Chapter 8. Hormones and Sex
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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 Jenny Graves The claim that homosexual men share a “gay gene” created a furor in the 1990s. But new research two decades on supports this claim – and adds another candidate gene. To an evolutionary geneticist, the idea that a person’s genetic makeup affects their mating preference is unsurprising. We see it in the animal world all the time. There are probably many genes that affect human sexual orientation. But rather than thinking of them as “gay genes,” perhaps we should consider them “male-loving genes.” They may be common because these variant genes, in a female, predispose her to mate earlier and more often and to have more children. Likewise, it would be surprising if there were not “female-loving genes” in lesbian women that, in a male, predispose him to mate earlier and have more children. We can detect genetic variants that produce differences between people by tracking traits in families that display differences. Patterns of inheritance reveal variants of genes (called “alleles”) that affect normal differences, such as hair color, or disease states, such as sickle cell anemia. Quantitative traits, such as height, are affected by many different genes, as well as environmental factors. It’s hard to use these techniques to detect genetic variants associated with male homosexuality partly because many gay men prefer not to be open about their sexuality. It is even harder because, as twin studies have shown, shared genes are only part of the story. Hormones, birth order and environment play roles, too.
Ian Sample, science correspondent Research on children in Denmark has found that boys with autism were more likely to have been exposed to higher levels of hormones in their mother's wombs than those who developed normally. Boys diagnosed with autism and related disorders had, on average, raised levels of testosterone, cortisol and other hormones in the womb, according to analyses of amniotic fluid that was stored after their mothers had medical tests during pregnancy. The findings add to a growing body of evidence that the biological foundations of autism are laid down well before birth and involve factors that go beyond the child's genetic make-up. The results may help scientists to unravel some of the underlying causes of autism and explain why boys are four to five times more likely to be diagnosed with the condition, which affects around one percent of the population. Amniotic fluid surrounds babies in the womb and contains hormones and other substances that they have passed through their urine. The liquid is collected for testing when some women have an amniocentesis around four months into their pregnancy. Scientists in Cambridge and Copenhagen drew on Danish medical records and biobank material to find amniotic fluid samples from 128 boys who were later diagnosed with autism. Compared to a control group, the boys with autism and related conditions had higher levels of four "sex steroid" hormones that form a biological production line in the body that starts with progesterone and ends with testosterone. "In the womb, boys produce about twice as much testosterone as girls, but compared with typical boys, the autism group has even higher levels. It's a significant difference and may have a large effect on brain development," said Simon Baron-Cohen, director of the Autism Research Centre at Cambridge University. © 2014 Guardian News and Media Limited
By MARK OPPENHEIMER When our young daughters first decided to play on top of our Honda minivan, parked in our driveway, my wife was worried. But to me, it seemed no less safe than chasing a ball that frequently ended up in the street. And they loved the height, the novelty, the danger. So I let them stay. They never fell. And with the summer weather here, playing on the car is once again keeping them occupied for hours. Now that I have read Paul Raeburn’s “Do Fathers Matter?,” I know that my comfort with more dangerous play — my willingness to let my daughters stand on top of a minivan — is a typically paternal trait. Dads roughhouse with children more, too. They also gain weight when their wives are pregnant and have an outsize effect on their children’s vocabulary. The presence of dads can delay daughters’ puberty. But older dads have more children with dwarfism and with Marfan syndrome. In Mr. Raeburn’s book, there is plenty of good news for dads, and plenty of bad. A zippy tour through the latest research on fathers’ distinctive, or predominant, contributions to their children’s lives, “Do Fathers Matter?” is filled with provocative studies of human dads — not to mention a lot of curious animal experiments. (You’ll learn about blackbirds’ vasectomies.) But above all, Mr. Raeburn shows how little we know about the role of fathers, and how preliminary his book is. Its end is really a beginning, a prospectus for further research. Mr. Raeburn writes that “as recently as a generation ago, in the 1970s, most psychologists” believed that “with regard to infants, especially, fathers were thought to have little or no role to play.” When it came to toddlers and older children, too, the great parenting theories of the 20th century placed fathers in the background. Freud famously exalted, or damned, the mother for her influence. John Bowlby’s attachment theory, which he developed beginning in the 1940s, focused on the mother or “mother-figure.” © 2014 The New York Times Company
Keyword: Sexual Behavior
Link ID: 19686 - Posted: 06.03.2014
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
By Denali Tietjen If you watch porn, you probably have a small brain, a new study published in the Journal of the American Medical Association (JAMA) shows. The study, conducted by the Max Plank Institute for Human Development in Berlin, found a significant negative correlation between frequent pornography consumption and grey matter in the brain (that’s the stuff that tells your brain how to react to sensory information.) The keyword here is correlation. While the study’s findings are significant, the researchers don’t know if it’s the porn that causes the low grey-matter volume in porn-watchers, or if it’s the other way around. It could be a neurological pre-condition that makes watching porn particularly satisfying. However, researchers have reason to believe that porn does negatively impact the brain. Previous research proves that frequent porn consumption can cause negative social behavior. Porn consumption can cause viewers to be less satisfied during sex and viewers often want to adopt acts they’ve seen in illegal pornography, according to the report. If porn can affect social behavior, it can probably affect cognitive behavior, too. The study examined the cognitive structure of 64 males ages 21 to 45 years old that consumed porn at varying levels of frequency. While few people openly admit to watching porn, 66 percent of all men and 41 percent of American women view pornography at least once a month, and an estimated 50 percent of internet traffic is sex-related, according to the journal.
