By Angie Voyles Askham Rats, like people, jump at the chance to repeat a task that rewards them handsomely, but they are less eager when the reward is paltry: They learn from past experience and update their behavior accordingly. That learning is shaped by the hormone estradiol, according to a new study. And when estradiol levels peak during the estrus cycle, female rats adapt their behavior in response to reward size more quickly than they do during other phases—and faster than males overall. The female rats also have a larger release of dopamine in response to an unexpected reward, along with reduced expression of dopamine transporters in a reward center of their brain after the hormone peaks, the new work shows. “It’s giving mechanistic insight into how estrogen modulates reinforcement learning—all the way down to the molecular mechanism,” says Ilana Witten, professor of neuroscience at Princeton University and Howard Hughes Medical Institute investigator, who was not involved in the study. The team behind the new work used a task that measures how much an animal values an anticipated reward: Thirsty rats poke their nose into a central port and then listen for a tone that indicates how much water one of two side ports will dispense. The animals choose to either hold out at the cued location for the reward or to abandon the trial and start a new one by poking their nose into the other side. Rats learn to initiate their next trial more quickly when the experiment is doling out large rewards and to hold off on initiating new trials when rewards are small, previous work from the group has shown. “It takes a lot of energy to initiate a trial, so if there are small rewards, it’s not as motivating,” says study investigator Carla Golden, a postdoctoral researcher in Christine Constantinople’s lab at New York University. © 2025 Simons Foundation

Keyword: Hormones & Behavior; Attention
Link ID: 30028 - Posted: 11.26.2025

By Ali Watkins The act has been called many things: Centrifugal motion. Perpetual bliss. The thrill of the moment. Unstoppable. In technical terms, it is “non-agonistic interaction involving directed, intraspecific, oral-oral contact with some movement of the lips/mouthparts and no food transfer.” Or, as her majesty Faith Hill might say, “This kiss.” And, it turns out, it’s also really old. British scientists say they’ve traced the age of the kiss, to anywhere from 16 million to 21 million years ago, and have found that it was far more common among other species than previously understood. Ants? They smooch. Fish? Kissers. Neanderthals? Yep, they puckered up, too — sometimes even with us. But kissing, the researchers said, has always been something of a so-called evolutionary mystery. It doesn’t present much benefit for survival, it has minimal reproductive benefits, and it’s mostly symbolic. “Kissing is a really interesting behavior,” said Matilda Brindle, an evolutionary biologist at Oxford University who led the study. Dozens of societies and cultures use it, it’s common, and it has weighted symbolism. But, she said, “we’ve not really tested it from an evolutionary perspective.” In prehistoric kissing, it seems, could be the primitive origins of our search for intimate connection. The act inherently requires vulnerability, and trust. It’s not always sexual and is often used among and between genders simply to show affection, and often between parents and offspring. Though researchers found evidence of kissing in several species, they narrowed the focus of the study mostly to the behavior of large apes, like gorillas, orangutans and baboons. © 2025 The New York Times Company

Keyword: Sexual Behavior; Evolution
Link ID: 30022 - Posted: 11.22.2025

By Roni Caryn Rabin The most stressful part of the trip for Sunny Brous came when she had to part with her wheelchair so that the flight crew could put it in the luggage hold. You just never know what shape it will be in when you get it back, she said. “I tell them, ‘Take the best care of it you can,’” she said. “Those wheels are my legs! Those wheels are my life.” Ms. Brous, 38, who lives in Hico, Texas, was one of dozens of women who converged on the Sea Crest Beach Resort on Cape Cod toward the end of summer for the gathering of a club no one really wanted to be a member of: women diagnosed in their 20s and early 30s with amyotrophic lateral sclerosis, or A.L.S. The terminal neurodegenerative disorder robs them of the ability to talk, walk, use their hands or even breathe. It has long been seen as a disease of older men, who make up a majority of patients. There is no cure. The women traveled with husbands, mothers, sisters and aides, and they did not travel light. Their packing lists included heavy BiPAP machines to help them breathe, formula for their feeding tubes, commodes, portable bidets, myriad chargers, leg braces and canes, pills and pill crushers and bottles of a medication with gold nanoparticles that was still being tested in clinical trials. Half of Ms. Brous’s suitcase was filled with party gifts for the friends she texts with throughout the year on an endless WhatsApp chat, including bags of popcorn with Texan flavors like Locked and Loaded, a Cheddar, bacon, sour cream and chives combo that you can only get in Hico. Desiree Galvez Kessler’s sister drove her, her mother and an aide up from Long Island in a van with a clunky Hoyer transfer lift in the back. Ms. Kessler — Desi to her friends — was diagnosed at 29, and has not been able to walk or speak for 10 years; the large computer tablet that she communicates with using eye-gaze technology is mounted on her wheelchair. © 2025 The New York Times Company

