LOCALIZATION OF LEARNING PROCESS 211 



being reduced to a condition of imbecility by the 

 operation, has none of the inhibitions of cerebral ori- 

 gin ("fear reactions"), and the lower reflexes have 

 free and unhampered play. Unfortunately, in these 

 and in most other experiments on decerebrate frogs 

 no precise information is given as to how much brain 

 tissue was removed. 



In reality, the cerebral influence in the case of the 

 normal frogs is probably not an inhibition in the or- 

 dinary sense of the term. It is more likely a distract- 

 ing activation of lower centers from the cerebral hemi- 

 spheres which blocks the elemental reflexes by inter- 

 ference on the lower levels. Upon decerebration 

 this interference is eliminated. The stupor and lack 

 of "spontaneity" of completely decerebrate mam- 

 mals may result from the loss of these same dynamo- 

 genie cortical influences, but acting in a still different 

 way upon the lower centers, as we shall see in a mo- 

 ment. 



Evidently the case of the partially decerebrate rats 

 is very unlike that of the wholly decerebrate frogs, 

 and no direct comparisons can be made. Yet in both 

 cases the intact cerebrum may exert a type of regu- 

 latory control over lower reactions which is lacking 

 after injury. The normal healthy rat is frisky, enter- 

 prising, and inquisitive. A part of this activity is un- 

 doubtedly mediated by the complex intracortical as- 

 sociation fibers passing between those various cortical 

 fields which are colligated with specific sensori-motor 



