science of the orgasm

Principles of Pleasure

Sexual desire and orgasm are subject to various influences on the brain and nervous system, which controls the sex glands and genitals.
The ingredients of desire may differ for men and women, but researchers have revealed some surprising similarities. For example, visual stimuli spur sexual stirrings in women, as they do in men.

Achieving orgasm, brain imaging studies show, involves more than heightened arousal. It requires a release of inhibitions engineered by shutdown of the brain’s center of vigilance in both sexes and a widespread neural power failure in females.

She did not often have such strong emotions. But she suddenly felt powerless against her passion and the desire to throw herself into the arms of the cousin whom she saw at a family funeral. “It can only be because of that patch,” said Marianne, a participant in a multinational trial of a testosterone patch designed to treat hypoactive sexual desire disorder, in which a woman is devoid of libido. Testosterone, a hormone ordinarily produced by the ovaries, is linked to female sexual function, and the women in this 2005 study had undergone operations to remove their ovaries.

After 12 weeks of the trial, Marianne had felt her sexual desire return. Touching herself unleashed erotic sensations and vivid sexual fantasies. Eventually she could make love to her husband again and experienced an orgasm for the first time in almost three years. But that improvement was not because of testosterone, it turned out. Marianne was among the half of the women who had received a placebo patch—with no testosterone in it at all.
Marianne’s experience underlines the complexity of sexual arousal. Far from being a simple issue of hormones, sexual desire and orgasm are subject to various influences on the brain and nervous system, which controls the sex glands and genitals. And many of those influences are environmental. Recent research, for example, shows that visual stimuli spur sexual stirrings in women, as they do in men. Mari­anne’s desire may have been invigorated by conversations or thoughts about sex she had as a result of taking part in the trial. Such stimuli may help relieve inhibitions or simply whet a person’s appetite for sex.

Achieving orgasm, brain-imaging studies show, involves more than heightened arousal. It requires a release of inhibitions and control in which the brain’s center of vigilance shuts down in males; in females, various areas of the brain involved in controlling thoughts and emotions become silent. The brain’s pleasure centers tend to light up brightly in the brain scans of both sexes, especially in those of males. The reward system creates an incentive to seek more sexual encounters, with clear benefits for the survival of the species. When the drive for sex dissipates, as it did with Marianne, people can reignite the spark with tactics that target the mind.

Sex in Circles

Biologists identified sex hormones such as estrogen and testosterone in the 1920s and 1930s, and the first studies of human sexuality appeared in the 1940s. In 1948 biologist Alfred Kinsey of Indiana University introduced his first report on human sexual practices, Sexual Behavior in the Human Male, which was followed, in 1953, by Sexual Behavior in the Human Female. These highly controversial books opened up a new dialogue about human sexuality. They not only broached topics—such as masturbation, homosexuality and orgasm—that many people considered taboo but also revealed the surprising frequency with which people were coupling and engaging in sexual relations of countless varieties.

Kinsey thus debuted sex as a science, paving the way for others to dig below statistics into the realm of biology. In 1966 gynecologist William Masters and psychologist Virginia Johnson—who originally hailed from Washington University before founding their own research institute in St. Louis—described for the first time the sexual response cycle (how the body responds to sexual stimulation), based on observations of 382 ­women and 312 men undergoing some 10,000 such cycles. The cycle begins with excitation, as blood rushes to the penis in men, and as the clitoris, vulva and vagina enlarge and grow moist in women. Gradually, people reach a plateau, in which they are fully aroused but not yet at orgasm. After reaching orgasm, they enter the resolution phase, in which the tissues return to the preexcitation stage.

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