CEREBRAL FUNCTION IN LEARNING 



83 



The results of these tests are summarized in table 2. The 

 maximum number of trials required by any member of the group 

 was 107 (7). The minimum number was 45 (9). The average 

 number is 68.8. 



The total extent of the lesions is shown in figure 4. Every 

 part of the occipital third of the cortex was destroyed in some one 

 of the animals without any significant increase in the amount 

 of practice required for learning. The average time per trial 

 required in successive day's practice is shown in table 3. 



The greatest lesion appeared in number 9 (plate I, figure 9) 

 and this annual learned more quickly than any of the others. 



Group 4- Parietal region destroyed. In these experiments the 

 attempt was made to destroy the middle third of the cortex, an 



FIG. 4. THE TOTAL EXTENT OF THE LESIONS IN ANIMALS OF GROUP 3 AFTER 

 OPERATIONS ON THE OCCIPITAL POLE 



area including the motor cortex of the hind legs and extending 

 caudad to the visual cortex. Autopsy showed in each case a 

 saddle shaped area, including from 14 to 31 per cent of the cor- 

 tex, destroyed. Accounts of the individual experiments follow. 



Number 11. Small female, about 150 days old. The parietal re- 

 gions were injured by passing a scalpel laterad and messiad from each of 

 two trephine openings just caudad to the fronto-parietal suture. Re- 

 covery was uneventful with no abnormalities of behavior. Training 

 was begun 25 days after operation. The animal was inactive at first, 

 but aften ten trials her reactions to the problem box became normal. 



Number of trials required for learning 101 



Per cent of total cortex destroyed 21.2 



