‘Efficient coding theory’ describes the most perfect, low-energy way to design a light-detecting device for a future camera or prosthetic retina. Or you could just look at a mammalian retina that’s already organized this way. In a pair of papers on retinal structure, a team of neurobiologists has shown that the rigors of natural selection and evolution shaped our retinas to capture noisy data just as this theory of optimization would prescribe.

Or you could just look at a mammalian retina.

In a pair of papers on retinal structure, Duke University neurobiologists have shown that the rigors of natural selection and evolution have shaped the retinas in our eyes just as this theory of optimization would predict. And that puts retinas miles ahead of anything human engineering can achieve at this point.

In a previous paper published last March in Nature, the researchers showed that rat and monkey retinas are laid out in patterns of sensitivity that mimic what efficient coding theory would predict. Different sets of retinal neurons are sensitive to individual stimuli: bright, dark, moving, and so on, and they’re arranged in a three-dimensional mosaic of cells that works to add up the image.

Now, in a paper appearing this week in the Proceedings of the National Academy of Sciences, «we set out to understand that, through a lot of simulation and a little bit of pencil and paper math,» said John Pearson, an assistant professor of biostatistics & bioinformatics in the School of Medicine. «The mosaics don’t just randomly overlap, but they don’t overlap in a highly ordered way.»

«We’re making a prediction about how literally thousands of cells of multiple different types arrange themselves across space,» said Greg Field, an assistant professor of neurobiology in the Duke School of Medicine. «The monkey retina and our retinas are nearly indistinguishable,» he said. «The fact that we observed this in the monkey retina gives us incredible confidence that our retinas are laid out in the same way.»

In a cross-section of the retina, the bodies of the ganglion cells, round orbs that contain the nucleus, line up in a layer together, but they extend their tree-like, branching dendrites into a thick layer that looks like the tangled roots of a pot-bound houseplant. It’s in this thicker, spectacularly complex layer that mosaics of different sensitivities are laid out in ordered patterns.

Story Source:
Materials provided by Duke University. Original written by Karl Leif Bates. Note: Content may be edited for style and length.