Memory systems in the brain drive food cravings that could influence body weight

New research uncovers neurons in the hippocampus that encode memories of sugar and fat, shaping feeding behavior and metabolic health

Monell Chemical Senses Center

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A specific population of neurons in the mouse brain encodes memories for sugar and fat, impacting food intake and weight.

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Credit: Guilliaume de Lartigue, PhD, Monell Chemical Senses Center

PHILADELPHIA, PA (January 15, 2025) - Can memory influence what and how much we eat? A groundbreaking Monell Chemical Senses Center study, which links food memory to overeating, answered that question with a resounding “Yes.” Led by Monell Associate Member Guillaume de Lartigue, PhD, the research team identified, for the first time, the brain’s food-specific memory system and its direct role in overeating and diet-induced obesity. 

Published in Nature Metabolism, they describe a specific population of neurons in the mouse brain that encode memories for sugar and fat, profoundly impacting food intake and body weight. “In today’s world, we are constantly bombarded with advertisements and environmental triggers designed to remind us of pleasurable food experiences,” said Dr. de Lartigue. “What’s surprising is that we’ve pinpointed a specific population of neurons in the hippocampus that not only forms these food-related memories but also drives our eating behavior. This connection could have significant implications for body weight and metabolic health.”

These neurons encode memories of the spatial location of nutrient-rich foods, acting as a “memory trace,” particularly for sugar and fat. Silencing these neurons impairs an animal's ability to recall sugar-related memories, reduces sugar consumption, and prevents weight gain, even when animals are exposed to diets that contribute to excessive weight gain. Conversely, reactivating these neurons enhances memory for food, increasing consumption and demonstrating how food memories influence dietary behavior.

These findings introduce two new concepts: first, evidence that specific neurons in the brain store food-related memories, and second, that these memories directly impact food intake. “While it’s no surprise that we remember pleasurable food experiences, it was long assumed that these memories had little to no impact on eating behavior,” said Dr. de Lartigue. “What’s most surprising is that inhibition of these neurons prevents weight gain, even in response to diets rich in fat and sugar.” 

Memory’s Underappreciated Role
Memory is often overlooked as a key driver of food intake, but this study demonstrates a direct link between memory and metabolism. What sets this discovery apart from other studies related to memory is its implications for understanding metabolic health. Deleting sugar-responsive neurons in the hippocampus of the animals not only disrupts memory but also reduces sugar intake and protects against weight gain, even when animals are exposed to high-sugar diets. This highlights a direct link between certain brain circuits involved in memory and metabolic health, which has been largely overlooked in the field of obesity research.

“Memory systems in the hippocampus evolved to help animals locate and remember food sources critical for survival,” said first author Mingxin Yang, a University of Pennsylvania doctoral student in the de Lartigue lab. “In modern environments, where food is abundant and cues are everywhere, these memory circuits may drive overeating, contributing to obesity.”

Specific, Yet Independent Circuits
Another key discovery is that food-related memories are highly specific. Sugar-responsive neurons encode and influence only sugar-related memories and intake, while fat-responsive neurons impact only fat intake. These neurons do not affect other types of memory, such as spatial memory for non-food-related tasks.

“The specificity of these circuits is fascinating,” said de Lartigue. “It underscores how finely tuned the brain is for linking food to behavior, ensuring animals can differentiate between various nutrient sources in their environment.” We have separate types of neurons that encode memory for foods rich in fat versus memory for foods rich in sugar. These separate systems presumably evolved because foods in nature rarely contain both fat and sugar, surmise the authors. 

Implications for Treating Obesity
The study’s findings open new possibilities for addressing overeating and obesity. By targeting hippocampal memory circuits, it may be possible to disrupt the memory triggers that drive consumption of unhealthy, calorie-dense foods.

“These neurons are critical for linking sensory cues to food intake,” said Dr. de Lartigue. “Their ability to influence both memory and metabolism makes them promising targets for treating obesity in today’s food-rich world.”

This collaborative study was conducted with colleagues from the University of Pennsylvania and the University of Southern California and was supported by the National Institutes of Health and the American Heart Association.

