Chapter 5. Hormones and the Brain
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By LISA SANDERS, M.D. On Wednesday, we challenged Well readers to solve the case of a middle-aged woman who suddenly began to have episodes of confusion caused by low blood sugars. Her endocrinologist thought she might have an insulinoma, an insulin-producing tumor of the pancreas, but the testing he did seemed to rule out that diagnosis. Nearly 200 of you took on the challenge of trying to figure out what was causing her life-threatening drops in blood sugar level. The correct diagnosis is… Insulinoma The first respondent to make the diagnosis was Karen Unkel of Kinder, La. She is not a doctor but has a longstanding interest in hypoglycemia that allowed her to recognize the disease even in the face of an apparently negative work-up. Well done, Ms. Unkel. An insulinoma is a rare tumor of pancreatic tissue that makes and secretes insulin independently of blood glucose levels. This results in episodes of hypoglycemia that can be quite severe, even life-threatening. The diagnosis is suspected when a patient fulfills what is known as Whipple’s triad: 1) symptoms of hypoglycemia 2) associated with low measured blood sugar and 3) which improve when blood sugar is raised to the normal range. The diagnosis is made when doctors show that the patient is making too much insulin given his or her blood sugar level. Measuring insulin levels is not always accurate because insulin is processed rapidly in the body and because it is difficult to distinguish between insulin made naturally in the pancreas and any insulin that the patient might be injecting. What is measured instead is something known as C-peptide. Insulin is first made as a larger molecule known as proinsulin. When blood sugar rises, an extra bit is shaved off the molecule; that extra bit is C-peptide, and both the resulting insulin and C-peptide are released into the bloodstream. © 2014 The New York Times Company
by Laura Sanders Some brain cells need a jolt of stress to snap to attention. Cells called astroglia help regulate blood flow, provide energy to nearby cells and even influence messages’ movement between nerve cells. Now, scientists report June 18 in Neuron that astroglia can be roused by the stress molecule norepinephrine, an awakening that may help the entire brain jump into action. As mice were forced to walk on a treadmill, an activity that makes them alert, astroglia in several parts of their brains underwent changes in calcium levels, a sign of activity, neuroscientist Dwight Bergles of Johns Hopkins University School of Medicine and colleagues found. Norepinephrine, which acts as a fight-or-flight hormone in the body and a neural messenger in the brain, seemed to cause the cell activity boost. When researchers depleted norepinephrine, treadmill walking no longer activated astroglia. It’s not clear whether astroglia in all parts of the brain heed this wake-up call, nor is it clear whether this activation influences behavior. Norepinephrine might help shift brain cells, both neurons and astroglia, into a state of heightened vigilance, the authors write. © Society for Science & the Public 2000 - 2013.
Virginia Morell If we humans inhale oxytocin, the so-called “love hormone,” we become more trusting, cooperative, and generous. Scientists have shown that it’s the key chemical in the formation of bonds between many mammalian species and their offspring. But does oxytocin play the same role in social relationships that aren’t about reproduction? To find out, scientists in Japan sprayed either oxytocin or a saline spray into the nostrils of 16 pet dogs, all more than 1 year old. The canines then joined their owners, who were seated in another room and didn’t know which treatment their pooch had received. The owners were instructed to ignore any social response from their dogs. But those Fidos that inhaled the oxytocin made it tough for their masters not to break the rule. A statistical analysis showed the canines were more likely to sniff, lick, and paw at their people than were those given the saline solution. The amount of time that the oxytocin-enhanced dogs spent close to their owners, staring at their eyes, was also markedly higher, the scientists report online today in the Proceedings of the National Academy of Sciences. Getting a whiff of oxytocin also made the dogs friendlier toward their dog pals as determined by the amount of time they spent in close proximity to their buddies. The study supports the idea, the scientists say, that oxytocin isn’t just produced in mammals during reproductive events. It’s also key to forming and maintaining close social relationships—even when those are with unrelated individuals or different species. © 2014 American Association for the Advancement of Science.
