Eye transmits to brain at ethernet speed

By Ker Than

Staff Writer

updated 1:32 p.m. ET July 28, 2006

Using a retina from the eye of guinea pigs as a model, scientists estimate that our eyes transmit visual information to our brains at about the same rate as an Ethernet connection.

The finding is detailed in the July issue of the journal Current Biology.

The guinea pig retina was placed in a dish and made to "watch" movies containing four types of biological motion, such as a salamander swimming in a tank of water. Electrodes measured the electrical spikes emitted by ganglion cells in response to the clips.

The retina is a light sensitive membrane that gets bombarded with light entering the lens of the eye. Ganglion cells are specialized brain cells that relay the visual information from the retina to other parts of the brain via the optic nerve.

"It's the combination and patterns of spikes that are sending the [visual] information," said Vijay Balasubramsanian, a physicist at the University of Pennsylvania who was involved in the study.

"The patterns have various meanings. We quantify the patterns and work out how much information they convey, measured in bits per second," he said.

The researchers calculate that the 100,000 ganglion cells in a guinea pig retina transmit roughly 875,000 bits of information per second. The human retina contains about 10 times more ganglion cells than that of guinea pigs, so it would transmit data at roughly 10 million bits per second, the researchers estimate.

This is comparable to an Ethernet connection, which transmits information between computers at speeds of 10 million to 100 million bits per second.

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