The retina of the eye in many mammals has what is known as a 'duplex' property, with photoreceptor cells for color vision, called cones, as well as photoreceptor cells for night vision called rods. The cones only work in fairly bright light, while the rods work well in dim light. These photoreceptor cells send information via an intermediate group of retinal cells, called bipolar cells, then the signal passes eventually to the retinal ganglion cells, which are the neurons that give rise to the optic nerve to the brain. It is thought that there are two distinct pathways for the signal of light intensity from the rods to be transmitted within the retina to the ganglion cells. In one pathway the rod signal travels directly to rod bipolar cells; in the other pathway the rod signal is believed to cross a junction between rods and cones, then enters the cone pathway. This project uses a unique approach combining physiological recording of retinal activity with specific pharmacological blockers of certain kinds of neurotransmitters to isolate the contribution of these two pathways to vision. The results will further our understanding of the complex visual processing that occurs in the retina. Results will be important not only to retinal physiology, but to understanding visual perception and perhaps to artificial vision devices.