Keyword: Hormones & Behavior
Link ID: 19716 - Posted: 06.10.2014
By NICHOLAS BAKALAR The hormone estrogen is the recommended treatment for menopausal night sweats and hot flashes, but some women are unable or unwilling to use it. Now a clinical trial suggests that the antidepressant venlafaxine, often used as an alternative, is equally effective. In an eight-week placebo-controlled double-blind study, researchers randomly assigned 339 perimenopausal and postmenopausal women to one of three treatments: 0.5 milligrams a day of estrogen (in the form of estradiol), 75 milligrams a day of the antidepressant venlafaxine (a generic form of Effexor), or a placebo. Before the start of the study, all the women had had symptoms at least 14 times a week. Compared to the rate before the study — an average of 8.1 episodes a day — the frequency of hot flashes and night sweats declined by 52.9 percent in the estradiol group, 47.6 percent in the Effexor group, and 28.6 percent among those who took a placebo. Both Effexor and estradiol were effective treatments, but the study, published online in JAMA Internal Medicine, was not large enough to show that one was significantly better than the other. “Women have important choices of different medications to discuss with their doctors,” said the lead author, Dr. Hadine Joffe, an associate professor of psychiatry at Harvard. “They should know, as they think about these options, that both are effective.” © 2014 The New York Times Company
Keyword: Hormones & Behavior
Link ID: 19673 - Posted: 05.31.2014
Lida Katsimpardi Could the elixir of youth be as simple as a protein found in young blood? In recent years, researchers studying mice found that giving old animals blood from young ones can reverse some signs of aging, and last year one team identified a growth factor in the blood that they think is partly responsible for the anti-aging effect on a specific tissue--the heart. Now that group has shown this same factor can also rejuvenate muscle and the brain. "This is the first demonstration of a rejuvenation factor" that is naturally produced, declines with age, and reverses aging in multiple tissues, says Harvard stem cell researcher Amy Wagers, who led efforts to isolate and study the protein. Independently, another team has found that simply injecting plasma from young mice into old mice can boost learning. The results build on a wave of studies in the last decade in which investigators sewed together the skins of two mice, joining their circulation systems, and studied the effects on various tissues. “It’s still a bit creepy for many people. At meetings, people talk about vampires,” says Stanford University neuroscientist Tony Wyss-Coray, who led the study of learning. But he, Wagers, and others think unease will give way to excitement. The new work, he says, “opens the possibility that we can try to isolate additional factors” from blood, “and they have effects on the whole body.” Hope and hype are high in the anti-aging research arena, and other researchers caution that the work is preliminary. “These are exciting papers,” but “it’s a starting point,” says neuroscientist Sally Temple of the Neural Stem Cell Institute in Rensselaer, NY. Adds Matthew Kaeberlein, a biologist who studies aging at the University of Washington, Seattle, “The therapeutic implications are profound if this mechanism holds true in people.” But that “is the million dollar question here, and that may take some time to figure out.” © 2014 American Association for the Advancement of Science
by Andy Coghlan A pregnancy hormone could prove a simple way to treat multiple sclerosis, after showing promise in a trial of 158 women with MS. MS is a neurological condition that results from damage to the brain and nerves inflicted by the body's own immune system. It affects 2.3 million people worldwide. Symptoms include extreme tiredness, blurred vision, muscle weakness and problems with balance and movement. The symptoms of women with MS tend to ease when they are pregnant, but worsen again after giving birth. This could be because of a hormone called oestriol, which is only produced in significant amounts during pregnancy. The hormone is thought to help suppress the mother's immune system to prevent it attacking the fetus. Fewer relapses Rhonda Voskuhl of the University of California, Los Angeles, and her colleagues wondered whether giving oestriol to people with MS who aren't pregnant might also help with symptoms. They gave 8 milligrams of oestriol daily to 86 women with MS, along with their medication, Copaxone (glatiramer acetate). The women had the most common form of MS, called relapsing-remitting MS, which results in periodic flare-ups of symptoms followed by recovery. After one year, they had 47 per cent fewer relapses than a control group that took Copaxone and a placebo. After two years, the relapse rate was 32 per cent lower than the control group in the group given the hormone, suggesting the effects had plateaued. "We think the oestriol group had bottomed out, and there was nothing left to improve," Voskuhl said, as she presented the preliminary results at the annual meeting of the American Academy of Neurology in Philadelphia last week. © Copyright Reed Business Information Ltd.
