Editing Adult neurogenesis (section)

{{Short description|Generating of neurons from neural stem cells in adults}}
{{cs1 config|name-list-style=vanc}}
{{Not to be confused with|Neuroregeneration}}
[[File:Proliferating cells in the dentate gyrus (crop).jpg|thumb|240px|[[Bromodeoxyuridine|BrdU]] (red), a marker of [[DNA]] replication, highlights neurogenesis in the [[subgranular zone]] of hippocampal [[dentate gyrus]]. Fragment of an [[:commons:File:Phenotypes of proliferating cells in the Rostral Migratory Stream and Dentate Gyrus.jpg|illustration]] from Faiz et al., 2005.<ref name="pmid15826306">{{cite journal |author1=Faiz M |author2=Acarin L |author3=Castellano B |author4=Gonzalez B |title=Proliferation dynamics of germinative zone cells in the intact and excitotoxically lesioned postnatal rat brain |journal=[[BMC Neuroscience]] |volume=6 |pages=26 |year=2005 |pmid=15826306 |pmc=1087489 |doi=10.1186/1471-2202-6-26 |doi-access=free }}</ref>]]

[[File:Doublecortin expression.png|thumb|right|[[Doublecortin]] expression in the rat [[dentate gyrus]], 21st postnatal day. Oomen et al., 2009.<ref name="dcx">{{cite journal |author1=Oomen CA |author2=Girardi CE |author3=Cahyadi R |display-authors=etal |editor1-last=Baune |editor1-first=Bernhard |title=Opposite effects of early maternal deprivation on neurogenesis in male versus female rats |journal=PLOS ONE |volume=4 |issue=1 |pages=e3675 |year=2009 |pmid=19180242 |pmc=2629844 |doi=10.1371/journal.pone.0003675 |bibcode=2009PLoSO...4.3675O|doi-access=free }}</ref>]]

'''Adult neurogenesis''' is the process in which [[neuron]]s are generated from [[neural stem cell]]s in the adult. This process differs from [[prenatal development|prenatal]] [[neurogenesis]].

In most mammals, new neurons are born throughout adulthood in two regions of the brain:<ref name="pmid25621867">{{cite journal|last1=Ernst|first1=A|last2=Frisén|first2=J|title=Adult neurogenesis in humans- common and unique traits in mammals.|journal=PLOS Biology|date=January 2015|volume=13|issue=1|pages=e1002045|doi=10.1371/journal.pbio.1002045|pmid=25621867|pmc=4306487|doi-access=free}}</ref>
* The [[subgranular zone]] (SGZ), part of the [[dentate gyrus]] of the [[hippocampus]],<ref name="dentate" /><ref>{{cite journal|last1=Vadodaria|first1=Krishna C.|last2=Gage|first2=Fred H.|title=SnapShot: Adult Hippocampal Neurogenesis|journal=Cell|volume=156|issue=5|pages=1114–1114.e1|doi=10.1016/j.cell.2014.02.029|pmid=24581504|year=2014|doi-access=free}}</ref> where neural stem cells give birth to [[granule cell]]s (implicated in memory formation and learning).<ref>{{cite journal |last1=Duan |first1=Xin |last2=Kang |first2=Eunchai |last3=Liu |first3=Cindy Y |last4=Ming |first4=Guo-li |last5=Song |first5=Hongjun |date=February 2008 |title=Development of neural stem cell in the adult brain |url=|journal=Current Opinion in Neurobiology |volume=18 |issue=1 |pages=108–115 |doi=10.1016/j.conb.2008.04.001 |pmid=18514504 |pmc=2464621 |issn=0959-4388}}</ref>
* The [[subventricular zone]] (SVZ) of the [[lateral ventricle]]s, which can be divided into three microdomains: lateral, dorsal and medial.<ref>{{cite journal|last1=Fiorelli|first1=Roberto|last2=Azim|first2=Kasum|last3=Fischer|first3=Bruno|last4=Raineteau|first4=Olivier|date=2015-06-15|title=Adding a spatial dimension to postnatal ventricular-subventricular zone neurogenesis|journal=Development|volume=142|issue=12|pages=2109–20|doi=10.1242/dev.119966|issn=1477-9129|pmid=26081572|doi-access=free}}</ref> Neural stem cells migrate to the [[olfactory bulb]] through the [[rostral migratory stream]] where they differentiate into [[interneuron]]s participating in the [[olfaction|sense of smell]].  In humans, however, few if any olfactory bulb neurons are generated after birth.<ref name="pmid24561062">{{cite journal |vauthors=Ernst A, Alkass K, Bernard S, Salehpour M, Perl S, Tisdale J, Possnert G, Druid H, Frisén J |title=Neurogenesis in the striatum of the adult human brain |journal=Cell |volume=156 |issue=5 |pages=1072–83 |year=2014 |pmid=24561062 |doi=10.1016/j.cell.2014.01.044 |doi-access=free }}</ref><ref>{{cite journal |last1=Bergmann |first1=O. |last2=Liebel |first2=J. |last3=Bernard |first3=S. |last4=Alkass |first4=K. |last5=Yeung |first5=M.S.Y. |last6=Steier |first6=P. |last7=Kutschera |first7=W. |last8=Johnson |first8=L. |last9=Landen |first9=M. |last10=Druid |first10=H. |last11=Spalding |first11=K.L. |last12=Frisen |first12=J. |title=The age of olfactory bulb neurons in humans |journal=Neuron |date=2012 |volume=74 |issue=4 |pages=634–9 |doi=10.1016/j.neuron.2012.03.030|pmid=22632721 |doi-access=free }}</ref>

