Illusion - Is Seeing Really Believing?/Illusion - Is Seeing Really Believing (1998)(Marshall Media)[Mac-PC].iso/pc/illusion/rock_fie.cxt/00385_Field_385.txt

Text File | 1996-12-31 | 2KB | 67 lines

    One approach to the problem
is to consider apparent motion
as a special case of real motion
and to explain the perception
as the result of motion-detector
neurons firing in the visual
nervous system. If the
successive stimulation of
adjacent retinal cells leads to
the rapid firing of neurons that
are specialized to detect such
stimulus motion, then the
successive stimulation of
retinal cells that are farther
apart may cause the rapid firing
of neurons that detect the
stroboscopic stimulus
sequence.

    Horace Barlow and William
Levick at the universities of
California and Cambridge have
shown that precisely such a
successive stimulation of
neighboring, but not directly
adjacent, regions of a rabbitΓÇÖs
retina will trigger the response
of neurons in its visual nervous
system.

    We might regard this
approach as a sensory theory of
apparent movement. While a
theory of this kind may provide
the explanation of perceived
movement under stroboscopic
conditions in animal species
lower on the phylogenetic scale
(fish, for example), it is
inadequate to explain how we
perceive it. First, apparent
movement can be seen across a
considerable angular distance,
far enough for it to be unlikely
that the two stimulated regions
of the retina would be
associated with the same
motion-detector neuron in the
brain. We can see such motion
when a stimulus, A, falls on
one side of the retina and a
second stimulus, B, on the
other. In fact, this probably
occurs often, such as when the
eyes are fixating between A and
B. Under such conditions, A is
projected to one hemisphere of
the brain and B to the other. As
can be seen in the illustration
in Chapter 1 of the projection of
neural fibers from the retina to
the visual cortex, the only
connection is through neurons
that cross in the structure of
the brain known as the corpus
callosum.