A UBC neuroscientist says motherhood permanently alters the brain, exposing moms to different health risks than women without children. Liisa Galea, a professor in the university's psychology department, says some changes are temporary while others are permanent. The most obvious example is size. According to Galea, a mother's brain shrinks by up to eight per cent during pregnancy. While it bounces back about six months after birth, she notes the reaction could have repercussions. “Our research shows that, as a result of these transformations, mothers experience different cognitive abilities and health risks than women without children,” said Galea. And she warns that women who’ve borne children may even react to medication differently. “If mothers’ brains are different than other women’s brains, as our research finds, it means we must embrace greater personalization of medical care – not only for men versus women, but even among women with different life experiences,” she said. But that’s a challenge that may be insurmountable given that medical research studies at the animal model level have relied predominantly on the use of male rats. “Why would we assume that what works in a male rat automatically works in a female patient before testing it on a female rat?” questioned Galea. She claims one of the big failures of translational studies is that most fail to acknowledge how subjects’ gender, or other unique characteristics, like motherhood, plays a role. © CBC 2014
Guys, do you prefer more feminine faces? If so, chances are you grew up in a relatively healthy place. New research suggests that men raised in countries with higher average lifespans and lower child mortality more strongly prefer women with softer features than do men raised in less healthy nations. The finding bolsters the idea that years of human evolution have made men attracted to faces that could help them survive. Previous studies have found that women living in harsher conditions—such as communities with high homicide rates and low income—are more inclined to find more masculine men attractive. Urszula Marcinkowska, a biologist at the University of Turku in Finland, and her colleagues wanted to know whether culture also influenced males’ preferences for females, or whether men judged females in a more universal way. Using an online survey conducted in 16 different languages, the researchers presented 1972 heterosexual males between the ages of 18 and 24 from 28 different countries with 20 pairs of Caucasian female faces. Each pair contained one face with more feminine traits—such as larger eyes, fuller lips, and a less angular jaw—as well as a more androgynous face, with thinner lips and a wider chin. Participants were asked to select which face in each pair they found more sexually attractive. While men across all cultures generally preferred a more feminine face, the strength of that preference varied between countries. The difference couldn’t be explained by the ratio of men to women in a country, its gross national income, or the race of the participants, but it did correlate with the national health index of the men’s countries—a measure of overall well-being. Those from countries like Japan, with high national health index scores, chose the more feminine face more than three-quarters of the time, the authors report online today in Biology Letters. Men from countries such as Nepal, which has a lower health rating, selected the more feminine face in only slightly more than half of the cases, on average. © 2014 American Association for the Advancement of Science
THAT health and beauty are linked is not in doubt. But it comes as something of a surprise that who is perceived as beautiful depends not only on the health of the person in question but also on the average level of health in the place where she lives. This, though, is the conclusion of a study just published in Biology Letters by Urszula Marcinkowska of the University of Turku, in Finland, and her colleagues—for Ms Marcinkowska has found that men in healthy countries think women with the most feminine faces are the prettiest whilst those in unhealthy places prefer more masculine-looking ones. Ms Marcinkowska came to this conclusion by showing nearly 2,000 men from 28 countries various versions of the same female faces, modified to look less or more feminine, and thus reflect the effects of different levels of oestrogen and testosterone. Oestrogen promotes features, such as large eyes and full lips, that are characteristically feminine. Testosterone promotes masculine features, such as wide faces and strong chins. As the chart shows, the correlation is remarkable—and statistical analysis shows it is unconnected with a country’s wealth or its ratio of men to women and thus the amount of choice available to men. The cause, though, is unclear. Previous studies have shown that women with feminine features are more fertile. A man’s preference for them is thus likely to enhance his reproductive success. Ms Marcinkowska speculates that testosterone-induced behavioural characteristics like dominance, which might be expected to correlate with masculine-looking faces even in women (they certainly do in men), help in the competition for resources needed to sustain children once they are born. But why that should be particularly important in an unhealthy country is unclear.
Combining the estrogen hormone estriol with Copaxone, a drug indicated for the treatment of patients with relapsing forms of multiple sclerosis (MS), may improve symptoms in patients with the disorder, according to preliminary results from a clinical study of 158 patients with relapsing remitting multiple sclerosis (RRMS). The findings were presented today by Rhonda Voskuhl, M.D., from the University of California, Los Angeles, at the American Academy of Neurology Annual Meeting in Philadelphia. The study was funded by the National Institute of Neurological Disorders and Stroke (NINDS), part of the National Institutes of Health; and the National Multiple Sclerosis Society. “While these results are encouraging, the results of this Phase II study should be considered preliminary as a larger study would be needed to know whether benefits outweigh the risks for persons affected by MS. At present, we cannot recommend estrogen as part of standard therapy for MS. We encourage patients to talk with their doctors before making any changes to their treatment plans,” said Walter Koroshetz, M.D., deputy director of NINDS. MS is an autoimmune disorder in which immune cells break down myelin, a protective covering that wraps around nerve cells. Loss of myelin results in pain, movement and balance problems as well as changes in cognitive ability. RRMS is the most common form of the disorder. Patients with RRMS experience relapses, or flare-ups, of neurological symptoms, followed by recovery periods during which the symptoms improve.
