Anastomotic Nets Combating Noise 297 



connections. The dynamics of the picture is beginning to show up, 

 but the matliematics is too comphcated for us as yet. 



Eugene Pautler (Akron, Ohio) : What type of detector would 

 be required to recognize the results of this output — the computa- 

 tions inherent in this output neuron? 



McCulloch: I think it is probably all done in the eye. Suppose 

 you tell your eye to look for four-leaf clovers. You simply send 

 out the message, "Find a particular pattern in those leaves"; and 

 when you have found it signal, "Here is one! Here is another!" 

 You knew what you were looking for so you set your filter ac- 

 cordingly. 



A frog, when he jumps, sends back impulses to his eye to give 

 as great a response as possible to an affair of lesser curvature or 

 greater radius of curvature, which informs his eye. This works 

 during the first part of the jump while his eyes are open. One 

 tells one's eye what to see, what too look for. It would be almost 

 unthinkable that otherwise one could go into, say, Grand Central 

 Station, look off across the hall, and, knowing that there is a 

 chance of so-and-so being there, find him, unless one has in some 

 manner set a filter. Just how much of that matching is done 

 in the eye, I do not know. The mouse, which does not turn its 

 eyes and keeps them open, is another nice animal to work on. 

 His retina is the same all over, and whether you get a response 

 from a particular ganglion cell or from a particular axon depends 

 upon whether the mouse is hungry or whether it has smelled its 

 cheese. If it has, then it bothers to look, but it will not look the 

 rest of the time. The mouse shows very little response to any 

 visual stimulus. The situation is far too complicated to be solved 

 with a set of electrodes. 



Homer F. Weir (Houston, Texas): In the use of the injured 

 neuron, you are apparently producing noise from non-input 

 sources. Is it correct to say that your injured neuron is putting 

 out output without input? 



McCulloch: Yes. Either it is doing that or it is dead. 



Weir: At what level would this have to occur, relatively speak- 

 ing, before it would override this protective error mechanism that 

 you were speaking of? 