Keyword: ALS-Lou Gehrig's Disease ; Sexual Behavior
Link ID: 30009 - Posted: 11.12.2025

By Daniel Bergner Marie began taking fluoxetine, the generic form of Prozac, when she was 15. The drug — an S.S.R.I., a selective serotonin reuptake inhibitor — was part of her treatment in an outpatient program for an eating disorder. It took its toll on her sexuality. “I was in touch with initial sparks of sexual energy relatively young,” she said, remembering crushes as far back as the age of 6 or 7. Shortly before starting on the drug, she was dazzled, from a distance, by a blue-eyed hockey player at school, tall and funny and charismatic. She recalled the fluster and fantasies he stirred. But on the medication, she felt the infatuation vanish swiftly. Listen to this article, read by Eric Jason Martin “And then,” Marie said, “I realized, Oh, I’m not developing new crushes.” She had no clue that the drug might be the cause: “I wasn’t informed about sexual side effects.” Even as the worst of the eating disorder abated, psychiatrists and family doctors told Marie and her parents that she should stay on an antidepressant. She complied, while trying and failing to escape the sexual side effects. She traded fluoxetine for other antidepressants, including Wellbutrin, a different class of antidepressant, which is sometimes prescribed to combat low libido. She’s 38 now and has been off psychiatric medication for six years. But sexual desire remains absent. “For me it’s just an empty dark space,” she said. “There’s nothing there.” Marie told me she has PSSD, post-S.S.R.I. sexual dysfunction, a loss of sexuality that persists after the drug is no longer being taken. It’s a controversial designation, because while the sexual side effects of S.S.R.I.s are well established — depleted or deadened desire, erectile dysfunction for men, elusive arousal for women, delayed and dulled orgasms or the inability to reach orgasm at all — the general assumption is that they subside completely when the drug is no longer in your system. Some psychiatrists suspect that PSSD is actually a result not of repercussions from the drugs but of the problem that led the patient to be medicated in the first place. Depression itself can stymie sexuality. So can anxiety, the other leading reason patients are prescribed S.S.R.I.s. © 2025 The New York Times Company

Keyword: Depression; Sexual Behavior
Link ID: 30006 - Posted: 11.12.2025

By Susan Dominus Spend enough time speaking to women who are taking testosterone — specifically, in very high doses — and you start to notice that they sound messianic. They’re often talking fast and intensely; they’re amped up; they’re describing what they clearly consider a miracle drug; and they have no intention of lowering their dose, despite the unknown risks or some problems with facial hair. After all, how can they worry about facial hair when they feel so alive? It’s nothing they can’t take care of with a quick waxing, which they now have the energy to do at the end of the day — right after they prepare a high-protein dinner for their family and before they put the finishing touches on their spreadsheets, close their laptops and light a few mood candles for the sex that they know will be great, maybe even better than the sex they had last night, even though they’re a day older. “It’s changed my marriage,” Jessica Medina, a 41-year-old marketing consultant in Orange County, Calif., told me. With four kids in the house, and sex happening six times a week (up from “How about never?” pre-testosterone), she had to put a lock on the bedroom door. She and her husband had attended a “marriage growth” group at church for years, but it took testosterone for their relationship to be, as she put it, “100 times closer.” She was a little less emotional, a little less sentimental than she used to be, but she didn’t have time for that kind of thing, anyway. “It’s more like: Get stuff done, handle business, work out,” she said. “In order to do all that and still have time for our kids and their sports, there’s no time to whine about how hard it is.” Catherine Lin, a single mother who ran a bicoastal fashion media company, went on testosterone in her early 40s to raise her energy. She got the boost she wanted, started lifting heavier weights, decided to pursue a degree in holistic nutrition and enjoyed an unexpected side effect: She started having orgasms for the first time in years. © 2025 The New York Times Company

