Physiology of Libido

Abstract

Libido has always been associated with sexual motivation. The Latin root refers specifically to sexual lust, a term that conjures images of highly motivated behavior. Libido is observed in the strength of desire and responding toward a sexual incentive, and therefore can be regarded as a conscious reflection of sexual motivation, which we define here as the energizing force that generates our level of sexual interest at any given time. It drives our sexual fantasies, compels us to seek out and evaluate sexual incentives, regulates our levels of sexual arousal and desire, and enables us to masturbate, copulate, or engage in other forms of sex play. Although sexual motivation is often viewed as an internal process built upon neuroendocrine mechanisms, such as alterations in brain neurochemical function set forth by steroid hormone actions, it is also modulated by experiences and expectations, learned patterns of behavior and underlying neural activity related to sexual arousal, desire, reward, and inhibition. In turn, these aspects of sexual function feed back on mechanisms of motivation, either to increase (as in the case of arousal, desire, or reward, Fig. 3.1a) or decrease (as in the case of reward or inhibition, Fig. 3.1b) the expression of sexual interest or libido. Delineating the neural mechanisms that underlie these aspects of sexual function has been the focus of recent research in animals and humans.