The human brain can generate new nerve cells, or neurons, throughout an individual’s life. This process, known as adult neurogenesis, challenges the long-held belief that we are born with all the neurons we will ever have. These newly formed neurons are not just spare parts; they integrate into the brain’s complex wiring as active participants. Understanding what these new neurons do reveals a dynamic and adaptable brain that maintains functions from learning and memory to emotional well-being.
How New Neurons Are Formed and Integrated
Adult neurogenesis is the process of creating new neurons, which primarily occurs in two specific regions of the mammalian brain. One area is the subgranular zone of the dentate gyrus, located within the hippocampus, a structure associated with learning and memory. The other main site is the subventricular zone, which supplies new cells to the olfactory bulb, though in humans this process appears minimal after birth.
The creation of a new neuron is a multi-stage journey that begins with neural stem cells. These cells divide and renew themselves before they differentiate, committing to becoming neurons. Following differentiation, these young neurons migrate to their designated location within a brain structure like the hippocampus.
Once in position, the final phase of functional integration begins. The new neuron must extend its axons and dendrites—the long fibers that transmit and receive signals—to connect with existing brain cells. The neuron must form synaptic connections and learn to communicate effectively within the pre-existing network. Many of these newborn cells do not survive this challenging process, with a significant portion dying off shortly after they are born.
Key Roles of Newly Formed Neurons
Once successfully integrated, new neurons undertake specific jobs within the brain’s circuitry, with a notable impact on learning and memory formation. Young neurons in the hippocampus are more excitable than their mature counterparts, making them highly responsive to new information. This heightened plasticity allows them to contribute to a sophisticated memory function called pattern separation.
Pattern separation is the brain’s ability to distinguish between two very similar experiences, such as remembering where you parked your car today versus yesterday. New neurons help create unique neural codes for each distinct memory, preventing them from becoming a jumbled, overlapping recollection. This function is necessary for accurate recall and navigating a world filled with similar yet distinct events.
Beyond memory, hippocampal neurogenesis plays a role in mood regulation and our response to stress. A healthy supply of new neurons appears to contribute to emotional resilience, helping to buffer the effects of stress. Studies have observed that conditions like chronic stress can suppress neurogenesis, a link that has prompted research into how promoting neuron growth might influence emotional stability.
Significance of Neurogenesis for Brain Plasticity and Health
The continuous addition of new neurons is a component of brain plasticity, which is the brain’s capacity to change and reorganize itself in response to experiences. This adaptability allows the brain to continually remodel its own structure and function throughout life. Neurogenesis provides a fresh supply of adaptable cells that can be molded by new activities, environments, and information.
This ongoing process of cellular renewal is important for maintaining cognitive function, especially as we age. By contributing to the brain’s “cognitive reserve,” neurogenesis helps bolster the brain’s ability to withstand challenges and maintain performance. The integration of new neurons into established circuits ensures that the brain remains a dynamic and responsive organ, helping to preserve the function of neural networks over time.
Influences on New Neuron Growth
The rate at which new neurons are produced is not fixed and is influenced by a variety of lifestyle and environmental factors. Several factors are known to encourage the growth and survival of new neurons.
- Physical activity, particularly aerobic exercise
- Engaging in mentally stimulating activities and continuous learning
- Living in an enriched and complex environment
- Certain dietary habits, such as consuming omega-3 fatty acids and flavonoids found in fish, berries, and dark chocolate
- Getting sufficient, quality sleep, as the brain undertakes restorative processes during rest
Conversely, several factors can have a negative impact. Chronic stress is a well-documented inhibitor of neurogenesis, largely through its effects on stress hormones. The natural process of aging also leads to a decline, though this can be counteracted by positive lifestyle choices. A sedentary lifestyle, poor diet, and sleep deprivation can all contribute to a reduced rate of new neuron growth.