More attention has been given to the neurogenesis in the [[dentate gyrus]] than in the [[striatum]].  In [[rodent]]s, many of the newborn dentate gyrus neurons die shortly after they are born,<ref name="dentate">{{cite journal |last1=Dayer |first1=A.G. |last2=Ford |first2=A.A. |last3=Cleaver |first3=K.M. |last4=Yassaee |first4=M. |last5=Cameron |first5=H.A. |title=Short-term and long-term survival of new neurons in the rat dentate gyrus |journal=The Journal of Comparative Neurology |date=2003 |volume=460 |pages=563–572 |doi=10.1002/cne.10675 |pmid=12717714 |issue=4|s2cid=7153599 |url=https://zenodo.org/record/1229143 }}</ref> but a number of them become functionally integrated into the surrounding brain tissue.<ref>{{cite journal|last1=Toni |first1=N. |last2=Teng |first2=E.M. |last3=Bushong |first3=E.A. |last4=Aimone |first4=J.B. |last5=Zhao |first5=C. |last6=Consiglio |first6=A. |last7=van Praag |first7=H. |last8=Martone |first8=M.E. |last9=Ellisman |first9=M.H. |last10=Gage |first10=F.H. |title=Synapse formation on neurons born in the adult hippocampus |journal=Nature Neuroscience |date=2007 |volume=10 |issue=6 |pages=727–734 |doi=10.1038/nn1908 |pmid=17486101|s2cid=6796849 }}</ref><ref>{{cite journal |last1=Vivar |first1=C. |last2=Potter |first2=M.C. |last3=Choi |first3=J. |last4=Lee |first4=J. |last5=Stringer |first5=T.P. |last6=Callawy |first6=E.M. |last7=Gage |first7=F.H. |last8=Suh |first8=H. |last9=van Praag |first9=H. |title=Monosynaptic inputs to new neurons in the dentate gyrus. |journal=Nature Communications |date=2012 |issue=1038 |doi=10.1038/ncomms2101 |pmid=23033083 |pmc=4603575 |volume=3 |pages=1107|bibcode=2012NatCo...3.1107V }}</ref><ref>{{cite journal |last1=Toni |first1=N. |last2=Laplagne |first2=D.A. |last3=Zhao |first3=C. |last4=Lombardi |first4=G. |last5=Ribak |first5=C.E. |last6=Gage |first6=F.H. |last7=Schinder |first7=A.F. |title=Neurons born in the adult dentate gyrus form functional synapses with target cells |journal=Nature Neuroscience |date=2008 |volume=11 |issue=8 |doi=10.1038/nn.2156 |pmid=18622400 |pmc=2572641 |pages=901–7}}</ref>  Adult neurogenesis in rodents is reported to play a role in learning and memory, emotion, stress, depression, response to injury, and other conditions.<ref name=":0">{{cite journal |last1=Cameron |first1=Heather A. |last2=Glover |first2=Lucas R. |date=2015-01-03 |title=Adult Neurogenesis: Beyond Learning and Memory |journal=Annual Review of Psychology |volume=66 |issue=1 |pages=53–81 |doi=10.1146/annurev-psych-010814-015006 |issn=0066-4308 |pmc=5612417 |pmid=25251485}}</ref>