Keyword: Hormones & Behavior; Sexual Behavior
Link ID: 29978 - Posted: 10.22.2025

By Giorgia Guglielmi Male and female human fetuses show distinct patterns of gene activity and DNA regulation in the cerebral cortex, according to a new analysis of thousands of individual brain cells. The study offers one of the most detailed maps to date of how such activity differs between boys and girls’ brains during the second trimester. It also compares sex differences in gene activity in fetuses with spontaneous genetic changes in autistic people, revealing clues as to how these de novo changes affect boys and girls. “As the field evolves, this [work] will be a helpful reference” for exploring sex-related molecular differences in early brain development, says Matthew Oetjens, assistant professor of human genetics at Geisinger Medical Center, who was not involved in the study. Understanding these differences may help explain why certain neurodevelopmental conditions are more common in one sex than the other, he says. Autism, for example, is diagnosed about four times more often in boys than in girls, but scientists are still trying to understand why. Theories include the possibility that boys are more vulnerable, girls are sometimes protected, or a combination of both. “We know that autism … has a very strong genetic component. What is not known is how the genetic risk architecture intersects with any differences at the molecular level that might exist between male and female human brains,” says study investigator Tomasz Nowakowski, associate professor of neurological surgery, anatomy and psychiatry, and behavioral sciences at the University of California, San Francisco. More than 940 genes are expressed differently between the sexes, according to the new analysis of more than 38,000 brain cells from 21 female and 27 male mid-gestation fetuses. Most of these differentially expressed genes are more active in females. © 2025 Simons Foundation

Keyword: Autism; Genes & Behavior
Link ID: 29977 - Posted: 10.22.2025

By Michele Cohen Marill Like many first-time mothers, Lisette Lopez-Rose thought childbirth would usher in a time of joy. Instead, she had panic attacks as she imagined that something bad was going to happen to her baby, and she felt weighed down by a sadness that wouldn’t lift. The San Francisco Bay Area mother knew her extreme emotions weren’t normal, but she was afraid to tell her obstetrician. What if they took her baby away? At about six months postpartum, she discovered an online network of women with similar experiences and ultimately opened up to her primary care doctor. “About two months after I started medication, I started to feel like I was coming out of a deep hole and seeing light again,” she says. Today, Lopez-Rose works at Postpartum Support International, coordinating volunteers to help new mothers form online connections. About one in eight US women go through a period of postpartum depression, making it among the most common complications of childbirth. It typically occurs in the first few weeks after delivery, when there’s a sudden drop in the reproductive hormones estrogen and progesterone. As scientists unravel chemical and genetic changes caused by those shifting hormones, they are discovering new ways to diagnose and treat postpartum depression, and even ways to identify who is at risk for it. Graph showing a steady rise in levels of estradiol and progesterone after conception and then a very steep drop-off right after birth. The hormones estradiol (the main form of estrogen) and progesterone rise during pregnancy. In some women, their sudden drop after childbirth triggers the onset of postpartum depression. The first-ever drug for postpartum depression, containing a derivative of progesterone, received US Food and Drug Administration approval in 2019. That marked a new approach to the disorder. This winter, in another major advance, a San Diego-based startup company will launch a blood test that predicts a pregnant woman’s risk of postpartum depression with more than 80 percent accuracy. © 2025 Annual Reviews

