512 



BRAIN MECHANISMS AND LEARNING 



Six monkeys, four experimental and two control animals, were used. 

 Three or 4 months after the first operation, they were adapted to the 

 testing situation with the red and green discrimination. Because of the 

 homonymous hemianopsia, many devices were needed to help the 

 animals overcome this defect. The animals were then trained on the two 

 visual pattern discriminations described in the preceding section. After 

 they had acquired these two habits, the two controls were operated upon 

 for the removal of the rcmaming temporal cortex. They forgot these two 

 habits following this operation but relearned them. Thus, the effect of 



Ca 3 



Ca I 



Fig. 2 



Reconstruction of lesions (solid black) of one experimental monkey (Ca 3) and one control 



animal (Ca i). R, right; L, left. 



bilateral temporal lesions on retention of visual discriminations were not 

 augmented by the additional interruption of one optic tract, the hippo- 

 campal commissure, and the corpus callosum. For the four monkeys in 

 the experimental group, they retained the two discriminations after the 

 extensive unilateral decortication of the second operation. They lost these 

 habits after the third operation (temporal lesion), but reacquired the two 

 problems with further training. Table II summarizes the results. Fig. 2 

 shows the reconstruction of lesions of one experimental and one control 

 animal. 



In addition, the four experimental monkeys were given a more complex 



