330 Information Storage and Neural Control 



quency domain* requires exactly the same number of sampling 

 points plus one, or: 



2TW + 1 



where T is the duration of a signal, W is the spectral band width, 

 and the sampling points are spaced at fixed intervals. 



If we can say in the electroencephalographic (EEG) signal, as 

 an example, that the highest frequency which carries neuro- 

 physiological information is 100 cycles per second, we know that 

 we must sample at least 200 times a second — perhaps much more 

 often if there is considerable noise in the system — in order to 

 retain all of the information. While we are now satisfied that in 

 both the time and frequency domain we may ask of the EEG 

 signal "how much" at 200 points per second, we have also posed 

 ourselves a massive problem in data handling. Further, we have 

 not learned anything of the optimum analytic procedure, since 

 to retain all information in the original signal "defeats the very 

 purpose of analysis, which is to abstract and emphasize only 

 significant changes." (4). 



There remain the case of coding "how much" related to a 

 selected event and the even simpler case of asking only "when" 

 the event occurs. In both of these remaining cases, the coding 

 event must be defined and the assumption made that all 200 points 

 per second in the EEG do not contain the same amount of infor- 

 mation. Let us for a moment suppose that some of these points 

 contain ten times the information of other points. Then we may 

 drop the low information points, retain the high information 

 points and sacrifice a unique characterization of the wave for a 

 good approximation. Such a process would be highly economical 

 in terms of handling the data. 



The critical problem is, of course, the generation of the coding 

 event which acts as a "metasignal" in the sense in which Gregory 

 Bateson used the term for us earlier. In the first paper of this 

 symposium, Bernard Saltzberg introduced you to Maxwell's 

 demon. I would like to propose another hypothetical information 

 demon, one that might look at each of our points and say, "We'll 



*If fi(w) represents the spectrum of a function G(t), which is zero everywhere 

 except in the range Tj < t < T2, then i2(w) is exactly determined for all values of 

 w by giving its values at a series of points ^ / {Ti — T2) cycles per second apart in fre- 

 quency, the series extending throughout the frequency domain. (3) (Case 1). 