Keyword: Depression; Hormones & Behavior
Link ID: 29972 - Posted: 10.18.2025

Rachel Fieldhouse During ageing, men experience a greater reduction in volume across more regions of the brain than women do, according to a longitudinal study published today in the Proceedings of the National Academy of Sciences1. The authors suggest this means that age-related brain changes do not explain why women are more frequently diagnosed with Alzheimer’s disease than men are. “It’s really important that we understand what happens in the healthy brain so that we can better understand what happens when people get these neurodegenerative conditions,” says Fiona Kumfor, a clinical neuropsychologist at the University of Sydney, Australia. This study adds to scientists’ understanding of typical brain ageing, she adds. Nearly twice as many women are diagnosed with Alzheimer’s disease as men, and ageing is the biggest risk factor for the disease. This has prompted research into age-related sex differences in the brain. “If women’s brains declined more, that could have helped explain their higher Alzheimer’s prevalence,” says co-author Anne Ravndal, a PhD student at the University of Oslo. Previous research investigating sex differences in brain ageing has shown mixed results, Ravndal adds. Several studies have found that men experience greater loss of total grey matter and hippocampus size compared with women, whereas other work has reported a sharper decline of grey matter in women. Brain scans The latest study included more than 12,500 magnetic resonance imaging (MRI) brain scans from 4,726 people — at least two scans per person, taken an average of three years apart — who did not have Alzheimer’s disease or any cognitive impairments and were control participants in 14 larger data sets. The researchers compared how the individuals’ brain structures changed over time, looking at factors including the thickness of grey matter and the size of areas that are associated with Alzheimer’s disease, such as the hippocampus, which is essential to memory. © 2025 Springer Nature Limited

Keyword: Alzheimers; Sexual Behavior
Link ID: 29968 - Posted: 10.15.2025

Natasha May Health reporter Women carry a higher genetic risk of depression, a new study has found. Claiming to be the largest genetic study to date on sex differences in major depression, the research published on Wednesday in Nature Communications has found 16 genetic variants linked to depression in women and eight in men. The study, led by Australia’s QIMR Berghofer Medical Research Institute, showed a large proportion of the variants associated with depression were shared between sexes, but there was a “higher burden of genetic risk in females which could be due to female-specific variants”. Dr Brittany Mitchell, a senior researcher at QIMR Berghofer’s genetic epidemiology lab, said “we already know that females are twice as likely to suffer from depression in their lifetime than males”. “And we also know that depression looks very different from one person to another. Until now, there hasn’t been much consistent research to explain why depression affects females and males differently, including the possible role of genetics.” The study acknowledged explanations have been put forward spanning behavioural, environmental and biological domains, including men being less likely to seek help leading to under-diagnosis, and environmental exposures such as women being more frequently exposed to sexual abuse and interpersonal violence. The study stated that together these factors highlight the need for a “multifaceted approach” to understanding the underlying mechanisms of depression but proposed that a “key component of the biological mechanisms underlying these disparities could be differences in genetics”. © 2025 Guardian News & Media Limited

Keyword: Depression; Genes & Behavior
Link ID: 29958 - Posted: 10.08.2025

By Calli McMurray Studying animal behavior in the wild often gets hairy, with little experimental control and an abundance of extraneous data. And when multiple animals get together, the way they look, act and smell all influence one another, making it difficult to parse complex social interactions, says Andres Bendesky, associate professor of ecology, evolution and environmental biology at Columbia University. Robotic or animated partners, however, can simplify that equation. Studying animal-robot interaction gives researchers complete control over one partner during any tête-à-tête, Bendesky says. It makes it possible to present the same stimulus to an animal repeatedly or compare how different individuals react. And the method complements observation-based research: Scientists can use a robot- or animation-based paradigm to test ideas gleaned from studies that use artificial-intelligence tools to track behavior. Bendesky is part of a growing cohort of neuroscientists turning to robots to help them decode social interactions. The quirks are still being ironed out, but the approach is already helping several groups tackle questions about schooling, fighting and chatting behaviors. The rigor of the results depends on whether a critter believes what it sees, says Tim Landgraf, professor of artificial and collective intelligence at Freie Universität Berlin, who uses robots to study group behavior in guppies. That can be hard to gauge; there’s no handbook that describes what traits make a robot believable, he says. But researchers can compare how animals act toward a real peer versus a counterfeit one, says Steve Chang, associate professor of psychology and neuroscience at Yale University, who doesn’t work with robots but studies the social behavior of macaques and marmosets. © 2025 Simons Foundation

