In some women after orgasm, a negative feedback loop is triggered, with prolactin secretion making them sleepy, dopey, and, often, significantly less horny. Still other women respond to the heightened pleasure with one thought in mind: I wanna go again. Sometimes all that dopamine, norepinephrine, and testosterone continue to trigger sexual desire. Also, the oxytocin creates more touch sensitivity and a desire for more skin-to-skin cuddling, which can trigger another round of testosterone surge.
Brain Blood Flow in Orgasm—All the Wonky Details
Barry Komisaruk’s lab at Rutgers University in northern New Jersey is the world’s largest orgasm research laboratory. Here, men and women are slid into an MRI chamber, where they must lie completely still, their heads held immobile in a mesh cage. Their brain blood flow is then measured while they give themselves, or receive, orgasms. Over the years, this lab has studied just what it takes to climax, including looking at women who can orgasm through fantasy alone and others who’ve had their spinal cords severed, to see if they can climax. (They can, as long as their vagus nerve, which innervates the genitalia, is intact.)
The lab’s more recent studies are delineating the difference between self-stimulation and partner stimulation. Most of us would be quick to agree that these two orgasms are qualitatively different, especially in the emotional realm. The question is: are they physiologically different? Early results suggest they are.
During orgasm, fresh oxygen- and nutrient-rich blood floods the brain. Leading up to orgasm, a series of brain blood flow changes occur. First is activation of the somatosensory cortex, the part of the brain that maps out bodily sensations. Next seen is decreased blood flow to the frontal cortex. You want less frontal flow because you need your foot off the brakes to move a car forward. Frontal inhibition will put the kibosh on the entire sequence. Soon after, the secondary somatosensory cortex, which adds the emotional piece to your physical sensations, is activated. Then increased blood flow is seen in the amygdala, your emotional center, and then in the part of the hypothalamus that is responsible for the release of oxytocin.
The last piece of the puzzle is the dopamine circuitry that underlies reward seeking, pleasure, and euphoria. The final push into orgasmic bliss is the job of this brain area. Dopamine not only helps you pay attention, focus, and keep your eyes on the prize, but it also marks an event as salient. So don’t be surprised if the guy you were only moderately into suddenly becomes more important in your eyes after he’s given you the big O. Dopamine surges also decrease sensory thresholds for more sensation, priming the brain for more pleasure. Multiple orgasms, anyone? (For more on sexual pleasure, please enjoy the sex chapter.)
The chemistry of attraction changes over time, ebbing over six to eighteen months, being slowly supplanted by the chemistry of attachment. Committed love is calmer, with none of the sweaty palms and churning stomach, thanks to less circulating dopamine, norepinephrine, and phenylethylamine (PEA). Because of that seesaw effect, lower dopamine means higher serotonin. The reward circuitry isn’t firing, and the frontal lobes are fully online, so rational thought wins out over emotional upheaval, due to normalized serotonin levels. The study comparing the serotonin levels of patients with OCD to those who were infatuated showed that the levels do finally normalize during the attachment phase, as your lover becomes less of an obsessive fixation. Less dopamine also means less testosterone, for both of you, so the lust factor has died down considerably. Men’s testosterone levels are lower after they’ve been partnered for more than a year compared to those in the first six months of a committed relationship.
Recall the dads-versus-cads issue. In men, higher levels of testosterone (cad) can reduce the attachment drive. A manly guy may be great pickings for a one-night stand and may provide top-shelf genetic material, but it may not be in his nature to stick around to change diapers. Birds that are given an extra dose of testosterone abandon their nests. A man with lower testosterone may be a great father and less likely to stray, but he may not have the most chiseled chin. One plus: typically, during the parenting phase, lower testosterone levels help ensure that fathers will focus on their newborn and not stray. So parenthood could potentially help turn a cad into a dad. Not only are men with lower testosterone levels more responsive to infants’ cues but “paternal effort” can lower a man’s testosterone levels.
Longer-term, attached love is sometimes called companionate love. This familiarity and companionship creates feelings of comfort, well-being, a sense of calm, and even decreased perceptions of pain, courtesy of oxytocin and endorphins that are still on board.
While the neurochemistry of committed love may lack the intensity of the early attraction phase, the effect of a long-term relationship on your well-being can hardly be underestimated. But once the chemical dependence of the early days fades away, couples who choose to stay together have to work harder to remain connected. Monogamy can complicate libido in particular and may affect women more than men.
Emotional connectedness is all about oxytocin (and estrogen, which enhances oxy’s functioning) in women and a hormone called vasopressin in men. These are the molecules of attachment and bonding. Vasopressin, in particular, is considered the molecule of monogamy and exclusivity. Vasopressin not only enhances a man’s commitment to a woman but also underlies male bonding (the “bromance”). In the same way that oxytocin and testosterone compete with each other, vasopressin and testosterone are often at odds as well. Vasopressin diminishes the impact of testosterone on competition and aggression, encouraging the defense and protection of progeny and, importantly, preventing promiscuity and infidelity. In monogamous prairie voles given a vasopressin blocker, their testosterone takes the lead; they screw one female and then abandon her for another.
Studies of the vasopressin receptor gene (dubbed the “monogamy gene” in The Female Brain) show two versions, long and short. The longer version of the gene is associated with improved bonding and mating behaviors and more appropriate social behaviors. This version is present in our primate cousins the bonobos, who are quick to hug, kiss, and even have sex to keep the peace. The shorter gene variant is seen in the more aggressive chimp population. Also, interestingly, the shorter gene is seen in autism in humans, where there are some deficits in social and bonding behaviors.
Vasopressin also facilitates clear thinking, attention, memory, and emotional control. In Helen Fisher’s brain-imaging studies, people in longer love relationships show increased activity in the anterior cingulate cortex (where attention, emotion, and memory interact) and the insular cortex, which processes emotions. So the brain is formulating and filing emotional memories. The early phases of attraction are fiery and passionate. Attachment is calmer, more relaxed, and solidified. Oxytocin is the common chemical in both phases, pulling two people together, lowering their defenses that are suspicious of trusting and connecting, and then keeping them bonded. Eye contact, the “anchoring gaze,” is a powerful way to connect with women, creating intimacy and, often, sexual longing. Looking away, turning
