1238 



HANDBOOK OF PHYSIOLOGY 



NEUROPHYSIOLOGY II 



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FIG. 9. Effects of progesterone on thresholds in an unanesthetized estrogen-primed castrate 

 female rabbit. RF, reticular formation; VMH, ventromedial region of hypothalamus; "after-reac- 

 tion,' refers to EEG changes such as those seen in fig. 8, after vaginal stimulation. [From Sawyer 

 (80).] 



SUMM.-^RY 



Hormones may exert their effects at various levels 

 within the nervous system to influence reproductive 

 behavior. In general, subcortical centers appear to be 

 more important than cortical. No level of integra- 

 tion below the hypothalamus can inaintain more than 

 a partial pattern of se.xual behavior in either sex. 

 Evidence from lesions, direct stimulation, direct appli- 

 cation of hormones, electrical self-stimulation experi- 

 ments and electrical recording data implicate the 

 hypothalamus as a most important center of mating 

 behavior. It is influenced especially by the rhinen- 

 cephalon and the reticular activating system. In cer- 



tain species the olfactory bulbs play a very important 

 role, particularly in the male. The cortex, especially 

 the medial, cingulate or retrosplenial area, appears 

 to play an essential part in integrating reproductive 

 activities which require initiative such as male mat- 

 ing, feinale maternal and maze-learning phenomena. 

 Female mating behavior does not require the cerebral 

 cortex in lower mammals, but it is especially de- 

 pendent on hormone levels. Certain direct effects of 

 hormone levels on thresholds within the nervous 

 system have been demonstrated and correlated with 

 mating behavior in the female rabbit. Neural corre- 

 lates of behavioral after-reactions in mating ha\-e 

 been recorded in the rabbit and cat. 



REFERENCE.S 



1. .\dev, \V. R., N. C. R. Merrillees ?md S. .Sunderl.and. 

 Brain 79: 414, 1956. 



2. Adev, W. R., S. Sunderland and C. \V. Dunlop. Elec- 

 troencephalog. & Clin. Neurophysiot, 9; 309, 1957. 



3. B.^LL, J. J. Comp. (S Physiol, Psychol. 18: 419, 1934. 



4. Ball, J. Comp. Psychol. .Monogr. 14: i, 1937. 



5. B.ARD, P. A. Res. .Veri: & Alenl. Dis., Proc. 19: 190, 1939. 



6. B.ARD, P. A. Res. Nerv. & Ment. Dis., Proc. 20; 551, 1940. 



7. Baiter, H. G. J. Clin. Endocrinol. 14: 13, 1954. 



8. Beach, F. .A. J. Comp. Psychol. 29: 193, 1940. 