Keyword: Robotics; Sexual Behavior
Link ID: 29936 - Posted: 09.20.2025

By Claudia López Lloreda Mouse pups, like other infants across the animal kingdom, cry to get their mother’s attention. The oxytocin system drives this communication and shapes how baby mice interact when reunited with their mothers, according to a study out today in Science. Oxytocin, known colloquially as the “love” or “cuddle” hormone, stimulates milk release during nursing and promotes maternal care behaviors. But most oxytocin research thus far has focused solely on the mother, overlooking the neuropeptide’s potential effects on an infant’s brain and behavior. This new study shows “the other half of the equation to what we already knew,” says Zoe Donaldson, associate professor of behavioral neuroscience at the University of Colorado Boulder, who was not involved with the study. Oxytocin is “this social signal that ultimately reinforces relationships,” she says. The work employed a novel optogenetic tool that enabled the team to turn off neurons deep in the hypothalamus of mouse pups. After being separated from their mothers for three hours, the pups vocalized more using distinct patterns when reunited with their mothers than did pups that had not been separated, a process controlled by oxytocin neurons in the pups’ hypothalamus, the team found. “It would make sense if oxytocin is on both sides of this: making moms want to take care of their pups that are calling, and making pups call in a manner that makes mom want to take care of them,” Donaldson says. “Then we have this sort of convergence where oxytocin is once again doing everything.” © 2025 Simons Foundation

Keyword: Sexual Behavior; Animal Communication
Link ID: 29928 - Posted: 09.13.2025

Ian Sample Science editor The cry of a distressed baby triggers a rapid emotional response in both men and women that is enough to make them physically hotter, researchers say. Thermal imaging revealed that people experienced a rush of blood to the face that raised the temperature of their skin when they were played recordings of babies wailing. The effect was stronger and more synchronised when babies were more distressed, leading them to produce more chaotic and disharmonious cries. The work suggests that humans respond automatically to specific features in cries that ramp up when babies are in pain. “The emotional response to cries depends on their ‘acoustic roughness’,” said Prof Nicolas Mathevon at the University of Saint-Etienne in France. “We are emotionally sensitive to the acoustic parameters that encode the level of pain in a baby’s cry.” Evolution equipped baby humans with a hard-to-ignore wail to boost their odds of getting the care they need. But not all infant cries are the same. When a baby is in real distress, they forcefully contract their rib cage, producing higher pressure air that causes chaotic vibrations in the vocal cords. This produces “acoustic roughness”, or more technically, disharmonious sounds called nonlinear phenomena (NLP). To see how men and women responded to infants’ cries, scientists played recordings to volunteers with little or no experience with babies. While listening, the participants were filmed with a thermal camera that captured subtle changes in their facial temperature. © 2025 Guardian News & Media Limited

Keyword: Sexual Behavior; Emotions
Link ID: 29924 - Posted: 09.10.2025

By Sofia Caetano Avritzer When Canada legalized cannabis in 2018, its effects on human health were all over the news. Cyntia Duval, a women’s health researcher at the University of Toronto at the time, wondered how its consumption might affect female fertility. To her surprise, there was almost no information on the subject — though there was plenty of data on marijuana’s effects on pregnancy and male fertility. Chemicals in cannabis may push eggs to become ready for fertilization. But this may come at a cost: more eggs with the wrong number of chromosomes, Duval and colleagues now report in a study published September 9 in Nature Communications. Delta-9-tetrahydrocannabinol, or THC, is the main psychoactive chemical in marijuana. It binds to cannabinoid receptors in the brain. But these receptors are all over our bodies, including in our reproductive organs. The receptors usually bind endocannabinoids, molecules naturally produced by the body and essential for normal bodily functions like the production of eggs and sperm. Consuming THC can affect cannabinoid receptors in the reproductive system. Many studies report that using cannabis decreases sperm count and motility. Men are usually told to avoid cannabis for at least three months before trying to conceive, Duval says. But what about women? © Society for Science & the Public 2000–2025.

