CHAPTER XLIX 



Reproductive behavior 



CHARLES H. SAWYER 



Department of Anatomy, School oj Medicine, University of 

 California at Los Angeles, California and Veterans 

 Administration Hospital, Long Beach, California 



CHAPTER CONTENTS 



Historical Background 



Methods of Assessing Sex Drive 



Endocrine, Genetic and Social Factors in Sex Behavior 



Neural Mechanisms and Centers as Revealed by Lesion 

 Experiments 

 Peripheral and Spinal Mechanisms 

 Lower Brain-Stem Mechanisms 

 Neocortical and Rhinencephalic Mechanisms 

 Diencephalic and Hypothalamic Mechanisms 

 Effects of Nerve Lesions in Maternal Beha\ior 



Neural Mechanisms and Centers as Revealed by Stimulation 

 and Recording Experiments 

 Peripheral Mechanisms 

 Hypothalamic Mechanisms 

 Rhinencephalic and Reticular Mechanisms 



Summary 



THE INFLUENCE OF INTERNAL SECRETIONS Oil neiVOUS 



function is nowhere more pronounced than in the 

 dramatic effects of sex hormones on reproductive 

 behavior. Patterns of courtship, mating and parental 

 behavior have ijeen described extensively and have 

 been shown to be activated by hormones in both in- 

 vertebrate and vertebrate phyla. The present paper 

 will not attempt to review the multitude of interesting 

 beha\ioral .sequences in the lower animal forms; for 

 accounts of these, reference is made to the monograph 

 by Tinbergen (92) and to the excellent reviews of 

 Beach (10, 11). The present work will concentrate 

 on the far better known mammalian patterns, their 

 anatomical and physiological neural correlates, and 

 mechanisms of neuroendocrine interaction. 



Many of the more active research contributors to 

 this field have published authoritative reviews of their 



own extensive studies. In order to keep the present 

 list of references within reasonable limits much of tjie 

 work of these investigators will receive reference 

 through their re\iews rather than their original indi- 

 vidual publications. 



HISTORIC'VL B.ACKGROUND 



Early in the nineteenth century Gall and Spurzheim 

 (87), as part of their phrenological considerations, 

 located a center of sexual ijehavior or "amatixeness' 

 in the cerebellum. This concept has never been sup- 

 ported by evidence from animal experiments. In his 

 now famous experiments on the dog brain Goltz (36, 

 37) reported that the cerebral cortex was an essential 

 substrate for sexual behavior in the male but not in 

 the female. Electrical stimulation experiments by von 

 Bechterew (93) supported the cortical location of a 

 center controlling erection and ejaculation in dogs. 

 In 1900 Sherrington (86) described refle.xes related 

 to sexual activity in spinal dogs. Around the turn of 

 the century Steinach (89) stres.sed the dependence of 

 sexual behavior on the stimulating action of gonadal 

 internal secretions on the nervous system. 



During the first half of the twentieth century a few 

 investigators should be cited for the considerable in- 

 fluence of their research on the field of reproductive 

 behavior. Marshall (64) emphasized the importance 

 of exteroceptive factors such as light and temperature 

 on sexual periodicity. From the 1920's Stone (90) ob- 

 served that rabbits and rats with large cortical 

 lesions remained sexually potent and active. Bard 

 (5, 6) has made a careful study of the sexual capacities 

 of cats with well delineated lesions in various cortical. 



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