ELECTROENCEPHALOGRAPHY — WALTER 253 



study of brain physiology. For example, when an engineer observes a 

 sustained electrical oscillation he looks for what he calls "positive 

 feedback'' and it seems likely that, in the brain, feedback circuits 

 actually exist, and that their properties can be studied exactly as if 

 the living organ were a complex transmission system. Going a step 

 further, it has been found possible to construct models using devices 

 similar to those postulated in the brain, and these models behave in 

 a very lifelike fashion, particularly when positive and negative feed- 

 back circuits are combined. The positive feedbacks provide mechan- 

 isms for hunting, scanning, and testing the model's environment for 

 stimuli and information, and the negative feedbacks or reflexes ensure 

 that any action the model may decide to take will be as near as possible 

 to that necessary for stability and survival. It is surprising how 

 complex and apparently unpredictable the behavior of one of these 

 models can be when it is placed in the irregular environment of an 

 ordinary room, even when it contains only half a dozen units as com- 

 pared with the millions in the human brain. 



The great fertility of the marriage between brain physiology and 

 engineering has suggested to many people that the family of subjects 

 thus united is worthy of a special name, and Wiener [5] has proposed 

 "cybernetics," from the Greek word meaning "steersmanship," since 

 the fundamental common problem seems to be the way in which 

 complex dynamic systems direct themselves toward various goals. It 

 has been predicted that when properly established this new branch of 

 science may have as gi'eat an effect upon our life and surroundings 

 as the achievements of nuclear physicists. 



A comparison has already been made with the great calculating 

 machines, but these are of course enormously more specialized than 

 any viable living organism, since their sole function is to perform 

 certain types of calculation at immense speed. In contrast to this, 

 the brain performs innumerable functions, though none with very 

 great accuracy or velocity — but it can design the machines. A good- 

 quality human brain has more possibilities than any other known 

 structure in the universe, and we should not be far wrong in calling 

 it "the universal machine." 



REFERENCES 



1. Dawson, G. D. Journ. Neurol., Neurosurg., and Psychiat., vol. 10, pp. 137-140, 



1947. 



2. Waltee, W. Grey, Dovey, V. J., and Shipton, H. Nature, vol. 158, pp. 540-541, 



1946. 



3. Walter, W. Grey. Proc. Assoc. Res. Nerv. and Ment. Dis., vol. 46, pp. 237-251, 



IMQ. 



4. Walter, V. J., and Walter, W. Grey. .Tourn. Electro-enceph. and Clin. 



Neurophysiol., vol. 1, pp. 57-86, 1949. 



5. WiENEE, N. Cybernetics. London, 1948. 