Keyword: Drug Abuse; Sexual Behavior
Link ID: 29922 - Posted: 09.10.2025

Ian Sample Science editor Women should ensure they are getting enough omega fatty acids in their diets according to researchers, who found unusually low levels of the compounds in female patients with Alzheimer’s disease. The advice follows an analysis of blood samples from Alzheimer’s patients and healthy individuals, which revealed levels of unsaturated fats, such as those containing omega fatty acids, were up to 20% lower in women with the disease. The low levels were not seen in men with Alzheimer’s, suggesting there may be sex differences in how the disease takes hold and affects a person’s physiology. “The difference between the sexes was the most shocking and unexpected finding,” said Dr Cristina Legido-Quigley, a senior author on the study at King’s College London published in the Alzheimer’s & Dementia journal. “There’s an indication that having less of these compounds could be causal in Alzheimer’s, but we need a clinical trial to confirm that.” Alzheimer’s disease is twice as common in women as in men. Factors including women’s longer average lifespan, differences in hormones, immune responses and educational opportunities can all play a role in the development of the disease. In the latest study, researchers analysed the levels of lipids, which are fatty compounds, in the blood of 306 people with Alzheimer’s, 165 people with mild cognitive impairment and 370 people who were cognitively healthy controls. Lipids can be saturated or unsaturated, with the former generally considered unhealthy and the latter broadly healthy. © 2025 Guardian News & Media Limited

Keyword: Alzheimers; Sexual Behavior
Link ID: 29898 - Posted: 08.23.2025

By Sofia Caetano Avritzer Vomiting up a droplet of sugar might not seem like the most romantic gesture from a potential suitor. But for one fly species, males that spill their guts are quite a catch. Drosophila subobscura flies’ peculiar “romantic” barfing might have evolved by repurposing brain cells that usually control digestion for more romantic pursuits, researchers report August 14 in Science. Most male fruit flies court by following the females around and vibrating their wings to serenade them with a species-specific love song, says Adriane Otopalik. But some fly species, like D. subobscura, spice things up a little. The males will vomit a bit of their last meal and offer it to females they are interested in, says Otopalik, a neuroscientist at Howard Hughes Medical Institute’s Janelia Research Campus in Ashburn, Va. Nuptial gifts like these are common in some animals, like male spiders attempting to win over their mates without getting their heads bitten off. Scientists think female flies, which can be “very choosy,” might use this romantic barf to pick suitable suitors, says Otopalik, who was not involved in the study. The thousands of neurons that control most of male fruit flies’ courtship produce a male-specific version of a protein called fruitless. Artificially activating these neurons can make D. subobscura males go through the motions of their seduction dance — even when there aren’t any females around, says Daisuke Yamamoto, an evolutionary biologist at National Institute of Information and Communications Technology in Kobe, Japan. Yamamoto and his collaborators wondered if somewhere in these courtship brain cells was the key to understanding how nuptial gift giving evolved. © Society for Science & the Public 2000–2025