About Monell Chemical Senses Center

The Monell Chemical Senses Center is an independent nonprofit research institute in Philadelphia, Pennsylvania. Founded in 1968, its mission is to advance and share discoveries in the science of the chemical senses of smell, taste, chemesthesis, and interoception to solve world health, societal, and environmental challenges.
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Journal

Nature Metabolism

DOI

10.1038/s42255-024-01194-6 

Method of Research

Experimental study

Subject of Research

Animals

Article Title

Separate orexigenic hippocampal ensembles shape dietary choice by enhancing contextual memory and motivation

Article Publication Date

15-Jan-2025

FEMINISM

Strength connected to sexual behavior of women as well as men

Washington State University

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VANCOUVER, Wash. – While many studies have looked at possible evolutionary links between men’s strength and sexual behavior, a Washington State University study included data on women with a surprising result. Women, as well as men, who had greater upper body strength tended to have more lifetime sexual partners compared to their peers.

The study, published in the journal Evolution and Human Behavior, was designed to test evolutionary theories for human sexual dimorphism—namely that in early human history there was likely a reproductive advantage selecting for men’s greater upper body strength.  

Another finding in this study did hint at a reason for that physical difference: men with greater upper body strength were also more likely to to be in long-term relationships.

“People have assumptions about men’s sexual behavior and how that’s related to evolution. Besides acquiring more sexual partners, establishing long-term relationships was likely also important for men in evolutionary history,” said lead author Caroline Smith, a recent WSU Ph.D. graduate in anthropology.

For this study, Smith and her advising professor, WSU evolutionary anthropologist Ed Hagen, analyzed data on 4,316 U.S. adults from 2013-2014 from the National Health and Nutrition Examination Survey conducted by the Centers for Disease Control and Prevention. They primarily used grip strength, a common measure to approximate upper body strength, and compared it to participants’ survey responses about their sexual behavior.

The findings present a mixed picture, the authors said.

There are several hypotheses around why men have greater upper body strength. One popular theory, known as the sexual selection hypothesis, is based on competition: that like other primates, human males competed against each other for access to mates so needed to be physically formidable to pass their genes on. This theory predicts little relationship between women’s strength and their mating success.

“Men are stronger than women, on average, and men report more lifetime partners than women, but men and women are on the same regression line,” said Hagen. “Regardless of whether they’re males or females, stronger individuals have more lifetime sexual partners. That was a surprising finding and somewhat contrary to the sexual selection hypothesis.”

On the other hand, this study’s finding about long-term partners seems to support another theory based on “provisioning.” Since human babies require a lot of care and resources, particularly from women during pregnancy and lactation, men were more desirable as partners when they could provide meat through hunting, which for hundreds of thousands of years before the modern era required upper body strength. The stronger human males, who also stuck around and helped provide more food resources to those children as they grew, also would better ensure their survival.

While there are theories for men’s strength in relation to reproductive success, there are not so many for women’s strength, in part because women are not often included in these types of studies.

There was not an obvious explanation in this study’s data why women with greater upper body strength also had greater number of lifetime partners. The researchers controlled for many variables, including general health and testosterone levels, but the connection still held. They did cite a few potential theories, including that it is due to “assortative mating,” meaning physically stronger people tend to partner with each other more frequently. It could also be that women who are physically stronger require less male investment or feel like they can take more risks.

Ultimately, more studies involving women would be needed to uncover more evidence for the reasons behind this connection as well as a better understanding of human evolution in general.

“I believe it’s important to continually test our theories, especially by expanding our research questions to include women,” said Smith.

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Journal

Evolution and Human Behavior

DOI

10.1016/j.evolhumbehav.2024.106647 

Article Title

Strength, mating success, and immune and nutritional costs in a population sample of US women and men: A registered report

CTL

New study explores how tightness and looseness shape global entrepreneurship

Strategic Management Society

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A new study by researchers Valentina A. Assenova and Raphael Amit from The Wharton School, University of Pennsylvania, reveals how cultural tightness and looseness significantly influence entrepreneurial activity worldwide. Published in the Strategic Entrepreneurship Journal, the research investigates why some nations and regions produce more startups than others, offering a fresh perspective on the intersection of culture and entrepreneurship.

Drawing on data from 156 nations and 50 U.S. states, the study introduces cultural tightness-looseness (CTL) as a pivotal factor shaping entrepreneurial ecosystems. CTL measures the strength and enforcement of social norms—with tighter cultures exhibiting strict adherence to rules and looser cultures favoring flexibility and tolerance for deviation. The research found that cultural looseness explains 56% of the variation in new firm formation rates across nations and 71% of the variation in new entrepreneur rates within U.S. states.

