HORMONES AND MATING BEHAVIOR 



1207 



diA'crt effort from investigations of other 

 parts of tlie brain. In this connection, the 

 concluding statements by Kawakami and 

 Sawyer (1959a) are relevant and caution- 

 ary. In their words, ''the areas in the brain 

 which are affected by steroids are so ex- 

 tensive as to suggest that the whole nervous 

 system is influenced primarily and localized 

 systems of integrated behavior secondarily. 

 Sex steroids affect simultaneously . . . the 

 midbrain reticular system, which probably 

 includes a mamillary body mating-behavior 

 'center' and the rhinencephalic-hypothala- 

 mic system, which includes the basal tuberal 

 gonadotropic 'center'." 



When the male is considered, very differ- 

 ent facets of the problem of the mechanism 

 of hormone action are encountered (Nissen, 

 1929; Beach, 1942e. 1958; Soulairac, 

 1952a-e; Soulairac and Coppin-Monthil- 

 laud, 1951; Larsson, 1956; Lehrman, 1956; 

 Rosenblatt and Aronson, 1958a, b). 



The concept that male sexual behavior has 

 appetitive and consummatory portions has 

 been discussed (p. 1178). Not unrelated in 

 the minds of investigators interested in the 

 mechanism of hormonal action, is the cir- 

 cumstance that these parts of the pattern 

 are thought to be mediated by different parts 

 of the nervous system. Walton (1950) stated, 

 the motor activities in the pattern, associ- 

 ated by the writer with the appetitive por- 

 tion, are innervated by the voluntary central 

 nervous system and all have a high degree 

 of cortical representation. Erection and ejac- 

 ulation, regarded as consummatory, are in- 

 nervated through the sacral autonomic 

 ner\-es and may be stimulated to function 

 independently of the motor part of the pat- 

 tern. 



Beach who has considered this dichotomy 

 more persistently than any other investi- 

 gator states in his review published in 1958 

 that the mechanisms cannot yet be described 

 in ])recise neurologic terms, but it is possible 

 to indicate something with respect to their 

 composition. According to him, the consum- 

 matory mechanism (CM) of male (and fe- 

 male) primates embrances centers and sys- 

 tems extending into the neocortex. The 

 cortex and various subcortical tracts and nu- 

 clei are thought to be involved in the CM of 

 male carnivores, but not in female carni- 



vores, and not in the male or female rat. In 

 the animals composing these last groups, the 

 highest essential centers of the CM lie in the 

 diencephalon. It is because of this, appar- 

 ently, that the coital act can be performed 

 without practice. The latter, however, is cer- 

 tainly not true in the guinea pig, another 

 rodent (Valenstein, Riss and Young, 1955; 

 Valenstein and Young, 1955; Goy and 

 Young, 1957a); consequently cortical in- 

 volvement would be assumed in males and 

 females of this species. The arousal mecha- 

 nism (AM) is said not to depend on the 

 cortex in female rodents or carnivores. In 

 these groups the AM is diencephalic, but 

 the AM of male rodents and carnivores and 

 of male and female primates includes corti- 

 cal elements. Influenced by the observation 

 that castrated carnivores and primates can 

 copulate, provided the requisite degree of 

 arousal is attained, Beach concluded that in 

 the males of many species the CM does not 

 dei^end on androgen. To the reviewer, this 

 conclusion may require modification. For 

 one thing, agreement is not general that cas- 

 tration of carnivores and primates is without 

 effect (p. 1183) and that any apparent effects 

 can be counteracted by a sufhciently high 

 degree of arousal. For another, ejaculation, 

 a consummatory response in the male, is the 

 first element to disappear following castra- 

 tion. 



The dependence of the AAI on gonadal 

 hormone stimulation is not questioned. A 

 hypothesis that has long had general ac- 

 ceptance was advanced by Beach (1942e, 

 1944b, and elsewhere). Androgens are as- 

 sumed to raise the excitability of the central 

 excitatory mechanism (c.e.m.), thus increas- 

 ing the male's susceptibility to arousal, and 

 to lower the thresholds in the neural circuits 

 mediating the male copulatory pattern. Ele- 

 vation of the c.e.m. is also related to the 

 excitatory value of the stimulus object; con- 

 sequently, hormonal and psychologic factors 

 are mutually compensatory in elevating ex- 

 citability. Like androgen, estrogen when 

 present in the male is said to raise the excita- 

 bility of the c.e.m. and thus to increase his 

 susceptibility to arousal. In the female it is 

 believed to function by lowering the thresh- 

 old in the neural circuits mediating the 

 copulatory pattern. 



