586 



BRAIN MECHANISMS AND LEARNING 



conic into intimate contact with the laniinarly organized, closely grouped 

 apical dendritic trees of the hippocampal pyramidal cells. The patterns oi 

 phase relations and the changes observed in these patterns in training, 

 particularly between the entorhinal area and hippocampal areas CA., and 



CROSS-CORRELATIONS — IN LATE TRAINING 

 CAT 7 — TRIAL 20 — RUN I 



40 SAMPLINGS/SEC. 



„ DORSAL HIPR 



(REGION CA4) 



BANDPASS I 



^ Jrso 



5 C.RS. 

 DORSAL HIPR 

 (REGION CA2) 



LEADS 



♦ 'b 



20 MSEC 



ENTORHINAL AREA LEADS 



Fig. 6 

 Cross-correlation functions in late training, from the same animal as in Figs. 4 and 5. By 

 contrast with Fig. 5, the entorhinal area now leads hippocampal region CA4 by as much as 

 65 msec, and CA, by 20-25 msec. These findings are consistent with activity following the 

 pathways proposed by Cajal (see text). 



CA4, may be interpreted on the basis of such a mechanism. McLardy 

 (1959) has recently proposed an elaborate series of intrahippocampal 

 connections which might also subserve such functions. 



If, then, the concept of phase-comparator mechanisms should be found 



