580 BRAIN MECHANISMS AND LEARNING 



correlated with those head movements of the stationary animal which 

 constitute many aspects of an orienting reflex. 



Certain aspects of the hippocampal slow-wave activity have been 

 correlated with the orienting reflex of Pavlovian physiology by Grastyan 

 ('/ al. (1959). It is not proposed to enter here into a discussion of definitive 

 aspects of this reflex, although it may be observed that Konorski (1948) 

 has defined it as the turning of the head and eyes towards a sudden stimu- 

 lus, and that such a definition has no connotation of locomotion towards 

 a goal. Our fmdhigs in some twenty-one animals have consistently 

 indicated a correlation of bursts at 5-6 cycles/sec. in the dorsal hippocampus 



NAIVE ANIMAL - FIRST TRIAL 



RUN 2 - VENTRAL HIPPOCAMPAL SYNCHRONtZATlON WITH ENTORHINAL RECORD 



gg^^l'-'aK' ADV«.CES| ^°l1i„JH ■ . ="u'if=l 





VENTRAL HIPPOCAMPAL SYNCHRONIZATION DECREASED BUT SUSTAINED IN ENTORH! 

 DOORS LIGHT ADVANCES LOOKS AT LIGHT STEPS UP 



OreN ) ON , , . , . 



, 1 I SEC 



Fig. 2 

 Records from the left (LVH) and right ventral hippocampus (RVH) and cntorhinal area 

 (ENT), showing the rapid disappearance of much of the synchronized slow-wave activity from 

 the ventral hippocampus between the second and twentieth runs of the first trial. At the same 

 time, a sustained 6 cycles/sec. discharge is present at the twentieth trial in the cntorhinal record 

 in relation to the approach performance. 



and in the cntorhinal area with the motor performance, rather than with 

 simple aspects of orientation. It may be further emphasized that this 

 6 cycles/sec. activity was singularly unadapting in the course of training, 

 persisting unaltered in as many as 1 200-1 400 trials in immature and adult 

 animals. Throughout training it remained maximal in the dorsal hippo- 

 campus and particularly in the entorhmal area. 



In studyuig the distribution of hippocampal slow-waves in the young 

 animal, we have implanted a number of young animals weighing about 

 1.8 kg. Their head size approached that of the adult, and it was possible 

 to implant and record from them for a period of 2 to 3 months without 

 significant electrode displacement from gro\\th changes. Initially, their 



