This has been a topic of intensive research for several decades [0]. In a nutshell, people have looked, repeatedly, and have failed to find very much.
There are two main stem cell populations in the brain, which produce new neurons in two discrete regions. One stem cell population is adjacent to the substantia nigra, but produces neurons which migrate to an entirely different region of the brain (involving a "cell highway" known as the rostral migratory stream). There are experimental ways to "misdirect" these new neurons towards the substantia nigra, but there have been no durable experimental or clinical successes. Furthermore, it is relatively straightforward to look for neural stem cells in brain tissue, and to my knowledge, none have been found in the substantia nigra per se.
In spite of the efforts, it is true that finding new neurons in the brain is very challenging, if for no other reason than that there are very few of them. One fascinating study from a few years ago actually used the elevated levels of atmospheric carbon-14 during the Cold War as a label with which to identify new neurons from the second stem cell population [1]. It's now considered that they greatly overestimated the number of new neurons, but it is still a seminal paper in the field.
> One stem cell population is adjacent to the substantia nigra, but produces neurons which migrate to an entirely different region of the brain (involving a "cell highway" known as the rostral migratory stream).
However, the migration can be demand driven, in response to disease conditions.
gwerbret|5 years ago
There are two main stem cell populations in the brain, which produce new neurons in two discrete regions. One stem cell population is adjacent to the substantia nigra, but produces neurons which migrate to an entirely different region of the brain (involving a "cell highway" known as the rostral migratory stream). There are experimental ways to "misdirect" these new neurons towards the substantia nigra, but there have been no durable experimental or clinical successes. Furthermore, it is relatively straightforward to look for neural stem cells in brain tissue, and to my knowledge, none have been found in the substantia nigra per se.
In spite of the efforts, it is true that finding new neurons in the brain is very challenging, if for no other reason than that there are very few of them. One fascinating study from a few years ago actually used the elevated levels of atmospheric carbon-14 during the Cold War as a label with which to identify new neurons from the second stem cell population [1]. It's now considered that they greatly overestimated the number of new neurons, but it is still a seminal paper in the field.
[0]: Good review, though somewhat technical: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6659986/
[1]: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4394608/
wombatmobile|5 years ago
However, the migration can be demand driven, in response to disease conditions.
https://pubmed.ncbi.nlm.nih.gov/18394605/
unknown|5 years ago
[deleted]