to see the potential for confusion in regard to the interpretation of one’s experiences of intimacy and belonging; that is, to sexualise a nurturing event, or to feel connected in a sexual event where there is otherwise little emotional connection.
With regard to the activation of various brain regions, the orbitofrontal cortex, the prefrontal cortex and the anterior cingulate cortex may be involved in the evaluation of sexual attractiveness. Other regions of the prefrontal cortex and the anterior cingulate cortex may play a role in sexual desire through the evaluation of the reward value of external reward stimuli.88 Diamond & Dickenson (2012) report that activation of the caudate, insula and putamen brain regions appear to relate both to the experience of sexual desire and romantic love. Pfaus, et al. (2014) note that because of the extensive anatomical and functional connections these neural areas have with many other parts of the brain, ready access is allowed to contextual information to inform both the judgement of sexual attraction and the stimulation of sexual desire. This represents the neural parallel of the many associations made at a subjective and meaning level, and underscores the complexity of the sexual experience.
However, as the arousal level associated with sexual pleasure is prolonged, neural changes occur in regions of the amygdala and the frontal and prefrontal cortex. This adversely affects capacity for moral affiliations, self-other relations, self-awareness, and interpersonal judgements.89 (Perhaps the reverse is also true: that is, that a strong focus on moral affiliations, self-other relations, self-awareness, and interpersonal judgements act to inhibit sexual arousal and sexual pleasure by way of increased activity in these same regions.) Pfaus, et al. (2014) suggest that the function of such neural changes is to help ‘dissolve normal body boundaries, thereby facilitating sexual interactions, which in turn might contribute significantly to the experience of sexual arousal’ (p. 174). We observe here a neural equivalent to the notion of shared subjective space in the experience of sexual activity. During orgasm, reward-related regions of the limbic system and the cerebellum are activated, while the regions associated with vigilance are inhibited.90 Simply put, prolonged sexual arousal negatively affects a person’s capacity for objective judgement.
When it comes to sexual inhibition, other neurochemicals are involved. Some prevent a sexual event occurring in the first place; others bring a sexual event to an end. Opiods, for example, are released in the cortex, limbic system, hypothalamus, and midbrain during orgasm, and mediate sexual reward. In providing the experiential reward found in sexual pleasure and thus serving to sate the drive, its release quickly reduces sexual desire and arousal.91 Both serotonin (which counters the effect of dopamine) and endogenous cannabinoids are released immediately after a sexual event, shutting down sexual arousal, with serotonin creating a sense of peace and sexual satiety, and endogenous cannabinoids mediating sedation.92
Not only does sexual inhibition immediately follow orgasm, it can also result from stress or threat.93 However, the latter is subject to individual differences in perception of the degree of threat: a limited amount of stress or threat can have the reverse effect, stimulating arousal for some (especially in those with a high threshold for the capacity to be aroused) but creating inhibition in others. Generally, stress is associated with negative emotions: of guilt, fear, anger, grief, and shame. These emotions result in cortisol release, contributing to inhibition of sexual arousal. In conditions of sexual inhibition, those areas in the forebrain relating to good judgement, alertness, and saliency detection are activated, preventing focus on sexual desire and arousal.94 Dual-control theories of sexual arousal such as Perelman’s sexual tipping point dual control model95 have been structured around the competing neurochemical activities that determine whether sexual excitation or inhibition ultimately occurs.
The hormonal profile: Priming for sexual desire
We now look at the changing hormonal profile which plays a role both in the priming of sexual interest and in the activation of sexual arousal. Determining the hormonal contribution during various periods of development and determining the effect of various contexts on the hormonal profile is difficult, both in the measurement of hormonal fluctuation and in the isolation of variables — not only in relation to what might result from hormonal change, but also in relation to what might contribute to it. Nevertheless, it is clear that hormones influence sexual desire in the most general sense, and that various neurochemicals are activated both in the process of sexual arousal and in the subsequent sexual encounter. In a woman, for example, the rhythm of sexual desire is intimately connected with the biology of her reproductive systems as expressed in her hormonal profile, both in her monthly cycles, and in the seasons of her lifetime.
As is true of other aspects of the mind-body relationship, biochemical and psychological processes interact. And so, for example, subjective mood states can affect the hormonal profile affecting sexual desire, while subjective experiences (for example, sexual thoughts or fantasies) can translate into neuro-chemical activation that creates subsequent conditioned arousal responses to those particular thoughts and fantasies. Furthermore, a person’s hormonal profile is in a constant state of flux,96 responding to physiological events (the internal biological context, such as the menstrual cycle and pregnancy in women97), to external circumstances (the prevailing environmental context, such as relationship circumstances), and to developmental and life-cycle changes. The prevailing hormonal profile at critical developmental periods can also have enduring effects, especially when it contributes to subjective associations and conditioning processes. That is, hormones can activate or inhibit certain sexual behaviours at one time, which creates implicit memories affecting later sexual behaviour.
On the basis of such research as has been done in this area, we have glimpses into the complexities of the interaction of the hormonal profile and these various factors. But we begin with the reminder that although both men and women carry the hormones testosterone and oestrogen, their profiles are different. Testosterone, a hormone of the androgen group, has been associated not only with the development of male physical sexual characteristics, but also with the regulation of cognitive and physical energy. Testosterone associates with sexual motivation in men, although it does not affect the ability to engage in sexual activity.98 In women, the release of oestrogen relates to sexual motivation, while release of progesterone has the reverse relationship.99
But the effect of the hormonal profile on sexual behaviour begins long before men and women develop sexual interest. It begins before birth, as a mother’s hormonal activity affects the baby within her. The sperm fertilising the egg determines whether the baby will be male or female. However, the baby’s physical masculine or feminine characteristics is shaped by the mother’s prevailing hormonal profile during the first trimester of her pregnancy. The correct concentration of testosterone at the right time is prerequisite to the physical development of male features; otherwise, female features develop. This in turn sets the biological framework for later patterns of sexual attraction and desire as the baby grows and eventually enters adulthood.
During the second trimester, evidence suggests that the mother’s androgen levels shape aspects of the baby’s brain, influencing gender formation. Testosterone (converted to oestradiol) contributes to masculinisation in interest and behaviour. Too much testosterone can have a masculinising effect on a developing girl, so that she later comes to prefer ‘male’ toys, activities, and playmates, has decreased interest in feminine behaviours such as playing with dolls, is more socially detached, engages in less verbal aggression (but more physical aggression) and is later less likely to have exclusively heterosexual orientation.100 In corresponding manner, a deficit of androgen hormones prenatally may lead to a ‘predominantly female differentiated brain’ which in a boy has been associated with later homosexual tendencies.101
The idea that sexual orientation may be influenced by brain development under the influence of hormonal secretions during critical periods of prenatal development has also found other support.102 For example, a higher incidence of lesbian orientation has