The hormone oxytocin appears to increase social behaviors in newborn rhesus monkeys, according to a study by researchers at the National Institutes of Health, the University of Parma in Italy, and the University of Massachusetts, Amherst. The findings indicate that oxytocin is a promising candidate for new treatments for developmental disorders affecting social skills and bonding. Oxytocin, a hormone produced by the pituitary gland, is involved in labor and birth and in the production of breast milk. Studies have shown that oxytocin also plays a role in parental bonding, mating, and in social dynamics. Because of its possible involvement in social encounters, many researchers have suggested that oxytocin might be useful as a treatment for conditions affecting social behaviors, such as autism spectrum disorders. Although oxytocin has been shown to increase certain social behaviors in adults, before the current study it had not been shown to do so in primate infants of any species. Working with infant rhesus monkeys, the NIH researchers found that oxytocin increased two facial gestures associated with social interactions— one used by the monkeys themselves in certain social situations, the other in imitation of their human caregivers. “It was important to test whether oxytocin would promote social behaviors in infants in the same respects as it appears to promote social interaction among adults,” said the study’s first author, Elizabeth A. Simpson, Ph.D., postdoctoral fellow of the University of Parma, conducting research in the Comparative Behavioral Genetics Section of the NIH’s Eunice Kennedy Shriver National Institute of Child Health and Human Development. “Our results indicate that oxytocin is a candidate for further studies on treating developmental disorders of social functioning.” The study was published online in Proceedings of the National Academy of Sciences.
By Karen Kaplan There are lies, damn lies – and the lies that we tell for the sake of others when we are under the influence of oxytocin. Researchers found that after a squirt of the so-called love hormone, volunteers lied more readily about their results in a game in order to benefit their team. Compared with control subjects who were given a placebo, those on oxytocin told more extreme lies and told them with less hesitation, according to a study published Monday in Proceedings of the National Academy of Sciences. Oxytocin is a brain hormone that is probably best known for its role in helping mothers bond with their newborns. In recent years, scientists have been examining its role in monogamy and in strengthening trust and empathy in social groups. Sometimes, doing what’s good for the group requires lying. (Think of parents who fake their addresses to get their kids into a better school.) A pair of researchers from Ben-Gurion University of the Negev in Israel and the University of Amsterdam figured that oxytocin would play a role in this type of behavior, so they set up a series of experiments to test their hypothesis. The researchers designed a simple computer game that asked players to predict whether a virtual coin toss would wind up heads or tails. After seeing the outcome on a computer screen, players were asked to report whether their prediction was correct or not. In some cases, making the right prediction would earn a player’s team a small payment (the equivalent of about 40 cents). In other cases, a correct prediction would cost the team the same amount, and sometimes there was no payoff or cost. Los Angeles Times Copyright 2014
|By Meredith Knight Add another credential to oxytocin's impressive resume: the hormone crucial for bonding also reduces the calories people consume when they are snacking for pleasure, making it a possible therapeutic target for obesity. German researchers gave a group of men a dose of oxytocin thought to be roughly the amount released by the brain after breast-feeding or sex, according to lead author Manfred Hallschmid of the University of Tübingen. These men and another group who took a placebo then had a chance to eat as much as they wanted at a breakfast buffet, and later the same day they were offered snacks. Those who took oxytocin ate fewer snack calories, but the hormone did not change how much the men ate during the main meal, suggesting that oxytocin affected pleasure eating without suppressing normal appetite mechanisms. The researchers hypothesize that the hormone diminished reward-seeking behavior initiated in the ventral tegmental area of the brain, a region found to be highly sensitive to oxytocin in rodent studies. The effect may also be stress-related: subjects who took oxytocin saw a drop in their levels of the stress hormone cortisol, according to the paper published in 2013 in the journal Diabetes. More work is needed to understand whether oxytocin could be used to treat obesity, but until then the finding at least hints that it may be possible to curb your cravings by having more sex. © 2014 Scientific American
