You can view the locations of the photoreceptors. Choose View/Photoreceptor Locations from the menu.
Receptive Field
The photoreceptor is the first stage of processing in the
retina. A photoreceptor responds to the brightness at a certain location on the
screen. It has a steady-state (DC) response and a transient response. The gain
of the transient response is higher than that of the steady state response by a
factor of 2 or 3. The transient response adapts away after a second or
so.
In this simulation we have not modeled the amazing gain-control of
real photoreceptors that let them function over many decades of illumination.
(There's no need for this in the controlled environment of a virtual tangent
screen). We have also not modeled the known feedback from the horizontal cells
to the photoreceptor, via the interesting triad synapse.
We can compute the
photoreceptor response to the simple stimuli you can use in the simulation because people
have developed very fast algorithms for computing the intersections of convex polygons. If
we needed to do a general convolution of the shape
of the photoreceptor and an arbitrary stimulu,s the simulation would probably not run
in real time. These polygon intersections are shown in the output from
one of the test classes below.