Elizabeth Norton Cultures around the world have long assumed that women are hardwired to be mothers. But a new study suggests that caring for children awakens a parenting network in the brain—even turning on some of the same circuits in men as it does in women. The research implies that the neural underpinnings of the so-called maternal instinct aren't unique to women, or activated solely by hormones, but can be developed by anyone who chooses to be a parent. "This is the first study to look at the way dads' brains change with child care experience," says Kevin Pelphrey, a neuroscientist at Yale University who was not involved with the study. "What we thought of as a purely maternal circuit can also be turned on just by being a parent—which is neat, given the way our culture is changing with respect to shared responsibility and marriage equality." The findings come from an investigation of two types of households in Israel: traditional families consisting of a biological mother and father, in which the mother assumed most of the caregiving duties, though the fathers were very involved; and homosexual male couples, one of whom was the biological father, who'd had the child with the help of surrogate mothers. The two-father couples had taken the babies home shortly after birth and shared caregiving responsibilities equally. All participants in the study were first-time parents. Researchers led by Ruth Feldman, a psychologist and neuroscientist at Bar-Ilan University in Ramat Gan, Israel, visited with the families in their homes, videotaping each parent with the child and then the parents and children alone. The team, which included collaborators at the Tel Aviv Sourasky Medical Center in Israel, also took saliva samples from all parents before and after the videotaped sessions to measure oxytocin—a hormone that's released at times of intimacy and affection and is widely considered the "trust hormone.” Within a week of the home visit, the participants underwent functional magnetic resonance imaging scanning to determine how their brains reacted to the videotapes of themselves with their infants. © 2014 American Association for the Advancement of Science
Eliana Dockterman @edockterman A new study that could affect whether adoption agencies are willing to work with gay couples shows that after adopting, gay men's brain activity resembles that of both new moms and new dads Research has shown that a new mother’s brain activity changes after having a baby. Turns out, gay men’s pattern of brain activity also adapts to parenthood, and resembles that of both new moms and new dads, in findings published Monday. A study published Monday in the Proceedings of the National Academy of Sciences sought to determine whether mothers’ brains became hyper-reactive to emotional cues, like hearing their child cry after birth, because of hormonal changes or parenting experience. Researchers videotaped 89 new moms and dads taking care of their infants at home. They then measured parents’ brain activity in an MRI while the parents watched videos in which their children were not featured, followed by the footage shot in their home with their kids. The 20 mothers in the study—all of whom were the primary caregivers—had heightened activity in the brain’s emotion-processing regions; the amygdala, a set of neurons that processes emotions, was five times more active than the baseline. The 21 heterosexual fathers had increased activity in their cognitive circuits, which helped them determine which of the baby’s body movements indicated the need for a new diaper and which ones signaled hunger. The 48 gay fathers’ brain waves, on the other hand, responded similarly to both the heterosexual mom and dad. Their emotional circuits were as active as mothers’, and their cognitive circuits were as active as the fathers’. Researchers also found that the more time a gay father spent with the baby, the greater a connection there was between the emotional and cognitive structures.
