The researchers found that whereas adults build integrated memories with inferences already baked in, children and adolescents create separate memories that they later compare to make inferences on the fly.

“How adults structure knowledge is not necessarily optimal for children, because adult strategies might require brain machinery that is not fully mature in children,” said Alison Preston, professor of neuroscience and psychology and senior author of the study published today in the journal Nature Human Behaviour. She co-led the study with first author Margaret Schlichting, formerly a doctoral student in Preston’s lab and currently assistant professor of psychology at the University of Toronto.

To understand the distinction between how adults and children make inferences, imagine visiting a day care center. In the morning, you see a child arriving with one adult, but in the afternoon that child leaves with a different adult. You might infer that the two grown-ups are the child’s parents and are a couple, and your second memory would include both the second person you saw and information from your earlier experience in order to make an inference about how the two adults — whom you didn’t actually see together — might relate to each other.

This new study finds that a child who has the same experiences isn’t likely to make the same kind of inference that an adult would during the second experience. The two memories are less connected. If you ask your child to infer who that child’s parents are, your child can still do it; he or she just has to retrieve the two distinct memories and then reason about how each adult might be related.

The neural machinery of children and adults differs, and the strategy that children use may be optimal for the way their brains are wired before key memory systems in the hippocampus and prefrontal cortex fully mature, the researchers believe. That difference could keep children from recalling past memories during new learning and limit their ability to connect events.

“In the absence of a mature memory system, the best thing a child can do is lay down accurate, non-overlapping memory traces,” Preston said. “From those accurate memory traces, children can later bring them to mind to promote inferences about their connections.”

The researchers asked 87 subjects, ages 7 to 30, to look at pairs of images while lying in an fMRI (functional magnetic resonance imaging) scanner, which measures brain activity by detecting small changes in blood flow with images that, as in the day care example above, provide opportunities to infer relationships between objects that had not appeared together.

The researchers found that the strategy adolescents used for making inferences was different from both that of young children and adults. Going back to the example of the parents at the day care, when an adolescent stores a memory of the second grown-up with the child, the adolescent suppresses the earlier memory involving the first one. Each memory becomes even more distinct than with younger children, and there are even fewer automatic inferences about how the two adults relate.

“Teenagers may have learning strategies that are tuned to explore the world more so than exploiting what they already know,” Preston said.

This and other lessons from the study could inform strategies for improving teaching and learning at various ages.

“From a brain maturation perspective, different people are going to be at different places,” Preston said, “and we can devise learning strategies that take advantage of the neural machinery that an individual has at hand, no matter if they are 7 years old or 70 years old.”

The study’s other authors are Katharine Guarino at Loyola University Chicago and Hannah Roome of UT Austin.

This work was supported by the National Institutes of Health and by the Canada Foundation for Innovation. Preston holds the Dr. A. Wilson Nolle and Sir Raghunath P. Mahendroo Professorship in Neuroscience.

“Complex, interdependent forces are shaping the future of our forests,” said study lead author Avery Hill, a graduate student in biology at Stanford’s School of Humanities & Sciences. “We leveraged an immense amount of ecological data in the hopes of contributing to a growing body of work aimed at managing these ecosystem transitions.”

As the climate changes, animal and plant species are shifting their ranges toward conditions suitable for their growth and reproduction. Past research has shown that plant ranges are shifting to higher, cooler elevations at an average rate of almost five feet per year. In many studies, these range shifts lag behind the rate of climate change, suggesting that some species may become stranded in unsuitable habitats. The factors that impact plant species’ ability to keep up with climate change are key to maintaining healthy populations of the dominant trees in western forests, yet have remained largely mysterious.

To better understand the distance, direction and rate at which tree ranges are shifting, Hill and study co-author Chris Field, the Perry L. McCarty Director of the Stanford Woods Institute for the Environment, looked at how the phenomenon is affected by wildfire, a potent and widespread driver of ecosystem structure and composition in the western United States.