The findings have far-reaching implications for governments, investors, and educators aiming to nurture entrepreneurship. Policymakers can foster startup ecosystems by promoting cultural looseness, such as reducing bureaucratic hurdles and encouraging open dialogue. Investors and accelerators can use CTL insights to identify high-potential regions for entrepreneurial growth, while educators can tailor programs to build resilience and innovation among entrepreneurs in tighter cultural contexts.

“Understanding cultural tightness-looseness provides a powerful lens for shaping entrepreneurial policy and practice,” said Valentina A. Assenova, lead author of the study. “By creating environments that celebrate diversity and innovation, we can unlock the full potential of individuals and communities.”

About the Study

This research draws on extensive data from the World Bank’s Entrepreneurship Database, the Global Entrepreneurship Monitor, and the Kauffman Foundation. The authors used advanced causal mediation analysis to dissect the individual and institutional mechanisms linking CTL to entrepreneurship.

To read the full context of the study and its methods, access the full paper available in the Strategic Entrepreneurship Journal.

About the Strategic Management Society

The Strategic Management Society (SMS) is the leading global member organization fostering and supporting rigorous and practice-engaged strategic management research. SMS enjoys the support of 3,000 members, representing more than 1,100 institutions and companies in more than 70 countries. SMS publishes three leading academic journals in partnership with Wiley: Strategic Management Journal, Strategic Entrepreneurship Journal, and Global Strategy Journal. These journals publish top-quality work applicable to researchers and practitioners with complementary access for all SMS Members. The SMS Explorer offers the latest insights and takeaways from the SMS Journals for business practitioners, consultants, and academics.

Click here to subscribe to the monthly SMS Explorer newsletter.

Click here to learn more about the programs and opportunities SMS has to offer.

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Journal

Strategic Entrepreneurship Journal

DOI

10.1002/sej.1520 

Method of Research

Data/statistical analysis

Subject of Research

Not applicable

Article Title

Why are some nations more entrepreneurial than others? Investigating the link between cultural tightness–looseness and rates of new firm formation

 

Vanderbilt Transplant Center sets world record for heart transplants in 2024

Vanderbilt University Medical Center

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In 2024, more than 500 patients were referred to Vanderbilt for transplant consideration from more than 15 U.S. states, including many patients considered too high risk for transplant at other programs.

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Credit: Photo by John Russell

The Vanderbilt Transplant Center had a banner year in 2024, setting a world record by performing 174 adult and pediatric heart transplants. The number of patients whose lives were saved by Vanderbilt’s heart transplant team far surpasses any previous total by an individual transplant center. 

“I have to say, even I was surprised at the final number of transplants,” said Ashish Shah, MD, professor and chair of Cardiac Surgery. “But this one year was really built on 10 years of hard work, innovation and our reputation to do difficult things.” 

Kelly Schlendorf, MD, associate professor of Medicine and section head of Heart Failure and Transplantation, is quick to point out that a busy transplant program depends on a busy waitlist.

“Equally important to achieving our volume,” Schlendorf said, “is a widespread heart failure outreach presence and the tremendous efforts of our multidisciplinary team in shepherding patients quickly through an extensive transplant evaluation process while simultaneously taking care of their heart failure.”

Schlendorf notes that in 2024, more than 500 patients were referred to Vanderbilt for transplant consideration from more than 15 U.S. states, including many patients considered too high risk for transplant at other programs.

Vanderbilt transplanted 36% more hearts in 2024 than 2023. In 2024, 10 of the lifesaving procedures were performed on pediatric patients.

Shah, who holds the Alfred Blalock Directorship in Cardiac Surgery, and Schlendorf agree that a major factor in the growth was that VUMC increasingly accepts organs that other centers decline and has successful outcomes because of its advanced organ preservation technologies. They also credit an organ recovery team that can mobilize at a moment’s notice and fly throughout the country, and expertise in cardiac anesthesia, intensive care, infectious diseases and other disciplines that help care for patients during and after surgery.

“This milestone reflects the extraordinary skill of our entire transplant team and the seamless collaboration across every aspect of patient care,” said Bret Alvis, MD, associate professor of Anesthesiology and interim medical director of the Surgical Cardiovascular Intensive Care Unit. “It’s truly exciting to see how our combined efforts continue to push the boundaries of what’s possible in heart transplantation.”

