H. ENGER ROSVOLD AND MORTIMER MISHKIN 575 



Dr Schumilina performed a large number ot ablations ot the trontal cortex and 

 studied the consequence ot that removal under specific experimental conditions. 

 Research on the secretion and motor components of the conditioned reflex was 

 carried out jointly. 



This work has led us to consider that it is quite impossible to define the functions 

 of the frontal lobes on the only basis of the 'inhibition' or 'loss of inhibition' 

 concept. Such functions, it appears, are considerably more complex; we have, 

 moreover, gathered evidence that their interpretation is directly determined by the 

 specific tiicthod clioscn for the control of the test's resiihs. 



In other words, the decisive factor here is the elaboration of an adequate test 

 method for checking the experimental data. Any correct understanding of results 

 will depend upon that choice. 



Our research has also shown the fact that even after extirpation of the frontal 

 lobes normal internal inhibition can develop ; this means that this specific cortical 

 function has not been impaired by the operation. However the animal is no longer 

 capable of a higher form of inhibition whereby its brain may store and co-ordinate 

 harmoniously a number of factors of different nature which have simultaneously 

 acted upon its nervous system. 



In particular the frontal lobes normally contribute to preventing the enormous 

 amount of stimuli from the environment from releasing a full-scale digestive reflex, 

 even when the stimulating action ot the various test conditions is clearly apparent. 

 But, at the moment when the conditioned stimulus starts acting, this hidden 

 integration of the different environmental stimuli becomes eflective also and 

 spreads to the peripheral system. 



We have also shown that after removal of the frontal lobes, what happens is not 

 an over-all loss of inhibition ot anv stimuli inhibited up to then, but the release of 

 quite specific stimuli. The stimuli pattern involved specifically requires an alterna- 

 tive motor discrimination between right and left side. 



Extensive and valuable literature on the subject has appeared in our country, and 

 I would be glad to provide Dr Rosvold with some of our studies. I shall not fail to 

 send them to him upon returning home. 



Rosvold. Dr Anokhin refers to his experiment in which in a situation involving 

 two feeding stands the animals are disinhibited, he interprets it as a loss of afferent 

 inhibition or suppression of stimulus inhibition. Dr Konorski would interpret this 

 as a loss of locomotor or response inhibition. The same experimental material can 

 apparently be interpreted in different ways. Thus, the point of our paper: there are 

 so many varieties of the inhibition notion that it soon becomes impossible to set up 

 a critical experiment. 



Myers. Dr Rosvold has been for a long time concerned with the comparative 

 effects of frontal lesion in different species. I wonder what he feels human studies 

 have to contribute to our understanding of the etfects of prefrontal damage? 



Rosvold. With respect to the comparative approach to this problem we have 

 considerable evidence of progressive changes in effect from dog to man. Tliis 

 makes us wonder whether we are dealing with a unitary phenomenon or not. For 

 example, delayed response performance is invariably impaired in monkeys after 

 prefrontal lesions, but in chimpanzees this is temporary even with radical lesions 

 and has never been demonstrated at all in human. In answer to Dr Myers's question 

 I would say that the principal value of the studies ot humans with injured frontal 



