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Lecture 9

Lecture 9 - Feb 9.doc

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PSYC 342
Jens C Pruessner

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PSYC 342 Lecture 9 - Feb. 9 Male Reproductive Behaviour: • Testosterone alone is not determining sexual behaviour • In castrated rats, copulatory behaviour is predicted by dopamine rather than testosterone. Dopamine experimented in mice will use reward as a classical conditioning (via dopamine) to en- gage in copulating behaviour Individual Differences Related to Sexual Behaviour: Individual differences in sex drive are retained following castration and testosterone restoration • • After testosterone therapy, those who came from a high drive will go back to a high drive and same thing for low and medium drive. The individual variation is preserved • Behaviour is different amongst different groups of animals and it may not all be attributed to testos- terone (condition, reward, another hormone, etc.). It is not purely hormonal • The hormone alone does not cause the behaviour but rather it helps facilitate a potential behaviour Changes of Male Sexual Behaviour With Age: • The decrease in sexual behaviour with age is not associated with the change in hormone concen- trations • Other factors mediating the hormone-behaviour associations? • Answer lies in ‘The Coolidge Effect’ - See below • Study of ‘sexual experience promotes adult neurogenesis in the hippocampus despite an initial ele- vation in stress hormones • Regrowth ability to smell (olfactory system) • Regrowth ability of hippocampus (memory and learning, contextualization, spatial development) Female Reproductive Behaviour: • Frank A. Beach • Psychobiologist from UC Berkeley who wrote “Sexual Attractivity, Proceptivity, and Receptivity in Female Mammals” Proposed three components to divide female behaviour: attractivity, proceptivity and receptivity • Estrous Cycle: • Period during a female’s reproductive cycle when mating is most likely to occur • Usually coincides with ovulation, when egg cells are released from the ovary • Four stages: Proestrus: period of follicle development in which one or several follicles • • Estrus: ovarian follicles are maturing and estrogen secretions exert their biggest influence • Metestrus: early corpus luteum development • Diestrus: mature corpus luteum regression and reorganization for the next cycle • The three components of female sexual behaviour occur in the estrus phase Estrus Phase: • When the female in ‘in heat’. Immediately precedes ovulation during which the female exhibits a sexually receptive behaviour to mating. Behaviour may be signaled by visible physiologic changes Attractively: • A theoretical construct inferred from observation of behavior of conspecific males toward the female in question • Various masculine responses have been employed to measure a female’s value as a sexual stimu- lus • Different aspects of the male’s performance are related to different forms of stimulation provid- ed by the female • Attractively is powerfully affected by ovarian hormones, being most intense when estrogen is secret- ed in high concentrations (during follicular or estrus phase) Since estrogen production is closely associated with the timing of ovulation, sexual attractively is • essential to survival of the species because it maximizes the probability of copulation when the fe- male is fertile and susceptible to impregnation • Definition: “Female’s stimulus value in evoking sexual responses by the male” • Adaptive functions of attractivity: Bringing the male to the female • • Allowing male to identify female’s reproductive status • Eliciting emission of sperm for fertilization Measuring Attractivity: • Acceptance Ration (AR): the ratio of female invitations that elicit mounting behaviour by the male PROX score: male moving to be next to a female (i.e. Male in proximity of female) • • Visual fixation • Male erection • Male performance of a learned response • Copulatory behaviours terminating in ejaculation Role of Hormones in Attractivity: • Attractivity is highest when estrogen concentrations in the female are highest • This is what we would expect, since estrogen concentrations are highest around the time of ovula- tion • This makes sense from an evolutionary perspective, since this ensures that mating occurs at the time where female is the most fertile Behavioural Stimuli: • Females who solicit copulatory behaviour have a higher level of attractivity than those who do not • Dixon et al (1973) showed female rhesus monkeys who engage in highest frequency of presenting behaviour are the most frequently mounted by males Non-Behavioural Cues: Visual • Sex skin: swelling and reddening of the female perineal skin during estrous • When ovarectomized talapoin monkeys are injected with estrogen, socially dominant males engage in mating behaviour with them • Subordinate males will not engage in mating behaviour if a dominant male is around • But they show an increase in visual fixation on these females Non-Behavioural Cues: Chemical • Red-sided garter snake • Males detect a specific methyl ketone which is produced by females • Once a male begins mating with a female, she then expresses a different chemical to prevent other males from attempting to mate with her Some males also express the attractive methyl ketone • • This serves as a distraction to the other males Non-Behavioural Cues: Fellowmen Response • Many male mammals (especially ungulates) investigate the female genital region before mating • This elicits the Fellowmen response Curling back of upper lip and tilting back of the head • • Severs the purpose of allowing chemosignals to reach the vomeronasal organ Non-Normonal Effects: The Coolidge Effect • Attractivity of a female to a particular male decreases after the pair has copulated several times (i.e. Time to ejaculate increases and eventually stops) When presented with a new female, male response time returns to normal • • This is not a hormonal effect since both females are at the same stage of cycle and equally recep- tive • Seen in many mammals (sheep, cattle, rodents, cats) Perceptivity: Proactive behaviour consists of appetitive activities shown by females in response to stimuli re- • ceived from males • In actual mating sequence, appetitive and consummatory reactions often alternate and the same re- sponse (ex. Coital posture) can be appetitive in one circumstance and part of the consummatory complex in another • Prospective actions by the female constitute response to stimuli normally provided by conspecific males, the female’s appetitive behaviour is a reflection of the male’s sexual attractivity • Prospective behaviour is functionally as important as other patterns traditionally termed receptive, but the female’s tendency to display appetitive responses finds little opportunity for expression in lab experiments • In laboratory settings, we tend to look at receptive patterns and ignore prospecti
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