A. FESSARD ET TH. SZABO 37I 



transient hyperactivity of: another group. If the common neurone is an 

 auto-active one and the afferent impulses have no fn-ing effect upon it, the 

 transfer is nevertheless possible through the resulting frequency change 

 AF of its pace-maker. 



Afferent impulses of one kind producing no detectable effect at the 

 output of a network are thus assumed to be able to acquire efficacy if they 

 arrive during the subsidence interval of the activity traces left by a 

 stronger activation brought about by another kind of afferent impulses. 



7. Sequential pairs of associated stimuli as are applied in classical con- 

 ditioning procedures may operate in the way described above when 

 progressively establishing new functional links within the central nervous 

 system. 



8. Some experimental proofs supporting the validity of the preccdnig 

 assumptions have been obtained. Auto-rhythmic ganglion cells of Aplysia 

 have been used to show the long-lasting frequency changes of the pace- 

 maker that survive the immediate effects of a brief tetanus applied to an 

 afferent tract. A satisfactory test of the facilitation transfer mechanism as 

 suggested in our theory has been applied to the disynaptic system of 

 neurones that control the discharges of electric organs in Torpedo. 

 Pyramidal cells in Hippocampus have also been proved to be able to 

 reveal potentiation transfers when activated through different pathways 

 that converge on to the intermediate polysynaptic structures leading to 

 them. 



9. In concluding, the necessity of completing our experimental evidence 

 with microphysiological explorations of network-like structures has first 

 been emphasized and attention has been drawn towards the fact that our 

 conception has been entirely derived from classical data, that have here 

 been considered jointly instead of separately: autogenic cellular 

 rhythmicity, post-tetanic potentiation, multivalent neurones and net- 

 work-like architectonics. 



GROUP DISCUSSION 



EccLEs: It is very important for the theory of learning that the stimulated line is 

 the only one that increases in efficacy. But it is also important to show what Dr 

 Fcssard has shown — that interneuroncs which are common to both lines, fire and 

 they increase the effectiveness of their synaptic action in turn. In other words, you 

 are converging through an intcrncurone which both lines arc firing but which is 

 not powerful enough for one of the lines to transmit to the next stage of the 

 synaptic relay. This has to be built in to any theory of learning or conditioning. I 

 did set up a very provisional diagram — in 1953 — which did presuppose what Dr 



BB 



