TEDYouth is in its second year of putting together an afternoon of short talks for high school students. I’ll be joining in with a quick introduction to my favorite parasite. The event, which takes place in New York City, will be live-streamed–visit this page for more information for viewing. It will run from 1 pm to 6 pm ET. I’m scheduled to talk at 2:45.
In May I wrote in Discover about a major experiment in neuroscience. Ahmad Hariri, a neuroscientist at Duke, is gathering lots of data from hundreds of college students–everything from genetic markers to psychological profiles to fMRI scans. He hopes that the Duke Neurogenetics Study, as he’s dubbed it, will reveal some of the ways in which the variations in our genes influence our brain circuitry and, ultimately, our personality and behavior.
Hariri plans to collect data from over 1000 people, but he and his colleagues are already starting to analyze the hundreds of students they’ve already examined to look for emerging patterns. In the open-access journal Biology of Mood and Anxiety Disorders, they’ve just published some of their first results. While the results are, of course, preliminary, they do offer an interesting look at the future of neuroscience. Rather than pointing to some particular gene or brain region to explain some feature of human behavior, neuroscientists are learning how to find patterns that emerge from several factors working together.
For their new study, Hariri and his colleagues looked in particular at problem drinking. They hoped to find factors that predicted whether students would start imbibing worrisome amounts of alcohol. Other scientists have previously found evidence that a stressful event–the death of a parent, failing a class, and such–sometimes leads students to hit the bottle. But plenty of students endure these hardships and don’t end up getting drunk so often. Hariri and his colleagues suspected that the difference might have to do with how our brains respond to both stress and alcohol.
When they sifted through their data from 200 students, they found two factors helped predict whether a student was a problem drinker or not. One was how strongly their brains responded to rewards. Hariri and his colleagues tested this reward response by having students play a guessing game while having their brains scanned. They had to guess the value of a number on a card, and then they saw whether they got it right or not. Success brought a surge of blood to a region of the brain called the ventral striatum–a region that responds to many pleasures. Recovering alcoholics who see a picture of a bottle will experience a surge in the ventral striatum, for example. The surge was stronger in some students than others. Students who had a stronger surge in the ventral striatum had higher levels of problem drinking in the wake of stressful events.
But that wasn’t the whole story, Hariri found. There was one more requirement. In another test, he and his colleagues tested how people’s brains responded to fearful images–pictures of scared faces, for example. Such sights usually trigger a surge of activity in a region called the amygdala. And some people have a stronger response there than others to the same picture. Hariri found that people with a strong reward response started drinking after a stressful event if they also had a weak response from the amygdala to fearful images.
The suffering that comes from losing a job or being assaulted can lead people to seek solace through alcohol. Hariri’s research suggests that the stronger a reward a person experiences from a drug like alcohol, the more they’ll drink. But that’s not the case if a high-reward person also has a high fear response in the amygdala. A person with a strong amygdala response may feel anxiety about the dangers of getting too drunk and back away from problem drinking. If people don’t sense the threat so keenly, however, then they may have nothing standing in the way of taking in too much alcohol. The scientists found this three-way interaction between stress, reward, and threat when they looked at students who were problem drinkers at the time of the study, and they also found it when they followed up three months later and discovered some of their students had developed a new drinking problem.
As with any study like this, we’ll have to wait and see if it gets supported by replicated studies. Hariri himself will be able to run that sort of study when he has collected more data from other students. If it holds up, scientists may eventually be able to find gene variants that are associated with the high-reward low-threat brain. Some studies even have suggested that a single variant can produce both changes. Perhaps a report from a DNA-sequencing company might include a list of the variants that make some people more prone to drink in stressful situations. On the other hand, it’s also possible that the problem drinking among the students came first, and led to their experiencing stressful events. Teasing apart all the strands will take some time.
PS: For the data geeks, here’s a figure from the paper. The brain in (A) shows the reward-related activity in the ventral striatum. B shows the amygdala’s response to fear. The graphs show how likely people are to experience problem drinking after a stressful event. The left graph shows the response from people with a low reward response from the ventral striatum, and the graph to the right shows high-responders. In each graph, the scientists break out the high amygdala response (green line) and low (blue). The one line that stands out belongs to the high-reward, low-threat subjects.