Maricar Malinis, MD, associate professor of Medicine and medical director of the Transplant Infectious Diseases Program, said, “We are honored to be part of this significant achievement. Each specialty, including infectious diseases, plays a crucial role in optimizing transplant candidates before surgery and minimizing potential post-transplant complications. Transplantation truly is a team effort, with the shared goal of enhancing patients' quality of life.”

The transplant team includes cardiologists and cardiac surgeons, intensivists, nurses, advanced practice providers, pharmacists, social workers, case managers, rehab specialists, financial coordinators, nutritionists, organ procurement coordinators, preservationists, operating room staff, cardiac anesthesiologists and nurse anesthetists, among others, led on the adult side by Shah and Schlendorf and on the pediatric side by Carlos Mery, MD, MPH, professor and chief of Pediatric Cardiac Surgery at Monroe Carell Jr. Children’s Hospital at Vanderbilt; and David Bearl, MD, MBA, associate professor of Pediatrics and medical director of the Pediatric Heart Transplant Program at Monroe Carell.

 

 

Researchers discover how cigarette smoke impairs critical lung immune cells

How multiple chemicals in cigarette smoke & e-cigarettes alter the function of a key type of lung immune cell

Monash University

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This illustration explores how smoke components in cigarette and e-cigarette smoke obscures critical molecules like Smole-binding ligands and MR1 complexes, disrupting T cell responses 

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Credit: Erica Tandori

Cigarette smoking is widespread and deadly, yet our understanding of how cigarette smoke actually causes serious respiratory illnesses is incomplete, which has severely hampered the development of effective treatments. Today (TBC) Australian researchers reveal how multiple chemicals found in cigarette smoke and e-cigarettes alter the function of a key type of immune cell found in the lungs.

 

The study, published in the Journal of Experimental Medicine (JEM), suggests that these alterations make cigarette smokers, and those exposed to second- and third-hand smoke, more susceptible to respiratory infections, and worsen smoking-related inflammatory diseases such as chronic obstructive pulmonary disease (COPD).

Cigarette smoking is known to impair the immune system’s response to infections and promote inflammation in the lungs that can lead to or exacerbate COPD, the third leading cause of death worldwide. COPD patients are more susceptible to influenza infections that can, in turn, worsen the underlying disease by increasing airway inflammation and promoting the destruction of the lung’s air sacs. There are currently no effective treatments for COPD.

According to Dr Wael Awad, from Monash University’s Biomedicine Discovery Institute, first author on the new JEM study, “until now the mechanisms underlying the skewed immune responses in people exposed to cigarette smoke, and how they are related to smoke-associated diseases like COPD remain unclear.”

Professor Jamie Rossjohn of Monash University’s Biomedicine Discovery Institute co-led the study with Professor David P. Fairlie of the Institute for Molecular Bioscience at University of Queensland, Professor Alexandra J. Corbett of the University of Melbourne, based at the Peter Doherty Institute for Infection and Immunity, and Professor Philip M. Hansbro of the Centenary Institute and University of Technology Sydney.

In their study, the researchers looked at the effects of cigarette smoke on Mucosal-Associated Invariant T (MAIT) cells, a type of immune cell found in the lungs and other tissues of the body. MAIT cells help fight off bacterial and viral infections and can promote inflammation or tissue repair.

MAIT cells are activated by a protein called MR1 that is found in almost every cell of the body. MR1 recognises chemicals produced by bacteria and presents them at the surface of infected cells in order to activate MAIT cells and initiate an immune response. “While we know that smoke from cigarettes, bushfires, cooking, vehicle exhausts and burning waste pose significant health risks, we still surprisingly know relatively little about how the specific components pf smoke affect our immune system and how they impact multiple parts of the human body,” Professor Fairlie said.

“We suspected that some of the more than 20,000 chemicals present in cigarette smoke that smokers inhale might also bind to MR1 and influence the activity of MAIT cells in the lungs”, Dr Awad said.

The researchers used computer modeling to predict which components of cigarette smoke might be recognised by MR1 and found that several of these molecules not only bound to the protein but also either increased or decreased in amounts on the surface of cells. These chemicals, including benzaldehyde derivatives that are also used as flavorings in cigarettes, e-cigarettes, blocked activation of human MAIT cells by compounds produced by bacteria.

