CEREBRAL FUNCTION IN LEARNING 111 



Summary and discussion 



The total extent of the injuries in the frontal and parietal regions 

 (animals, 5, 6, 7, and 8) is shown in figure 11. Practically all 

 of the anterior two-thirds of the cerebrum was covered by these 

 tests. The animals all gave unmistakable evidence of retention 

 of the habit and the slight reduction in accuracy in some cases 

 is no more than would be expected from the general systemic 

 results of the operation. 



The experiments reported on page 94 ff . show that the frontal 

 regions of the cerebrum are not necessary for visual discrimina- 

 tion. These experiments show, in addition, that the perfected 

 habit of visual discrimination is not mediated by the frontal, 



FIG. 11. THE TOTAL EXTENT OF LESIONS IN ANIMALS WHICH RETAINED THE 

 HABIT OF VISUAL DISCRIMINATION AFTER OPERATION 



parietal, or orbital surfaces of the cerebrum, and that these areas 

 probably have no part in its normal formation. 

 H^The last three cases give equally clear evidence that the occipi- 

 tal pole is intimately concerned with habits of visual discrimi- 

 nation. Table 8 gives their retention records in comparison with 

 the others. Every one of the animals lost the habit completely 

 after injury to the occipital pole. That the loss was due to cere- 

 bral destruction and not to the mere shock of operation is indi- 

 cated by the results with number 9, and by the fact that equally 

 extensive operations in other regions adjacent to this produced 

 no disturbance in behavior. 



These data justify the conclusion that the entire cortical j 

 mechanism of the perfected visual habit is included within the \ 