Eleven years on, I still remember the evening I decided to kill my baby daughter. It's not something you're supposed to feel as a new parent with a warm, tiny bundle in your arms. But this is how postnatal depression can twist your logic. At the time it made perfect sense. Catherine was screaming, in pain. She had colic, there was nothing I could do about it. If an animal were in this much pain you'd put it out of its misery, so why not a human? Postnatal depression can have this kind of effect even on the most reasonable woman, yet you won't find much about it in baby books. We're expected to love our kids the moment they pop out, even while the memory of the labour pains is still raw. I knew a baby would be hard work, of course, but I expected motherhood to be fulfilling. As it happened I had a wonderful pregnancy, followed by a quick and easy birth. But the problems started soon after. Catherine wouldn’t feed, her blood sugar levels tumbled and I ended up bottle-feeding her, in tears, in a hospital room filled with posters promoting the breast. I was a Bad Mother within 48 hours. Things were no better after the first month. This was meant to be a joyous time, but all I seemed to feel was rage and resentment. In pregnancy all the attention had been on me, and suddenly I was a sideshow to this wailing thing in a crib. I was tired, tetchy and resentful. My daughter had rapidly become a ball and chain. My freedom was over. I kept hoping this was just the “baby blues” and that it would soon pass, but things only got worse. When colic set in, for around five hours each evening Catherine would scream, her face a mix of red and purple rage. No amount of pacing, tummy-rubbing or soothing words could stop this tiny demanding creature. So one night, alone with her in her room, I decided it would be best to put her out of her misery. © 2014 Guardian News and Media Limited
By RONI CARYN RABIN For decades, scientists have embarked on the long journey toward a medical breakthrough by first experimenting on laboratory animals. Mice or rats, pigs or dogs, they were usually male: Researchers avoided using female animals for fear that their reproductive cycles and hormone fluctuations would confound the results of delicately calibrated experiments. That laboratory tradition has had enormous consequences for women. Name a new drug or treatment, and odds are researchers know far more about its effect on men than on women. From sleeping pills to statins, women have been blindsided by side effects and dosage miscalculations that were not discovered until after the product hit the market. Now the National Institutes of Health says that this routine gender bias in basic research must end. In a commentary published on Wednesday in the journal Nature, Dr. Francis Collins, director of the N.I.H., and Dr. Janine A. Clayton, director of the institutes’ Office of Research on Women’s Health, warned scientists that they must begin testing their theories in female lab animals and in female tissues and cells. The N.I.H. has already taken researchers to task for their failure to include adequate numbers of women in clinical trials. The new announcement is an acknowledgment that this gender disparity begins much earlier in the research process. “Most scientists want to do the most powerful experiment to get the most durable, powerful answers,” Dr. Collins said in an interview. “For most, this has not been on the radar screen as an important issue. What we’re trying to do here is raise consciousness.” Women now make up more than half the participants in clinical research funded by the institutes, but it has taken years to get to this point, and women still are often underrepresented in clinical trials carried out by drug companies and medical device manufacturers. © 2014 The New York Times Company
Ewen Callaway In the silk business, sex is money. Male silkworms weave cocoons with more silk of a higher quality than females do, and the multibillion dollar sericulture industry has long sought an easy way to breed only males. That might now be a realistic goal, as researchers have identified the process that determines sex in the silkworm Bombyx mori1. The sex factor is found to be a small RNA molecule — the first time that anything other than a protein has been implicated in a sex-detemination process. In nearly all Lepidoptera — the order that includes moths and butterflies — sex is determined in silkworms by a WZ chromosome system, in contrast to the XY system used in mammals. Female silkworms carry W and Z sex chromosomes, whereas males boast a pair of Z chromosomes. Last year, researchers showed how to genetically modify silkworms so that the females would express a deadly protein (see 'Genetic kill switch eradicates female silkworms for a better crop'). But efforts to identify the genes on the W chromosome that make silkworms female have come up short: the W does not seem to have any protein-making genes, and is instead almost completely filled with parasitic, mobile genetic elements called transposons. In 2011, a team led by entomologist Susumu Katsuma at the University of Tokyo reported that the W chromosome produces short RNA molecules that keep transposons at bay in newly formed egg cells2. Katsuma and his team report in Nature today1 that one such molecule, which the authors called Fem, is specific to female silkworms, suggesting that it has a role in sex determination. The Fem RNA breaks down a corresponding molecule made by a gene known as Masculinizer, which is found on the Z chromosome. When the researchers silenced Masculinizer, embryos execute a genetic programme that makes female tissue. © 2014 Nature Publishing Group
Keyword: Sexual Behavior
Link ID: 19611 - Posted: 05.15.2014