The numbers of neurons born in the human adult hippocampus remains controversial; some studies have reported that in adult humans about 700 new neurons are added in the hippocampus every day,<ref>{{cite journal|last1=Spalding|first1=Kirsty L.|last2=Bergmann|first2=Olaf|last3=Alkass|first3=Kanar|last4=Bernard|first4=Samuel|last5=Salehpour|first5=Mehran|last6=Huttner|first6=Hagen B.|last7=Boström|first7=Emil|last8=Westerlund|first8=Isabelle|last9=Vial|first9=Céline|date=2013-06-06|title=Dynamics of hippocampal neurogenesis in adult humans|journal=Cell|volume=153|issue=6|pages=1219–27|doi=10.1016/j.cell.2013.05.002|issn=1097-4172|pmc=4394608|pmid=23746839}}</ref> while more recent studies show that adult hippocampal neurogenesis does not exist in humans, or, if it does, it is at undetectable levels.<ref>{{cite journal|last1=Sorrells|first1=SF|last2=Paredes|first2=MF|last3=Cebrian-Silla|first3=A|last4=Sandoval|first4=K|last5=Qi|first5=D|last6=Kelley|first6=KW|last7=James|first7=D|last8=Mayer|first8=S|last9=Chang|first9=J|last10=Auguste|first10=KI|last11=Chang|first11=EF|last12=Gutierrez|first12=AJ|last13=Kriegstein|first13=AR|last14=Mathern|first14=GW|last15=Oldham|first15=MC|last16=Huang|first16=EJ|last17=Garcia-Verdugo|first17=JM|last18=Yang|first18=Z|last19=Alvarez-Buylla|first19=A|title=Human hippocampal neurogenesis drops sharply in children to undetectable levels in adults.|journal=Nature|date=15 March 2018|volume=555|issue=7696|pages=377–381|doi=10.1038/nature25975|pmid=29513649|pmc=6179355|bibcode=2018Natur.555..377S}}</ref>  Recent evidence shows that adult neurogenesis is essentially extinct in humans.<ref>{{cite journal |last1=Duque |first1=Alvaro |last2=Arellano |first2=Jon I. |last3=Rakic |first3=Pasko |date=January 2022 |title=An assessment of the existence of adult neurogenesis in humans and value of its rodent models for neuropsychiatric diseases |journal=Molecular Psychiatry |volume=27 |issue=1 |pages=377–382 |doi=10.1038/s41380-021-01314-8 |issn=1476-5578 |pmc=8967762 |pmid=34667259}}</ref> The experiments advocating for the presence of adult neurogenesis have focused on how dual antigen retrieval finds that DCX antibodies are staining many cells within the adult human dentate gyrus. This finding is not as clear though as supporters of adult neurogenesis suggest; the dentate gyrus cells stained with DCX have been shown to have a mature morphology, contrasting the idea that novel neurons are being generated within the adult brain.<ref>{{cite journal |vauthors=Sorrells SF, Paredes MF, Zhang Z, Kang G, Pastor-Alonso O, Biagiotti S, Page CE, Sandoval K, Knox A, Connolly A, Huang EJ, Garcia-Verdugo JM, Oldham MC, Yang Z, Alvarez-Buylla A |title=Positive Controls in Adults and Children Support That Very Few, If Any, New Neurons Are Born in the Adult Human Hippocampus |journal=J Neurosci |volume=41 |issue=12 |pages=2554–65 |date=March 2021 |pmid=33762407 |pmc=8018729 |doi=10.1523/JNEUROSCI.0676-20.2020 }}</ref> The role of new neurons in human adult brain function thus remains unclear.