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By "children" I mean young people at the age of 10 or lower.

I know that the adult brain cannot restore brain cells, but what about children? I mean, the brain must develop from a few cells to a 90 billion cells somehow, when do we lose this ability?

I'm also interested in cases when a child gets hit into the head (concussion). Can the damage be fixed over time?

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There is a misconception in your question about the absence of neurogenesis in adults. It is definitely present in adults as has been shown by a host of recent studies. If you want some technical details on neurogenesis or a question about what exactly changes in children at the end of critical period. –  Artem Kaznatcheev Oct 14 '12 at 15:42
@Artem Kaznatcheev: true, however neurogenesis and regeneration are not necessarily the same thing (i.e.: neurogenesis does not imply regeneration, although the opposite is obviously true). –  nico Oct 14 '12 at 16:19
@nico I didn't mean to suggest that they were, otherwise I'd submit my comment as an answer. I was just going off a vibe I got from the question. I don't know anything about regeneration and so did not got beyond a comment. –  Artem Kaznatcheev Oct 14 '12 at 16:40
@Artem Kaznatcheev: surely I was merely pointing that out in case it was not completely clear especially for the OP :) –  nico Oct 14 '12 at 16:55
Just a note, the definition of the word 'children' is 'pre-pubescent'. It is frequently misused to refer to adolescents and even post-adolescent young adults colloquially, but in scientific settings you should be safe using it properly. –  otakucode Sep 25 at 18:51

4 Answers 4

I am not an expert in neurobiology, but this is what I have been able to find:

In general, the PNS (peripheral nervous system) does have remarkable neuroregeneration capabilities. However, the CNS (central nervous system), which includes the brain, has extremely limited neuroregeneration abilities. However, there are some interesting examples of CNS recovery:

Children under six who undergo, unfortunately, a hemiectomy, whereby one half of their brain is taken out, are able to regain almost normal function because of the brain’s ability to rewire and literally take over the functions of the missing other half of the brain.

I am guessing one thing that can explain this is that in children, the CNS is still developing, and so if there is damage, the CNS can just entirely replace damaged parts (this might be different than "fixing" which is required in adults).

Again, I am not an expert on this and would be glad to hear a neurobiologist's opinion.

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Would be nice to find a proper source for the hemiectomy quote –  nico Dec 2 '12 at 19:47
@nico here is one relevant reference I found: –  Bitwise Dec 3 '12 at 0:26
Hemispherectomy is prognosed with good outcome results in kids, but not because they re-generate all the lost neurons. The example is an interesting one, but not so relevant in the light of the question. –  AliceD Sep 28 at 14:01

Speaking to Artem Kaznatcheev's comment, it is not true that the adult brain is post-mitotic.

Dr Bernard Rabin has shown is his scientific research, often in collaboration with and funded by NASA, that the adult brain is not post-mitotic, meaning that cell growth and division does occur. The primary focus of his work is to examine the relationship between high-energy irradiation of the brain (such as on a long-term space mission, say to Mars) and normal aging, and how diet can affect that age-mimicking decline. A list of papers he has published in the field of the aging brain is here.

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As to your first question: Also adults can regenerate brain cells, albeit in a few restricted, specific regions of the brain. A continuous level of neural regeneration occurs throughout adult life in at least two locations. The first is the subgranular zone of the dentate gyrus of the hippocampus, the region of the brain involved in learning and memory. The other is located in and near the anterior lateral ventricular wall of the cerebral cortex. While neurogenesis in the adult hippocampus is relatively limited, the subventricular zone is thought to continuously replace interneurons in the olfactory bulb (Clarke, 2003).

As to your second question: a single blow to the head is generally considered not much of an issue. It is repeated injuries to the brain that kills neurons. For example, a knockout in boxing seems impressive and damaging to the brain, but it is in fact the repeated hits to the head, e.g. during the course of numerous bouts of boxing (or American football), that irreversibly injure the brain. A single blow will likely be dealt with by healing processes of the neural damage. Multiple blows will eventually kill neurons. As to whether those killed cells are regenerated; perhaps a few, as it is known that brain damage can result in the attraction of new cells, but it is the plasticity of the brain that will play the biggest role in the healing process, i.e., lost functions are redirected to other parts of the brain, but not regenerated.

- Clarke, Bone Marrow Transplantation (2003); 32: S13–S17

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This isn't quite the same; however, children can have parts of their brains removed and then the remaining parts of the brain can take over for that removed part. There are not also lasting effects of this even.

There is a neurosurgeon by the name of Benjamin Carson who has done a procedure called a hemispherectomy. A hemispherectomy is the act of removing one side of the person's brain. This procedure can only be done in children under the age of either 10 or 12 (I am so sorry, I can't remember right now).

The reason this can only be done in children is because the side of the brain not removed is able to take over for the removed side, this cannot occur in adults.

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As far as I recall, the age cut off for the procedure you're describing is closer to 1-2 than 10-12 –  Rory M Apr 26 '14 at 20:28
@RoryM sorry about that. I guess I definitely didn't remember the age:) –  L.B. Apr 27 '14 at 0:29
This answer can be ascribed to neuroplasticity alone (existing cells take over other functions). –  AliceD Aug 29 at 14:27

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