they not only identified numerous new cell types: they also found that the retina seems to possess some 40 different channels into the brain, twice as many as previously assumed. The results of their study are published in the latest edition of Nature.

"What the frog's eye tells the frog's brain" was the title that cognition scientist Jerome Lettvin gave to a seminal paper published in 1959. He assumed that the eye not only sees, but also processes images – even before they are transmitted to the brain for further processing. Lettvin was able to show that the eye neither simply takes pictures like a camera, nor does it send them to the brain without filtering. Instead, the eye itself extracts valuable information from what it sees. In the case of the frog, for example, it might 'tell' the brain: "There is something small and dark there, possibly a fly." For his revolutionary hypotheses, Lettvin was at first laughed off stage at conferences. In the meantime, though, his oft-quoted paper is considered a milestone. The questions raised in Lettvin's time are still pursued by scientists today.

A Tübingen-based team of researchers has now tackled these questions anew, led by Prof. Thomas Euler and Prof. Matthias Bethge (Werner Reichardt Centre for Integrative Neuroscience, Bernstein Center for Computational Neuroscience, and Institute for Ophthalmic Research). The neuroscientists wanted to find out which kinds of information about the world the retina transmits to the brain. To this end, they undertook a study on an unheard-of scale, investigating more than 11,000 individual retinal cells in mice - far bigger than the largest similar study to date, which had been content with investigating approx. 450 .

Combining state-of-the-art experimental methods, the researchers studied (RGCs). They made use of electroporation, a staining technique which makes whole populations of nerve cells visible under the microscope. This enabled the researchers to watch individual cells at work in real time. The vast amounts of data were analyzed using advanced machine learning techniques. The scientists were most interested in the diverse functions of these cells: different ganglion cells respond to different properties of images, and send this information to the brain via different channels, each specialized in either contrast, color, direction and movement, edges etc. From these information channels, the brain assembles our image of the world surrounding us. The scientists tested for the response behavior of the ganglion cells to various simple images and moving optical stimuli.

Based on this functional differentiation, the team was able to identify up to 40 types of in the retina, very likely representing as many information channels. This is far more than the at most 20 types which had been heretofore assumed. While the results from the mouse model cannot be applied directly to humans, the retina is similar in all mammals. This brings an analogous classification in humans within reach.

The large number of different information channels suggests that the retina does not simply transform received light signals into nerve cell signals. Instead, it also interprets the signals in fundamental ways. Their work in basic research has brought the Tübingen neuroscientists a large step closer to understanding how images are interpreted in the . Since many diseases of the eye only affect certain retinal cell types and channels, these insights can also help in developing more specific treatments. In Tübingen, research on prosthetic technology to restore sight to blind people (retina implants) has been going strong for many years. This research stands to profit massively from the new results: current models still stimulate the retina relatively unspecifically. New insights provided by the study at hand might help future versions to feed visual information directly into suitable channels.

Explore further: The end of a dogma: Bipolar cells generate action potentials

More information: Tom Baden et al. The functional diversity of retinal ganglion cells in the mouse, Nature (2016). DOI: 10.1038/nature16468

Related Stories

The end of a dogma: Bipolar cells generate action potentials

December 19, 2012

To make information transmission to the brain reliable, the retina first has to "digitize" the image. Until now, it was widely believed that this step takes place in the retinal ganglion cells, the output neurons of the retina. ...

Early retina cell changes in glaucoma identified

February 11, 2015

Glaucoma, the second leading cause of blindness, usually stems from elevated eye pressure, which in turn damages and destroys specialized neurons in the eye known as retinal ganglion cells. To better understand these cellular ...

Can the eyes help diagnose Alzheimer's disease?

November 13, 2013

An international team of researchers studying the link between vision loss and Alzheimer's disease report that the loss of a particular layer of retinal cells not previously investigated may reveal the disease's presence ...

Retina's cancer-like metabolism could lead to new treatments

December 5, 2014

Eye surgeons at the University of Adelaide have discovered that the retina in human eyes uses energy in a very similar way to cancer, which could lead to improved understanding of cancers as well as eye disease such as macular ...

Recommended for you

Suppressing epileptic seizures via Anderson localization

March 22, 2017

More than 50 million people of all ages suffer from epilepsy, otherwise known as seizure disorder, the fourth most common neurological disease in the world. Patients diagnosed with epilepsy often experience recurrent seizures ...

Scientists study Pavlovian conditioning in neural networks

March 22, 2017

In the decades following the work by physiologist Ivan Pavlov and his famous salivating dogs, scientists have discovered how molecules and cells in the brain learn to associate two stimuli, like Pavlov's bell and the resulting ...

0 comments

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.