A small study uses genetic engineering with the goal of curbing vast stray feline populations.For all the cats who share our homes as companion animals, there is a vast shadow world of strays — a sprawling and fast-breeding crowd.Their lives are plagued by the threat of infectious diseases, predators and fast-moving cars. And they are major predators themselves, hunting down millions of birds and small mammals annually.In the United States, volunteers are especially active in trapping the cats, bringing them to clinics to get surgically sterilized, and then returning them to their colonies. But controlling stray cat populations is costly and logistically cumbersome. Many communities, especially in countries outside the United States and Europe, lack the veterinary and economic resources to coordinate such efforts.“Coming up with an alternative to surgery has been a goal for a lot of people for decades, and there just hasn’t been anything else that’s proven to be effective,” said William Swanson, director of animal research at the Cincinnati Zoo & Botanical Garden.Such a method might finally be on the horizon. In a study published Tuesday in the journal Nature Communications, a single shot of a gene therapy prevented pregnancy in cats for at least two years. The study was extremely small: Six female cats that received the gene therapy shot were compared to three who did not.By limiting the study size to just a few cats, the researchers were able to track each one extensively, analyzing 15,220 freeze-dried poop samples for estrogen and progesterone levels and examining 1,200 hours of video of mating behavior, Dr. Swanson said.The contraceptive shot delivers a gene that enters muscle cells, enabling them to pump out a substance called anti-Müllerian hormone, or AMH, which interferes with the development of egg follicles in the ovaries.Researchers cautioned that much more research would be needed to test the preliminary findings. And if larger studies confirm that the treatment — the first gene therapy developed specifically for animals — is safe and effective over a cat’s lifetime, controlling cat populations won’t require the surgical expertise of veterinarians, Dr. Swanson said.David Pépin, a reproductive biologist at Massachusetts General Hospital in Boston, was originally studying AMH as a potential therapy for ovarian cancer, but decided to look at its effect on ovaries. When he injected the hormone into mice, their ovaries shrunk to newborn size, suggesting AMH might have contraceptive properties.Dr. Pépin is investigating the potential use of AMH in people, not as a gene therapy but as a pill or injection that must be taken continuously. Most contraceptives today prevent ovulation, but AMH would act earlier, blocking follicles from maturing.He thinks that it might be useful for women who could not take birth control pills with progesterone or estrogen for medical reasons or that it could help women undergoing cancer treatments preserve their fertility. “It’s a hormone that we didn’t get to play with before that potentially has many different applications in women’s health,” he said.As a gene therapy that could be permanent, the use of AMH in people is unlikely. “But it’s actually the perfect tool to control cat overpopulation,” he said. Four of the cats in the study did not show behaviors indicating they were ready to mate, and two allowed male cats to mate with them, but did not ovulate.Dr. Pépin and Dr. Swanson, an expert in feline reproduction (and a scientific advisory board member of the Michelson Found Animals Foundation, which funded the work), are planning a larger study that could support an application to the Food and Drug Administration to consider approving the therapy to be marketed for use in cats.They are also testing the therapy in kittens, which can be treated starting at eight weeks of age, as well as in dogs, which also have enormous stray populations, particularly in other countries.“This is really exciting, and I hope it will pan out,” said Julie Levy, a veterinarian at the University of Florida College of Veterinary Medicine in Gainesville, who was not involved with the study. “Wouldn’t it be great if we could send out a technician into the field to inject cats and then let them go?”The study is an example of the Michelson foundation’s practice of “throwing a lot of big money at the problem” to find nonsurgical contraception for stray cats and dogs, said Dr. Levy, who works with cats in outdoor colonies and shelters, both in the United States and abroad.But she cautioned that there was still much to learn from a larger study, such as how long the shot lasts, whether it is as safe as it seems, and what proportion of cats it will actually protect from pregnancy, “because it probably won’t be 100 percent.”Others note that it might not be quite so easy. If the shot is effective, long-lasting and cheaper than spay and neuter surgery, it could be very valuable, said Autumn Davidson, a veterinarian at Cornell’s College of Veterinary Medicine in Ithaca, N.Y. But to receive the injection, animals have to be captured, and queens who are adept at evading people’s traps might still make population control a struggle.