Keyword: Sexual Behavior; Genes & Behavior
Link ID: 29890 - Posted: 08.16.2025

By Phie Jacobs When it comes to telling males and females apart, many bird species reject subtlety altogether. Roosters stand out thanks to their big, bright comb and ear-splitting “cock-a-doodle-doo.” Bachelor birds-of-paradise flaunt their vibrant plumage to attract more subdued females. And the male peacock’s feathered train is so ostentatious it famously threw even Charles Darwin for a loop. But that’s not the case for all bird species. When males and females look pretty much the same, scientists must try harder—often using DNA testing—to separate the sexes. According to a new study of wild Australian birds, these methods may be leading to misidentification in cases where an individual’s gonads and outward appearance don’t align with the genetic sex determined by its chromosomes. As scientists report today in Biology Letters, this phenomenon—known as sex reversal—may be more common than anyone expected. The discovery is likely to “raise some eyebrows” (or is it ruffle some feathers?), says Blanche Capel, a biologist at Duke University who wasn’t involved in the new work. Although sex determination is often viewed as a straightforward process, she explains, the reality is much more complicated. In humans, individuals with XX chromosomes typically develop as female, whereas those with XY chromosomes are usually male. But Judith Mank, a zoologist at the University of British Columbia, notes it’s the genes carried on those chromosomes—not the chromosomes—that are the main players. The SRY gene on the Y chromosome, for example, kick-starts male development in mammals. Anyone missing this key gene will end up developing as female, even if they have XY chromosomes. “We think of sex chromosomes as being sex determining,” says Mank, who also wasn’t involved in the new research. “That’s not true.” What’s more, it can matter how these genes are expressed on a cell-by-cell basis. In some species such as fruit flies, zebrafish, and chickens, individual cells have their own sexual identity based on the genes they happen to contain or express, rather than being influenced by the body’s overall hormone levels. When different cells contain different sets of chromosomes, this process can give rise to individuals called gynandromorphs, which exhibit both male and female characteristics. © 2025 American Association for the Advancement of Science.

Keyword: Sexual Behavior; Evolution
Link ID: 29886 - Posted: 08.13.2025

By Holly Barker Prairie voles do not need oxytocin receptors to bond with a mate or care for their pups, but the receptors are indispensable for forming robust friendships, according to a study published today in Current Biology. Female voles that lack the receptors struggle to make friends with other females, and when they do, they are not motivated to spend time with friends over strangers and quickly lose track of their friends in a group, the study found. The findings suggest that oxytocin is required for nurturing specific relationships, rather than for general sociability, says principal investigator Annaliese Beery, associate professor of integrative biology and neuroscience at the University of California, Berkeley. That concept—known as selectivity—is a “really important component of human friendships,” she says. Until now, prairie voles have typically been used to probe the neural basis of love: The animals are unusual among rodents for selecting a single partner to nest and raise pups with. Compared with non-monogamous vole species, prairie voles have a high density of oxytocin receptors in multiple brain regions, including the nucleus accumbens. Drugs that block the receptors there impair mate attachment in prairie voles, whereas brain infusions of oxytocin fast track the animal’s choice of a lifelong partner. Oxytocin appears to be especially important in the initial stages of bond formation, according to studies of transgenic prairie voles. Voles genetically engineered to carry loss-of-function mutations in both copies of the oxytocin receptor gene are less likely to bond with a littermate they have been housed with for less than a week, according to work reported in a 2024 preprint. © 2025 Simons Foundation

Keyword: Hormones & Behavior; Evolution
Link ID: 29883 - Posted: 08.09.2025

By Shaena Montanari Leafcutter ants’ roles can be reprogrammed by manipulating two neuropeptides, according to a new study. These ants are known for their rigorous division of labor in a caste system, with groups performing roles ranging from cutting leaves to nest defense to tending the fungus that is their food source. Despite physical differences among the ants—the heads of the nest defender ants can be five times the size of the fungal carers’ heads, for instance—it’s still possible to “pharmacologically reprogram them to assume some of the roles that typically other castes assume,” indicating behavioral flexibility, says Daniel Kronauer, professor at Rockefeller University, who was not involved in the work. The researchers induced the behavioral changes by first using RNA sequencing to uncover target neuropeptides and then manipulating neuropeptide levels in the ants. The study was published in June in Cell. The work illustrates the close relationship between neuropeptides and behavior, says Shelley Berger, professor of cell and developmental biology at the University of Pennsylvania and principal investigator of the study. Defender ants are “so big and awkward and clumsy,” she says, but after a certain neuropeptide level is lowered, the ant becomes a “nurse tending to the brood.” The study shows the “importance of neuropeptides as these molecular controllers of incredibly complex” behavioral traits, says Zoe Donaldson, professor of behavioral neuroscience at the University of Colorado Boulder, who was not involved in the study. “I think it’s a really elegant demonstration of just how powerful they are.” Almost all species of ants live in colonies, but leafcutter ants (Atta cephalotes) have a particularly intricate labor division, says study investigator Karl Glastad, assistant professor of biology at the University of Rochester. He and Berger previously explored hormonal controls of social behavior in Florida carpenter ants, which have two worker subtypes, but leafcutter ants are a “really elaborated version” of that species, Glastad says. © 2025 Simons Foundation

