Adult Neurogenesis

Friday, November 27, 2009

what is adult neurogensis?
Adult neurogenesis is the formation of new neurons in adult brain. It was a prevailing belief that mature brain can not produce new neurons.

A number of reasons behind this belief, includes
- limited capacity of self-reparing in mammal brain and spinal cord.
- structural consistency of mammalian brain throughout the life with an unchanging number of neurons of about 100 billion.

Besides, it is very difficult to imagine how new neurons could develop and integrate successfully into the mature brain structure. However ,due to scientist's arduous search for unknown and enormous technical development, many evidence are found regarding adult neurogenesis and it is now widely accepted by the scientific community.

Where does adult neurogenesis occur?
Most cells in the brain are formed during embryonic and early post-natal period while new neurons are also generated throughout life and are added to at least two areas of the brain: the hippocampus ( involved in certain types of learning and memory) and the olfactory bulb ( involved in the sense of smell). New neurons are spawned from the division of neural precursor cells — cells that have the potential to become neurons or support cells.


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New hippocampal neurons are generated by neural precursors located in the hippocampus, in a region known as the subgranular zone. In contrast, new olfactory neurons arise from neural precursors located outside of the olfactory system, in a region known as the subventricular zone of the lateral ventricle. These cells migrate to the olfactory bulb through a tract known as the rostral migratory stream.

What are the functional significance of newly synthesized neurons?
Experimental studies suggest that new neurons integrate into the circuitry of the brain and actively participate in its functions. The hippocampus is known to play a critical role in learning and memory and many scientists have hypothesized that newly generated neurons within the hippocampus contribute to these processes. Although currently limited, there is support for this hypothesis. For instance, conditions that impair adult neurogenesis, such as stress, also impair learning. In contrast, conditions that promote the generation of new neurons, such a physical exercise , often are associated with improved memory and learning.

Studies have shown that the beneficial effect of many antidepressant are diminished when neurogenesis is blocked. Again many therapies and medication that are used to treat patients suffering from depression can cause an increase in hippocampal neurogenesis .So clearly, there is a link between adult neurogenesis and neurological disorder. We can expect, in near future neurological disorder can be cured by manipulating neurogenesis, though its still very much impossible.

Many studies have shown that neurogenesis is stimulated in the mammalian brain in response to injury and disease. Although this injury-induced neurogenesis does not lead to recovery, many scientists believe it represents brain's attempt to mend itself. Now, if we can understand the mechanism of neurogenesis and the integration of new neurons to nervous system its may be possible to cure or give life to a patient having severe brain stroke !!!

Once it was thought, once you were grown all you could do was watch your brain cells die. But things are changed. The discovery of life-long neurogenesis in humans has redefined the understanding of the brain and spinal cord. Lots of expectation has already been arisen with this discovery. We can suddenly hope that new strategies will be developed to treat injuries and diseases of the brain and spinal cord in future.

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