Our skin is encased in a snug microbial suit, from our scalps to the tips of our toes. Bacteria begin to colonize our skin from the moment we are born, and they continue to coat us throughout life. They do us many favors. They moisturize our skin to keep it supple; they unleash anti-microbial toxins to ward off pathogens that might make us ill. Scientists know that our skin is home to many species, but they can’t yet say exactly how many–or why some species are found more often on the elbow than on the chin.
Two years ago at a conference in North Carolina, I ran into Rob Dunn, a biologist who was conducting a survey of this menagerie. He was interested in the life found in one particular spot on the human body: the belly button. At the conference, he was handing out Q-tips people could use to swab their navels, which he and his colleagues could then study to tally up the species dwelling there.
Five months later, Dunn sent me a preliminary report: “You, my friend, are a wonderland.” I was the proud host of 53 different types of bacteria, including some decidedly weird creatures, such as a microbe only known from the ocean, and another from the soils of Japan.
I was only one of many human hosts to offer up our navel’s residents to Dunn’s scrutiny. Today, Dunn and his colleagues published a scientific paper on the biological diversity found in 60 bellybuttons in the journal PLOS One. They show that the diversity of my navel was not freakish. Even in a tiny divot of human flesh, dozens or even hundreds of species of bacteria can coexist. All told, Dunn and his colleagues identified 2368 different species living in our 60 belly buttons. The average person had 67 species, with the number ranging from a low of 29 species to a swarming high of 107.
Out of those 2368 species, the majority–1458–are new to science. A few of them are very common, while most are exquisitely rare. Dunn and his colleagues found that eight types of bacteria made up nearly half the microbes the scientists detected. Each of them was present on over seventy percent of us. But the vast majority of the species–2188 all told–lived on six or fewer people. Most were found only on a single individual.
It’s possible that the rare microbes are only visitors, dropping by for a short stay in our navels before dying out or traveling on. The most common species the scientists found may have long-term leases, having evolved adaptation that help them thrive in the bellybutton’s distinctive habitat. Dunn and his colleagues found that these abundant species were also closely related to each other compared to the rarer ones. It’s a pattern similar to the one found in rain forests, were only a few lineages of trees dominate, with many species only contributing a few trees. Your belly button, in other words, really is a jungle.
For more information, read Dunn’s account of the study.
P.S. I refer to these bacteria as belonging to “species.” It’s a convenient term but, when it comes to bacteria, not a precise one. Feel free to mentally substitute “operational taxonomic unit” or “phylotype.”
Evolution: Making Sense of Life, the textbook Doug Emlen and I have just published, is now evolving into a full-blown app for the iPad. Once you get the free app, you can download some of the book’s chapters. We’ve now got the first eight chapters in the iTunes store. Chapters 1 (the introduction) and Chapter 8 (natural selection in the wild) are available for free. Chapters 2-7 can be purchased individually for between $4.99 and $9.99. The full book will be available December 1st, 2012; all 18 chapters will be priced at $80.
I recently gave a talk in San Francisco about the future of viruses, based in part on my book, A Planet of Viruses. I talk about how deadly new outbreaks may emerge, how we may harness viruses for technology and medicine, and just how many viruses there are out there (hint: 10000000000000000000000000000000).
Download the Universe, the science ebook review I started up with some colleagues nine months ago, continues to grow. Here’s the latest batch of reviews:
The Most Ingenious Book: How to Rediscover Micrographia My survey of the digital experiences of Robert Hooke’s 1665 masterpiece.
NASA’s 30 years of Shuttle Missions Is Both Dull and Compelling John Timmer explores NASA’s online history
The Long Quest to Catch a Poisoner Deborah Blum finds the science in a true-crime thriller.
A Medieval Bestiary: When a Book Breaks Your Heart Maggie Koerth-Baker has great hopes for an ebook from the British Library. Hopes are dashed.
Did You Like My Ebook? Don’t Lie! Maia Szalavitz reviews Sam Harris’s ebook on lying.
The Beautiful Planet Meets The Immortal Cassini I take a look at an elegant collection of NASA’s images of Saturn.
Death and Other Options: How To Think (Hopefully!) About Global Health Tom Levenson reviews a TED book on the medical future of our species
Deep Water: A Pretty Good TED Ebook (Really!) About Climate Change John Dupuis considers the strengths and weaknesses of an ebook on climate change.
Interplanetary Cuisine What do people eat in space? Veronique Greenwood tucks in.
The Science of Sports: An eBook Goes for the Gold, Gets A Bronze Jaime Green reviews an ebook from Scientific American on the Olympics. (Remember the Olympics? That creepy giant baby on opening night? Remember?)