How New Brain Cells Are Generated

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?

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.

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.

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.

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.

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.

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.

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.

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.