Are the amount neurons fixed in the brain from birth?

[historian3x]

Can someone please confirm if the amount of neurons are fixed at birth, as in all that changes throughout life is the neural connections? I ask because topics of neurogenesis keep coming up, and if creating neurons isn't possible then why is the term not simply called synapticgenesis?

[tomgwyther]

AFAIK, Most of the neural development [in humans] occurs before birth, but this development continues afterward for a few year, including the creation of new neurons.

[historian3x]

Thank you for replying. Well I thought so too. That is what my professor seem to have indicate, as well as every other source I have read in past. However, I recently came across a small book in the library about exercise inducing neurogenesis and wanted confirmation if this was even possible, so I asked here. However, now it seems there may be more it. I was listening to "Brain Science Podcast #87" on aging with brain a couple days ago and that researcher said they now finding that neurogenesis occurs even in older people with aging. This is fascinating to me now since what I believed was wrong.

Edited October 10, 2012 by historian3x

[iNow]

The number of neurons is not fixed. New ones are constantly growing and old ones are constantly dying.

[CharonY]

Indeed. Different organs have different turnover rates with the brain having one of the somewhat lower ones, but development is ongoing.

[cbrons]

Can someone please confirm if the amount of neurons are fixed at birth, as in all that changes throughout life is the neural connections? I ask because topics of neurogenesis keep coming up, and if creating neurons isn't possible then why is the term not simply called synapticgenesis?

 

Neural stem cells were not thought to exist in the adult, but we know better now. A small fraction (less than 0.5%) of ventricular ependymal cells (i.e. astrocytes) remain as neural stem cells (form neuroblasts that give rise to new neurons even in the adult). They are found in the hippocampus and olfactory cortex (in fact olfactory mucosa generates new olfactory neurons throughout life).