240 Information Storage and Neural Control 



formation is measurable, and tliat, in fact, Shannon in his classical 

 paper gave a precise mathematical definition of information. It is 

 so difficult to define information measures for ensembles in biology 

 that most biologists who use information theory usually do not 

 attempt to do so in a quantitative way. Generally, they do not 

 actually measure the information; and hence, they fail to exploit 

 the full potentialities of the theory. Yet many feel that someday, 

 somehow, more exactly defined information measures may be 

 brought into neurophysiology. I need only mention as an example 

 Shannon's formulation of the problem of channel capacity and his 

 solution for dealing with equivocation. C^hannel capacity is surely 

 a basic factor in the communication functions of the nervous system. 



It is so tempting to think of information transfer in the brain 

 as being simply a matter of transniission in specific nerve tracts. 

 If this simple-minded concept could for one moment be defended, 

 one would then begin to study such communication channels in 

 terms of the finite set of signals that can be initiated in the 

 channel, the set of signals that arrives and the probability of the 

 reception of any given signal. If only the brain worked like a simple 

 telegraph system we would immediately be able to make precise 

 statements about such things as channel noise and would be able 

 to calculate channel capacity. 



In contrast, all the work that the neurophysiologists have 

 pursued has revealed to us the enormity of interaction within the 

 brain — the correlations, couplings, linkages, and statistically inter- 

 dependent elements that contribute to its organization and make 

 any measurement of its interacting ensembles or any mathematical 

 statement of its entropy conditions formidable in the extreme. 



In closing, let me say that the application of quantitative in- 

 formation theory to neurophysiology lies largely in the future. 

 Possibly a partial answer to the question in the title of this paper 

 is that if information theory has not led to the uncovering of many 

 new facts in neurophysiology, it may have led to many new ideas. 



REFERENCES 



1. Adey, W. R., Dunlop, C. W., Hendrix, C. E.: Hippocampal slow 

 waves; distribution and phase relations in the course of approach 

 learning. AM A Arch. Neurol., 3.-74-90, 1960. 



