The first brain scans of men and women having sex and reaching orgasm have revealed striking differences in the way each experiences sexual pleasure. While male brains focus heavily on the physical stimulation involved in sexual contact, this is just one part of a much more complex picture for women, scientists in the Netherlands have found.

The key to female arousal seems rather to be deep relaxation and a lack of anxiety, with direct sensory input from the genitals playing a less critical role.

The scans show that during sexual activity, the parts of the female brain responsible for processing fear, anxiety and emotion start to relax and reduce in activity. This reaches a peak at orgasm, when the female brain’s emotion centres are effectively closed down to produce an almost trance-like state.

The male brain was harder to study during orgasm, because of its shorter duration in men, but the scans nonetheless revealed important differences. Emotion centres were deactivated, though apparently less intensely than in women, and men also appear to concentrate more on the sensations transmitted from the genitals to the brain.

This suggests that for men, the physical aspects of sex play a much more significant part in arousal than they do for women, for whom ambience, mood and relaxation are at least as important.

"Men find it more important to be stimulated on the penis than women find it to be stimulated on the clitoris," Gert Holstege of the University of Groningen told the European Society of Human Reproduction and Embryology conference in Copenhagen today. "We know from these images that each sex experiences stimulation differently."

The experiments also revealed a rather surprising effect: both men and women found it easier to have an orgasm when they kept their socks on. Draughts in the scanning room left couples complaining of "literally cold feet", and providing a pair of socks allowed 80 per cent rather than 50 per cent to reach a climax while their brains were scanned.

The scans also show that while women may be able to fool their partners with a fake orgasm, the difference is obvious in the brain. Parts of the brain that handle conscious movement light up during fake orgasms but not during real ones, while emotion centres close down during the real thing but never when a woman is pretending.

In the study, a team at the University of Groningen led by Gert Holstege scanned the brains of 13 women and 11 men using a technique called positron emission tomography (PET), while they manually stimulated to orgasm by their partners. All were heterosexual and right-handed, the latter to ensure that all their brains could be easily compared.

The subjects’ heads were restrained in the PET scanner during the procedure, as it only works if the body area being scanned remains still. The dimensions of the scanner and the need for stillness also explain why the researchers were unable to study intercourse itself.

In both sexes, activity in the amygdala, which processes fear and anxiety, was reduced during stimulation. Women, but not men, showed lower activity in the hippocampus, important for memory, as well.

In men, greater activity was seen in the insula, which deals with emotion, and particularly in the secondary somatosensory cortex, which rates the significance of physical sensations. This suggests that the sensory input coming from the genitals is being judged highly important and pleasurable by the brain.

Women, however, show very little increased brain activity, and only in the primary somatosensory cortex - which registers purely that a sensation in the genitals is there."In women the primary feeling is there, but not the marker that this is seen as a big deal," Dr Holstege said."For males, touch itself is all-important. For females, it is not so important."

As orgasm lasts much longer in women than in men, it is easier to study using PET - male ejaculation is over so quickly it is hard to get a reliable reading. The scans showed that in the female orgasm, activity is reduced across all the brain regions - conscious and subconscious - that handle emotion, including the amygdale, medial prefrontal cortex and orbitofrontal cortex.

"What this means is that deactivation, letting go of all fear and anxiety, might be the most important thing, even necessary, to have an orgasm," Dr Holstege said.

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