Scientists have estimated that the human retina can transmit data at approximately 10 million bits per second, equivalent to a standard ethernet connection. The researchers at the University of Pennsylvania came to that number by measuring spikes of electrical impulses from a (disembodied) guinea pig retina "looking" at movies of biological motion, like a salamander swimming. The ganglion cells in the retina were then classified as either "brisk" or "sluggish," depending on how fast they fired. From the University of Pennsylvania School of Medicine:
The researchers found that the electrical spike patterns differed between cell types. For example, the larger, brisk cells fired many spikes per second and their response was highly reproducible. In contrast, the smaller, sluggish cells fired fewer spikes per second and their responses were less reproducible.
But, what's the relationship between these spikes and information being sent? "It's the combinations and patterns of spikes that are sending the information. The patterns have various meanings," says co-author Vijay Balasubramanian, PhD, Professor of Physics at Penn. "We quantify the patterns and work out how much information they convey, measured in bits per second."
Calculating the proportions of each cell type in the retina, the team estimated that about 100,000 guinea pig ganglion cells transmit about 875,000 bits of information per second. Because sluggish cells are more numerous, they account for most of the information. With about 1,000,000 ganglion cells, the human retina would transmit data at roughly the rate of an Ethernet connection, or 10 million bits per second.
