Реферат: Computer History Essay Research Paper ABSTRACTCurrent neural
The First Steps
The study of the brain was once limited to the study of living tissue. Any attempts at an
electronic simulation were brushed aside by the neurobiologist community as abstract conceptions
that bore little relationship to reality. This was partially due to the over-excitement in
the 1950?s and 1960?s for networks that could recognize some patterns, but were limited in
their learning abilities because of hardware limitations. In the 1990’s computer simulations
of brain functions are gaining respect as the simulations increase their abilities to predict
the behavior of the nervous system. This respect is illustrated by the fact that many
neurobiologists are increasingly moving toward neural network type simulations. One such
neurobiologist, Sejnowski, introduced a three-layer net which has made some excellent predictions
about how biological systems behave. Figure 2 illustrates this network consisting of three
layers, in which a middle layer of units connects the input and output layers. When the network
is given an input, it sends signals through the middle layer which checks for correct output.
An algorithm used in the middle layer reduces errors by strengthening or weakening connections
in the network. This system, in which the system learns to adapt to the changing conditions,
is called back-propagation. The value of Sejnowski’s network is illustrated by an experiment
by Richard Andersen at the Massachusetts Institute of Technology. Andersen?s team spent years
researching the neurons monkeys use to locate an object in space (Dreyfus and Dreyfus 42-61).
Anderson decided to use a neural network to replicate the findings from their research. They
“trained” the neural network to locate objects by retina and eye position, then observed
the middle layer to see how it responded to the input. The result was nearly identical to what
they found in their experiments with monkeys.
Computer-Synthesized Senses
? Visual Recognition
The ability of a computer to distinguish one customer from another is not yet a reality. But, recent breakthroughs in neural network visual technology are
bringing us closer to the time when computers will positively identify a person.
? Current Research
Studying the retina of the eye is the focus of research by two professors at the California
Institute of Technology, Misha A. Mahowald and Carver Mead. Their objective is to electronically