370 Information Storage and Neural Control 



any shift in ion balance would disturb it. It seems to me this is 

 exactly what one would expect. 



John: That is one possible explanation. Yet experiences learned 

 under normal circumstances may be retrieved in situations in 

 which it is unreasonable to argue that the configuration of excita- 

 bility of neuron populations is quite as it was during the experience. 

 An alternative to your suggestion might be that the altered 

 electrolyte surround directly affects storage mechanisms on the 

 molecular level. 



Gerard: It is a matter of how it has shifted. These are probably 

 very big shifts, even with small amounts of electrolytes. You 

 remember the work Ochs did with the Bures potassium technique. 

 It is a nice way of locating the engram, besides the split-brain 

 technique. He had rats learn a performance with one hemisphere 

 inhibited with high potassium chloride. He removed this and the 

 animals behaved perfectly well. But sometime later, when he 

 blocked the other hemisphere with potassium chloride, with the 

 first still ticking away happily, the rats had no knowledge of what 

 they had learned. The engram was in only the part of the brain 

 which was active during learning. It is this kind of an effect, I 

 think, that you are dealing with. 



Let me discuss your last question. Maybe we should not go 

 into it because this whole planaria business, while fascinating, is 

 a bit off the line of the discussion. You may not know, though, 

 that your student Corning turned up with Jim McConnell and 

 reported the RNAse results, but could not interpret them. My inter- 

 pretation, and I think the one you have used, seemed reasonable. 



Let me remind the group of the basic experiment. A flatworm is 

 trained, cut in two pieces, and the head allowed to regenerate a 

 tail and the tail a head. Both new worms remember, as McConnell 

 demonstrated. Dr. John and his group showed, further, that if each 

 of these two parts is regenerated in RNAse, the head worm still re- 

 members but the tail worm does not. One can explain this in 

 terms of the fact that the head worm has more organized structural 

 units in it to begin with and does not have to re-create many neu- 

 rons. Now, would something of this kind apply to your question? 



John: I am sorry. I am talking about the cannibalism studies. 

 One group of planaria is fed shredded, trained worms. Another 



