[Effect of mammillary body ablation on extinctive inhibition in cats]

Chronic extinction of chain closed conditioned reflex in intact rabbits took five to six days. The order of extinction of the reflex links was as follows: the nearer to reinforcement the link of the chain, the sooner it was inhibited. In the course of extinction different "compensatory" movements appeared with a high frequency. Unlike the conditioned movements they were not fully extinguished: in the rest periods (lying for 4 to 10 min.), running and sniffing took place 4 to 8 times in the session. After the ablation of the mammilary bodies, extinctive inhibition was developing slower (9 to 13 days) than in the norm. The order of extinction became reverse: the nearer the link of the chain to reinforcement, the greater the difficulty of inhibition. The appearance of "compensatory" movements sharply differed from the norm. The general behaviour of the operated rabbits was peculiar in that during extinction of conditioned movements the short periods of rest (1 to 3 min.) alternated with running, sitting, scratching, washing, etc.