New Brain Cell Formation After Birth

 Brain Cell Growth After Birth.

PKGhatak, MD

The study of Postnatal Neurogenesis of the brain, meaning brain cell growth after birth has become an urgent issue in order to find a cure for Alzheimer's disease and Parkinson's disease.

The word “growth” includes new neuron formation and growth of the size of individual nerve cells. In the brain nerve cells are mainly of three kinds - 1. Neurons, 2. Supporting cells called Microglia and 3. Limited numbers of Ependymal cells which secrete the cerebrospinal fluid. Nerve fibers - axons and dendrons proliferate beyond comprehension. The growth of the brain after birth encompasses all these components. But scientists are mainly interested in New Neuron Formation.

Few eye-opening numbers about the brain:

By the time of birth, the newborn brain has 100 billion neurons and 100 trillion synapses. To meet that goal, the developing brain generated about a quarter million cells per minute.  Though smaller in size, the child's brain makes 50 % more synaptic connections along with the growth of nerve fibers. By the age of 8, the brain of a child has achieved near complete growth and development. Thereafter, remodeling of the brain takes place which is primarily of pruning of synapses; migration of neurons and new neuron formations take place in the Hippocampus, Cerebellum and Prefrontal Cortex of the brain.

Stages of growth:

There are several stages of growth and development. They are - Neuron generation, Differentiation, Neuron Migration, Synaptogenesis, Myelination and Synapse Pruning.

                This article is a brief discussion of new neuron formation.

Studies are performed in the laboratory on small mammals like rats. Then those experiments that do not require invasive procedures are carried out on humans. 

                                                           Memory.

Memory acquisition in children grows in geometric proportion and then continues at a much slower pace throughout the entire adult life. Research is going on to verify whether new information stored as memory requires new neuron generation. Hippocampus, which is the site of memory formation and short time storage site, is the main area of interest for the researchers.

New nerve cells grow from Neuronal Stem Cell:

 In the subgranular layer of the Dentate Gyrus (DN) close to the hilum, the Neuronal Stem Cells are present. The stem cells divide and increase in numbers and form new neurons. The newly formed neurons migrate to the granular layer of the DN and then migrate to the hippocampus. Neurons produce new synapses very rapidly in 5 stages, including the capacity to generate calbindin, a marker for synaptic integration.

Factors influencing Neuron formation:

Stress, glucocorticoids, depression and chronic illness delay or suppress new neuron formation and synaptic connections and in fact, may even prune the already existing synapses.

Enhancement of neurogenesis is seen by the action of brain-derived neurotrophic factor (BDNF), fibroblast growth factor (FGF), serotonin and those drugs block the reuptake of serotonin, an example, Fluoxetine. Metformin also increases neurogenesis in cell cultures containing human neuronal stem cells and in animal models.

The question is whether these experimental successes can be duplicated in patients suffering from Alzheimer's disease, Parkinson's disease, ALS and Huntington’s disease.

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