By Lee Anna Sherman
You don’t think of voles as paragons of virtue. Yet one species of these drab mouse-like creatures is loyal to its mate for life, helps around the den, cuddles its young, and generally exhibits what humans would call “family values.” Meet the true-blue prairie vole.
Its cousin the meadow vole, however, is a cad. Despite being 99 percent genetically identical to the prairie vole, the meadow vole is profligate in its ways — sleeping around, shirking nest-building and abrogating pup-rearing.
It’s not moral rectitude that makes the difference in voles’ domestic behavior but rather a couple of compounds called oxytocin and vasopressin. Doubling as hormones and neurotransmitters, these neurochemicals are major players in how animals, including humans, relate to each other both romantically and socially. They may even help to explain worldview differences among liberals and conservatives.
Scientists think that animals like the prairie vole, whose cerebral reward centers have evolved to associate vasopressin with pleasure, get more positive reinforcement for pair bonding and therefore seek it out. But exactly how these hormones function in the body and the brain is still largely unknown. Teasing out oxytocin’s and vasopressin’s precise mechanisms drives Rodrigues’ research as an assistant professor in the Department of Psychology.
“Oxytocin,” says OSU neuropsychologist Sarina Rodrigues, “is just such a marvelous, amazing and elegant hormone. It’s related to generosity, trust, empathy, mating, pair bonding, parenting. It facilitates social behaviors.”
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This “elegant hormone” influences stress as well as love, not only strengthening pair bonds and social attachments, but soothing the mind and calming the body when faced with difficult or dangerous situations. Thus, along with the related compounds serotonin, vasopressin and dopamine, it has earned the designation “neuromodulator” — basically, a social lubricant and a brake on stress reactions.
“It dampens how much stress hormone our body releases,” Rodrigues explains. “It curbs our brain’s response to emotional stimuli and even how much our heart freaks out during stress.”
Inspired by her Ph.D. adviser at New York University, Joseph LeDoux, author of The Emotional Brain and the Synaptic Self, Oregon-born Rodrigues started her career dissecting both human and animal brains to map emotions at their source, in a part of the brain known as the amygdala. As a postdoctoral scholar at Columbia University, she studied the brains of psychiatric patients, looking for biochemical clues to mental illness. From there, she headed to Stanford to work with Robert Sapolsky, who discovered that brain cells shrink and die under severe stress. Before joining the faculty at OSU, Rodrigues did yet another postdoc, this time at Berkeley’s Greater Good Science Center, a move she laughingly describes as reflecting her “hippy-dippy” idealism. “Berkeley was my bridge from neuroscience to social psychology,” she says.
Although she sees herself as a “geek” at heart (“I love microscopes and pipettes and test tubes and all that sort of stuff”), she has veered from the merely molecular to the more broadly social. Whether seeking the physical loci of emotions in gray matter or exploring chemical responses to stress, she hopes her neurological knowledge will ultimately benefit the human condition.
“How can we use this information to make people’s lives better?” she wonders. “If we can better understand how people process emotions, we can create tools for dealing with feelings more effectively.”
The Mind’s Eye
Rodrigues’ most recent study, published in the November 2009 Proceedings of the National Academy of Sciences, has broken new ground in the field for a couple of reasons. One, it’s the first simultaneous investigation of empathy and stress on a hormonal level. And two, it’s the first to link a specific gene to both empathy and stress reactivity. “This was the first study that really looked at how one gene can affect our social behavior and our stress reactivity in tandem,” Rodrigues says.
If you think of oxytocin molecules as boats floating through the human body, you can think of oxytocin receptors as the docks where the boats tie up. Rodrigues calls these docks “targets.”
“Oxytocin has targets all over our body and brain,” she says. The heart and the spinal cord, even the uterus, have oxytocin docks. It’s not surprising, then, that the hormone affects such maternal functions as uterine contractions and breastfeeding.
Genetic variations in these receptors affect how people respond to hormonal signals from the brain. In her two-pronged experiment, Rodrigues tested the DNA of 200 college students grouped by genotype. Group A had a genetic variation associated with low levels of empathy and social affiliation (emotional bonds with others) and high levels of stress reactivity (jumpiness). Group B, in contrast, had genes associated with strong empathy and low stress reactivity. Each student was then tested for empathy by measuring his or her score on an instrument called “Reading the Mind in the Eyes Test,” which asks subjects to guess which emotion (such as “hateful, jealous, arrogant or panicked” for one image and “playful, irritated, comforting or bored” for another) is revealed in a photograph of a pair of human eyes. Stress reactivity was gauged by measuring the students’ heart rates after unexpected bursts of noise in a headphone.
The findings were strong and clear: Students in Group A were nearly 25 percent more likely to make an error on the facial expression test, and were also more jumpy on the stress test.
“It does seem that we are biologically hardwired,” Rodrigues says. “We do have a lot of inborn tendencies.”
She cautions, however, that our destinies aren’t ordained by biology. “We are this huge slurry of both nature and nurture, of genes and upbringing and experience,” she says. “It’s our social connections that really chart which trajectory we will go down.”
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In general, people high on the autism scale don’t do particularly well on tasks where they are asked to read other people’s emotions.
Rodrigues’ discovery adds to the growing scientific understanding of why some people are more tuned in to the feelings and needs of others. It even bolsters a growing body of literature pointing to oxytocin receptors as possible culprits in autism, which has been associated with the same low-empathy, high-stress variation in Rodrigues’ Group A.
“You can’t change your genes,” Rodrigues points out. “But you can change how genes are expressed.” Extreme loneliness, for example, can weaken genetic defenses against germs. She likens our genetic inheritance to a bottle. Its shape and composition are set. But by capping or uncapping it, by replacing a twist top with a cork, a glass stopper with a funnel, the bottle can be opened or closed, made more receptive or less receptive to new input, turned on or turned off.
For young Sarina Rodrigues, it all started with a mystery experiment in her Portland high school chemistry class. “We had no idea what we were making,” she recalls. The blending of sucrose crystals, 3M glucose, protein pellets, solidified mixed esters, 4-hydroxy-3-methoxybenzaldehyde, sodium chloride, sodium bicarbonate and water yielded something a teenager could appreciate: peanut brittle. An apprenticeship at a neuroscience lab arranged by the same St. Mary’s Academy chemistry teacher set her on her current path.
She recently got a shock after testing her own DNA. To her astonishment, she found that she was born with a genetic predisposition for low empathy, high stress reactivity.
“At first I wanted to keep it a secret,” she confesses. “I like to think that I’m a very caring person with empathy for others. But In fact, 75 percent of the people in our study were in the low-empathic, high stress-reactive group. The uber-gooey, lovey-dovey, very empathic, low stress-reactive people were a really small proportion of our sample. Many of us have to really work at forming social bonds and not freaking out.”
To support research in the OSU College of Liberal Arts, contact the OSU Foundation, 800-354-7281.
CATEGORIES: Healthy People