A group of researchers at the University of Groningen in the Netherlands (where else?) scanned the brains of 13 women and 11 men as they were brought to orgasm by their partners. The resulting brain images were compared to images the subjects' brains while at rest.

Can you imagine writing this research proposal? The subjects will then be brought to climax using a variety of simulating agents, both biological and mechanical...

Oh course the best part is:

There was no mention of whether the results may have been affected by the fact the couples were being watched by a bunch of geeks in white coats while at least one partner had their head connected to a machine that goes bing.

Scientists see women's brains switch off during sex | The Register