Keyword: Hormones & Behavior; Evolution
Link ID: 29856 - Posted: 07.16.2025

By Sydney Wyatt The shape and density of dendritic spines fluctuate in step with the estrous cycle in the hippocampus of living mice, a new study shows. And these structural changes coincide with shifts in the stability of place fields encoded by place cells. “You can literally see these oscillations in hippocampal spines, and they keep time with the endocrine rhythms being produced by the ovaries,” says study investigator Emily Jacobs, associate professor of psychological and brain sciences at the University of California, Santa Barbara. She and her colleagues used calcium imaging and surgically implanted microperiscopes to view the dynamics of the dendritic spines in real time. The findings, published in Neuron in May, replicate and expand upon a series of cross-sectional studies of rat brain tissue in the early 1990s that documented sex hormone receptors in the hippocampus and showed that changes in estradiol levels across the estrous cycle track with differences in dendritic spine density. “The field of neuroendocrinology was really changed in the early ’90s because of this discovery,” Jacobs says. The new work is a “very important advancement,” says John Morrison, professor of neurology at the University of California, Davis, who was not involved in the research. It shows that spines change across the natural cycle of living mice, supporting estradiol’s role in this process, and it links these changes to electrophysiological differences, he says. “The most surprising part of this study is that everything seems to follow each other. Usually biology doesn’t cooperate like this,” Morrison says. Before the early 1990s, estrogens were viewed only as reproductive hormones, and their effects in the brain were thought to be limited to the hypothalamus, says Catherine Woolley, professor of neurobiology at Northwestern University, who worked on the classic rat hippocampus studies when she was a graduate student in the lab of the late Bruce McEwen. For that reason, her rat hippocampus results were initially met with “resistance,” she adds. A leader in the field once told her to “get some better advice” from her adviser “because estrogens are reproductive hormones, and they don’t have effects in the hippocampus,” she recalls. © 2025 Simons Foundation

Keyword: Hormones & Behavior; Learning & Memory
Link ID: 29841 - Posted: 06.28.2025

Nicola Davis Science correspondent Birds of a feather flock together, so the saying goes. But scientists studying the behaviour of starlings have found their ability to give and take makes their relationships closer to human friendships than previously thought. About 10% of bird species and 5% of mammal species breed “cooperatively”, meaning some individuals refrain from breeding to help others care for their offspring. Some species even help those they are unrelated to. Now researchers studying superb starlings have found the support cuts both ways, with birds that received help in feeding or guarding their chicks returning the favour when the “helper” bird has offspring of its own. Prof Dustin Rubenstein, a co-author of the study from the University of Colombia, said such behaviour was probably necessary for superb starlings as they live in a harsh environment where drought is common and food is limited. “Two birds probably can’t feed their offspring on their own, so they need these helpers to help them,” he said, adding that as each breeding pair produces few offspring, birds must be recruited from outside the family group to help the young survive. “What happens is the non-relatives come into the group, and they breed pretty quickly, usually in the first year, maybe the second year, and then they take some time off and some of the other birds breed – and we never understood why,” said Rubenstein. “But they’re forming these pairwise reciprocal relationships, in the sense that I might help you this year, and then you’ll help me in the future.” The results chime with previous work from Rubenstein and colleagues that found superb starlings living in larger groups have a greater chance of survival and of producing offspring, with the new work suggesting the give-and-take approach helps to stabilise these groups. © 2025 Guardian News & Media Limited

Keyword: Sexual Behavior; Evolution
Link ID: 29785 - Posted: 05.14.2025