Using U.S. Forest Service data collected from over 74,000 plots across nine Western states, the researchers identified tree species that are shifting their ranges toward cooler, wetter sites — an expected response to the recent warming and drying. Then, they compared the rate of these range shifts between places that were burned by wildfire and places that were not.

Of eight species that had seedlings growing in climates significantly different from mature trees of the same species, Hill and Field found strong evidence that two — Douglas fir and canyon live oak — had larger range shifts in areas that burned than in areas that did not.

Although the analysis did not reveal the mechanism for how wildfire accelerates range shifts for certain trees, the researchers hypothesized that burned areas with their open canopies and scorched understory present less competition from other plant species.

The findings demonstrate not only that fire can accelerate tree migration, but that some species may be slowing the range shifts of others through competition. This, in turn, raises questions about the impact of fire management on trees’ ability to keep up with climate change, and points to the importance of low-intensity prescribed and natural fires.

“This study highlights a natural mechanism that can help forests remain healthy, even in the face of small amounts of climate change,” said Field. “It also illustrates the way that ecosystem processes often have several layers of controls, a feature that emphasizes the value of detailed understanding for effective management.”

Field is also the Melvin and Joan Lane Professor for Interdisciplinary Environmental Studies, a professor of Earth system science and biology, and a senior fellow at the Precourt Institute for Energy.

The research was funded by the Gordon and Betty Moore Foundation.

Story Source:

Materials provided by Stanford University. Original written by Rob Jordan. Note: Content may be edited for style and length.

The “Great Green Wall” initiative aims to compensate for and reverse this loss through mass planting of native trees and grasses. 100 million hectares of land are to be restored in this way. So far, however, this ambitious goal is very far from being achieved — partly because of a lack of financial resources.

However, this could change in the future: Earlier this year, various donor countries pledged nearly $15 billion to the project at the One Planet Summit for Biodiversity. “In order to use these funds efficiently, we now have to ask ourselves where and for which measures they should be used most sensibly,” emphasizes Dr. Alisher Mirzabaev of the Center for Development Research (ZEF) at the University of Bonn.

Every dollar invested yields a 20-cent of net returns

The agricultural economist has led a study that provides an answer. The researchers divided the Sahel region into 40 million plots of 25 hectares each. For each of these, they then analyzed which land restoration measures would be possible and how much they would cost. They compared this calculation with the economic benefits that could be achieved.

“On the one hand, these include the so-called provisioning services,” explains Mirzabaev: “These are the things that are produced by the ecosystems: Food and drinking water, raw materials such as wood or medicinal plants.” There are also other effects, such as a better climate, less wind erosion or pollinators services, which in turn increase the farmers’ crop yields. They, too, can have a price tag attached to them today.

The results show that building the “Green Wall” is also economically worthwhile. But how much depends on a number of factors. As a rule, reforestation would be the most advantageous economically and ecologically. But it takes decades for a few hundred seedlings to grow into a forest. The investment therefore only bears fruit in the very long term.

The situation is different when degraded areas are converted into farmland. “Ideally, the first harvest is then possible after just one year,” says Mirzabaev. Cropland restoration can thus pay for itself comparatively quickly, with many poor smallholder farmers also preferring quick returns from their restoration activities. However, the profits that can be achieved as a result are significantly lower, as are the environmental effects.

“In our analysis, we work with different scenarios, some of which are aimed more at short-term benefits, while others are more long-term,” explains the agricultural economist, who is a member of the Transdisciplinary Research Area “Sustainable Futures” at the University of Bonn. The so-called baseline scenario, for example, includes a mixture of both short-term and long-term returns. In it, every dollar spent yields an average net return of 20 cents.

Half of the profitable regions are too uncertain for action

However, there are huge regional variations in this. The most positive economic balance is for parts of Nigeria, Eritrea and Ethiopia. This is where the investment in the “Green Wall” is most worthwhile. To finance all the proposed measures in this scenario, a sum of 44 billion U.S. dollars would be needed. This would allow 28 million hectares of land to be restored.

