Research

E. J. Chichilnisky, a professor in the Systems Neurobiology Laboratories, uses multi-electrode recording to study the function of the retina. For many years, neuroscientists have examined nervous system function by recording the electrical activity of individual nerve cells or a small number of cells. Chichilnisky and his team are taking such research to the next level by recording the activity of hundreds of neurons at once. This step is necessary because even the simplest functions of the nervous system involve many 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 the cellular circuitry of the retina performs the neural computations essential for vision. Other areas of investigation include the role of synchronized activity in signalling by populations of cells, 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 a visual prosthesis that could be implanted in the eye and substitute for retinal tissue damaged by degenerative diseases.

"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."

About 1.25 million retinal ganglion cells–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. There are 20 or so distinct ganglion cell types, and because the receptive fields of each type form a regular lattice covering visual space, each lattice is thought to transmit a complete visual image to the brain. Within any given regular lattice, however, the individual cells' receptive fields have irregular and inconsistent shapes, which could potentially result in patchy coverage of the visual field and pose a problem for high-resolution vision.

To understand how the visual system overcomes this problem, Chichilnisky and his team used a microscopic electrode array to record the activity of ganglion cells in isolated patches of retina. After monitoring hundreds of ganglion cells over several hours, they were able to distinguish between different ganglion cell types based on their light response properties. With this information, they were able to deduce that receptive fields fit together like pieces of a puzzle, preventing "blind spots" and excessive overlap that could blur our perception of the world.

This finding brings scientists one step closer to the ultimate goal of vision research: the development of visual prosthetics that could one day restore vision to people whose retina has been damaged by disease (e.g., macular degeneration or retinitis pigmentosa). In principle, retinal implants could bypass the damaged retina with the help of tiny electrode arrays that mimic the electrical signals sent to the brain in response to light. In order to engineer these prosthetics, however, scientists need to understand how neurons in the retina function as a network to produce an image. Chichilnisky's work is focused on building the foundation for that understanding, with an emphasis on distinguishing one cell type from another when studying sensory encoding by a population of neurons.

Left to right:
Clare Hulse, Max Schiff, Jeff Gauthier, Martin Greschner, EJ Chichilnisky, Peter Li, Lauren H. Jepson, Greg Field

Selected Publications

Field GD, Gauthier JL, Sher A, Greschner M, Machado TA, Jepson LH, Shlens J, Gunning DE, Mathieson K, Dabrowski W, Paninski L, Litke AM & Chichilnisky EJ (2010) Functional connectivity in the retina at the resolution of photoreceptors. Nature 467:673.

Shlens J, Field GD, Gauthier JL, Greschner M, Sher A, Litke AM, & Chichilnisky EJ (2009) The structure of large-scale synchronized firing in primate retina. Journal of Neuroscience 29:5022-5031.

Gauthier JL, Field GD, Sher A, Greschner M, Shlens J, Litke AM, & Chichilnisky EJ (2009) Receptive fields in primate retina are coordinated to sample visual space more uniformly. PLoS Biology, 2009; 7:1. e63 DOI: 10.1371/journal.pbio.1000063.

Pillow JW, Shlens J, Paninski L, Sher A, Litke AM, Chichilnisky EJ & Simoncelli EP (2008). Spatio-temporal correlations and visual signalling in a complete neuronal population. Nature 454:995-9.

Sekirnjak C, Hottowy P, Sher A, Dabrowski W, Litke AM, & Chichilnisky EJ (2008) High-resolution electrical stimulation of primate retina for epiretinal implant design. Journal of Neuroscience 28:4446-4456.

Salk News Releases

• Salk Institute promotes latest generation of extraordinary scientists
  April 15, 2011
• From eye to brain: Salk researchers map functional connections between retinal neurons at single-cell resolution
  October 6, 2010
• How the retina works: Like a multi-layered jigsaw puzzle of receptive fields
  April 7, 2009
• For the first time, miniature electrode array records from hundreds of nerve cells simultaneously
  July 11, 2005

Awards and Honors

• Howard Hughes Medical Institute fellow, 1991-1995
• Helen Hay Whitney fellow, 1996-1998
• Alfred P. Sloan Foundation Research Fellowship, 2000-2002
• McKnight Scholar's Award, 2001-2003
• McKnight Technological Innovation in Neuroscience Award (with A. Litke), 2004-2005

Links

Chichilnisky lab