J. OLDS AND M. E. OLDS 



157 



In some earlier attempts to answer this question following the example 

 of Lashley (1929), surgicallesions were used, the neocortex was the prnnary 

 locus of the search, and each animal learned only once so he could not 

 serve as his own control. Very often, surgical lesions appeared to leave 

 parallel structures to do the job; the neocortex seems ipsoJiUto a narrow 

 constraint upon the search; and individual as well as surgical differences 



FOUR DAYS 

 FIRST RUNS 



EXTINCTION 



S group 

 ( 8 rots ) 



Fig. 5 

 Multiple-choice maze in which animals improved performance from trial to trial and from 

 day to day, the only reward being an electric stimulus below the septal area (solid line). 

 They are compared with a control group running for food (dotted line). Insert shows day-to-day 

 improvement m terms of first run of the day indicating that no primer-stimulation is necessary 

 to get rats running for electric reward. 



from animal to animal make it desirable tor animals to serve as their own 

 controls. 



Thus we turned to an electric stimulation (ci. Thompson, 1958; 

 Mahut, 1957; Stein and Hearst, 1958) to jam' the network, to cause, that 

 is, a temporary disarrangement of pattern which is believed to function as 

 a temporary (reversible) lesion. We believe this has three advantages: 

 (i) it is reversible; (2) it can be expected to project to parallel structures 



