Lose your sense of smell, lose your sex drive?

Posted in news by jenapincott on May 25, 2009

22445 When it comes to human pheromones, there are naysayers. And although there are fewer naysayers now than ever before, they’ve long used one tricky argument to deny the existence of human pheromones. There’s no vomeronasal organ (VNO) in homo sapiens, they say. What good are pheromones without a VNO?

The VNO, a bulb buried deep in the nasal cavity, is rich with neuronal receptors that detect chemical signals from others of the same species. It processes those signals which, in turn, stimulate the hypothalamus which triggers the production of sex hormones. Other animals use their VNOs all the time. When a female pig or dog assumes the butt-up bow-backed mating stance, it’s because her VNO had responded to pheromones from a male. People have vestiges of a VNO, but there’s no evidence that it still works. Many studies suggest our VNOs start to form during fetal development but regress and become non-functional by the time we’re born.

The naysayers say we lost our VNOs when we lost our need for pheromones. We’re not animals, they say. We don’t need to sniff out our mates.

But how do you explain the abundant evidence that we still use pheromones when dating and mating (as I detail in BLONDES)?

It turns out that we may have lost our VNOS, but not our noses. That is, we don’t need a VNO anymore because we process pheromones through our regular olfactory channels. We inhale them just as we inhale any other smell. They hit the brain in the same way they would if we still had a VNO.

There’s fresh proof of this in a new study. Neuroscientist Ivanka Savic and her team at the Karolinska Institute in Sweden recruited volunteers to smell known pheromones ( estrogen-related compounds). The volunteers were unusual in the one thing they had in common: they were all straight men who had lost their sense of smell (amnosia) due to nasal polyps. Their olfactory channels were dysfunctional.

Savic and her colleagues knew from their previous experiments that the areas of the brain involved in mating are activated when people smell pheromones. (Their studies are fascinating; they help answer questions in the book such as “Can you tell people’s sexual orientation by their smell?”) When straight guys smell estrogen-related compounds, researchers normally see the hypothalamus normally light up on a fMRI scan. The hypothalamus triggers the release of sex hormones. But does the hypothalamus get stimulated when people lose their ability to smell?

The answer is no. None of the amnosiac men in Savic’s study could process the estrogenic pheromones the way other straight men do. Their brains showed none of the usual activity. The hypothalamus was silent.

This is important. It suggests that, yes, we do appear to process pheromones through the main olfactory system. It’s good news because it implies that we don’t need a VNO to get a pheromonal punch. But we do need to smell. (An interesting study would compare the sex lives of amnosiacs with others.)

The bad news is that it’s possible that if you lose your sense of smell…lust may lose its luster.

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