From the preceding section you have learned what chain codes are and how to write them. But what does any of this have to do with understanding vision? Remember, a chain code gives us a simple example of an algorithm that can be used to represent the size and shape of an object. Since a digital computer can perform the operations of any algorithm, it can therefore implement a chain code. So it is possible for a machine a computer to represent the shape and size of an object in the form of a chain code.
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Technology Report ARTICLE
For more than fifty years, the neuroscience community has been engaged in an intensive debate on how information is coded in the brain and transmitted reliably from one brain region to the next. Mutually exclusive coding systems have been proposed and are being energetically supported. Scientists from Freiburg University have now been able to demonstrate in a forthcoming issue of Nature Reviews Neuroscience that earlier studies were based on rather extreme propositions. Instead, it is possible that under certain conditions, both proposed codes can be simultaneously employed within the brain. One of the unsolved puzzles of the brain is the question of which code is being used when nerve cells communicate with each other. It has been known for more than a century that the basic unit of communication within the nervous system is the pulse-like fluctuation in voltage at the membrane of neurons. But there is still an ongoing debate about how these so-called action potentials are combined to form a code for the actual processing and transmission of information. Two forms of coding are popular candidates: one is based on the rate of action potentials rate coding and the other relies on the timing of their occurrences temporal coding. So far, the nature of the neural code has remained largely elusive to experimental brain research. Even the brains of insects are too complex for today's scientists to determine which code they use.
The Dark Side
In What Is Life? Genetic information was stored in the simple arrangement of nucleotides along long strings of DNA. The question was what all those strings of DNA meant. As most schoolchildren now know, there was a code contained within: adjacent trios of nucleotides, so-called codons, are transcribed from DNA into transient sequences of RNA molecules, which are translated into the long chains of amino acids that we know as proteins. Cracking that code turned out to be a linchpin of virtually everything that followed in molecular biology. As it happens, the code for translating trios of nucleotides into amino acids for example, the nucleotides AAG code for the amino acid lysine turned out to be universal; cells in all organisms, large or small—bacteria, giant sequoias, dogs, and people—use the same code with minor variations. Will neuroscience ever discover something of similar beauty and power, a master code that allows us to interpret any pattern of neural activity at will? At stake is virtually every radical advance in neuroscience that we might be able to imagine—brain implants that enhance our memories or treat mental disorders like schizophrenia and depression, for example, and neuroprosthetics that allow paralyzed patients to move their limbs. Because everything that you think, remember, and feel is encoded in your brain in some way, deciphering the activity of the brain will be a giant step toward the future of neuroengineering. Future biofeedback systems may even be able to anticipate signs of mental disorder and head them off.
Resume Reading — Safecracking the Brain. You've read 1 of 2 free monthly articles. Learn More. This three-pound blob of tissue holds an estimated 86 billion neurons, cells that rapidly fire electrical pulses in split-second response to whatever stimuli our bodies encounter in the external environment.
