286 



Information Storage and Neural Control 



To explain this, I would like to introduce to you the only 

 symbols with which I have been able to teach the necessary 

 probabilistic logic. I use a X with a jot for true, a blank or 

 for false, a dash for "I don't care which," and a p for a 1 with 

 probability p. For "A alone is true" {i.e., a sign for A alone), X; 

 for B alone, X; for both, X; and for neither, X. Then I can write 

 the sixteen logical functions, or firing diagrams, of a neuron with 

 two inputs, as shown in Figure 1, and we can draw the diagrams, 

 as in Figure 2, to show how the computed function depends upon 

 the threshold 9. 



X 'X X X' 'X ^ X- 'X' X 'X ^ X* 't, X' X' '^ 



Figure 1 



■X 







X 



Figure 2 



You will note that the first four neurons, without interaction of 

 afferents, compute all but two of the sixteen logical functions, 

 and these missing ones can be computed by the two neurons at 

 the right in Figure 2. The upper right neuron does the trick in 

 the superior olive. 



