Highlights
- Scientists once believed adults couldn't grow new brain cells.
- Research suggests neurogenesis may continue in the adult hippocampus.
- The amount of adult neurogenesis in humans is still debated.
- Exercise, learning, sleep, and low stress appear to support it.
For most of the 20th century, scientists believed that adults couldn't grow new brain cells. You were born with all the neurons you would ever have, the thinking went, and from adulthood onward, it was a slow, steady decline. Lose a brain cell, and it was gone forever.
That belief has been seriously challenged. Research over the past few decades suggests that, at least in certain parts of the brain, new neurons may continue to form throughout adult life. This process is called neurogenesis, and it remains one of the most exciting and debated topics in brain science. This article explains what we know about adult neurogenesis, the ongoing debate, and how you can support your brain's ability to grow and change.
What Is Neurogenesis?
Neurogenesis is the process of creating new neurons from neural stem cells. It happens extensively before birth and in early childhood, when the brain is growing rapidly. The question is whether, and how much, it continues in adulthood.
A Changing Understanding
The Old View
Early neuroscientists, including the famous Spanish scientist Santiago Ramón y Cajal, believed the adult nervous system was fixed and unable to regenerate. This view dominated for decades.
Early Evidence of Change
In the 1960s, researcher Joseph Altman reported evidence of new neurons forming in the brains of adult rats. His findings were largely overlooked at first. Later, in the 1980s and 1990s, researchers found clear evidence of neurogenesis in adult birds, rodents, and other animals.
Evidence in Humans
In 1998, a landmark study led by Peter Eriksson and Fred Gage, published in Nature Medicine, found evidence of new neurons in the hippocampus of adult humans. The researchers studied tissue from cancer patients who had received a substance that marks dividing cells.
In 2013, researchers at the Karolinska Institute in Sweden used an ingenious method based on carbon-14 levels from Cold War nuclear testing to date brain cells. They estimated that roughly 700 new neurons are added to each hippocampus every day in adults, with only a modest decline with age.
The Ongoing Debate
Not all scientists agree. In 2018, a study published in Nature by Shawn Sorrells, Arturo Alvarez-Buylla, and colleagues examined human brain tissue and found that new neurons in the hippocampus dropped sharply in childhood and were barely detectable in adults.
Just weeks later, a study led by Maura Boldrini at Columbia University, published in Cell Stem Cell, reported evidence that healthy older adults continued to produce new neurons in the hippocampus into their 70s.
In 2019, researchers in Spain, led by MarÃa Llorens-MartÃn, published a study in Nature Medicine reporting thousands of immature neurons in the hippocampus of healthy adults up to their late 80s, with lower numbers in people with Alzheimer's disease.
Scientists believe differences in methods, such as how brain tissue is preserved and analyzed, may explain the conflicting results. The debate continues, but many researchers believe some degree of adult neurogenesis occurs in the human hippocampus.
Where Does Neurogenesis Happen?
In adults, neurogenesis appears to be concentrated in the hippocampus, specifically in a region called the dentate gyrus. The hippocampus is vital for learning, memory, and mood regulation. In animals, new neurons also form in an area that supplies the smell system, but this appears to be much less significant in humans.
Why New Neurons Might Matter
Research in animals suggests that new neurons in the hippocampus may help with:
- Learning and memory: especially distinguishing between similar memories, a process called pattern separation
- Mood regulation: some studies link neurogenesis with resilience to stress and the effects of antidepressants
- Flexibility: adapting to new information and environments
Neurogenesis Is Only Part of the Story
Even if the number of new neurons in adults is limited, the brain has another powerful way to change: neuroplasticity. Existing neurons can form new connections, strengthen or weaken synapses, and reorganize networks throughout life. This is how we learn new skills, form habits, and recover from some injuries. So whether or not you grow many new neurons, your brain remains capable of change.
What May Boost Neurogenesis?
Most evidence comes from animal studies, but several factors appear to support the birth and survival of new neurons, as well as brain plasticity more broadly:
Exercise
Aerobic exercise is the most well-documented booster of neurogenesis in animals. In humans, a well-known 2011 study by Kirk Erickson and colleagues found that a year of walking increased the size of the hippocampus in older adults. Exercise also raises BDNF, a protein that supports brain cell growth.
Learning and Enrichment
Animals living in stimulating environments with toys, exploration, and social interaction show more neurogenesis and better survival of new neurons. Learning new skills appears to help new neurons survive and integrate into brain networks.
Sleep
Sleep deprivation reduces neurogenesis in animal studies. Good sleep supports overall brain health.
Stress Management
Chronic stress and high cortisol reduce neurogenesis in animals. Reducing stress may help protect the hippocampus.
Diet
Some research suggests diets rich in omega-3 fatty acids and flavonoids, found in fish, berries, and other plant foods, may support neurogenesis, while diets high in sugar and saturated fat may reduce it.
Social Connection
Social isolation has been linked with reduced neurogenesis in animal studies.
Limiting Alcohol
Heavy alcohol use reduces neurogenesis in animals.
Practical Steps for a Growing Brain
- Get regular aerobic exercise, such as brisk walking, cycling, or swimming
- Learn new skills and seek novel experiences
- Challenge your memory and attention with puzzles and brain games
- Prioritize seven to nine hours of sleep
- Manage stress through mindfulness, nature, and relaxation
- Eat a diet rich in vegetables, berries, fish, and nuts
- Stay socially active
- Limit alcohol
Why This Research Matters
Understanding adult neurogenesis could have important implications for health. If scientists can learn how to encourage new neuron growth safely, it may lead to new approaches for memory loss, depression, and brain injury. Researchers are studying how neurogenesis changes in Alzheimer's disease and whether supporting it could help protect memory. For now, the most practical message is clear: the same healthy habits that may support neurogenesis also benefit the brain in many other ways.
Frequently Asked Questions
Can adults grow new brain cells?
Evidence suggests adults may continue to form new neurons in the hippocampus, though scientists are still debating how much.
Where are new brain cells made in adults?
Mainly in the dentate gyrus of the hippocampus, a region important for memory.
Does exercise grow new brain cells?
In animals, exercise strongly boosts neurogenesis. In humans, exercise has been shown to increase hippocampal size.
Does neurogenesis decline with age?
It appears to decline, but some studies suggest it continues into old age.
Can the brain change without new neurons?
Yes. Neuroplasticity allows existing neurons to form and strengthen connections throughout life.
Key Takeaways
- Scientists once believed adults couldn't grow new brain cells.
- Research suggests neurogenesis may continue in the adult hippocampus.
- The amount of adult neurogenesis in humans is still debated.
- Exercise, learning, sleep, and low stress appear to support it.
- Whatever the debate, the brain remains capable of change throughout life.
Your brain is far more dynamic than scientists once thought. With healthy habits and a curious, active mind, you can support its ability to grow, adapt, and thrive at every age.
This article provides general educational information and is not medical advice. A qualified healthcare professional can help you evaluate choices in relation to your health history, medications, and individual needs.