All organisms that engage in sexual behavior share a common set of principles and end-points that define the behavior, along with particular neural mechanisms that make it successful. First, we must be able to respond to that signal our ownhormonal and neurochemical changes sexual arousal and desire. We must be able to identify external stimuli that predict where potential sex partners can be found, and seek out, solicit, court, or otherwise work to obtain sex partners and copulate with them. Neural mechanisms exist that allow the stimulation received during sexual contact to be perceived as rewarding. Such reward alters subsequent behavior by contributing to the formation of preferences for salient stimuli associated with positive sexual reinforcement. These aspects of sexual responding go well beyond the traditional focus on copulation and genital reflexes. Although some appetitive and preparatory responses made by animals prior to copulation are not specific to sexual behavior, they can be considered “sexual” if they are conditioned using sexual reward as the positive reinforcer. Sexual desire is expressed in the vigor with which animals will work to obtain these sexual rewards. Accordingly, this lecture will first discuss the type of responses and behaviors from which sexual desire may be inferred in humans and animals. A major focus will be on the relationship of different neuroendocrine (e.g., steroid hormone) and neurochemical (e.g., monoamine and neuropeptide) systems in the brain and periphery that underlie these behaviors, and how they are they bring reward systems into alignment with the reproductive needs of the animal. Finally, the ways that conditioned stimuli associated with sexual reward activate these pathways will be discussed. Although objective measures of sexual desire remains elusive in humans, animal models of desire may well help to establish neurophysiological and behavioral processes that will have predictive validity to humans.
Conflict of Interest: None disclosed
Financial Support/Funding: All Research From My Laboratory Is Supported By Grants From The Canadian Institutes For Health Research And The Natural Sciences And Engineering Research Council Of Canada.
Sydney Australia, April 2007
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