THE RECEPTIVE FIELDS OF 
RETINAL GANGLION CELLS: THE 
OUTPUT OF THE EYE
Left: Four recordings from a 
typical on-center retinal 
ganglion cell. Each record is a 
single sweep of the 
oscilloscope, whose duration is 
2.5 seconds. For a sweep this 
slow, the rising and falling 
phases of the impulse coalesce 
so that each spike appears as a 
vertical line. To the left the 
stimuli are shown. In the 
resting state at the top, there is 
no stimulus: firing is slow and 
more or less random. The lower 
three records show responses to 
a small (optimum size) spot, a 
large spot covering the 
receptive-field center and 
surround, and a ring covering 
the surround only. Right: 
Responses of an off-center 
retinal ganglion cell to the 
same set of stimuli shown at 
the left.

    In studying the retina we are 
confronted with two main 
problems: First, how do the rods 
and cones translate the light 
they receive into electrical, 
and then chemical, signals? 
Second, how do the subsequent 
cells in the next two layers--
the bipolar, horizontal, 
amacrine, and ganglion cells--
interpret this information? 
Before discussing the 
physiology of the receptors and 
intermediate cells, I want to 
jump ahead to describe the 
output of the retina--
represented by the activity of 
the ganglion cells. The map of 
the receptive field of a cell is a 
powerful and convenient 
shorthand description of the 
cell's behavior, and thus of its 
output. Understanding it can 
help us to understand why the 
cells in the intermediate stages 
are wired up as they are, and 
will help explain the purpose of 
the direct and indirect paths. If 
we know what ganglion cells 
are telling the brain, we will 
have gone far toward 
understanding the entire 
retina.