|By Jason G. Goldman When a male fallow deer wants to mate, he isn't shy about letting everyone around him know. The males, also called fallow bucks, can produce their mating calls as many as 3,000 times each hour during the mating season. Those calls serve two functions: to attract females and to deter rival males. Yet there is more hidden in the groans of fallow bucks than first meets the ear, according to a new study in Behavioral Ecology. Every October around 25 bucks gather in Petworth Park in England's county of West Sussex, where each stakes out a territory, hoping to entice a female at a feral conclave of romance, combat and deer calling, an event known as a lek. “Leks are really rare in mammals, and they're really rare in ungulates. Fallow deer are the only species of deer that we know that lek,” says Alan McElligott of Queen Mary, University of London, who oversaw the study. Mating calls reveal information about the caller, such as body size or dominance rank, which is useful both to interested females and to rival males—and every conceivable type of fallow deer utterance turns up at the lek. In one study, McElligott found that the quality of groans decreased over time. “The mature bucks stop eating for a couple of weeks,” over the course of the lek, McElligott explains, so “they are really worn out.” That fatigue is reflected in their calls, but do other males notice? Because the lek is such a spectacle, the deer in Petworth Park are accustomed to human interlopers, which allowed Queen Mary postdoctoral scholar Benjamin J. Pitcher to cart a sound system around without interrupting the festivities. © 2014 Scientific American
By Pippa Stephens Health reporter, BBC News A key difference in the brains of male and female MS patients may explain why more women than men get the disease, a study suggests. Scientists at Washington University School of Medicine in the US found higher levels of protein S1PR2 in tests on the brains of female mice and dead women with MS than in male equivalents. Four times more women than men are currently diagnosed with MS. Experts said the finding was "really interesting". MS affects the nerves in the brain and spinal cord, which causes problems with muscle movement, balance and vision. It is a major cause of disability, and affects about 100,000 people in the UK. Abnormal immune cells attack nerve cells in the central nervous system in MS patients. There is currently no cure, although there are treatments that can help in the early stages of the disease. Researchers in Missouri looked at relapsing remitting MS, where people have distinct attacks of symptoms that then fade away either partially or completely. About 85% of people with MS are diagnosed with this type. Scientists studied the blood vessels and brains of healthy mice, mice with MS, and mice without the gene for S1PR2, a blood vessel receptor protein, to see how it affected MS severity. They also looked at the brain tissue samples of 20 people after they had died. They found high levels of S1PR2 in the areas of the brain typically damaged by MS in both mice and people. The activity of the gene coding for S1PR2 was positively correlated with the severity of the disease in mice, the study said. Scientists said S1PR2 could work by helping to make the blood-brain barrier, in charge of stopping potentially harmful substances from entering the brain and spinal fluid, more permeable. BBC © 2014
By Diana Kwon Would you rather have $50 now or $100 two weeks from now? Even though the $100 is obviously the better choice, many people will opt for the $50. Both humans and animals show this tendency to place lower value on later rewards, a behavior known as temporal discounting. High rates of temporal discounting can lead to impulsive behavior, and at its worst, too much of this “now bias” is associated with pathological gambling, attention deficit hyperactivity disorder and drug addiction. What determines if you’ll be an impulsive decision-maker? New evidence suggests that for women, estrogen levels might be a factor. In a recent study published in the Journal of Neuroscience, Charlotte Boettiger and her team at the University of North Carolina revealed that greater increases in estrogen levels across the menstrual cycle led to less impulsive decision making. The researchers tested the “now bias” in 87 women between the ages of 18 and 40 at two different points in their menstrual cycle – in the menstrual phase when estrogen levels are low and the follicular phase when estrogen levels are high. Participants were given a delay-discounting task where they had to choose between two options: a certain sum of money at a later date or a discounted amount immediately (e.g. $100 in one week or $70 today). Subjects showed a greater bias toward the immediate choice during the menstrual phase of the cycle, when estrogen levels were low. Estrogen levels vary between women and can change with factors like stress and age. When the researchers measured amounts of estradiol (the dominant form of estrogen) from the saliva in a subset of the participants at the two points in their menstrual cycles, they found that not all of them showed a detectable increase. Only those with a measureable rise in estradiol showed a significant change in impulsive decision-making. © 2014 Scientific American
The gene that most likely determines the sex of the platypus and echidna has been identified by Australian and Swiss researchers. The study also shows that the Y chromosome, contrary to previous assumptions, carries genes that are important to the basic viability of male mammals, says geneticist Dr Paul Waters from the University of New South Wales. Although the Y chromosome is known to be important in sex determination, little is known about the function and evolution of its genes, says Waters. He says this is because it has so many repetitive and palindromic sequences, which make it hard to reconstruct the true sequences of its genes from fragments of sequenced DNA. Monotremes (the platypus and the echidna), whose males have 5 X chromosomes and 5 Y chromosomes, are especially challenging. "No one had really characterised any Y chromosomes in platypus before because they've got quite a complex sex chromosome system," says Waters. Waters and colleagues from the University of Adelaide and the University of Lausanne now report on their new analysis of male and female DNA from 15 representative mammals, including human, elephants, marsupials and monotremes. The study, reported recently in the journal Nature, is the largest of its kind, and relied on a rapid new sequencing technique. © 2014 Discovery Communications, LLC.
