Using Physics to Explain the Neuroscience of Sight

Lizzie Buchen in Symmetry:

Seeing is easy. We open our eyes, and there the world is–in starlight or sunlight, still or in motion, as far as the Pleiades or as close as the tips of our noses. The experience of vision is so common and effortless that we rarely pause to consider what an astounding feat it is: Every time our eyes open, they encode our surroundings as a pattern of electrical signals, which the brain translates into our moving, colorful, three-dimensional perception of the world.

This everyday miracle has attracted the devotion and expertise of an unlikely individual–Alan Litke, an experimental particle physicist based at the University of California, Santa Cruz. When not in Geneva, Switzerland, where he is working on the ATLAS particle detector for the Large Hadron Collider, Litke is working with neuroscientists and engineers, adapting the technology of high-energy physics to study the visual system.

The central challenge is to understand the language the eye uses to send information to the brain. Light reflected from our surroundings enters our eyes through the transparent window of the cornea and is focused by the lens, forming an image on the retina. The retina of each eye contains about 125 million light-sensitive rods and cones, which translate light into electrical and chemical signals. These signals travel to the visual centers of the brain through a million retinal ganglion cells, or RGCs.

The retina thus encodes the activity of 125 million cells in the signals of one million output cells, which deliver the brain a highly compressed neural code from which our entire visual experience is derived. Litke wants to understand how this neural network processes information from our surroundings and portrays it to the brain.