30S BRAIN MECHANISMS AND LEARNING 



hormones, whereas that in the classical sensory pathway was cssentialK' unchanged. 

 It seems likely then that the adrenal cortical hormones influence behaviour to a 

 large extent through their eifects upon the non-specific brain stem structures. 



Olds. Dr Lissak's work and ours have run parallel but different courses. He 

 observes effects of stimulation on hormones; we observe the effects of hormones on 

 stimulation ; he has observed the effects of stimulation on preformed conditioned 

 responses; we have observed the effect of stimulation reinforcement to form 

 conditioned responses. But the same areas are always involved, indicating, I believe, 

 reciprocal relations. For example in the hypothalamic amygdaloid system self- 

 stimulation rate or, that is, the reinforcement of electrical stimulation is stopped by 

 castration and renewed by replacement therapy, with electrodes in some places. 

 With electrodes in quite different places of the same system, self stimulation is 

 stopped by satiation and replaced by hunger. I believe that the places where he 

 provokes sexual behaviour arc the places where castration stops self stimulation. 

 Similarly in the other studies of the posterior hypothalamus, the places where his 

 stimulation evoked the preformed alimentar)- reactions our stimulus seems to us a 

 positive reinforcement, related to food. 



LissAK. Do you hnd a sexual difference, with anngdala stimulation between the 

 male and female ratsf I think that the main point is to find the structure in C.N.S. 

 where the sexual difference can be made. 



AsRATYAN. Though little is known at present may I refer to the question of 

 structural and functional relationships between the reticular formation and auto- 

 matic centres, especially the hypothalamic structures in the mid-brain. It seems to 

 me that Dr Lissak's results show that a certain role is played bv higher sympathetic 

 structures in this region. The basis for such an assumption is that sympathetic 

 structures innervate all endocrine glands 'and in addition exert a powerful imme- 

 diate influence on the functions of different svstems of the organism, particularly on 

 the activity of the N.S. as was piroved by Orbeli and his collaborators. I think that 

 these data may be partially explained as follows: the structures stimulated in Dr 

 Lissak's experiments also activate sympathetic structures of hypothalamus and 

 therefore the changes in the aciivitv of the brain cortex may be partialK- conditioned 

 by this factor. 



LissAK. In the tradition of Cannon our first line of investigations was directed to 

 the sympatho-adrenal activity. The neuro-humoral factors in the control of 

 animal behaviour and the manifestations of higher nervous activity in the adapta- 

 tion of the organism constitute a very complicated mechanism in which sym- 

 pathetic activity also plays a role. 



