Iggy Pop, the rat nucleus accumbens, and your excellent sex life

You guys, chapter 3 is my nemesis.

Chapter 3 is about the role of context in sexual desire and arousal, and it requires an awful lot of stuff about stress, attachment, and the mesolimbic cortex.

I’m trying to write it so that it’s interesting in itself and also obviously relevant to Your Sex Life, and there’s this one study in particular that I just find SO IMPORTANT and also it made me laugh out loud. But I can’t tell if I’m making it clear.

So here, can you read it and tell me what you think?

Think of the rat nucleus accumbens (NAc) as a tiny, misshapen jellybean deep within the brain, whose job is to tell the rat which direction to go – toward or away from things in the environment. When you stimulate the front-and-top half of the NAc – the rostral region, in medical-speak – the rat engages in “approach” behaviors, exploring, curious, attracted to things in the environment. Relationship researcher John Gottman calls these “What’s this?” behaviors in infants. Curious. Exploring. Moving toward. And when you stimulate the back-and-bottom half – the caudal region – the rat exhibits “avoidance” behaviors, stressed, wanting to escape. Gottman calls these “What the hell is that?!” behaviors. Fearful. Avoidant. Moving away.

So let’s do an experiment. Imagine that you’re a lab rat, and you’re in a three-chambered room. In the first chamber, you find just the ordinary set up that you always encounter in the lab – the lights are on, but it’s fairly quiet. In this chamber, your NAc is doing what we’ve already described: if the researcher zaps the rostral part, you engage in approach, “What’s this?” type behaviors. And if the researcher zaps the caudal part, you engage in “What the hell is that!?” behaviors.

Now you go into the next chamber, and the lights turn off, it’s quiet and calm, and it smells like home. So you explore for a while and it feels really nice. You love it here, it’s like a spa for rats. In this place, when the researcher zaps your rostral NAc, the same thing happens – approach behaviors. But this is where it gets crazy: when the researcher zaps your caudal NAc… approach behaviors! In a safe, relaxing environment, almost the entire NAc changes to approach motivation!

But there’s more! Eventually you move into the third chamber and as soon as you do, ultra-bright lights turn on and suddenly Iggy Pop is blaring – “Lust for Life” is playing at randomly varying volumes, so you can’t even get used to it. Everything about this environment stresses you out. And when the researchers zap your rostral NAc, it doesn’t activate curiosity or “approach” behaviors, as it has in every other environment; no, the new, stressful environment causes the NAc to switch, so that now zapping almost anywhere on the NAc generates avoidance, the “What the hell is that?” behavior.

Remember how I keep saying that perception of sensation is context dependent? Here it is. The functioning of a specific brain region within the eagerness system actually switches what it’s eager for, when the context is different! In a safe, comfortable environment, it hardly matters where you stimulate; you’ll activate approach, curiosity, desire. And in a stressful, dangerous environment, it hardly matters where you stimulate; you’ll activate avoidance, anxiousness, dread.

There’s mounting evidence that in a variety of ways, in both rats and humans, context changes how the midbrain responds to stimuli – human brain imaging studies have found that the presence of alternative incentives can influence how responsive NAc is to a target incentive, and that the NAc’s of people with chronic back pain respond differently to “noxious thermal stimulation” (i.e., burning) compared with people who don’t live with pain; the NAc even appears to be important in placebo studies – remember the placebo effect from Chapter 2? 40% of folks taking a sugar pill that they are told will increase their interest in sex, do indeed experience more interest in sex? I wonder what’s happening to their nucleus accumbens.

So when I say, “perception of sensation is context dependent,” I don’t just mean candles, corsets, and a locked bedroom door. I mean that very old parts of your brain can respond in opposite ways, approach or avoidance, depending on the circumstances in which they are functioning. I mean that when you’re in a great, sexually relevant context almost everything can activate your “What’s this?” desirous approach to sex. And when you’re in a not-so-great context, it doesn’t matter how sexy your partner is, how much you love them, or how fancy your underwear is, almost nothing will activate that curious, appreciative, desirous experience.

Remember the tickling scenario: when you’re feeling flirty and your special someone tickles you, your emotional brain is primed and ready to feel good about that sensation; and when you’re pissed off and your special someone tickles you, your brain is all set to tell that special someone to stick it in their ear.

Context. It’s made of SCIENCE.