[Editor's note: On July 1, 2008, Wendy Sternberg began a three-year term as Associate Provost of Haverford College. A member of Haverford's faculty since 1995, Sternberg has served as chair of the psychology department from 2002-2003 and 2004-2008, and was the recipient of the Christian R. and Mary F. Lindback Teaching Award in 2003. She has also been an elected member of Academic Council and the Presidential Search Committee, and is currently the Middle States re-accreditation co-chair.“A model scholar-teacher, and a highly respected and trusted colleague, Wendy brings intelligence, drive, institutional expertise and personal warmth to her new job as Associate Provost,” says Provost Linda Bell.“I am honored that Wendy has accepted my invitation to serve Haverford in this important way.” ]

“Your life is often decided by small moments,” declares Wendy Sternberg, professor of psychology and a foremost authority on pain and the behavioral quirks it inspires.

She should know, as she wouldn't be where she is today if not for one such moment during her undergraduate days at Union College. She was taking a seminar called“Brain and Behavior,” and one of her assignments was to essentially teach the class one day in the form of an hour-and-a-half presentation. (She has resurrected this assignment for her present-day Haverford courses.)

“Pain was not my first choice of topic,” she says.“I wanted to do a presentation on bipolar disorder. But I realized it was the same day as a similar presentation I had to make in another class, so someone switched with me.” 

Ultimately, she came to love her accidental topic.“It's really interesting for psychologists to study,” she says,“and it's not obvious at first why it should be.” For one thing, pain affects just about everyone on the planet, and as people grow older, their pain lasts for longer periods of time due to the onset of age-related conditions such as arthritis and back trouble. Also, says Sternberg, pain can teach researchers things about the brain in ways that are different from every other sensory system.“In no other system is the fact that the sensation is unpleasant, or the hedonic value, part of its definition. Pain is not pain unless it has a negative hedonic quality—it is an unpleasant sensory and emotional experience. In no other sensory modality is the emotional content of the experience part of its defining features.”

One aspect of pain that is often overlooked—especially by those suffering from it—is its necessity to survival. Sternberg points out that people with congenital insensitivity to pain actually live short, injury-filled lives, unable to determine when they've burned an extremity or experienced a burst appendix.“Without pain sensation, you're doomed,” she says.“Pain gives you warnings about what's harmful in your environment.”

After her fortuitous seminar presentation, Sternberg dove into the study of pain, and the depth and breadth of her knowledge made her an attractive applicant in the eyes of many prestigious graduate schools. She chose UCLA, where she had what she describes as a“wonderful” mentor, John Liebeskind, a prominent pain researcher at the birth of the field.“When I started in 1990, this was a much smaller area of study. The American Pain Society was a tiny organization; now it has to change the nature of its annual meeting so it can accommodate everyone.” Liebeskind knew everyone in the field, and introduced them all to Sternberg. She also inherited his research equipment.“A lot of things in my life today,” she says,“flow directly from being in his lab.” She finished her doctorate in 1994 and joined Haverford's faculty in 1995.

One of Sternberg's longest-running research projects since her arrival at Haverford is a National Science Foundation-funded study of how untreated pain at birth can lead to altered pain sensitivity in adults.“There have been other studies showing that exposure to stress early in life alters the adulthood stress response,” she says.“The nature of that alteration depends in part on the nature of the stressor, how prolonged and chronic it is, and whether you're male or female—there are interactions with the hormonal gender system as well.” Sternberg's project works off the hypothesis that early pain, as a stressor, can cause a heightened stress response in adults—and perhaps higher levels of a certain stress hormone—that may result in their reduced sensitivity to all types of pain. 

To test this hypothesis, one of Sternberg's students, Aditya Vora '08, performed abdominal surgery on a group of newborn mice, while observing a“sham” group of mice who underwent the same stressful conditions as the surgical group—separation from mothers, cryoanesthesia (being encompassed in ice)—but didn't undergo the actual surgery. He also included a control group that was not manipulated at all. When the mice reached adulthood, Vora measured their response to induced stress behaviorally and hormonally, and discovered that the surgical group showed a trend towards having enhanced levels of the stress hormone corticosterone. 

“We don't know the mechanism,” says Sternberg,“whether it's a habituation or a change in the opioid (endorphin) system. The expression of pain at any moment in time is not just how much heat is applied at the periphery of the body or the state of the incoming pain signal, but also the state of the brain at the time it receives the signal.”

Gender disparities come into play because the male and female brains show marked differences in stress behavior, both in the hormonal state of the brain and how the brain is able to effectively shut out pain during times of extreme stress. Sternberg found in previous studies that the effects of neonatal stress appear to be greater in females than in males, but these effects could be eliminated by removing the female hormones. Therefore, many aspects of early stress seem to be dependent on hormones.

This isn't the only one of Sternberg's studies to address gender differences in pain sensitivity. In 2002 she explored the effects of competition on pain in a project funded by the National Institutes of Health, in which the Haverford students who served as her subjects (“We pay them,” Sternberg explains,“and there is never enough pain to cause tissue damage”) were assigned to compete against same-sex opponents in a track meet or an auto race video game. Another group completed a non-competitive treadmill run. The students' arms were then submerged in buckets of ice water for 90 seconds after the event, and their reactions were rated every 15 seconds on a scale of zero (no pain) to 20 (intolerable pain).

“Being in a competition activates the same mental state as escaping from a predator,” says Sternberg.“It's a sense of, ‘I can't deal with this right now, I will ignore all pain signals.' It's not a conscious ignoring of pain.”

Results showed that both men and women manifest pain-inhibitory responses to athletic competition, but they differ in what exactly they find stressful about the events.“For men, the stress-induced analgesia at the track meet and with the video games was due to the head-to-head competition,” says Sternberg.“Women also had stress-induced analgesia from the track meet, but the video game didn't do anything for them. We could mimic the effect they got from the track meet by having them run on a treadmill.” 

