282 Information Storage and Neural Control 



the rates of macromolecular synthesis. Global nonrandom, as well 

 as random influences, and localized random influences would 

 have no eff"ect on the relative interspike intervals of the ensemble 

 of cells. All messages are encoded in the same language in such 

 a scheme. I see no sort of information which could not be coded 

 by a spatio-temporal pattern of this sort. The memory readout 

 which would result from the simultaneous activation of a large 

 enough proportion of the cells in the assemblage to sustain itself 

 and propagate via re-entrant pathways would generate a spatio- 

 temporal distribution of electrical activity quite comparable to 

 the readin. The resting memory here is not a reverberation, but a 

 set of structurally mediated temporal relationships which generates 

 a reverberation only when the ensemble is excited. Would a 

 scheme of this sort seem to meet more of the constraints with 

 fewer ad hoc hypotheses than the sort of mechanism which you 

 had in mind? 



Morrell: I still do not see how your supposition does away with 

 the notion that the critical factor is the distribution of charged 

 sites available for bonding. 



John: I think there is an essential difference. Your code is the 

 specification of sequence on a molecule. 



Morrell: Only in a limited sense. For example, a possible 

 alteration might involve only the exchange of glutamic acid for 

 glutamine at a specific site. Perhaps potassium is involved as well. 

 We cannot say. All one can reasonably suggest is that a change 

 in charge distribution on an impermeable molecule would be 

 necessary to influence the ionic environment permanently. 



John: There would be many ways to accomplish the binding 

 of ionic charge which did not require the specification of sequence. 



Morrell: Well, to put your question back to you, would not 

 the readout from such a system be a temporal pattern of cell dis- 

 charge in space? 



John: Yes, the readout would be a spatio-temporal pattern 

 of cell discharge, but it could be a much smaller space than the 

 set of neurons initially excited by a stimulus. 



Morrell: Oh yes, there would be a difference. 



