Med thumb spring breakers

Science is slut-shaming you.

Well, not yet. But some day soon, brain scans may be able to help pinpoint those among us who are prone to sleeping around.

Neuroscientists from Duke University are using fMRI (functional Magnetic Resonance Imaging) to investigate the interconnected neural, genetic and environmental roots of teens who run in the fast crowd. In one slutty study, they found a link between distinct patterns of brain activity and high levels of bedroom activity in college students.

Thanks to modern medicine, we (well, the we with enough health-care access and money) live in an era in which predictive medical tests and genomic data-dives make it possible to learn about a grab-bag of health issues for which we’re at risk. The well-known Brca test, for example, looks for a gene mutation that signifies a predisposition to rare, inheritable cancer. People who may be at risk for Alzheimer's can take two early-diagnosis tests, one of which is a quick lipid analysis with a high rate of false positives. (Here’s an excellent explanation of the Alzheimer’s’ screening tests.)

In some cases, getting ahead of the problem is, without question, a responsible and reasonable decision. In other cases, the value of predictive tests is up for debate. We haven’t quite determined when it’s more beneficial than burdensome to treat our bodies like research projects.

We can measure activity in specific neural regions to identify people who are predisposed to risky behavior.

The value of medical forecasting is perhaps even less clear when it comes to the idea of using brain scans to detect mental disorders and associated behavior. Research in this area, while increasingly popular, is still exploratory. And clearing the scientific fog wouldn’t resolve a host of ethical questions attached to the act of picking out troubled brains.

The basic idea is that we can measure activity in specific neural regions to identify people who are predisposed to risky behavior — which might be both harmful in itself and symptomatic of mental illness.

Peering under the hood of teen and young-adult brains is of particular interest on account of what we’ve learned in the past decade about adolescence as a vital period of brain development. The neurological changes that occur during late teenagehood speak to teenagers’ moodiness and impulsivity — they’re basically wired to act like boneheads. Discovering that all teens take a neural rumspringa has prompted a scientific arms race to make sense of what’s going on inside their cranky craniums.

In said slutty study, published in June in the Journal of Neuroscience, researchers scanned the brains of 70 heterosexual college-aged participants who also divulged the number of sexual partners they’d had over an 11-month period. Co-eds who’d slept with a higher-than-average number of people exhibited similar patterns of brain activity. Interestingly enough, the signature promiscuity patterns were different in men and women.

The first slut-identifying brain region is the amygdala, an ancient structure that functions as a neural stress detector. Basically, amygdala activity flares when we perceive something in the environment as threatening or otherwise stressful.

The other region is the ventral striatum, the brain’s “reward center,” which is packed with receptors for the pleasure-neurotransmitter dopamine. Together, the two areas regulate responses to situations or substances that incite emotion and pleasure. Sex, obviously, covers both categories.

Even without fully understanding sex differences, the study authors see their work as a useful step toward identifying at-risk teens before they actually break bad.

Researchers predicted that teens who engage in risky sex would exhibit a disconnect between activity levels in these two regions. So, they expected good young prudes to have either high activity in both areas or low activity in both areas. Their hypothesis came directly from a previous study on the neural correlates of problem-drinking, in which researchers observed discordant activity in the same brain regions in irresponsible drinkers.

“We reasoned that imbalance between the amygdala and ventral striatum may emerge as many different forms of risky behavior,” lead author Ahmad Hariri told Van Winkle’s via email.

Their prediction for neural promiscuity did bear out — at least, in men. Sex-crazed college men had out-of-sync brains, coursing with high activity in the ventral striatum and low activity in the amygdala. Women with more sexual partners, however, had higher-than-normal activity in both areas, indicating strong neural responses to both reward and threat.

Traditionally, an amped-up amygdala is associated with threat detection. Recent research, however, suggests a less straightforward meaning behind activity in the region than previously believed. For starters, sex seems to matter. Scientists have seen similar amygdala activity correspond to different traits according to biological sex. In this case, researchers can’t yet explain sex-based differences with confidence.

“In women,” said Hariri in a release from Duke University, “amygdala activity might be driving general awareness, arousal, and responsiveness which, when combined with strong reward-related activity in the ventral striatum, leads to a greater number of partners. In contrast, in men, the amygdala signal could be more focused on detecting danger, a study author said.”

No brain structure is an island. This study emphasizes the importance of analyzing regional activity patterns together. Previous research linked ventral striatum activity to risky sex, but this was the first study to incorporate the amygdala too. “A more complete picture develops,” said Hariri, “when we also consider threat-related brain function supported by the amygdala.”

Women with more sexual partners had higher-than-normal activity in the brain’s threat detector and pleasure center.

When regions don’t communicate as they’re supposed to, issues arise. This appears to be the case, for example, in the sleep-deprived brain, in which an untethered amygdala corresponds to emotionally charged junk-food binges. To that end, the Duke team’s next step is looping in a third brain region, the prefrontal cortex, the brain’s managing director, which undergoes a period of rapid-fire development during adolescence.

“A high-functioning prefrontal cortex can calm an overactive amygdala or boost an underactive ventral striatum,” said Hariri. “In other words, the prefrontal cortex is capable of balancing these other brain functions.”

Hariri and his colleagues anticipate that a weak prefrontal cortex would compound risky behavior associated with an amygdala-ventral striatum imbalance.

Even without fully understanding sex differences, the study authors see their work as a useful step toward identifying at-risk teens before they actually break bad. “We hope that differences in brain function (i.e., imbalance between the amygdala and ventral striatum),” Hariri wrote, “are observable before differences in risky behaviors (i.e., having more partners), so that those behaviors may be minimized or prevented."

Thankfully, we’re nowhere near the point where, ahem, concerned parents will be able to drag their tweens to the neurologist for brain scans that augur promiscuity. All things considered, identifying kids with slut potential, while a totally weird concept, seems less stigmatizing than picking out fun-sized psychopaths — which has been done. The future will be freaky.