However, the analysis also shows that this will probably only work in theory. The reason is that, due to violent conflicts, many of the regions where it would make sense to build the Green Wall are simply too unsafe for such measures. “If we take out these areas, we are left with just 14 million hectares,” Mirzabaev points out. “This shows how much such disputes not only cause direct human suffering, but also prevent positive development of the affected regions.”

Researchers found patients who had the mitral valve surgery with the tricuspid annuloplasty were less likely to die, need a tricuspid valve reoperation, or have tricuspid regurgitation advance to a severe stage during a two-year period after treatment, compared to those who had the mitral valve surgery alone. However, patients who had both procedures were more likely to need a permanent pacemaker.

The surgical protocol aims to prevent regurgitation, which occurs when flaps on the heart valves don’t close properly and blood flows backward into the heart. This can make it harder for blood to move efficiently throughout the body. In severe cases, regurgitation can increase the risk for an irregular heart rhythm, stroke, or heart failure.

More than 8 million Americans are diagnosed with some form of heart valve disease each year. A standard procedure for regurgitation that affects the mitral and tricuspid valves typically involves mitral valve surgery — which usually starts with minor tissue repair but could advance to valve repair or replacement. Decisions for adding a tricuspid annuloplasty vary widely. In this procedure, surgeons use a ring to reshape or resize a widening valve. While many patients, about 78%, with severe tricuspid regurgitation pair a tricuspid annuloplasty with mitral valve surgery, only about 4% with mild tricuspid regurgitation and 35% with moderate tricuspid regurgitation do so.

To help health professionals and patients make informed decisions about what to do in these cases, researchers from the Cardiothoracic Surgical Trials Network (CTSN), which is supported by NHLBI, launched a multi-year randomized clinical trial in 2016 with patients being treated for worsening mitral valve regurgitation with mild to moderate tricuspid regurgitation. The surgical procedures took place at 39 medical centers in the United States, Canada and Germany.

For the study, researchers enrolled 401 patients who planned to have mitral valve surgery. They were then randomly assigned to one of two treatment groups. The first had the mitral valve surgery, and the other had mitral valve surgery, along with a tricuspid valve annuloplasty.

Researchers found that among patients who had the combined mitral valve and tricuspid valve repair, just 3.9% developed severe regurgitation, died, or needed a reoperation, compared to 10.2% who had the mitral valve surgery alone. Researchers observed no significant differences between patient groups in the number of major cardiovascular events, changes in functional status, or quality of life. However, 14.1% of patients who had the surgery and tricuspid annuloplasty needed a permanent pacemaker, compared to 2.5% who had the surgery alone.

In discussing these results, Annetine C. Gelijns, Ph.D., and Alan J. Moskowitz, M.D., the principal investigators of the study’s data and clinical coordinating center at the Icahn School of Medicine at Mount Sinai, New York City, indicated that this trial delineates the important trade-off that patients face in deciding between the benefits of reducing the risk of tricuspid regurgitation progressing and increasing the risk of requiring a permanent pacemaker. These types of decisions vary for each patient.

Over the next few years, researchers will evaluate other clinical measures among trial participants to assess if there is a long-term benefit in pairing the tricuspid valve annuloplasty with mitral valve surgery.

“In addition to following the health outcomes of patients who received a pacemaker, we look forward to following those with milder forms of tricuspid regurgitation to assess their outcomes also,” said Wendy C. Taddei-Peters, Ph.D., a clinical trials specialist in NHLBI’s Division of Cardiovascular Sciences and a study coauthor.

“This trial and others will support a larger body of research that surgeons, professional societies, and medical organizations can use as they update surgical treatment guidelines in the future,” said Marissa A. Miller, D.V.M., M.P.H., a study coauthor and senior advisor for cardiac surgical trials at NHLBI. “Our goal is to make these types of treatment decisions easier for patients and to support their long-term health outcomes.”

The clinical trial (NCT02675244) was funded by a cooperative research agreement from NHLBI (U01 HL088942) and a grant from DZHK, the German Centre of Cardiovascular Research.