On April 11, 1944, a doctor named T. C. Erickson addressed the Chicago Neurological Society about a patient he called Mrs. C. W. At age 43 she had started to wake up many nights feeling as if she were having sex—or as she put it to Erickson, feeling “hot all over.” As the years passed her hot spells struck more often, even in the daytime, and began to be followed by seizures that left her unable to speak. Erickson examined Mrs. C. W. when she was 54 and diagnosed her with nymphomania. He prescribed a treatment that was shockingly common at the time: He blasted her ovaries with X-rays.
Despite the X-rays, Mrs. C. W.’s seizures became worse, leaving her motionless and feeling as if an egg yolk were running down her throat. Erickson began to suspect that her sexual feelings were emanating not from her ovaries but from her head. Doctors opened up her skull and discovered a slow-growing tumor pressing against her brain. After the tumor was removed and Mrs. C. W. recovered, the seizures faded. “When asked if she still had any ‘passionate spells,’” Erickson recounted, “she said, ‘No, I haven’t had any; they were terrible things.’”
Mrs. C. W.’s experience was rare but not unique. In 1969 two Florida doctors wrote to the journal Neurology about a patient who experienced similar spells of passion. She would beat both hands on her chest and order her husband to satisfy her. Usually the woman would come to with no memory of what had just happened, but sometimes she would fall to the floor in a seizure. Her doctors diagnosed her with epilepsy, probably brought on by the damage done to parts of her brain by a case of syphilis. More recently, in 2004, doctors in Taiwan described a woman who complained of orgasms that swept over her when she brushed her teeth. Shame kept her silent for years, until her episodes also caused her to lose consciousness. When the doctors examined her, they diagnosed her with epilepsy as well, caused by a small patch of damaged brain tissue.
Each of these stories contains a small clue about the enigmatic neuroscience of sex. A hundred years ago Sigmund Freud argued that sexual desire was the primary motivating energy in human life. Psychologists and sociologists have since mapped the vast variations in human sexuality. Today pharmaceutical companies make billions bringing new life to old sex organs. But for all the attention that these fields of research have lavished on sex, neuroscientists have lagged far behind. What little they knew came from rare cases such as Mrs. C. W.’s.
The case studies do make a couple of things clear. For starters, they demonstrate that sexual pleasure is not just a simple set of reflexes in the body. After all, epileptic bursts of electricity in the brain alone can trigger everything from desire to ecstasy. The clinical examples also point to the parts of the brain that may be involved in sexual experiences. In 2007 cognitive neuroscientist Stephanie Ortigue of Syracuse University and psychiatrist Francesco Bianchi-Demicheli of the Geneva University Psychiatric Center reviewed the case of Mrs. C. W. and 19 other instances of spontaneous orgasms. In 80 percent of them, doctors pinpointed epilepsy in the temporal lobe.
The temporal lobe is still a big piece of real estate, though. To zoom in on the regions associated with sexuality, neuroscientists needed to scan people’s brains while they were having sex-related thoughts. But using brain scans to study sex is not easy. Most brain imaging technology works the way cameras did in the 19th century: If you want a clear picture, you have to hold very still. Even then, brain scans provide meaningful information only in carefully designed experiments. If you want to find the parts of the brain that are crucial for reading, for instance, you can’t just take pictures of people’s brains as they read; the visual cortex carries out many functions other than reading. Scientists therefore have to craft experiments that allow them to compare what happens to brains during reading with what happens when people look at random strings of letters or checkerboard patterns. The same precision is required to study sex in the brain.
As a result, the first imaging studies of sex in the brain have appeared only in the past few years. Serge Stoléru, a neuroscientist at Pierre and Marie Curie University in France, published one on sexual desire in 2003. He and his colleagues showed a series of pictures and films—some erotic, some ordinary—to 15 men. To record the activity in the subjects’ brains, the scientists used PET scans: They injected radioactive tracers into the volunteers and then tracked how the tracers moved in the brain. The radioactive signal accumulated in areas where neurons became active, as their energy was replenished by the surrounding blood vessels.
Eight of the men were ordinary, sexually speaking. The other seven suffered from hypoactive sexual desire disorder. People with this condition rarely experience sexual desires or fantasies. Stoléru and his colleagues found clear-cut differences between the two groups. In particular, a patch of neurons near the front of the brain—a region called the medial orbitofrontal cortex—was active in the desire-impaired men but quiet in the normal ones. Among its jobs, the medial orbitofrontal cortex keeps our emotions from getting out of control. Perhaps men with hypoactive sexual desire disorder couldn’t feel desire because their brains were keeping their emotions bottled up.