Plato's Cave: The Boundary Contour System
The Boundary Contour System (BCS) Model
Grossberg's BCS model accounts for collinear illusory contours such as
the Kanizsa figure in a dynamic neural network architecture. The
principle of operation involves a layer of oriented edge sensitive
cells, which respond to the visible edges in the Kanizsa figure, and a
higher level cooperative cell layer which receives activation from the
oriented cell layer by way of a bipolar receptive field in an
orientation specific manner. For example a horizontal cooperative
cell receives input only from horizontal oriented cells which are
horizontally disposed in the oriented layer, as shown below. This
ensures that the cooperative cell will only become active along
extended collinear edges. The cooperative cell in turn provides
top-down feedback to the corresponding oriented cell in the oriented
layer, as shown in the figure. It is this top-down feedback which
accounts for the appearence of an illusory contour in a region between
two collinear edges as in the Kanizsa figure.
A conjunctive constraint, or functional AND-gate is
also incorporated into the model in order to prevent cooperative
activation from extending outwards from isolated edge segments.
In the
full Boundary Contour System
model there are many other layers and interactions that serve various
purposes.
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