The research team then studied the effects of cigarette smoke on MAIT cells from human blood and mice and showed they reduced MAIT cell function. Mice repeatedly exposed to cigarette smoke developed symptoms of lung disease and this was worsened if also infected by influenza. Researchers found that long-term exposure to cigarette smoke altered the protection provided to mice by their MAIT cells, making them less able to fight off influenza infections and more prone to the development of COPD disease.

“We found that mice lacking MAIT cells were also protected from cigarette smoke-induced COPD, showing reduced levels of lung inflammation and no tissue deterioration in their lung’s air sacs” Professor Hansbro said.

“This study demonstrates the power of collaboration and the insights we can gain with inter-disciplinary science,” Professor Corbett said.

“Overall, our study reveals that components of cigarette smoke can bind to the protein MR1 and reduce the functions of protective immune cells called MAIT cells. This increases susceptibility to infections worsens progression of lung disease” Dr Awad said. The researchers now plan to investigate exactly which MAIT cell pathways are impacted by cigarette smoke, in order to learn how to better treat COPD and other lung diseases.

 

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Journal

Journal of Experimental Medicine

DOI

10.1084/jem.20240896 

Method of Research

Experimental study

Subject of Research

Cells

Article Title

Cigarette smoke components modulate the MR-1-MAIT axis

Article Publication Date

17-Jan-2025

 

Diving deep into dopamine

Bioengineering's Helen Schwerdt receives $2.5 million R01 to investigate dopamine’s role in learning

University of Pittsburgh

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Positive feedback is helpful for learning, but usually, our greatest lessons actually come from failure— and a new project at the University of Pittsburgh aims to uncover the neural mechanisms behind this phenomenon.

Helen Schwerdt, assistant professor of bioengineering at Pitt’s Swanson School of Engineering, received a five-year, $2.5 million R01 award from the National Institutes of Health (NIH) to study dopamine’s role in learning. Schwerdt’s team develops novel multimodal neural interfaces to understand how the brain and pathological mechanisms work and to improve treatment of debilitating neurological disorders.

“We’re interested in developing technologies to measure molecules in the brain, and figuring out how to optimally combine these types of molecular measurements with the conventional electrical measurements that we typically use to look at brain activity.” Schwerdt said. “Communication between neurons occurs both electrically and chemically, but the chemical aspect is less understood because we haven't had the right tools to measure these signals together.”

Dopamine is a neurotransmitter found in the brain that plays a role in many body functions, including memory, movement, motivation, mood, attention and more. Schwerdt plans to investigate the lesser-known role of dopamine in learning, especially its connection to learning from punishment, which has received less attention compared to its role in reward systems.

“Reward is very important, and it’s an incentive for us to learn new things. But in real life, we commonly learn from negative incentives as well.” Schwerdt said. “The question is, how does the brain handle these two different types of incentives — is it the same circuits and the same neurons that handle both reward and punishment, or are they different?”

Schwerdt’s team has developed a method for sustained dopamine monitoring by implanting neural interfaces in Rhesus monkeys. Monitoring dopamine in the brain for years at a time will help the team measure dopamine’s impact over the course of learning, and dispersing the sensors in different areas of the brain will help the team assess how dopamine levels fluctuate differently in different brain areas. 

“We fabricate the sensors in our lab, and when we implant them, we disperse the sensors all across the striatum, because the dopamine appears differently depending on where you record it in the brain.” Schwerdt said. “I believe that a lot of important past studies support the idea that the punishment-related dopamine signals are going to be in different areas of the brain than the reward-related signals.”

Once the neural interfaces are implanted, the team will test the monkeys with a set of trial and error learning tasks to examine how the dopamine behaves in real time. This will allow the team to learn if certain areas in the striatal brain region produce negative punishment related signals and assess how the signals evolve during the course of learning. 

This project could eventually lead to a baseline standard that reveals how dopamine is behaving across the primate striatum during important cognitive behaviors. Studies of humans with Parkinson’s disease have shown impairments in learning from rewards and punishments, and Schwerdt hopes that these findings can also be translated into better understanding the disease, where dopamine dysregulation is a major factor. 

"In the future, I would like to test these behaviors in a model of Parkinson's disease so we can study how dopamine signals in the striatum change and how these changes contribute to behavioral symptoms.” Schwerdt said. “I'm particularly interested in exploring how these dopamine signals could be used as biomarkers to guide future treatments."