The receptive field of a single optic nerve fiber
(plotted by the on and off responses to small fixed spots)
is often divisible into concentric zones
This suggests that the response of the fiber to a moving spot
may be polar with respect to a reference point
in the receptive field.
Movement is indeed polarly encoded and there exist at least
the following four types of fibers whose rate of firing depends on
the centrifugal component of a movement
with respect to some point internal to the receptive field
(centripetal and tangential movements never cause discharge):
Some fibers have wide receptive fields and low sensitivity. Of these some prefer the moving object darker than background, others prefer it lighter.
A second group has constricted fields and high sensitivity.
A fifth variety measures inversely
the average intensity of
in a region.
Its maximum rate is in the dark.
Part II (page 354)
The coding of movement described in Part I
suggests that the frog's eye is designed
(at least for land operation)
to abstract the vector and size of a moving object
and extrapolate the path.
Because our evidence implies that there exists a coordinate system
built into the retina and that the coding allows coordinates and velocity
to arise from general operations on the whole output of the optic nerve,
we propose some alternative guesses to account for
Sperry's results on dislocated eyes.
We do not propose that his notion of specific reconnection is wrong
but that it is not necessary.
We also present the law by which there is a point-to-point correspondence
from receptors to optic nerve, vis.,
if an object is moved within the visual field in a
the only fibers that show
at any time are those that have the centers of their receptive fields
at the center of the circle described.
This menu enables execution of emulators
for all five feature detections described in
the original paper to the far left.
Hover over a menu item to choose,
then mouse over to canvas and move the cursor
to either cross the shown boundaries centrifugally
or up/down for brighter/darker.
Emulator for neuron of kind 3Choice of Neuron Kind
Hover over a menu item to the right
to choose the kind being emulated here
and to read about its properties.
Use the "Click to hear/mute discharge emulator" button
to turn the loudspeaker on.
To turn off the sound, click the same button again.
Mouse motion crossing a circle away from the center above a minimum velocity
will trigger a decaying burst volley of discharges for neuron kinds 1-4.
This is the behavior described in the paper.
Mouse motion towards the center fails to trigger activity.
Mouse motion within the annuli and along any circle
also fails to trigger activity.
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