A hormone released during childbirth and sex could be used as a treatment for the eating disorder anorexia nervosa, scientists suggest. Small studies by UK and Korean scientists indicated patients were less likely to fixate on food and body image after a dose of oxytocin. About one in every 150 teenage girls in the UK are affected by the condition. The eating disorders charity Beat said the finding was a long way from becoming a useable treatment. Oxytocin is a hormone released naturally during bonding, including sex, childbirth and breastfeeding. It has already been suggested as a treatment for a range of psychiatric disorders, and has been shown to help lower social anxiety in people with autism. And one four-week study in Australia found people given doses of oxytocin had reduced weight and shape concerns. In the first of the most recent studies, published in Psychoneuroendocrinology, 31 patients with anorexia and 33 people who did not have the condition were given either a dose of oxytocin, delivered via nasal spray, or a placebo, or dummy, treatment. They then looked at a series of images to do with a range high and low calorie foods and people of different body shapes and weight. People with anorexia have previously been found to focus for longer on images of overweight people and what they perceive as undesirable body shapes. However after taking oxytocin, patients with anorexia were less likely to focus on such "negative" images of food and fat body parts. The second study, published in PLOS ONE, involved the same people and looked at their reactions to facial expressions, such as anger, disgust or happiness. It has been suggested that anorexia can be linked to a heightened perception of threat, and animal research has shown oxytocin treatment lessened the amount of attention paid to threatening facial expressions. BBC © 2014
By James Gallagher Health and science reporter, BBC News A tool for predicting the risk of clinical depression in teenage boys has been developed by researchers. Looking for high levels of the stress hormone cortisol and reports of feeling miserable, lonely or unloved could find those at greatest risk. Researchers at the University of Cambridge want to develop a way of screening for depression in the same way as heart problems can be predicted. However, their method was far less useful in girls. Teenage years and early adulthood are a critical time for mental health - 75% of disorders develop before the age of 24. But there is no way to accurately say who will or will not develop depression. Risky combination Now researchers say they have taken the "first step" towards a screening tool. Tests on 1,858 teenagers, reported in Proceedings of the National Academy of Sciences, combined hormone levels and mood questionnaires to assess risk. They showed that having both high cortisol levels and depressive mood symptoms posed a higher risk of depression than either factor alone and presented a risk of clinical depression 14 times that of those with low cortisol and no depressive symptoms. Around one in six boys was in the high-risk category and half of them were diagnosed with clinical depression during the three years of study. One of the researchers, Prof Ian Goodyer, said: "Depression is a terrible illness that will affect as many as 10 million people in the UK at some point in their lives. "Through our research, we now have a very real way of identifying those teenage boys most likely to develop clinical depression. BBC © 2014
Ian Sample, science correspondent, in Chicago Researchers have found evidence – if evidence were needed – that men have less sex after becoming a father for the first time. A study of more than 400 young men in the Philippines found that their sex lives declined significantly when they had their first child. The fall in sexual activity was associated with the men's testosterone levels, which are known to fall when men start families, but the latest research shows that the greater the fall in testosterone, the less sex men reported. Lee Gettler, an anthropologist at the University of Notre Dame in Indiana, gathered medical and lifestyle information on the men from the ages of 21 to 26 years old and found there were physiological and behavioural changes as some of them married and had children. When men got married their testosterone levels fell, and declined even further when they had their first child. That led to the question of whether falling testosterone might impact on their sex lives. "I didn't think that testosterone would be linked to men's sexual behaviour, but when we tested it we found that as men transitioned to fatherhood, the more their testosterone declined the less frequently they reported having sex with their partner," Gettler said. "Does this mean that men who care for children have low testosterone and no sex? No, it has nothing to do with childcare." The impact on men's sex lives was not linked to the amount of time and energy they invested in childcare, he said. Gettler described his research at the annual meeting of the American Association for the Advancement of Science in Chicago. © 2014 Guardian News and Media Limited
By JOHN LA PUMA SANTA BARBARA, Calif. — A FUNNY thing has happened in the United States over the last few decades. Men’s average testosterone levels have been dropping by at least 1 percent a year, according to a 2006 study in The Journal of Clinical Endocrinology and Metabolism. Testosterone appears to decline naturally with aging, but internal belly fat depresses the hormone further, especially in obese men. Drugs like steroids and opiates also lower testosterone, and it’s suspected that chemicals like bisphenol A (or BPA, commonly found in plastic food containers) and diseases like Type 2 diabetes play a role as well. Men feel the loss. Clinical testosterone deficiency, which is variously defined as lower than 220 to 350 nanograms of testosterone per deciliter of blood serum, can cause men to lose sex drive and fertility. Their bone density often declines, and they may feel tired and experience hot flashes and sweats. But “low T,” as the condition has been labeled, isn’t nearly as common as the drug ads for prescription testosterone would have you believe. Pharmaceutical companies have seized on the decline in testosterone levels as pathological and applicable to every man. They aim to convince men that common effects of aging like slowing down a bit and feeling less sexual actually constitute a new disease, and that they need a prescription to cure it. This is a seductive message for many men, who just want to feel better than they do, and want to give it a shot, literally. The problem is that prescription testosterone doesn’t just give your T level a boost: it may also increase your risk of heart attack. It can add huge numbers of red blood cells to your bloodstream and shrink your testes. In some men, it increases aggression and irritability. © 2014 The New York Times Company
