638 BRAIN MECHANISMS AND LEARNING 



phenomena are accompanied by dcsynchronization of records which prevent the 

 appearance of discharges. When a phenomenon of inhibition appears (induced by 

 habituation or by a conditioning process), a synchronization may favour spike-and- 

 wave discharges. 



It is then possible by this technique to prevent or facihtate critical discharges. But 

 as we see, these different states of synchronization and dcsynchronization of the 

 record are variable and do not depend on the conditioning alone. Therefore, it 

 seems difficult to me to apply, actually, this technique to therapeutics, at least in 

 cases which arc not preceded by an aura, and of which the onset is unknown to the 

 patient. 



Segundo. Do you think that conditioned facilitation ot seizures would act only 

 to a certain extent and within certain limits of discharges 'intensity' as is known to 

 be the case with central brain stem influence upon cortical strychnine spikes; 

 (Arduini and Lairy-Bounes, 1952). 



Naquet. I think so — I demonstrated with Drossopoulos and Salamon (1956) 

 the following phenomenon: after intravenous injection of Metrazol or Megiinide 

 in a cat, generalized spike-and-wave discharges are produced. According to the 

 dose of convulsivant injected, it is possible to obtain different effects after electrical 

 stimulation of the reticular formation or sciatic nerve : (a) with feeble doses, the 

 stimulation of the reticular formation is able to stop the generalized discharges, 

 which appear spontaneously or after sensory stimulations; (/>) with greater doses, 

 the stimulation threshold necessary to stop them increases, and just before the 

 appearance of generalized seizure, the reticular formation stimulation becomes 

 unable to stop them, and only a mere modification of the shape of the discharge is 

 obtained. 



Chow. How can this conditioning of repetitive discharge be explained on a 

 neuronal basis; We found that in cats with lesions of the anterior part of the thala- 

 mus, the conditioned repetitive discharge is very easily established. If you destroy- 

 some areas of the cortex and if the lesion is big enough, you cannot establish 

 conditioned repetitive discharge. 



Naquet. It is difficult to reach any conclusion on the significance of the condi- 

 tioned repetitive discharge. Perhaps we are facilitating the appearance of some 

 rhythnis existing before on the cortex. I do not know what the mechanism is, but 

 I agree with you as to the possibility of the cortical origin of these rhythmical 

 phenomena. For example, when repetitive responses appear at the level of the 

 cortex in animals it may mean that the experimenter has used frequencies, ordin- 

 arily found at the level of the cortex and that he has obtained conditions which 

 facilitate those frequencies more than others. It is interesting to note that it concerns 

 mostly some slow frequencies similar to focalized true spindles, and able afterwards 

 to become generalized. This fact results from experiments we made with Morrell, 

 after having provoked cortical irritative lesions, as well as from recent experiments 

 on the recruiting response just realized together with Fischer-Williams and Fernan- 

 dez-Guardiola on anoxia. 



Morrell. This repetitive response is especially apparent when there is evidence 

 of a decrease of reticular discharge to the cortex, i.e. when it is synchronized rather 

 than desynchronized. This represents then a hypersynchronous activity in cortical 

 cells rather than in deeper structures. We have done experiments with unilateral 

 epileptogenic lesions. In those experiments under electro-cortical conditioning we 



