652 BRAIN MECHANISMS AND LEARNING 



Galambos. I would like to extend Dr Konorski's remarks on brain 'levels' 

 where the neuronal events responsible for behavioural acts are oganized. We tend 

 to conceive these levels as 'higher' and 'lower' cortical and subcortical. What goes 

 on in the cortex is supposed to be both different from and superimposed upon what 

 transpires lower down; a kind of neuronal packing order exists, with cerebral 

 cortex on top. Several workers have recently been stressing a contrary view which 

 this symposium has not yet considered. According to it the neuronal organization 

 responsible for certain behavioural responses is essentially longitudinal, running 

 from front to back in the brain. The vomiting act, for instance, can be aroused by 

 shocks to localized areas of paleocortex, hypothalamus and medulla, and while 

 performance differs somewhat depending on which site is stimulated, the same 

 result, evacuation of the stomach, is achieved by all three. In some manner, there- 

 fore, the neural organizations responsible for the response are equal at several 

 different 'levels'. No clear pecking order is discernible. Whatever the 'liigher' level 

 imposes upon the 'lower' one is uniniportant compared to the fact that all are 

 involved in producing the act. 



The idea ot searching tor the plastic changes of learning in the longitudinal as 

 well as in the highest transverse (i.e. cerebral cortical) dimension of the brain is, as 

 Dr Konorski points out, an important new direction in which research efforts are 

 tending. It can in fact be argued from the accumulating evidence for widespread 

 involvement of cortical and subcortical structures during learning that an under- 

 standing ot the succession of events transpiring in cells organized in the rostro- 

 caudal dimension of the brain is actually what holds the key to the neural basis ot 

 learning. Cerebral cortex probably participates merely as a link in the chain of 

 events. Since animals without cerebral cortex obviously create the plastic brain 

 changes required for learning we must conclude that what cortex does so supremely 

 well can be accomplished by non-cortical brain tissue also. Despite the reasons for 

 denying an exclusive or unique role to the cortex in learning no reasonable objec- 

 tion whatever can be raised against the stand that knowledge of the cortical changes 

 that do occur in learning would be valuable to have. That plastic events occur only 

 there and that these are the most 'important' ones to study if we wish to compre- 

 hend the processes at work are, however, two ideas open to much question. 



Anokhin. I am very much interested in the role played in the process of learning 

 by the different structures of the brain, the cortex and the subcortical formations. 

 At the present time one can hardly maintain that the process ot learning is the 

 exclusive prerogative of anv one nervous structure, the cortex or subcortex. 



The principle of the dynamic activation ot nervous activit\- has shown that all 

 these component parts of the brain functioning at a given moment are jointly 

 involved in this dynamic activation. 



The main thing, however, is that each ot these parts brings its own specific 

 contribution to the process ot learning, i.e. to the activity of the whole brain. 

 This is why experiments made by extirpating different sections of the brain give 

 contradictory results, which we cannot understand so far. 



