While food insecurity is a problem for a growing segment of the U.S. population — exacerbated by the coronavirus pandemic — few studies have looked at the effect feasting or famine has on the developing brain, apart from other factors that contribute to adversity. .
A new study by neuroscientists at the University of California, Berkeley, simulated the effects of food insecurity in young mice and found lasting changes later in life.
“We show that infrequent access to food in late childhood and early adolescence affects learning, decision-making, and dopamine neurons in adulthood,” said Linda Wilbrecht, a psychology professor at UC Berkeley and a member of the Helen Wills Neuroscience Institute.
An important difference in behavior was cognitive flexibility: the ability to generate new solutions when the world changes.
“Mice seeking rewards can be inflexible, stick to just one strategy even if it no longer produces a reward, or they can be flexible and try new strategies quickly. We found that the stability of the food supply that mice had when they young determined how flexible they were under different conditions when they reached adulthood,” she said.
Epidemiological studies have linked food insecurity in children and adolescents with weight gain in later life, as well as learning disabilities and lower math, reading and vocabulary scores. But these studies are clouded by other poverty-related issues, such as maternal depression and environmental stressors. The new study is designed to look at the developmental and behavioral effects of food insecurity in a controlled environment that is not possible with human subjects.
The research has implications for people. Policymakers recognize the importance of good nutrition in early childhood through high school, with federally funded free or discounted breakfast and lunch programs available in schools across the United States. The federal Supplemental Nutrition Assistance Program (SNAP) also provides benefits to supplement the food budget of needy families. For families living paycheck-to-paycheck, these feeding programs have shown effects—particularly improved school performance and graduation rates.
But there may be times when kids don’t have access to feeding programs, such as during summer vacation. Programs can also inadvertently create a feast and famine cycle when benefits are split with weeks between payments, potentially leaving impoverished families unable to afford food at the end of each payment cycle. According to a recent report from the U.S. Department of Agriculture, 6.2% of households with children — a total of 2.3 million households — had food insecurity by 2021.
“I think we need to understand that even temporary food insecurity matters, not just the brain catching up later. Food insecurity can have long-term consequences on how a person’s brain functions,” Wilbrecht said. “The ability to learn and make decisions is something that develops during childhood and adolescence, and we see how these crucial skills are affected by access to food. Access to food is something that we can address in this province. nutrition and benefit programs, and we can make them better by making access to benefits or food more reliable and consistent. Supporting brain development is a good reason to support nutritional programs.”
The research, conducted with UC Berkeley faculty members Helen Bateup, Stephan Lammel and their lab colleagues, will appear in an upcoming print edition of the journal Current Biology. It was put online on July 20.
Flexibility under changing rules
Wilbrecht and her colleagues, including Robert Wood Johnson Foundation Health and Society Scholar Ezequiel Galarche, mimicked human food insecurity in mice by delivering food on an irregular schedule while still allowing enough food to maintain a safe body weight. This feeding regimen started a week before the onset of puberty in mice, which corresponds to late childhood in humans, and lasted for 20 days until the equivalent of late teenage age in mice. Another group of mice was offered food when they wanted it.
They then tested cognition in adulthood using foraging tasks in which mice searched for rewards in a changing environment. For example, a behavior – in this case learning which scent led to the Honey Nut Cheerios – may be successful for a short time, but not forever. A second scent now foretold where the reward was hidden.
The well-fed and food-insecure mice were tested as adults in both determined and precarious environments, with noticeable differences in cognitive flexibility. Food insecure mice were more flexible in precarious situations than well-fed mice, while well-fed mice were more flexible in more stable situations.
“You would have to test in the field to see how these different flexibility profiles affect survival,” she said. “The findings are nuanced, but hopeful, as we identify both gains and losses of function in learning and decision-making caused by the experience of scarcity.”
Although the effect of food insecurity on cognition in male mice was robust, female mice showed no effect on cognition.
“This is one of the most robust behavioral effects we’ve ever seen when modeling adversity,” Wilbrecht said.
However, food insecurity had other pronounced negative effects in female mice. Those women who were food insecure while growing up tended to gain weight if they were given unlimited food in adulthood, something that is reflected in people who grew up with food insecurity. Male mice showed no such effect.
PhD candidate Wan Chen Lin and researchers in the Bateup and Lammel lab also looked at the brain’s reward network, which is controlled by the neurotransmitter dopamine, and found changes there in male mice.
“We found that the neurons in the dopamine system, which is crucial for learning, decision-making and reward-related behaviors, such as addiction, were significantly altered in both their input and output,” Wilbrecht said. “It suggests that there are more large-scale changes in the learning and decision-making systems in the brain.”
For example, the researchers saw changes in the synapses of dopamine neurons projecting to the nucleus accumbens and also found changes in the release of dopamine in the dorsal striatum. Numerous other studies have shown that these dopamine neurons play a role in learning and decision-making.
The researchers are continuing their studies of food-insecure mice to determine whether they are more prone to addictive behaviors, which are linked to the dopamine network, as adults.
Other UC Berkeley authors of the paper include former postdoctoral fellow Polina Kosillo, former doctoral student Christine Liu, and senior scientist Lung-Hao Tai. The work was supported by the National Institutes of Health (R21 AA025172, U19NS113201) and the Robert Wood Johnson Foundation. Bateup is a Chan Zuckerberg Biohub researcher and a Weill Neurohub researcher.