THE HIPPOCAMPUS I 377 



A 12 



A 14 



Fic. 3. Schema of areas apparently receiving impulses from or distributint; impulses to the 

 hippocampus. On the lejt side of each brain section vertical hatching marks areas which when stimu- 

 lated evoke responses in the hippocampus which are always bilateral. On the right side of each 

 section, crosshatched areas are those bilaterally excited by stimulation of the hippocampus. Stippled 

 areas are ipsilaterally excited by hippocampal stimulation. [From Green & Adey (45).] 



effect on the entorhinal area on the basis of interaction 

 studies. In a second paper Adey el al. (i) reported tiie 

 use of electrophysiological techniques to trace a path- 

 way from the entorhinal cortex caudally through the 

 thalamus to the periaqueductal gray and dorsal 

 tegmentum. 



The gyrus cinguli presumably projects to the 

 hippocampus in a fashion similar to the entorhinal 

 cortex, establishing a.xodcndritic synapses with the 

 pyramidal and granule cells. It is also possible that 

 more or less direct connections are established from 

 the gyrus cinguli to the hippocampus through the 



fibrae perforantes corpus callosi, groups of fibers which 

 have been described from time to time as penetrating 

 the corpus callosum (64). 



TH.aiL.'Mnus. Thalamic connections of the hippocampus 

 are not well understood. Direct connections between 

 the hippocampus and the thalamus are probably 

 present. They were claimed by some of the older 

 anatomists and have recently been traced by the 

 bouton degeneration technique (52, 82). Green & 

 Adey (45) found short latency responses in the an- 

 terior thalamus following hippocampal stimulation 



