1 8 Information Storage and Neural Control 



Saltzberg: The principles involved in applying generalized 

 entropy concepts or information theory to biological systems and 

 quantum mechanical systems are not altered in essential ways. 

 There are differences in nomenclature which sometimes conceal 

 these basic similarities. 



Mayor: But could you treat them the same way? 



Saltzberg: Yes. In fact, all of these applications have an amaz- 

 ingly close parallel to the generalized treatment of entropy in 

 thermodynamics. 



Robert R. Ivers (Fargo, North Dakota): Would you define 

 a little better the term noise that you used during your discussion? 

 Is this interference with signals, or is it the interposing of randoin 

 signals in the systein, or is it just general inaccuracy of the system? 



Saltzberg: You have asked a very basic question. In order to 

 avoid confusion, I should like to refer to noise as a subclass of a 

 larger class of signals called undesired signals. Undesired signals 

 may be placed in three categories: namely, (a) noise, (b) inter- 

 ference, and (c) distortion. Noise signals may be defined as signals 

 which are not coherent with any signals to which meaning is 

 assigned. Interference may be defined as an undesired signal 

 which is a desired signal in some other system or is coherent with 

 desired signals of some other systein. Examples are cross-talk and 

 common channel interferences in broadcast programs. Distortion 

 introduces undesired signals due to effects such as non-linearities 

 or non-flat amplitude vs. frequency transmission characteristics. 

 In my discussion I have been referring to the first of these undesired 

 signals, namely, random noise. 



Mayor: In actually performing measurements on your system, 

 you no doubt introduce additional perturbations which could be 

 considered as "noise." Would you consider this a valid parallel? 



Saltzberg: This sort of parallel seems reasonable to me. If you 

 add an element of indeterminacy to the state of the system, you may 

 consider this as due to noise. There are some deep questions as 

 to what constitutes noise in systems, and these cannot be treated 

 in cjualitative terms or in brief comments. 



Arthur Shapiro (New York, New York) : Along the same line, 

 how would you treat what happens if you read onto a transmission 

 line a page from a table of random numbers and then another 



