CEREBRAL FUNCTION IN THE RAT 107 



Frontal pole destroyed: animals which lost the habit after opera- 

 tion and failed to acquire it again 



Experiment 29. The frontal poles of both hemispheres were 

 incised in a large male rat', 155 days old. He had been trained 

 for 85 trials on the inclined-plane box. The average time per 

 trial for the first five trials was: to plane, 2311 seconds; to door, 

 51 seconds. That for the last five trials was: to plane, 8.9 

 seconds; to door, 2.8 seconds. 



The animal was tested daily for a week after the operation 

 but did not once get on top of the food box. His activity was 

 equal to that of a normal animal but was confined to a few ster- 

 eotyped movements. He spent a great deal of time in climbing 

 up the sides of the restraining cage and pushing against the 

 wire top with his nose. This was gradually replaced by a rapid 

 pacing around the food box from the door to the back and to 

 the door again, interspersed with long pauses in front of the door 

 of the food box, which continued day after day without varia- 

 tion. There was no indication of the retention of any part of 

 the habit. 



Lesion (plate III, fig. 29). Right hemisphere. There is a 

 lesion through the lateral ventricle, passing laterad through the 

 posterior third of the corpus striatum to the cortex and ventrad 

 through the peduncle. There is a second lesion over the frontal 

 pole with complete degeneration of the cortex and formation of 

 a cyst. It is probable that the section of the cerebral peduncle 

 destroyed the lower connections of all the frontal region. 



Left hemisphere. There is an extensive superficial lesion 

 over the convexity of the frontal pole with a transverse cut ex- 

 tending laterad from the lateral ventricle to the cortex in front 

 of the corpus striatum, following the course of the fibers and 

 probably doing very little damage. 



After a complete section of one cerebral peduncle, destruction of 

 the frontal pole on that side, and destruction of half the cortex of the 

 frontal region on the other side this animal gave no evidence of 

 retention of the habit, and failed to reacquire it within the limits 

 of the experiment. 



