Editing Brain transplant (section)

== Existing challenges ==
[[File:Peripheral nerve, cross section.jpg|thumb|Cross section view of [[Nervous tissue|nerve tissue]].]]
One of the most significant barriers to the procedure is the inability of [[nerve]] tissue to heal properly; [[scar]]red [[nerve tissue]] does not transmit signals well, which is why [[spinal cord injuries]] devastate muscle function and [[Sense|sensation]].

Alternatively, a [[brain–computer interface]] can be used connecting the subject to their own body. A study<ref name="EthierOby2012">{{cite journal|last1=Ethier|first1=C.|last2=Oby|first2=E. R.|last3=Bauman|first3=M. J.|last4=Miller|first4=L. E.|title=Restoration of grasp following paralysis through brain-controlled stimulation of muscles|journal=Nature|volume=485|issue=7398|date=April 2012|pages=368–371|issn=0028-0836|doi=10.1038/nature10987 |pmid=22522928 |pmc=3358575|bibcode=2012Natur.485..368E|url=http://211.144.68.84:9998/91keshi/Public/File/34/485-7398/pdf/nature10987.pdf|archive-url=https://web.archive.org/web/20130721070518/http://211.144.68.84:9998/91keshi/Public/File/34/485-7398/pdf/nature10987.pdf|archive-date=21 July 2013}}</ref> using a monkey as a subject shows that it is possible to directly use commands from the brain, bypass the spinal cord and enable hand function. An advantage is that this interface can be adjusted after the surgical interventions are done where nerves can not be reconnected without surgery.

Also, for the procedure to be practical, the age of the donated body must be close to that of the recipient brain: an adult brain cannot fit into a [[skull]] that has not reached its full growth, which occurs at age 9–12 years.

When organs are transplanted, aggressive [[transplant rejection]] by the host's [[immune system]] can occur. Because [[immune cells]] of the [[central nervous system]] (CNS) contribute to the maintenance of [[neurogenesis]] and [[spatial learning]] abilities in adulthood, the brain has been hypothesized to be an [[Immune privilege|immunologically privileged]] (unrejectable) organ.<ref name="ZivRon2006">{{cite journal|last1=Ziv|first1=Yaniv|last2=Ron|first2=Noga|last3=Butovsky|first3=Oleg|last4=Landa|first4=Gennady|last5=Sudai|first5=Einav|last6=Greenberg|first6=Nadav|last7=Cohen|first7=Hagit|last8=Kipnis|first8=Jonathan|last9=Schwartz|first9=Michal |display-authors=3 |title=Immune cells contribute to the maintenance of neurogenesis and spatial learning abilities in adulthood|journal=Nature Neuroscience|volume=9|issue=2|year=2006|pages=268–275|issn=1097-6256|doi=10.1038/nn1629 |pmid=16415867|s2cid=205430936}}</ref><ref>{{cite magazine |first=Lou |last=Jacobson |url=http://linguafranca.mirror.theinfo.org/9708/fn.9708.html |title=A Mind is a Terrible Thing to Waste |magazine=Lingua Franca |date=August 1997}}</ref><ref>Mike Darwin: [http://www.alcor.org/Library/html/ButWhatWillTheNeighborsThink.html But What Will The Neighbors Think? A Discourse On The History And Rationale Of Neurosuspension]. ''Cryonics'', October 1988.</ref> However, immunorejection of a functional transplanted brain has been reported in monkeys.<ref name=McCrone2003>{{cite journal|last1=McCrone|first1=John|title=Monkey Business|journal=Lancet Neurology|date=Dec 2003|volume=2|issue=12|page=772|doi=10.1016/S1474-4422(03)00596-9|pmid=14636785|s2cid=5254407|url=http://www.dichotomistic.com/mind_readings_head_transplant.html|access-date=20 January 2015|quote=(As reproduced at author's personal webpage)|url-status=dead|archive-url=https://web.archive.org/web/20150228155418/http://www.dichotomistic.com/mind_readings_head_transplant.html|archive-date=28 February 2015|df=mdy-all|url-access=subscription}}</ref>