PHILADELPHIA - Physicists and neuroscientists from the University of Pennsylvania have linked the cell structure of the retina to the light and dark contrasts of the natural world, demonstrating the likelihood that the neural pathways humans use for seeing are adapted to best capture the world around us.
Researchers found that retinal ganglion cells that see darkness are more numerous and cluster closer together than those that see light, corresponding to the fact that the natural world contains more dark spots than light. Now physicists, and not just pessimists, see the world for the dark place it is.
The results suggest that the brain's separation of retinal circuitry into off and on mosaics that separately process dark and bright spots allows for structural adaptation to the natural scenes humans must see.
The team took the study a step further by constructing artificial images that matched the characteristics of the natural world and by testing what sorts of off and on mosaics best represented information from these images. According to the authors, the total flow of information peaked for mosaics with more densely clustered off cells, as in the human retina, suggesting that human vision has evolved to efficiently represent visual information in the natural world.
Researchers looked at the physiology of the retinal ganglion cells whose job it is to respond to a dark spot on a brighter background, simply called off cells, wondering why the brain would have clusters of off cells and not an even distribution across the retina. In addition to being more numerous and branching together in dense, bushy clusters, they also have smaller dendritic fields than the cells responsible for seeing light spots. By branching together more densely in clusters, they collect more synapses per visual angle. Thus, researchers concluded that the retina devotes more resources to processing dark contrasts, a natural capability reflected i
|Contact: Jordan Reese|
University of Pennsylvania