This month's Scientific American Mind unpacks the neurology of orgasm. It summarizes some very intriguing and also controversial research. For example, brain scans seem to show that orgasms aren't just about heightened arousal but also the silencing of the brain's "center of vigilance" to lose all inhibitions. From Scientific American Mind:

To find out whether orgasm looks similar in the female brain (as it does in the male brain), (University of Groningen neuroscientist Gert) Holstege's team asked the male partners of 12 women to stimulate their partner's clitoris–the site whose excitation most easily leads to orgasm–until she climaxed, again inside a PET scanner. Not surprisingly, the team reported in 2006, clitoral stimulation by itself led to activation in areas of the brain involved in receiving and perceiving sensory signals from that part of the body and in describing a body sensation–for instance, labeling it "sexual."

But when a woman reached orgasm, something unexpected happened: much of her brain went silent. Some of the most muted neurons sat in the left lateral orbitofrontal cortex, which may govern self-control over basic desires such as sex. Decreased activity there, the researchers suggest, might correspond to a release of tension and inhibition. The scientists also saw a dip in excitation in the dorsomedial prefrontal cortex, which has an apparent role in moral reasoning and social judgment–a change that may be tied to a suspension of judgment and reflection.

Brain activity fell in the amygdala, too, suggesting a depression of vigilance similar to that seen in men, who generally showed far less deactivation in their brain during orgasm than their female counterparts did. "Fear and anxiety need to be avoided at all costs if a woman wishes to have an orgasm; we knew that, but now we can see it happening in the depths of the brain," Holstege says. He went so far as to declare at the 2005 meeting of the European Society for Human Reproduction and Development: "At the moment of orgasm, women do not have any emotional feelings."