fig 8.1/1
camouflage
(ref 3, 288, 7.1)
The bird becomes camouflaged if a
transparency of the random lines is
superimposed on a transparency of
the bird. When the bird is moved relative to
the lines, it becomes visible (see the applet
above). |
fig 8.1/2
directional selectivity
(ref 9, 276, 8.13)
Schematic drawing of a direction selective cell
responsive
to rightward motion (see your book: p.
276!). |
fig 8.1/3
Ternus display
(ref 9, 286, 8.17)
An illustration of the correspondence
problem in motion
perception
(see
your book: p.286!). |
fig 8.1/4
Glass pattern
An example of a random-dot Glass pattern (named
after Leon Glass). Two copies of a random
dot
pattern were superimposed, rotated with
respect
to each other: a circular structure is
seen.
(remember the simple horizontal
translation
that results in perceived horizontal stripes;
try
to compare it to random- dot stereograms, and
cinematograms) |
fig 8.1/5
RFs and Glass patterns
When a pair of dots (where dot 1 belongs to
the
first pattern, and dot 2 belongs to the second, shifted
patern) is falling within the excitatory zone
of an
oriented receptive field, the neuron is going
to fire
as if there would be an oriented stimulus.
Those
neurons will fire the most that are tuned for
horizontal
orientation in this example. Neurons tuned
for
other orientationsy would not get both
dots
within the excitatory zone exactly, therefore
their
signals would be smaller. The horizontally
tuned
neurons define the perceived orientation
of
the pattern, because they have the largest
response.
That can solve the correspondence problem, because each dot will
have a pair in terms of the "largest neural response." |
fig 8.1/6
aperture problem
(ref 3. 305, 7.25)
left panel: This square is moving up and
tothe right,
but side A, viewed through
aperture a, appears to be movingto the
right, and side B, viewed through aperture
b,
appears to be moving up.
right panel: The arrows indicate that
themovement
across the aperture could be caused by movement
of
the contour directly to the right,
indicated
by the solid arrow, or by other
directions of
movement, indicated by the dashed arrows. The lengths of these
arrowsindicate
the velocity of movement thatwould be necessary to create the
movementcorresponding
to the solid arrow. Thus, if a square is actually moving upward
at an angle, it has to be moving faster than if it were moving
straight across to the right. |
