Adaptation, Perceptual Fill-In, and Cortical Plasticity
The visual system calculates visual information through both
brute force with millions of neurons, and through a number of short cuts,
extrapolations, and self regulating mechanisms. These non-linearities
in the visual system can be illustrated with visual illusions. Here, we
will illustrate some of the features of the visual system that are related
to those which we are currently investigating.
The visual system attempts to extrapolate information based upon what is
known. A particularly prominent example of this is the Filling-in
of missing information at the blind spot. The blind spot is where
the ganglion cell axons gather together and leave the the retina.
Since there are no photoreceptors here, it forms a spot of no visual input.
This spot is actually rather huge - about 4 X 6 degrees. At a distance
of 57 cm (about 22 inches), one degree of angle is 1 cm. That means
that if you close one eye, there is a hole in your visual world that is
an inch or two across at arms length!!! I don't know about you, but
when I try this with my computer monitor, I would swear that there is no
such "hole" in the visual world. That is because, the visual system
is very good at "repairing" itself, and has compensated for this blind
spot since early development. Here are some demonstrations of this
amazing feat, as well as demonstrations on other regulatory and compensatory
THIS SEMINAR WORKS BEST IN 1024X728 SCREEN RESOLUTION.