Keyword: Sexual Behavior
Link ID: 19582 - Posted: 05.07.2014
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.
by Bethany Brookshire When I was a lab scientist working with mice, I spent hours controlling variables. I stood on precarious chairs to tape tarps over lights to get the light level perfectly right. I made one undergraduate who wore perfume to the lab for animal training wear the same perfume for a whole semester. I was so worried about the mice “recognizing” me over long, overlapping experiments that I did not change the scents of any of my personal care products for nine years. Many of these variables got reported in the methods sections of my papers. “All experiments conducted between 5:00 and 7:00 a.m. Maze dimensions: 4 inches wide, with walls 6 inches tall. Lighting held constant at 10 lux.” All of these variables are reported to allow other people to repeat my experiments, and hopefully get the same result. Now, a new study suggests that maybe I should have included another element in my methods section: “All mice exposed to the scent of a woman.” Jeffrey Mogil’s lab at McGill University in Montreal, Canada, reports April 28 in Nature Methods that mice respond differently to men and women, and that men in fact are a stressful influence. The results show that there’s yet another variable to control when doing sensitive mouse behavioral studies, a variable that could impact fields from pain to depression and beyond. Every department that does animal research has stories about particular experimenters. I recall hearing a story of a lab technician who could get results no one else could, because mice just loved her strawberry-scented hair conditioner. Another colleague told of one experimenter who was so good at handling rats that no one believed her anxiety results. Her rats were just so relaxed. And Mogil’s lab had its own story. In their lab, the presence of human experimenters seemed to stop mice from showing pain. © Society for Science & the Public 2000 - 2013
Humans stink, and it’s wonderful. A few whiffs of a pillow in the morning can revive memories of a lover. The sweaty stench of a gym puts us in the mood to exercise. Odors define us, yet the scientific zeitgeist is that we don’t communicate through pheromones—scents that influence behavior. A new study challenges that thinking, finding that scent can change whether we think someone is masculine or feminine. Humans carry more secretion and sweat glands in their skin than any other primate. Yet 70% of people lack a vomeronasal organ, a crescent-shaped bundle of neurons at the base of each nostril that allows a variety of species—from reptiles to nonprimate mammals—to pick up on pheromones. (If you’ve ever seen your cat huff something, he’s using this organ.) Still, scientists have continued to hunt for examples of pheromones that humans might sense. Two strong candidates are androstadienone (andro) and estratetraenol (estra). Men secrete andro in their sweat and semen, while estra is primarily found in female urine. Researchers have found hints that both trigger arousal—by improving moods and switching on the brain’s “urge” center, the hypothalamus—in the opposite sex. Yet to be true pheromones, these chemicals must shape how people view different genders. That’s exactly what they do, researchers from the Chinese Academy of Sciences in Beijing report online today in Current Biology. The team split men and women into groups of 24 and then had them watch virtual simulations of a human figure walking (see video). The head, pelvis, and major joints in each figure were replaced with moving dots. Subjects in prior studies had ranked the videos as being feminine or masculine. For instance, watch the figure on the far left, which was gauged as having a quintessential female strut. Notice a distinctive swagger in the “hip” dots and how they contrast with the flat gait of the “male” prototype all the way to the right. © 2014 American Association for the Advancement of Science
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