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Neurogenesis of Child Development

Connection of neurons
Neural wiring

How does neurogenesis relate to child development?
  How does it relate to the concept of critical period?
The neuroplasticity of child development: looking at the concept itself, what does it really mean?

Neuroplasticity, 'neuro' meaning neuron and 'plasticity' means ability to change. The unification of these two etymological concepts now means the neuron's ability to change but in response to the changes in the internal and external environment of the organism. Neurons change their structures relative to homeostasis, environmental changes (learning experiences).

When the structure and connections of neurons change, their functions changes as well. How true is this? How does the structure and function of a neuron changes with other neurons relative to experiences from the environment? This can be explained by one principle discovered by a Canadian scientist in 1949.

Donald Hebb, a Canadian psychologist found that if two neurons fire together frequently that neuron A is able to excite neuron B. He called this 'the principle of neuroplasticity' which states that 'the neuron that fire together, wire together and the neuron that fire apart wire apart'.

   If for example, neuron A can fire neuron B, C, D, E, and F neurons as the firing rates of neuron A increases, it increases frequently when the neurons are in close connection due solely to some factors of which many are environmental stimuli such as music, light etc.

 Some neuronal connections and malleability too are a direct result of the internal (physiological) environment. In this regard, neurons that connect modulate the same kind of behavior based on their specific functions or related functions. 

Another way think about this is to assume the illustration that there are various types of road transportation which include the use of cars, lorries or trucks, motorcycles, and bicycles etc. all of which perform more or less the same function which is the transportation of people, goods and services. 

One thing that categorize this is just the fact that they convey people, goods and services to and fro the road but not the air neither is it water. This is also the function of trains in the case of rail transportation but not that kind of route, it uses railway. Road transportation in the above example is similar to that of neural connection in that many types of vehicle uses the road.

In 1883, Johannes Muller's 'law of specific nerve energy explains that neurons are energy-specific, stimulus-specific'. If a child is exposed to stimulus of music such as violin sonatas, orchestra, it follows therefore that repeated exposure to such stimuli is capable of modifying the neurological structures. Both the structure and function of neurons responsible for musical ability, perception of musical stimuli become thicker in close synaptic connection.

   This phenomenon has long existed ever since prenatal period of child development. Neurons during this phase multiply rapidly and notably during the embryonic period of prenatal development. What happens at this phase is cell differentiation including the ectoderm, mesoderm and the endoderm. 

As part of the ectoderm is the evolvement (evolution) of the nervous system. Starting from the neuroectoderm which will develop into what we recognize as the nervpous system consisting of the central and peripheral nervous system as well as the CNS's subdivision of the brain and the spinal cord-neurogenesis begins. At about 2 and 1/2 weeks of prenatal development or say 3 weeks, the neuroectoderm begins to develop in a gradual process.

Sequential development of precursor cells forming the:
  Neuroectoderm; Neural plate&
;Neural tube; Neural groove; Neural crest forms in the margin of the neural tube at the 4th week; Fore brain, Mid-brain and the Hind brain emerge at the 5th week. The immature or undeveloped brain of the neonate will soon begin to develop after the formation but in a gradual process. The number of neurons multiply rapidly from thousands to millions. This seem interesting... 
The neuroplastic human being better explains how much neurons we have and how they interact with the environment.

How Does Neuroplasticity Relates to Critical Period?

   Neuroplasticity is true as experimentally confirmed by neuropsychologist (in learning experiences of rats running through a maize). It proves that the brain is not as hard-wired as many people think. It is soft-wired and as such capable of changing through life course.
Neuroplasticity has not come to render the concept of critical period useless but rather to explain how critical period works.

Although critical period may seem archaic, it is correct as evident in the way it enables easy and adequate and precise explanation of some abnormal behaviors relating to abilities such as autism (in clinical diagnosis).

To the set of people who beleve in critical period, mathematical or musical or linguistic ability is considered an important behavior.
In the first years of life (critical period), there is quickened pace of brain organization which then becomes less rapid to 10 years of life to continue, so slow during the rest of life in a gradual decline fashion. So is critical period becomes justified here.

   Neurons that are not put to use become trimmed because there is no environmental stimulation that can possibly bring about synaptic efficiency. Increase in dendritic extensions and small branches which has been called dendritic aborization occurs enabling more thicker synaptic connection and efficiency, proving the Hebbian theory/principle of neuroplasticity to be true. So actually, it is now crystal-clear that "the neurons that fire together, wire together and the neurons thet fire apart, wire apart".

   The above is the unification of neuroplasticity and critical period of child development. The critical neuroplastic period is more elaborate way to ascertain the truth of both theories.

and efficacious to produce a new born genius. This is not always the case, in fact, a rarity. Following delivery i.e. after the 38th week of fetal development, there is a gradual but not immediate reduction in the number of neurons- a genetically programmed neural cell death (apoptosis) occurs.

The number of neurons in the fetal brain is between 30 and 70% higher than in adults. Surplus cells survive for days to weeks after which on their own starts a cascade degenerative changes and a physiological process of programmed cell death.

   As evident in the Dawinian survival of the fittest, it is popularly believed by many that the first years of life are the most crucial in the development of a person-critical period. That, if the said ability of behavior is not attained within a specific time limit, the likelihood to have such ability is odd. Because neurons are malleable in a person's life time, it may seem incorrect about neuroplasticity although this synopsis offered here has not come to invalidate or falsify the 'critical period'.

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