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E. J. Chichilnisky

 

E. J. Chichilnisky

E. J. Chichilnisky

Associate Professor
Systems Neurobiology Laboratories

"Visual information is transmitted from the eye to the brain in just 1.25 million optic nerve fibers–about as many fibers as there are pixels in a cheap digital camera. Somehow we exploit this information to navigate busy highways, something even the most advanced robots cannot do. I want to decipher how visual information is encoded by the retina in a manner that the brain can use it to produce visual experience."

Although it seems simple and effortless, vision is a complex process, involving the collective activity of billions of neurons distributed throughout the brain. For many years, scientists tried to glean information about the brain by recording the electrical activity of one neuron at a time. Because even the simplest functions of the nervous system involve many thousands of neurons, however, recording the activity of individual or only a handful of nerve cells does not provide the full picture. In collaboration with an international group of high-energy physicists, Chichilnisky developed a microscopic electrode array that allows him to monitor the activity of more than 500 nerve cells simultaneously. By comparing the visual input with the electrical output of the retina, a thin tissue lining the back of the eye, he can reconstruct the neural code used by the retina to relay meaningful information to the brain.

Importantly, this research also lays the technological and biological groundwork for the development of visual prosthetic devices that one day could restore vision to people whose retina has been damaged by disease (e.g., macular degeneration or retinitis pigmentosa). In principle, retinal implants can bypass the damaged retina with the help of tiny electrode arrays that mimic the electrical signals sent to the brain in response to light. Prior experiments in Chichilnisky's lab have shown that individual retinal ganglion cells, which transmit visual information from the retina to the brain, can be stimulated with very low and thus safe levels of current. Surprisingly, this kind of electrical stimulation is also extremely precise in terms of efficiency, timing, and spatial specificity in populations of neurons. Chichilnisky's group is preparing to record light responses from retinal ganglion cells and then "play back" these signatures with artificial electric current. This will allow them to connect the patterns of stimulation more closely to what they are learning about the normal patterns of activity in the population.

In the future, Chichilnisky hopes that retinal implants will play a role in restoring vision to blind patients that is analogous to the stunningly successful restoration of hearing made possible by cochlear implants.

Lab Photo

Left to right:
Standing: Clare Hulse, Martin Greschner, Greg Field Seated: Anastasia Anishchenko, Lauren Hruby, Timothy Machado, Jeffry Gauthier, EJ Chichilnisky

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E. J. Chichilnisky

Faculty

E. J. Chichilnisky

E. J. Chichilnisky

Associate Professor
Systems Neurobiology Laboratories

E. J. Chichilnisky, an associate professor in the Systems Neurobiology Laboratories, uses multi-electrode recording to examine the function of the retina. For many years, neuroscientists have been examining nervous system function by recording the electrical activity of individual nerve cells. Chichilnisky and his team are working to take such research to the next level by recording the activity of large groups of cells at once. This step is necessary because even the simplest functions of the nervous system involve many thousands of neurons.

Chichilnisky's laboratory is focused on how the retina processes visual information and transmits this information to the brain. A key area of interest is how retinal neurons collectively communicate visual motion information to areas of the brain responsible for motion perception and behavior guided by motion. Other areas of investigation include the role of synchronized activity in retinal signalling, and how retinal signals mediate the detection of small numbers of photons in dim lighting conditions. Chichilnisky's lab uses a state-of-the-art 512-electrode recording system, developed in collaboration with an international group of high-energy physicists, that allows them to monitor hundreds of cells at once while stimulating the retina with spatial and temporal patterns of light. A long-term goal of the research is to contribute to development of visual prosthetics, devices that could be implanted in the eye and substitute for retinal tissue damaged by disease or other trauma.

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