The study, published this month in the journal Neuron, and funded by a research grant from the National Eye Institute, National Institutes of Health, shows that the retina and its circuits are much more pliable than scientists previously thought.
"The retina has generally been thought of as a fixed circuitry where there shouldn't be much plasticity," said study co-author Henrique von Gersdorff, Ph.D., adjunct associate professor of cell and developmental biology, OHSU School of Medicine, and scientist at the Vollum Institute.
"But more and more people are finding that the retina does a lot of parallel things at the same time. For example, the direction of motion of objects that are moving into a visual scene is first detected in the retina and then transmitted to the brain."
The retina is a thin, light-sensitive sheet of neurons in the back of the eye that encodes three basic features of the objects in our environment color, shape and motion and sends the coded information to the brain. The early processing steps for vision, therefore, occur in the retina. Deep inside this sheet of interconnected neurons, at a depth called the inner plexiform layer, a tremendous processing of this visual information takes place, before it is projected to the brain through the optic nerve.
Small nerve cells called amacrine cells help bipolar cell terminals filter the bombardment of signals being sent by photoreceptors to bipolar cells before they're forwarded on to other nerve cells, called ganglion cells, which directly connect to the brain. This filtering process in the inner plexiform layer is believed to contribute to fundamental features of vision, such as sensitivity to light, temporal processing of motion, and detection of contrast.