Sternberg turned her attention from competition to couples during the spring and fall of 2007, collaborating with Assistant Professor of Psychology Benjamin Le and class of '07 students Stephen Selsor and Heather Shafi on a study focusing on the associations among empathy, human social relationships, and pain experiences. It was funded by the Provost's Office Faculty Research Grant, and was presented at the Neuroscience Annual Meeting in November 2007. The project's impetus was a high-profile paper published in 2006 by Sternberg's McGill University colleague Jeff Mogil, revealing that mice's pain sensitivity was heightened when viewing another mouse in pain, but not if the mouse in question was a stranger to them. The strength of the empathy was modulated by the degree of closeness between the animals.

“We wanted to try this with humans,” says Sternberg.“There had been some previous brain imaging studies [by neuroscientist Tania Singer] showing that, when female subjects watched their relationship partner in pain, the female's brain showed activation as if she was in pain. It was a self-other overlap. They had never actually tested the female's pain sensitivity when she was viewing her significant other in pain.”

Sternberg and her collaborators had students in romantic relationships, as well as same-sex friend pairs, view their partners undergoing pain testing while having their own pain tested themselves. The researchers videotaped each partner making a facial expression of pain, and assembled a package of clips to show the other partner. While watching the video, the partners' pain sensitivity and level of empathy were measured; heat stimuli was applied to their forearms, or their arms were dunked in buckets of ice water. Another group of subjects watched strangers undergoing pain testing, and a third group watched a nature video.

The research team anticipated that those who viewed videotapes of their romantic partner or friend in pain would show heightened sensitivity to painful stimuli, as opposed to those who watched a stranger or a nature video. But that's not at all what they saw.

“In fact, we didn't see any change over time, no effect of manipulations,” says Sternberg.“But we went back and looked at the data on the day the subjects viewed the video and had their pain tested, and ran an analysis to see if the subjects who reported empathy also had higher pain sensitivity. And we did find significant correlations between empathetic feelings and pain The more they were empathetic, the more pain they felt.”

To the researchers' surprise, many subjects seemed to be amused at the sight of their partners expressing pain.“It may simply have been a positive emotional state from viewing a significant other, or it could be because, frankly, asking people to make pain faces makes them look a little goofy,” says Sternberg.“Next time we'll try to get a better manipulation.”

This project, like many of Sternberg's studies, gave her students opportunities for hands-on participation in the implementation and analysis of the tests. In the empathy study, both Stephen Selsor and Heather Shafi recruited subjects and administered the pain tests themselves.“Wendy was wonderful to work with,” says Shafi, now serving an internship in the General Surgery Department of Bellvitge University Hospital in Barcelona, Spain.“She was most helpful in showing me how to write a professional scientific report, a skill that will be useful as I continue my academic career.”

Aditya Vora also considers himself lucky to have Sternberg as a teacher and mentor.“She's always ready to help, dedicated to her students, and she goes above and beyond the responsibilities of an adviser.” He also feels fortunate to have been able to design his own study within the context of Sternberg's research on early life pain, and to have experience with sophisticated lab equipment.“It's really taught me discipline,” he says—something that will come in handy for his future as a doctor.

Sternberg's own future may hold a new National Science Foundation grant; she's in the process of applying. She is seeking funding for two new projects: One concentrates on the relationship between neurogenesis (new cell growth in the brain) and pain sensitivity, and the second looks at the effects of a mouse's social environment on its pain expression.“It's about how animals behave when other animals are in their presence,” she says.“I'm interested in how the presence of a mouse ‘observing' alters pain behavior in another mouse, and also how the mouse's behavior changes when a mouse it knows is in pain.”  

Alex Tuttle '08 has been assisting Sternberg with this project since his sophomore year. Initially, they observed that male mice downplayed their behavior and did not express pain readily in the presence of other male mice who were strangers to them; when isolated or with their cage mates, they did not inhibit their pain responses. Most recently, Tuttle investigated the role of testosterone in the pain behavior of male mice by observing the interactions of hormonally intact mice with two groups that had been castrated; one group had testosterone injected back into their systems via capsule, while the second group had an empty capsule put into their systems. The intact mice had been injected with a substance that caused mild abdominal cramping; their way of expressing pain was to stretch out in an effort to relieve discomfort. He and Sternberg found that mice exposed to the testosterone-fueled group expressed less of this pain-related behavior in their company.

Now, they want to replicate these results using female mice.“We want to know, if you introduce testosterone, does it create the same kind of behavior in females as in males?” says Tuttle, whose involvement in Sternberg's research earned him a Beckman scholarship last year.

Tuttle, who in August will begin conducting diabetes research at the Children's Hospital of Philadelphia, is thrilled to have explored a topic that intrigues him with Sternberg as guide.“She has a wonderful teaching style,” he says,“and in the lab she's hands-on, teaching all of the methods herself. It's been a dream to work directly with her, to have individual attention and all my questions answered on a fundamental level.”

Sternberg believes that her research has a great deal of relevance outside of the lab.“Given the real world problems associated with the prevalence of pain as a clinical condition,” she says,“researchers need to understand how the brain produces pain experience, and how subtle environmental (or conversely, constitutional) factors affect one's experience of pain.”

With everything Sternberg has accomplished in the field of pain studies, it still awes her to think how close she was to traveling a completely different path.“I think all the time: What would have happened if I'd done that presentation on bipolar disorder?” she muses.“I wouldn't have known the big theories. I wouldn't have been able to talk to the people at UCLA about pain.”

Never underestimate the life-altering power of small moments.

-Brenna McBride