STUDIES OF HIPPOCAMPAL ELECTRICAL ACTIVITY 

 DURING APPROACH LEARNING 



W. R. Adey 



Attention has been directed, over the past two decades, to the role of the 

 hippocampus and adjacent structures of the temporal lobe in such func- 

 tions as emotional arousal and memory (Kluver and Bucy, 1939; Bard and 

 Mountcastle, 1948). Human studies have supported the view that inter- 

 ference with anterior and deep temporal structures, including the amygdala 

 and hippocampus, may disrupt both these functions (Scovillc and Milner, 

 1957; Meyer and Yates, 1955; Jasper and Rasmussen, 1958). However, a 

 global view of the functions of these rhinencephalic areas in the process of 

 learning might suggest that they are concerned in the execution of planned 

 behaviour rather than, perhaps, in the specific aspects of memory or 

 emotional functions as such. 



The latter point of view provided a frame of reference for the studies 

 reported here. Morphological considerations prompteci Elliot Smith 

 (1910) to draw attention to the early differentiation of the hippocampal 

 cortex in the brain of all vertebrates, and to the concurrent development of 

 the fornix as one of the earliest eticrcnt pathways from the cerebrum. The 

 possible role of these structures in aspects of motor performance relating 

 to learned behaviour appears to have attracted little attention from sub- 

 sequent workers, although Pribram and Mishkin (1955) and Fuller cr al. 

 (1957) have given elegant accounts of subtle changes in learned motor 

 performance resulting from interference with dicse deep temporal 

 structures. 



The experiments described here were conducted in collaboration with 

 Dr C. W. Dunlop, Dr E. Holmes and Mr C. Hendrix, and in the latter 

 part of the project wc were joined by Dr E. Grastyan. We have studied 

 certain aspects of slow-wave discharges in the hippocampal and adjacent 

 deep temporal lobe structures m the cat in the course of approach learning. 

 Our attention has been directed to the possibility of inhomogeneities in 

 the functional activities of different parts of the hippocampal arch, and 

 particularly between the dorsal and ventral parts of the arch. In cross- 

 sections at any one level, the hippocampal arch has been further subdivided 

 into regions CAj, CA2, CA3 and CA4 by Lorente de No (1934). Our 

 implantations have been carefully placed in regions CA^, CA3 and CA4 in 



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