What Is Neurogenesis?

How New Brain Cells Regenerate

Illustration of a human brain
PASIEKA / Science Photo Library / Getty Images

Neurogenesis refers to the formation of new neurons in the brain. It is an integral part of prenatal development, but neurogenesis in adults has been a topic of debate among scientists. Today, research suggests that neurogenesis continues in certain areas of the brain after birth and even into adulthood.

Conventional wisdom has long suggested that we cannot grow new brain cells in adulthood, that we are born with all of the brain cells we will ever have, and that once those gray cells expire, they're gone for good.

This belief was fueled, in part, by the fact that certain motor (movement) and cognitive (thought) functions tend to decline the older we get. But should this suggest that it's all downhill once we approach a certain age and that we have no choice but to wait for the inevitable decline?

At a Glance

Whether or not neurogenesis occurs into adulthood is an important topic for scientists and medical professionals. The ability to form new brain cells plays an important role in brain plasticity and cognitive function, offering hope that the brain can adapt and rewire itself in response to new learning, experience, injury, and disease

While it was previously believed that adult neurogenesis was not possible, more recent research suggests that it does happen, at least in key regions of the brain. Research is still ongoing, but recent evidence suggests that brain cells are capable of re-growing and restoring lost functions.

Research on Adult Neurogenesis

While the vast majority of our brain's cells are formed during prenatal development, there are certain parts of the brain that continue to create new neural cells during infancy. Until recently, however, the brain’s limited capacity to regenerate triggered the belief that neurogenesis—the birth of new brain cells—ceased soon after this stage.

However, research over the last two decades has suggested that at least one part of the brain continues to create new cells throughout a person's lifespan—part of the brain called the hippocapus.

Neurogenesis in the Hippocampus

During the late 1990s, researchers at Rockefellers University in New York City conducted studies in which marmoset monkeys were injected with a tracer chemical that could differentiate between slow-dividing mature brain cells and fast-dividing new ones.

They found that the hippocampus (a brain region associated with memories, learning, and emotions) continued to create new cells without the constraint of age or time.

Later studies using carbon-14 dating (which evaluates the age and process of cellular development) confirmed that cells in the hippocampus, while continually dying, were quickly replaced by new ones. It is only by the formation of these cells that the hippocampus can maintain its central functions.

Research suggests that the number of new cells and the frequency by which they are created declines with age. With that said, the rate of decline wasn't seen to be consistent and could vary significantly from one person to the next.

Neurogenesis Continues Through Life

Some studies have shown that neurogenesis occurs in the dentate gyrus of the hippocampus and that new brain cells continue to form into old age. Other research suggests that the formation of new cells in this region plays a role in learning and memory while also protecting the brain from stress.

Contradictory Findings

Other research performed at the University of California at San Francisco failed to demonstrate the development of new neurons in the hippocampus of almost 30 adult patients, fueling the controversy of whether neurogenesis in adults actually occurs.

Such findings indicate that more research is still needed to understand neurogenesis in adult brains.

The Gene That Influences Neural Regeneration

More recently, animal studies conducted by researchers at the UC San Diego School of Medicine found that when adult neurons are injured, they return to an embryonic state. This can help them regenerate, a process influenced by the Huntingtin (HTT) gene.

Mutations in the HTT gene lead to the progressive breakdown and death of brain cells, a condition known as Huntington's disease.

Why Neurogenesis Is Important

Research on neurogenesis is crucial because it suggests that there are factors that can stimulate and inhibit the process of adult neurogenesis.

  • Development of neuropsychiatric conditions: Researchers are interested in learning how neurogenesis might impact the pathogenesis of different mental health conditions. For example, if neurogenesis is possible, how would promoting it influence the course of conditions like depression or schizophrenia?
  • Role in memory and learning: Understanding neurogenesis can also provide researchers with more information about how new cell development might impact memory and learning throughout life.
  • Impact on age-related cognitive declines: Researchers know brain cells lose connections as people enter old age. Learning more about the process of neurogenesis might help them develop ways to retain these connections or encourage new ones.

It even hints at possible models for treating degenerative diseases, such as Alzheimer's and Parkinson's diseases, and even reversing damage caused by traumatic brain injury.

How to Promote Neurogenesis

Research on adult neurogenesis is still ongoing, but researchers do believe that there are certain things that you can do that might help promote the development of new brain cells (and protect old ones).

Exercise Your Body

Among the factors that can potentially "amp up" this process, exercise has been considered one of the most promising. Animal research conducted by scientists at the University of Chicago found that aerobic exercise led to both an increase in cell production in the hippocampus and an increase in the amount of genetic information being encoded.

What this tells us is that not only does the function of the brain improve, but the cells themselves are better able to store information for learning and memory.

Research from the University of Pennsylvania reported that aerobic exercise among 120 older adults increased the actual size of the hippocampus by two percent and effectively reversed the aging-related cell loss by one to two years.

A 2018 systematic review and meta-analysis found that aerobic exercise had no significant effect on total hippocampal volume. However, the results did indicate that exercise was connected with significant effects on left hippocampal volume. It also suggested that aerobic exercise played an important role in the retention of hippocampal volume over time.

Research suggests that exercise helps protect this critical brain region from age-related deterioration.

Exercise Your Brain

In addition to exercise, scientists have found that enriched environments can contribute to the survival of old cells and the production of new ones. In short, it is suggested that the more you exercise your brain, the more you can maintain optimal brain function.

On the flip side, there are factors that directly undermine neurogenesis. Chief among these is age. We know, for example, that by the time many adults reach their 80s, many of the neural connections in the hippocampus will be lost.

While time stops for no one, you may be able to hang on to your neural connections by staying active, physically, socially, and mentally.

Manage Your Stress

We also know that stress, both acute and chronic, can decrease neurogenesis in the hippocampus of adult brains. While the exact mechanisms are not entirely clear, researchers have found that stress increases glucosteroids, which in turn reduces molecules known as trophic factors.

Trophic factors are protein molecules that help neurons develop and maintain their connections with other cells. The decrease in these cells associated with stress appears to hamper neurogenesis in adults.

Managing your stress effectively can involve many practices, including adopting a positive mindset, using relaxation strategies, getting enough sleep, and engaging in leisure activities. Each person is different, so finding what works best for you is important.

What This Means For You

Future research with a large number of patients and the development of techniques that allow for imaging of new neurons in the living brain will be necessary to definitively confirm or refute the theory of neurogenesis in adults. However, this ongoing debate should not discourage you from exercising physically and mentally—even if it does not help neurogenesis, its effects on your overall health are without question.

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Verywell Mind uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
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By Kendra Cherry, MSEd
Kendra Cherry, MS, is a psychosocial rehabilitation specialist, psychology educator, and author of the "Everything Psychology Book."