An orgasm has now been imaged in 3D video in the brain as it happens — and for possibly the first time in the history of science, women came first.
The video, which was presented at the recent Society for Neuroscience conference in Washington, D.C., is the first to look at the exact order in which women’s brain regions are activated in the progression that culminates in sexual climax. The findings have not yet been peer reviewed for publication.
While this may seem like a silly line of research, in fact, understanding how the brain experiences the most pleasurable sensations may be essential for figuring out what underlies conditions in which desire and motivation go awry, like addiction and depression.
Lead author Barry Komisaruk, professor of psychology at Rutgers University, imaged brain activity in several women who were able to masturbate to orgasm in the decidedly unsexy atmosphere of a functional MRI machine. (Orgasm was achieved by either manual stimulation or use of a “passive dildo” in the form of a Lucite rod; vibrators contain metal, which cannot be placed in magnetic scanners.)
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Komisaruk discovered activity in more than 80 regions of the brain, including the prefrontal cortex, which is involved in higher-order thinking, and which earlier imaging of the female orgasm by Dutch researchers had found to be inactive. “There’s an apparent contradiction in the literature,” says Komisaruk. “The group in Holland says that the frontal cortex goes down in activity during orgasm and we see that it goes up.”
That could be due to differences in scanning technique, Komisaruk says. Or, a more interesting reason may involve the fact that in the Dutch study, sexual stimulation was applied by the women’s partners, rather than themselves. “It could be different [because] women inducing orgasm in themselves may involve executive control characteristic of the prefrontal cortex, whereas in partner-induced stimulation, women may surrender to their partner and that could be the basis for the reduction in activity,” he explains.
The sequence of brain activity itself is telling. First, not surprisingly, activation is seen in the sensory regions of the brain that map the genitals. Earlier research by Komisaruk’s group showed that nipple stimulation also excites this sensory region, helping explain why it can be erotic.
Next, a region called the insula lights up. “Not only is [the insula] active during orgasm, it’s also active in response to pain,” says Komisaruk, explaining that brain imaging is difficult to interpret because “activation” can mean different things in different brain cells. If inhibitory neurons are active, this actually reduces the signaling of other neurons — and could mean something is being prevented rather than processed. “We see strong inhibitory interaction between orgasm and pain,” he says. “During orgasm, women are much less sensitive to pain.”
Komisaruk notes that facial expressions during orgasm (the “O face”) are often indistinguishable from those made in pain, and suggests this may be explained by activity in the insula.
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Next, the anterior cingulate, an area related to the insula, lights up before the action moves to the amygdala. Although it is best known for processing fear-related information, the amygdala is actually involved in all types of emotion — and may provide some of the intense positive emotion typically experienced during orgasm.
Activity is seen next in the hippocampus, which processes memories and may be involved either in sexual fantasy or in recording the experience or both. The hippocampus is also able to activate many brain regions at once, which may underlie its role in both orgasm and seizure. “The hippocampus is often involved in epileptic seizure activity,” says Komisaruk. “There’s a lot of similarity between seizures and orgasms in the sense that they involve many brain regions concurrently.”
After the hippocampus, Komisaruk saw activity in the prefrontal cortex, the region involved in planning, abstract thought and behavior control. He’s currently doing a study comparing partner-induced and self-stimulated orgasm to see if he can resolve the question of why some studies show activation here and others don’t.
Following the cortex, activation flowed through a region involved in movement and muscle tension, which occurs during orgasm. Next, the hypothalamus came online. This region releases oxytocin, the notorious “love hormone” involved in social and emotional bonding and connection.
Finally, it’s on to the brain’s “pleasure center,” for the peak experience of orgasm, which likely involves release of dopamine in the highly activated nucleus accumbens.
And then, the brain goes quiet.
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Maia Szalavitz is a health writer at TIME.com. Find her on Twitter at @maiasz. You can also continue the discussion on TIME Healthland’s Facebook page and on Twitter at @TIMEHealthland.