An emerging branch of neuroscience asks a question long on the minds of researchers. Recent stimulus payments make the study more relevant.New monthly payments in the pandemic relief package have the potential to lift millions of American children out of poverty. Some scientists believe the payments could change children’s lives even more fundamentally — via their brains.Does cash aid to poor parents help their children’s long-term brain development?Karsten Moran for The New York TimesIt’s well established that growing up in poverty correlates with disparities in educational achievement, health and employment. But an emerging branch of neuroscience asks how poverty affects the developing brain.Over the past 15 years, dozens of studies have found that children raised in meager circumstances have subtle brain differences compared with children from families of higher means. On average, the surface area of the brain’s outer layer of cells is smaller, especially in areas relating to language and impulse control, as is the volume of a structure called the hippocampus, which is responsible for learning and memory.These differences don’t reflect inherited or inborn traits, research suggests, but rather the circumstances in which the children grew up. Researchers have speculated that specific aspects of poverty — subpar nutrition, elevated stress levels, low-quality education — might influence brain and cognitive development. But almost all the work to date is correlational. And although those factors may be at play to various degrees for different families, poverty is their common root. A continuing study called Baby’s First Years, started in 2018, aims to determine whether reducing poverty can itself promote healthy brain development.“None of us thinks income is the only answer,” said Dr. Kimberly Noble, a neuroscientist and pediatrician at Columbia University who is co-leading the work. “But with Baby’s First Years, we are moving past correlation to test whether reducing poverty directly causes changes in children’s cognitive, emotional and brain development.”Dr. Noble and her collaborators are examining the effects of giving poor families cash payments in amounts that wound up being comparable to those the Biden administration will distribute as part of an expanded child tax credit.The researchers randomly assigned 1,000 mothers with newborns living in poverty in New York City, New Orleans, the Twin Cities and Omaha to receive a debit card every month holding either $20 or $333 that the families could use as they wished. (The Biden plan will provide $300 monthly per child up to age 6, and $250 for children 6 through 17.) The study tracks cognitive development and brain activity in children over several years using a noninvasive tool called mobile EEG, which measures brain wave patterns using a wearable cap of 20 electrodes.The study also tracks the mothers’ financial and employment status, maternal health measures such as stress hormone levels, and child care use. In qualitative interviews, the researchers probe how the money affects the family, and with the mothers’ consent, they follow how they spend it.The study aimed to collect brain activity data from children at age 1 and age 3 in home visits, and researchers managed to obtain the first set of data for around two-thirds of the children before the pandemic struck. Because home visits are still untenable, they extended the study to age 4 and will be collecting the second set of brain data next year instead of this year.The pandemic, as well as the two stimulus payments most Americans received this past year, undoubtedly affected participating families in different ways, as will this year’s stimulus checks and the new monthly payments. But because the study is randomized, the researchers nonetheless expect to be able to assess the impact of the cash gift, Dr. Noble said.Baby’s First Years is seen as an audacious effort to prove, through a randomized trial, a causal link between poverty reduction and brain development. “It is definitely one of the first, if not the first” study in this developing field to have direct policy implications, said Martha Farah, a cognitive neuroscientist at the University of Pennsylvania and director of the Center for Neuroscience and Society who studies poverty and the brain.Professor Farah concedes, however, that social scientists and policymakers often discount the relevance of brain data. “Are there actionable insights we get by bringing neuroscience to bear, or are people just being snowed by pretty brain images and impressive-sounding words from neuroscience? It’s an important question,” she said.Skeptics abound. James Heckman, a Nobel Prize-winning economist at the University of Chicago who studies inequality and social mobility, said he didn’t see “even a hint that a policy would come out of it, other than to say, yes, there’s an imprint of a better economic life.”“And it still remains a question what the actual mechanism is” through which giving parents cash helps children’s brains, he said, adding that targeting such a mechanism directly might be both cheaper and more effective.Samuel Hammond, director of poverty and welfare policy at the Niskanen Center, who worked on a child allowance proposal by Senator Mitt Romney, agrees that tracking the source of any observed cognitive benefits is tricky. “I have trouble disentangling the interventions that actually help the most,” he said. For example, policy experts debate whether certain child care programs directly benefit a child’s brain or simply free up her caregiver to get a job and increase the family’s income, he said.Yet that is exactly why providing disadvantaged families with cash might be the most potent way to test the link to brain development, Dr. Noble said. “It’s quite possible that the particular pathways to children’s outcomes differ across families,” she said. “So by empowering families to use the money as they see fit, it doesn’t presuppose a particular pathway or mechanism that leads to differences in child development.”Neuroscience has a track record for transforming societal thinking and influencing policy. Research showing that the brain continues to mature past adolescence and into a person’s mid-20s has reshaped policies relating to juvenile justice.In another example, research on brain and cognitive development in children who grew up in Romanian orphanages from the mid-1960s into the 1990s changed policy on institutionalization and foster care, in Romania and worldwide, said Charles Nelson, a neuroscientist at Harvard and Boston Children’s Hospital who co-led that work.Those studies demonstrated that deprivation and neglect diminish IQ and hinder psychological development in children who remain institutionalized past age 2, and that institutionalization profoundly affects brain development, dampening electrical activity and reducing brain size.But that work also underscores how consumers of research, policymakers among them, are prone to give more weight to brain data than to other findings, as other studies show. When Professor Nelson presents these findings to government or development agency officials, “I think they find it the strongest ammunition to implement policy changes,” he said. “It is a very powerful visual, more so than if we said, well, they have lower IQs, or their attachment isn’t as strong.” (He is an adviser for Baby’s First Years.)The vividness of such data isn’t necessarily bad, Dr. Noble said. “If we find differences and the brain data make those differences more compelling to stakeholders, then that’s important to include,” she said. Moreover, brain data provides valuable information in its own right, particularly in infants and young children, for whom behavioral tests of cognition are often inaccurate or impossible to conduct, she said. Brain differences also tend to be detectable earlier than behavioral ones, she said.The field may simply be too young to clock its contributions to policy, Professor Farah said. But increasing understanding of how specific brain circuits are affected by poverty, along with better tools for gauging such circuits, may yield science-based interventions that get taken up at a policy level, she said.Meanwhile, Baby’s First Years hopes to address a broader question that is already relevant at the policy level: whether cash aid to parents helps their children’s brains develop in a way that helps them for a lifetime.Alla Katsnelson is a science journalist in Northampton, Mass. You can follow her on Twitter at @lalakat.