294 Information Storage and Neural Control 



A B 



Figure 10 



€ = 0.5 per cent, to have the bundle usably correct all but once 

 in one million times, he needed 5000 neurons and two more ranks 

 of 5000 to restore his signal so that it was usable. His difficulty 

 was chiefly the poverty of the anastomosis. We have found that, 

 with the same e and the requirement that the bundle be usably 

 correct all but once in one million times, if each axon is connected 

 to every neuron, we only need one rank of 10 neurons. 



Leo Verbeek has looked into the problem of the death and 

 fits of neurons, and has found that again the probability of an 

 erroneous output decreases as the number of inputs per neuron 

 and the width of the first rank (both 5 in number) increase, at 

 least for probabilities of death and fits reasonably under 50 per 

 cent. Figure 11 shows his graph, where 5 is the number of inputs, 

 p the probability of error in the input neurons, and a:s(p) the 

 probability of erroneous output. Even for a small 5, these calcu- 

 lations are enormously laborious. 



We are all much indebted to Jack Cowan for our knowledge of 

 many-valued logic for handling bundling, and for conclusive 

 evidence that this is not the cleverest way to obtain reliability. 

 He and Sam Winograd have made a much greater contribution, 

 which I could not expound to you if I wanted to, and I do not 

 because it will probably be communicated in full by Professor 

 Gabor for publication in the Philosophical Transactions. Vaguely, 

 its purport is this: 



