206 



BRAIN MECHANISMS AND LEARNING 



an afferent apparatus which forestalls the appearance of the conditioned 

 rellex action, as well as its afferent results. 



The first and most demonstrative form of experiment consists in the 

 fact that the experiiiwiitcr suddtiil)' replaces the qtiality of the uiicoiiditioiied 

 alimentary reiiiforceiiient. 



hi conducting these experiments we reasoned as follows: it the prepared 

 conditioned excitation of the afferent cells in the cortical representation of 

 the unconditioned centre precisely reflects the properties ot the Jiitiire 



Fig. 9 



CS. 



Stage of formation of the 'acceptor of action' consisting of the afferent traces of past reinforce- 

 ments. At this stage the reflex action itself has not formed as yet. 



return unconditioned excitation and the normally elaborated behaviour of 

 animals is based on this adequacy, the latter must iniallibly change if we 

 replace the unconditioned stimulus. Owing to this replacement the 

 anticipatory conditioned excitation in the additional afterent apparatus 

 would be of one quality (on the basis of the former reinforcements) while 

 the real unconditioned stimulus would suddenly (!) be of another quality 

 and, consequently, because of such a combination of the conditions the 

 composition of the nervous impulses of the return afterentation coming to 

 the cerebral cortex from the real unconditioned stimulus would not 

 correspond to the conditioned excitation prepared there. What will the 

 actual behaviour of the animal in this case be? 



