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I am attempting to understand neurogenesis related to learning. Does learning increase the number of neurons in the human brain? What would be some good scientific publications to read?

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  • $\begingroup$ So in other words the number of connections between neurons is just changed? Where could I find some good references for that? $\endgroup$ – user16406 Jun 25 '15 at 12:45
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    $\begingroup$ We should probably wait for @AliceD to answer, since he knows the field better. $\endgroup$ – Chris Jun 25 '15 at 12:48
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    $\begingroup$ @WYSIWYG: I am not so sure that it doesn't, and I think it actually does lead to new cells. $\endgroup$ – AliceD Jun 25 '15 at 12:48
  • $\begingroup$ @AliceD Not in most cases esp. in adults. There is some neurogenesis in the dentate gyrus which may perhaps be regulated by some hippocampal activity (there is a paper which says that). Another point of view is that neurogenesis might lead to amnesia (this was in science some months back). Anyways I just gave a casual comment- I take it back :) $\endgroup$ – WYSIWYG Jun 25 '15 at 12:51
  • $\begingroup$ @user16406 It does happen but in most cases learning basically adds/strengthens the synapses. $\endgroup$ – WYSIWYG Jun 25 '15 at 12:59
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Short answer
Training increases white and gray matter densities in the brain. This may reflect increases in neuronal cell counts especially in the hippocampus. In the cortex, however, such observed changes are probably more reflective of other processes, such as synaptogenesis.

Background
Gray matter is generally viewed as being the neuronal cell bodies, while white matter corresponds to myelinated fiber tracts. Changes in both can be reflective of changes in cellular content, but changes in gray matter are generally more directly related to changes in cell numbers, which you are after.

A striking example of the effects of learning on the brain is observed in subjects that start to learn to juggle. These people have been shown to have increased gray matter density in the occipito-parietal regions (the visual motion areas). These changes are apparent after as little as 7 days of training. Such experience-dependent changes are also observed in white matter. Occipito-parietal regions are involved in visuo-motor coordination, reaching and grasping. There have been a host of other studies that showed similar changes in the brain. For example, taxi drivers were shown to have increased hippocampal volumes.

There is good evidence for adult neurogenesis occurring with learning in the hippocampus. Adult neuro­genesis also produces thousands of new granule cells in the dentate gyrus every month, but this is a relatively small increase in total number of hippocampal neurons. Furthermore, although there have been reports of neurogenesis in the mammalian adult neocortex, this is controversial. Thus, neurogenesis is likely a minor factor in MRI changes, particularly those found outside the hippocampus.

Instead, other factors such as increase in glial cell numbers, synaptogenesis, changes in dendritic structures, axonal sprouting and re-routing and even vascular changes may underly the observed changes in imaging studies.

Note: there is a host of imaging studies available on effects of learning on structural changes in the brain. The referenced review article cites many.

Reference
- Zatorre et al., Nature Neurosci (2012); 15: 528–36

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The no. of neurons only increase during development.

As, a person grows, the no. of neurons is constant or decreases (degradation due to injury or other brain diseases). The no. never increases.

Effect of usage of neurons on conduction

Learning anything (say, a phone no.) requires repeated thinking. The thinking can be continuous in the brain or re-induced by revision. Therefore, learning anything STRENGTHENS the connections; not increase in neuron no.

I can't help you with any Scientific Paper. The image was taken from a Textbook.

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    $\begingroup$ Without proper references such a strong statement is unfounded. -1 $\endgroup$ – AliceD Jun 27 '15 at 15:09
  • $\begingroup$ The figure is from Campbell Biology $\endgroup$ – YAHB Jun 27 '15 at 16:17
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    $\begingroup$ The number of neurons does not only increase during development. $\endgroup$ – AliceD Jul 13 '15 at 11:27

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