Neurons, the fundamental units of the brain, are primarily formed before birth, but some new neuron creation, called postnatal neurogenesis, continues after birth in certain brain regions.
Prenatal Neurogenesis: The Majority of Neurons
The majority of the neurons that comprise your brain are formed before you are born. This process, called neurogenesis, occurs within areas of the brain rich in neural stem cells (NSCs) or precursor cells. These stem cells have the remarkable ability to differentiate into most, if not all, types of brain cells, including neurons. [^1, ^2, ^3] This intense period of neuronal development is crucial for the formation of the brain's complex structures and functions during embryonic development. ^4
Postnatal Neurogenesis: A Continued, but Limited, Process
While most neuron generation happens prenatally, neurogenesis doesn't completely stop after birth. Postnatal neurogenesis, although occurring at a much slower rate, is observed in specific areas of the brain in infancy, including the cerebellum and prefrontal cortex. [^5, ^6] However, the extent and significance of adult neurogenesis are still being actively researched. Some studies suggest that the hippocampus, a critical area for learning and memory, might show some neurogenesis throughout life but diminishes significantly during childhood, becoming undetectable in adulthood. [^7, ^8] Other research indicates that adult-born neurons in the hippocampus integrate into existing networks and contribute to various brain functions like spatial learning and even maintaining seizure duration. [^9, ^10, ^11, ^12]. However, the extent of this postnatal neurogenesis and its impact on cognitive function remains a subject of ongoing scientific investigation.
Key Areas of Postnatal Neurogenesis:
- Hippocampus: This brain region plays a significant role in learning and memory, and research indicates some degree of continued neurogenesis here throughout life, although it declines substantially during childhood. [^7, ^8, ^10, ^11, ^12]
- Olfactory bulb: This region is responsible for processing smell, and also shows evidence of adult neurogenesis. ^4
- Cerebellum and Prefrontal Cortex: These areas exhibit some postnatal neurogenesis during infancy. [^5]
The Process in Brief:
- Neural Stem Cells: The process begins with neural stem cells, which are capable of self-renewal and differentiation into various neural cell types, including neurons.
- Proliferation: Stem cells proliferate (multiply) to increase their numbers.
- Differentiation: These cells then differentiate, undergoing transformations to become mature neurons, each with specialized functions.
- Migration: Newly formed neurons migrate to their final destinations within the brain.
- Synapse Formation: Neurons form connections (synapses) with other neurons, establishing complex networks that underpin brain function.
[^1]: Most of the neurons in your brain were created before you were born. But some areas of the brain make new neurons after birth in a process called postnatal neurogenesis. A few areas, including the cerebellum and the prefrontal cortex, continue adding new neurons in infancy.23-Feb-2017
[^5]: Most of the neurons in your brain were created before you were born. But some areas of the brain make new neurons after birth in a process called postnatal neurogenesis. A few areas, including the cerebellum and the prefrontal cortex, continue adding new neurons in infancy.23-Feb-2017
