LOCALIZATION OF LEARNING PROCESS 207 



total absence of the visual cortex. When the visual 

 cortex does participate its activity is influenced by 

 everything else that is going on in the cerebral cortex 

 as a whole, that is, by the total situation at the mo- 

 ment and by cortical memories of previous experience. 

 This participation may facilitate this particular learn- 

 ing process, or under other conditions it may delay 

 it or block it altogether. 



Cortical participation in learning may involve as- 

 sociational neurons whose axons have very wide dis- 

 tribution, and the destruction of some particular cor- 

 tical field which may have been involved in the initial 

 learning evidently does not prevent the effective par- 

 ticipation of other uninjured neurons in the process of 

 relearning. In this sense we may agree with Lashley 

 (1926) when he says: 



No part of the cerebral cortex is better adapted for the forma- 

 tion of any particular habit than is any other. Any anatomically 

 continuous cerebral area may serve the learning function pro- 

 vided it presents sufficient mass. This must mean that in a prob- 

 lem situation the effects of stimulation irradiate to all parts of 

 the cortex. As the habit is established there comes into being a 

 definite structural modification having topographical position 

 and capable of destruction by brain injury. The learning process 

 is independent of locus, whereas the mnemonic trace or engram 

 has a definite localization. 



It must be borne in mind that so simple a state- 

 ment of cortical function, if admitted at all, can safely 

 be applied only to a brain as simple as the rat's, and 

 here only for the very circumscribed aspects of simple 



