130 BRAIN MECHANISMS AND LEARNING 



more powerful is the reverberating system of neurones within a given 

 analyser in a given species, the more perfect and long lasting is the recent 

 memory of the corresponding stimuli and the more rapid is the process of 

 consolidation of the respective CRs. 



GROUP DISCUSSION 



RosvoLD. I would like to ask Dr Konorski, from the point of view of the position 

 put forth in his paper, how he would account for the fact that in the literature there 

 are many papers that deal with the impairment of sensory discrimination following 

 frontal lobe lesions. 



Konorski. As we have established in our laboratory, prefrontal ablations produce 

 two different sorts of impairment: one is that discussed in this paper, namely the 

 loss of recent memory of directions involved in delayed response tests ; the second 

 is the impairment of inhibitory conditioned reflexes. While the first one is, 

 according to our data, irreversible, the second one is, on the contrary, compensated 

 with further training. It is clear that the symptom described in Rosvold and 

 Mislikin's paper belongs to the second category. We suppose that both these 

 symptoms are of different origin and mechanism, and we try now to check this 

 supposition by experiments. 



Rosvold. With reference to the permanence of these deficits, I would say that 

 contrary to Jacobsen's earlier statements, in the chimpanzee the deficit is not 

 permanent. Instead with training the animals gradually recover their ability to 

 perform very well on tests of recent memory. The chimpanzee tells us another 

 thing: a subjective thing to be sure, but we can see in watching the animals no 

 evidence that orientation is a critical factor for those tests. In fact it is not unusual 

 for the animal to be standing on his head when looking at the stimulus, and then 

 turn completely over and respond correctly. Thus, even though this notion of 

 proprioceptive recent memory being the unique function of the frontal lobes is 

 intrigunig, I am not entirely convinced that it is the answer to delayed response 

 deficit. As Dr Konorski stated, we simply do not know what the stimulus factors 

 in the delayed response problem really are. We have assiduously tried to determine 

 what it is in this problem that the animal is responding to or by what means he is 

 responding. We have not been able to demonstrate definitely what it is in the test 

 situation that the animal uses as the basis for his solution of the problem. This is 

 why there is so much speculation about the probable function of the frontal lobes. 

 Probably the only resolution is the development of a test method in which the 

 stimulus and response variables will be clearly delineated. 



Hebb. I would like to add to this that bilateral total removal in another species 

 produces no sign of defect: even better than in the chimpanzee. 



Konorski. In man, yes. 



EsTABLE. I am very much interested in Professor Konorski's communication 

 that gives rise to so many problems. Obviously the only objection, if it can be 

 called that, is that we have on one side techniques to study the central nervous 

 system and on the other side techniques to study psychological problems, and the 

 bridge is always there, but it is hard to correlate and the passage from one to the 

 other is hard to interpret. 



