596 BRAIN MECHANISMS AND LEARNING 



greater integrity of the cortex. In other words, we think that with a 

 similar lesion other types of avoidance CR to a light signal could have 

 been established. The results already mentioned of Wing (1947) and 

 Marquis and Hilgard (1937) would favour this assumption, since they 

 show that it is possible to condition a local motor reaction to a light signal. 

 It is also worth noticing that in these experiments the animal had its own 

 body as a reference for the performance of movements, while in our 

 experiments the movement of the rat involved spatial orientation to reach 

 the exit door from any point of the chamber. Orbach (1959) studied maze 

 learning in peripherally blinded monkeys that had subsequently an 

 ablation of the occipital cortex; he concluded that the visual cortex 

 probably did not have a visual role only but also a function in spatial 

 orientation. It may, therefore, be assumed that cortical integrity may not 

 be essential for the association light-US (shock in our experiments), but 

 that it would affect the integration of a general motor response to a 

 light signal. 



Lashley's (1935) experiments with rats eliminate the possibility that the 

 animals did not detect the light signal. It has been shown that although the 

 visual area is essential for the perception of detail vision, its ablation does 

 not alter the formation of habits which require discrimination between 

 degrees of light. In short, the most likely interpretation of our results 

 would be that a facilitating cortical' action is necessary to release a general 

 response requiring spacial orientation to a light signal. 



For the deficits shown by the anterior group there are two possible 

 reasons: (a) that a cortical lesion of about 41 per cent may determine a 

 serious deterioration of the animal's capacity to acquire an lACR to a 

 light signal, independent of its location; (b) that within the anterior region 

 there may be one or more specific areas the integrity of which is essential 

 for this type of learning. The relevant areas may be: somatic area I and II, 

 motor cortex and orbito-frontal cortex. Lawicka (1956), Lawicka and 

 Konorski (1959), Brutkowki (1959), found that pretrontal lesions deter- 

 mine changes in the behaviour of the animal in a second order conditioned 

 reflex. The first of these authors reports that conditioned inhibition dis- 

 appears after this ablation. St^pieii and St^^picn (1959) found a temporal 

 loss of an instrumental CR after ablation of somatic areas. These studies, 

 however, refer to changes observed on post-operative retention. The 

 integrity of the somatic and motor areas may be important for the 

 integration of tactile and proprioceptive cues utilized by the animal to 

 find its way to the door. The motor cortex may be necessary to facilitate 

 this general motor response. 



