Page 72 - Miracle in the Eye

MIRACLE IN THE EYE

The Visual Memory
The process of recognizing objects doesn't occur thanks to the eye and
the visual center only, because the memory plays an important role in this
process as well. 22 In order for the brain to achieve recognition, all the "visual
association areas" must work together, letting us to interpret perceptions at
an advanced level, with the help of memory.
Despite the field of neurophysiology's many significant advances over
the past half-century, we've yet to explain how memory works. What we do
know is overshadowed by far by what we have yet to learn. But we have
learned what symptoms arise when the visual association area of the brain
is damaged. A damage or a tumor in this area does not lead to blindness.
This area is activated by the impulses of the primary visual cortex, but the
sufferer becomes significantly less able (even totally unable) to recognize fa-
miliar objects on sight—a condition termed visual agnosia. 23
For a healthy individual, it's hard to imagine what such a condition is
like. The inability to recognize "familiar" objects puts sufferers in a helpless
position. When you consider that these symptoms can arise after even the
smallest impact to the brain, it is clearer that the organ we carry in our heads
is extremely sensitive.

Two Eyes, One Sight—Binocular Vision
We humans find ourselves born with two eyes, but never question why
this is so. Is it a coincidence that we have two, or is there a special reason for
this?
Each of the two eyes has a different perspective to the outside world, as
they are spaced apart from the other (Figure 2.7). The two images seen by
the eyes are subtly different, but complement each other. By picking out the
differences between them, the brain is able to determine depth and distance.
Even though a single eye can see only two-dimensionally, the brain creates
the "final" three-dimensional image.
Our interpretation of the minute differences between those two images
enables the image to be perceived as three-dimensional. If the two images
formed separately in the eyes were combined not fully in the brain, then we
would see double—and in two dimensions only.
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