I think we would all agree that any problem with sex originates in the mind. Our bodies are just answering nature’s call, and the higher self is only concerned with relationships. When we look at the functioning of the brain, the genetic based sexual impulses seem to work at the autonomic level. It is only when the impulses go to the prefrontal cortex for second appraisal do we begin to second guess what our bodies and old brains are telling us. To understand how this works, we can view sexuality as two separate functions: arousal and desire. Adams et al. in their thorough review of brain and hormone activity defined sexual desire as “the behavioral drive that motivates individuals to fantasize about or seek out sexual activity.” In contrast, sexual arousal is defined as “the autonomic physiological processes that prepare the body for sexual activity.”  For the purpose of this blog we will be mainly looking at desire.
 Adams, Kristian; Favaloro; Dundas, Brendan; Dillon, Aaron; Nixon, Daniel. The Neuroscience of Sexual Desire. (http://neurosciencefundamentals.unsw.wikispaces.net/Sex+and+the+Brain.+What+parts+are+involved%3F)
But first, let’s take a brief look at the nature of arousal. Arousal is an old brain/body function. The activities of the tests and ovaries are regulated by a complex chain of events known as the hypothalamic-pituitary-gonadal axis. Sexual arousal is controlled by the autonomic nervous system which interacts with the sex organs creating an increase in steroids, body heat, and heart rate. Male arousal is largely controlled directly by emotion through the limbic system, particularly the amygdala, with limited interaction with the rest of the brain. Males on average have a 16% larger cortico-medial which is the area responsible for steroid uptake which, among other effects, regulates flow of blood to the genitals. The activity of the limbic system precedes and triggers penile erection, sexual feelings, sensations of extreme pleasure, and memories of sexual intercourse. This creates a dopamine rush similar to a shot of heroin.
Female arousal appears to be more of a whole brain activity. A woman’s brain literally lights up when viewed in brain scans during stimulation of the brain via the vagus nerve. Increased activity was noted in the hypothalamic paraventricular nucleus (PVN) (sympathetic nervous system – increasing the dopamine rush – and regulating blood flow), midbrain central gray (GABA and increased sexual reception), amygdala (emotion), hippocampus (memory), anterior cingulate (blood pressure, heart rate and reward anticipation), frontal parietal (body sensations), temporal and insular cortices (sensory processing and memory), anterior basal ganglia (psychomotor behavior), and cerebellum (motor movement). This results in a complex interaction between the brain and body. It also results in increased lubrication and enhanced touch sensation.
Through the technology of improved use of brain scans, we see that desire on the other hand increases brain activity in both males and females . The center for sexual desire appears to come from the amygdala; however, it does not function in isolation. The amygdalofugal pathway connects the amygdala with the thalamus, median hypothalamus, brain stem and nucleus accumbens. The nucleus accumbens is a large cluster of dopamine generating neurons which produces extreme feelings of pleasure as well as motivation to pursue sexual behavior. The anterior commisure is also activated connecting the left and right amygdala combining left brain (thought) and right brain (visual imagery) stimulation. One theory states that the anterior commisure may be responsible for gender orientation with gay men having am anterior commisure more similar to a woman’s (left brain dominant); however, this has not yet been established by neuroscience. Oxytocin seems to be a major player in sexual desire serving both as a stimulus to arousal and a neuromodulator to the flow of information through the neurotransmitters in the brain. All this happens in a blink of an eye where arousal and desire seem to interact simultaneously. This creates a yo-yo effect with our sexual drive system with constant interplay between thought, emotion, and hormonal arousal.
A review of the literature on neuro-sexual activity by Carl Zimmer leads to some interesting additional information. One study observed that the medial orbito frontal cortex (OFC) was active in desire-impaired but quiet in the normal men. The OFC’s connection with the hippocampus produces emotional memories which create states of mind. Through the interaction of states on mind, the OFC mediates reward and punishment, creates personal assessment, and manages expectations. It is also responsible for understanding the thoughts, emotions and intentions of other people. It weighs action and consequences thereby influencing sexual desire. The OFC also connects to the neocortex particularly in the lobes involved in sensory integration including all somatosensory (body sensations) modalities. The OFC also connects to the anterior insula, which is what we use to reflect on the state of our own body sensations. This interplay between the OFC, the anterior insula, and the neocortex may produce the good or bad feelings we associate with sexual arousal. Another set of studies noted that information not only travels from the visual cortex and the emotional centers to the higher regions of the brain, but also goes from the top down. Therefore, the higher regions may be instructing the eyes on what looks sexually desirable. The brain regions that handle self-awareness and understanding others may also be telling the emotional centers what to feel.
The two main disorders relating to sexual desire are hyposexual desire disorder (HSDD) and hypersexuality. The causes of sexual desire disorders vary, but some may include a decrease in the production of oestrogen in woman or testosterone in both men and women. HSDD is characterized by low levels of sexual desire and fantasy. This may be due to genetic predisposition or brain damage to the medial orbitofrontal cortex or the limbic structures of the amygdala, hypothalamus, or the temporal lobes. Hypersexuality can be considered as increased desire for sex that makes it difficult to meet social commitments and/or personal development. Evidence has been found that hypersexuality occurs more often in the right hemisphere of the brain with far more cases in males. Studies also indicate that genetic predictors of homosexuality are associated with increased “risk taking” behavior (hypersexuality) due to irregularities of the serotonin production gene and over stimulus of the dopamine drive system.
I think we can conclude that sexual desire is the culmination of several different neural mechanisms, neural pathways, and states of mind, each of which is controlled in different areas of the brain and is activated at different stages of the sexual experience. In other words, arousal cannot be separated from desire. It is part of the bottom up process but almost simultaneously meets and meshes with the top town approach from the prefrontal cortex. Emotions, impulses and hormonal activity seem to pinball among various areas of the brain once arousal takes place.
Here are my five applications for bisexuals:
- Since sex is a whole brain activity, we can learn to control our mind and then use our mind to control our sexual impulses. We can do this through meditation and dealing with the pain stimuli coming from the ego (OFC). We can restructure our neural circuits through the wisdom of our higher self, affirm our desires as natural sources of pleasure, and rewire our mind with positive feelings of self-acceptance.
- Our sexual impulses are, by their nature, healthy. If we are attracted to men or women or both, it is merely part of our arousal system. We are free to indulge. However, before we can truly enjoy our sexuality, we must also heal the feelings coming from the prefrontal cortex (ego). We can do this by repeating step one whenever we experienced negative thoughts about our sexuality.
- I do not believe that hypersexuality is a legitimate problem except in rare cases. I do not believe it is due to a damaged limbic system. A strong sexual desire system is a sign of a healthy human body. The so-called addiction problems are a result of developed mind sets that involve implicit and explicit memories connected to negative emotions. We simply have to change the circuits and remove the unhealthy inhibitions which are usually based on shame induced structures from family and religion.
- Hyposexuality is a problem, but it is not usually centered in the physical brain structures. It is more likely an inhibitor from the orbito frontal cortex. We have to remove those inhibitors in order to enjoy our sexuality so that we can have fuller and more passionate relationships.
- Gay and bisexual men often have amazingly powerful sex drives. This is natural. We have to learn to enjoy it without shame or blame. When our sexual behavior involves a significant other, we have to be sure that he/she understands our drive, and we have to work out a general understanding that involves both of our needs and desires. We have to open up the doors of communication to take away the potential shame and blame.
 Zimmer, Carl. Discover, 2009. (http://discovermagazine.com/tags/?tag=carl+zimmer)