THE RETENTION OF HABITS BY THE RAT AFTER 



DESTRUCTION OF THE FRONTAL PORTION OF 



THE CEREBRUM 



S. I. FRANZ AND K. S. LASHLEY 



From the Government Hospital for the Insane and the Psychological Laboratory of 

 The Johns Hopkins University 



Much has been written regarding the neurology of learning 

 and especial attention has been directed to the cerebrum. Com- 

 paratively little evidence has been adduced to show what cere- 

 bral elements are used in the formation of habits, although 

 recent experimental investigations show that the frontal posi- 

 tions of the cerebrum are utilized by monkeys, dogs, and cats. 1 

 In only those animals with a highly developed brain is there 

 a distinct differentiation of the frontal (as an association area) 

 from the central (so-called motor and sensory-kinesthetic) 

 area, and in fact the possibility of the histological differen- 

 tiation of numerous areas of the brains of many of the lower 

 animals is slight. The relatively simple and homogeneous 

 character of the cerebral cortex in the rodents makes their 

 cerebral physiology worthy of study, and there is the added 

 advantage that the animals acquire habits rapidly and much 

 information is at hand regarding their normal reactions. 



At the same time, on account of their low cost and ease of 

 housing, many different experiments on the brain may be made 

 which are not possible with animals having larger and more 

 highly developed brains. Such experiments on rats may be 

 expected to give results of at least suggestive value respecting 

 the functions of corresponding parts of more highly evolved 

 brains. Thus, if it is found that these animals can acquire habits 

 after the removal of certain small or large parts of the cerebrum, 



1 For most of the evidence: S. I. Franz, The Frontal Lobes, New York: Science 

 Press, 1907, pp. 64. 



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