Neurogenesis vs. Plasticity: What’s the Difference?

The human brain can change and adapt throughout life, allowing it to respond to new experiences, learn, and recover from injury. Two processes underlie this adaptability: neurogenesis and neural plasticity. While often discussed together, they are distinct yet interconnected mechanisms. Understanding the unique characteristics of both neurogenesis and neural plasticity clarifies how each contributes to the brain’s ability to modify itself.

Understanding Neurogenesis

Neurogenesis is the process by which new neurons are generated. For a long time, it was believed the brain’s neuron count was fixed shortly after birth. Research has overturned this idea, revealing that neurogenesis continues in specific areas of the adult brain, though it is most prominent during embryonic development.

In adults, the birth of new neurons primarily occurs in two regions: the subventricular zone and the subgranular zone of the dentate gyrus in the hippocampus. The hippocampus is an area involved in memory formation and emotional regulation, and new neurons here are thought to contribute to learning and mood. These newborn neurons must migrate, mature, and integrate into established neural networks to become functional.

Understanding Neural Plasticity

Neural plasticity is the brain’s ability to reorganize its structure, function, and connections. This process does not involve creating new neurons, but rather modifying existing ones and the pathways between them. It is a lifelong phenomenon that occurs throughout the entire brain, allowing it to adapt in response to experiences, learning, or damage.

There are two primary categories of neural plasticity. Structural plasticity describes physical changes to the brain’s structure, such as forming new connections (synapses) between neurons or eliminating underused ones through synaptic pruning. This physical remodeling strengthens frequently used pathways.

Functional plasticity refers to changes in the strength of connections between neurons. This can involve long-term potentiation (LTP), where connections are strengthened through frequent activation. Conversely, long-term depression (LTD) involves the weakening of connections that are used less often, allowing the brain to fine-tune its circuits based on activity.

Distinguishing Neurogenesis from Neural Plasticity

The core difference is their fundamental action. Neurogenesis is the creation of entirely new neurons, adding new cellular hardware to the system. In contrast, neural plasticity involves modifying what already exists by rewiring and adjusting the connections and strength of the brain’s current neurons.

Their scope and location also set them apart. Adult neurogenesis is a highly localized process, largely restricted to the hippocampus and the subventricular zone. Neural plasticity, however, is a widespread phenomenon occurring across the entire brain, from the cerebral cortex to the cerebellum.

This leads to a difference in the scale of change. Neurogenesis introduces new, independent processing units that must then be integrated into the network. Plasticity is about refining and optimizing existing circuits, altering the functional properties of a network without adding new cells.

Finally, their timelines differ. Neurogenesis is most prolific during embryonic development and declines significantly in adulthood. Neural plasticity, while also active in the developing brain, remains a fundamental feature throughout our entire lives, allowing for continuous learning.

The Interplay Between Neurogenesis and Plasticity

Neurogenesis and neural plasticity are distinct processes that can work together. The successful integration of newborn neurons into the brain’s landscape is dependent on the mechanisms of plasticity. For a new neuron to become a functional part of a circuit, it must form connections with other neurons.

This integration process is guided by neural plasticity. Mechanisms like synaptogenesis allow the new neuron to physically connect with its neighbors, while processes like long-term potentiation help strengthen these new connections as they are used. Without plasticity, a newly formed neuron would remain isolated and non-functional.

This collaborative relationship is important for complex brain functions. For instance, in adapting to a new environment, neurogenesis in the hippocampus could provide new neurons to encode novel information. At the same time, plasticity would be responsible for refining connections throughout various brain regions to support the new skills being acquired.

Following certain types of brain injury, plasticity is the primary driver of recovery, allowing undamaged areas to take over lost functions. In some cases, neurogenesis may also contribute to this recovery, with plasticity-driven mechanisms helping to incorporate these new cells into reorganized pathways.