J. p. SEGUNDO, C. GALEANO, J. A. SOMMER-SMITH AND J. A. ROIG 2<S9 



symmetrical development ot tactile conditioned reHexcs, and turther, that in corpus 

 callosLim sectioned dogs one could tor the first time establish conflicting condi- 

 tioned responses to tactile stimulation of the separate homologous skin loci. I 

 wonder if vou have consiciered carrying out your series of experiments, Dr 

 Scgundo, in corpus callosum sectioned animals to see if your results with regard 

 to generalization between the extremities might not be different in such animals. 



Segundo. I ■was not aware ot Anrcp's or Bykov's results and they interest me 

 very much. Before proceeding further, however, we would like to perform other 

 experiments to be sure of the impossibility of 'ditierentiating between paws'. 



Naquet. Have you placed some electrodes in the afferent pathway: 



Segundo. With ink writer we explored potentials evoked by shocks in sensorv- 

 motor cortex, visual cortex, acoustic cortex, nucleus medialis dorsalis ot thalamus, 

 centre median ot thalamus, mesencephahc reticular formation and central grev; 

 with oscilloscope in primary cortical receiving area exclusiveK'. 



Naquet. If I remember your slides you do not find any reduction ot the first 

 part of the evoked potential during desynchronization, only the last two were cut. 

 Is that right; 



Segundo. Yes, when applied during subcutaneous shocks, tones blocked or 

 reduced sensory potentials evoked by same in somatic cortex: late waves were 

 susceptible, but the early spike was resistant. Waves evoked elsewhere (e.g. on 

 visual cortex b}- flashes) were sometimes left unaffected. Tones trec]uently produced 

 localized EEG "desvnchronization' but capacity to produce this effect was not 

 parallel with ability to 'block' sensory cortical evoked potentials. 



JouvET. In your last slides, during subcutaneous stimulation, it looked as if you 

 get slow waves on the cortical area, or at least the EEG is not desynchronized. Did 

 you get any slow waves in the reticular formation during subcutaneous stimulation ; 



Segundo. During shock application we occasionallv observed cortical and sub- 

 cortical spindles. 



JouvET. Because I wondered it this late component has not got something to do 

 with supra-liminal inhibition in Pavlovian terms. 



Asratyan. It I am not mistaken about the conditions ot vour experimentation 

 you have elaborated a backward conditioning. 



Segundo. The tone preceded the cessation of a prolonged subcutaneous stimulus. 



Asratyan. But the electrical stimulation precedes the tone by many minutes. 

 And in these cases tone became a conditioned stimulus and produced the same 

 effect as electrical stimulation. It seems to me that this is an expression of Reverse 

 connection from tone to electrical stimulation. Have you some signs that you have 

 also some direct conditioned connection ? That is that the application of the elec- 

 trical stimulus alone, after such a combination, is able to produce some change 

 characteristic ot the application of tone alone. 



Segundo. We believe shock 'interruption' and not shock 'application' acted as 

 absolute stimulus. Substraction of environmental agents may produce positive 

 effects within the central nervous system as, for instance, in the case of auditory 

 units that react to tone interruption (Galambos, 1952). On the other hand, it is 

 true that shocks preceded tones and therefore possible that the}- could acquire 

 some behavioural or electrographic feature corresponding to the latter. In the 

 behavioural sphere, we started off with tones to which cats had been habituated 

 and therefore were inoperant; it would thus be difficult to define an absolute tone 



