STUDIES OF CEREBRAL FUNCTION IN LEARNING. VII 



33 



THE EFFECT OF THALAMIC LESIONS 



One case, no. 49, with injury to the thalamus was found 

 in the series with training after operation. The number of 

 trials required by this animal was 280, with 132 errors. The 

 average for the group with which he was trained was 121.9 

 trials with 39.1 errors. The greatest amount of practice re- 

 quired by any member of the group was 200 trials, with 80 

 errors. This suggests that the thalamic lesion was effective 

 in retarding the learning, although one case is far from 

 proving the point. The extent of cortical lesion in this case 

 is shown in figure 49. The surface lesion is not greater than 

 that of animals which showed no retardation of learning. In 

 addition to the cortical lesion, there were severe injuries to 

 the optic radiations and to the pulvinar on both sides, com- 

 plete degeneration of the fornix in both hemispheres, and 

 extensive injury to the left superior colliculus. 



Among the animals with training before operation and re- 

 tention tests after, four were found with injuries to the thala- 

 mus. These were nos. 99, 100, 101, and 102. The surface 

 lesions are shown in figures 99 to 102. The training records 

 are given below. 



^ The extensive initial training of these animals is due to the fact that they 

 were given the first 100 trials without punishment for errors. 



The thalamic lesions in these cases were the following : 



No. 99. In the right hemisphere there was a very slight 



injury in the pulvinar, scarcely penetrating the surface. The 



optic radiations and lateral geniculate body were uninjured. 



On the left side there was extensive injury to the anterior 



