Intro | Amacrine Cells | Back of the Eyeball | Bipolar Cells | Blind Spot & Optic Nerve | Cone Receptors | Retinal Ganglion Cells | Horizontal Cells | Rod Receptors
Part 1: Image-Mapped Tutorial
Part 2: Matching Self-Test
Part 3: Multiple-Choice Self-Test
Ganglion Cells form the third and last layer of the retina. The signals transmitted from ganglion cells represent the integration of all retinal processing that is then conveyed to higher centers along the visual pathways. The axons of ganglion cells form the fibers of the optic nerve, destined for these higher centers.
Retinal ganglion cells are the output neurons that encode and transmit information from the eye to the brain. Their diverse physiologic and anatomic properties have been intensively studied and appear to account well for a number of psychophysical phenomena such as lateral inhibition and chromatic opponency. In this paper, we summarize our current view of retinal ganglion cell properties and pose a number of questions regarding underlying molecular mechanisms.
| Advanced |
Ganglion cells encode and transmit visual information to the brain. Their properties have been studied extensively and the results of these studies indicate that they are essential to the process of lateral inhibition (Xiang, Zhou & Nathans, 1996). Ganglion cells respond best to small spots of light, small rings of light, or edges of light in a center-surround pattern. The center-surround receptive field is created by the amacrine and horizontal cells via their lateral communication with bipolar and ganglion cells. When a receptor cell is activated by light, the bipolar cell directly in line with it is also activated. The bipolar cell in turn activates its corresponding ganglion cell. When neighboring receptor cells activate their bipolar and ganglion cells in sequence, they also activate horizontal cells. These horizontal cells inhibit the activity of any bipolar cells located in the center portion of the receptive field. With this situation, diffuse light will activate the center bipolar cell, but at the same time will inhibit that center cell via simultaneous stimulation of neighboring bipolar cells. In this situation, the ganglion cell will not be activated (no change in its tonic level of activity), and no visual event will be encoded. A small spot of light, however, will excite a single bipolar cell. Neighboring bipolar cells are not stimulated, and lateral inhibition via horizontal cells will not occur.
The response of a ganglion cell to a ring of light is considerably different. In this condition, only the neighboring receptor and bipolar cells are activated. The center bipolar cell is inhibited via the activation of horizontal cells by the surrounding cells. The ganglion cell in sequence with the inhibited bipolar cell will shut down until the light is turned off. When this occurs, the ganglion cell will activate, giving a so-called "off-response". This is an "on-center" cell. If the conditions above are reversed, the cell is called "off-center".
| Reference |
Xiang, M., Zhou, H. & Nathans, J. (1996). Molecular biology of retinal ganglion cells. Proceedings of the National Academy of Sciences, 93(2), 596-601.