Keyword: Hormones & Behavior
Link ID: 19238 - Posted: 02.11.2014
By RONI CARYN RABIN Nearly a decade ago, researchers in Boston decided to see whether older men who were not in very good shape could benefit from daily doses of testosterone. The scientists recruited several hundred volunteers and gave them the hormone or a placebo. Those taking testosterone got stronger, compared with those taking the placebo, and they could carry a load up stairs faster. But they also had nearly five times the number of cardiovascular problems, including heart attacks and strokes, and safety monitors ended the trial early. Since those findings were published in 2010, studies of testosterone treatment have produced mixed results. A 2012 study of veterans aged 40 and over with low testosterone found that those treated with the hormone were less likely to die, but more recent reports, including one published last week, have documented an increase in cardiovascular risk in men over age 65 taking testosterone, as well as in younger men with a history of heart disease. Officials at the Food and Drug Administration said on Friday that they were reassessing the safety of testosterone products in light of the recent studies, and will investigate rates of stroke, heart attack and death in men using the drugs. In recent years, testosterone has been heavily promoted as a cure-all for low energy, low libido, depression and other ills among middle-aged men. “Low T” is a ubiquitous diagnosis, heard in television commercials and locker rooms. Between 2001 and 2011, hormone use by men 40 and over nearly quadrupled. By the end of that period, nearly one in 25 men in their 60s was taking testosterone. Though the drug is indicated for men with abnormally low testosterone levels, a condition called hypogonadism, doctors have been prescribing it to many men with normal levels. © 2014 The New York Times Company
By PAM BELLUCK Scientists have been eager to see if oxytocin, which plays a role in emotional bonding, trust and many biological processes, can improve social behavior in people with autism. Some parents of children with autism have asked doctors to prescribe it, although it is not an approved treatment for autism, or have purchased lower-dose versions of the drug over the counter. Scientifically, the jury is out, and experts say parents should wait until more is known. Some studies suggest that oxytocin, sometimes called the “love hormone,” improves the ability to empathize and connect socially, and may decrease repetitive behaviors. Others find little or no impact, and some research suggests that it can promote clannish and competitive feelings, or exacerbate symptoms in people already oversensitive to social cues. Importantly, nobody knows if oxytocin is safe or desirable to use regularly or long term. Now, the first study of how oxytocin affects the brains of children with autism finds hints of promise — and also suggestions of what its limitations might be. On the promising side, the small study, published Monday in The Proceedings of the National Academy of Sciences, found that the hormone, given as an inhalant, generated increased activity in parts of the brain involved in social connection. This suggests not only that oxytocin can stimulate social brain areas, but also that in children with autism these brain regions are not irrevocably damaged but are plastic enough to be influenced. The limitations could include a finding that oxytocin prompted greater brain activity in children with the least severe autism. Some experts said that this could imply that oxytocin may work primarily in less-impaired people, but others said it might simply suggest that different doses are needed. © 2013 The New York Times Company
A whiff of oxytocin may help love not fade away. Researchers asked 20 unmarried men in multiyear relationships to rank the attractiveness of pictures of their partner, acquaintances, and strangers. When the men received a nasal spray of oxytocin—which is released by the body during sexual arousal—they rated their partners more highly but not the other women. MRI scans show that after an oxytocin dose, areas of the brain associated with rewards, which also drive drug addiction, were more active when the men saw pictures of their partner, the researchers report online today in the Proceedings of the National Academy of Sciences. The finding could help explain the biological roots of monogamy in humans: Being in a long-term relationship raises a person's oxytocin levels, which in turn increase the psychological reward of spending more time with that person. The cycle, the team concluded, could literally lead to an addiction to one’s lover. © 2013 American Association for the Advancement of Science