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Monkeys put a lot of thought into sex

Marmoset monkeys show unexpectedly high levels of  brain activity when they smell sex-related scents, researchers say.
/ Source: Reuters

Some people may joke that men don’t think with their heads when it comes to sex, but a study in monkeys suggests the brain plays a significant role in the decision to mate, researchers reported Wednesday.

Brain scans of tiny marmoset monkeys show a lot of thought goes into choosing mates, the team at the University of Wisconsin-Madison said.

They used functional magnetic resonance imaging, or fMRI, to look at the brain functions of the Brazilian monkeys. Writing in the Journal of Magnetic Resonance Imaging, they said the brains became busy when the monkeys smelled sexy scents.

“We were surprised to observe high levels of neural activity in areas of the brain important for decision-making, as well as in purely sexual arousal areas, in response to olfactory cues,” psychology professor Charles Snowdon said in a statement. “Lighting up far more brightly than we expected were areas associated with decision-making and memory, emotional processing and reward, and cognitive control.”

Like people, common marmosets live in family groups and do not mate freely with one another. They must make careful choices.

Snowdon’s team studied four male marmosets, offering them gland secretion samples from females at or close to ovulation. They also let the monkeys smell samples from females whose ovaries had been removed, and who therefore were not fertile and, presumably, not sexy.

The researchers were surprised to see how much more of the animals’ brain lit up when they smelled the samples from fertile females -- including areas of complex, cognitive reasoning.

“This is the first time anyone has imaged an awake nonhuman primate in response to emotionally arousing stimuli. It is also the first link between external sexual odors and the internal sexual arousal system,” Snowdon said. “This opens up a whole new field of research possibilities.”

He said the marmoset data corresponded surprisingly closely to human fMRI studies.