Why is a brain transplant not yet possible?

Is a brain transplant possible?

Short answer

Yes, a brain transplant is technically possible, but only for short periods of time and only in experimental settings.

background

Regarding a Whole brain transplant there was only one group that made serious attempts to do this (according to Wikipedia and a literature search on my end). In the 1960s transplanted White and colleagues Dog brains from one animal to another (White et al., 1965). A total of 6 brains were transplanted. However, the recipient's brain was not removed, and that Brain was merely surgically transplanted into the recipient animal's neck area and connected to the recipient's cervical vasculature (Carotid arteries and jugular vein) connected. Hence the recipient's canines had two brains . However, with these experiments the authors showed that brain transplantation was possible and that the transplants survived and remained functional, as evidenced by the EEG activity. The brain survived from 6 hours to two days.

White and colleagues later worked out a way to get one isolated (but blood-perfused) monkey brain outside of the skull to keep it alive possibly grafting a primate brain (White et al., 1975). The procedure could include longer term "storage" of the brain by cooling, making the possibility of transplantation more practical. However, White recognized the difficulties with this approach, as and I quote:

[...] By definition, the brain must be isolated prior to transplantation, and therefore all neural tissue connections (e.g. cranial nerves and spinal cord) must be severed. The isolated transplanted monkey brain has no mechanism for receiving or transmitting information.

To address this problem, White et al. Do it yourself , the entire Cephalon Transfer (head) of a monkey to the body of a recipient whose own cephalon in the center of the cervix had been removed. In these circumstances, the brain, which is in its own cephalon, still connects to the cranial nerves:


Source: University of Washington

White et al.A head transplant succeeded, but the specimen survived due to hemorrhagic shock rarely longer than three days (White et al., 1975). Basically the recipient was paraplegic as the face was fully functional and white comments, and I quote:

Observe the cephalon's alert look and apparent movement of the facial muscles with your mouth and eyes open. This preparation gives every proof that she is in intelligent contact with her surroundings. [...] The cortical [EEG] activity in this preparation shows awake images.

Hence it is with the technology currently available not very useful to do a brain transplant, as the transplanted brain cannot be functionally (neural) connected to the recipient body . However, steps are being taken to reconnect a severed spinal cord (Canavero, 2013). These efforts could bring head transplants a little closer.

Quadriplegics are obviously facing extreme psychological challenges (Sane Australia). Even if they are paraplegic as a result of a later event, they will not be mentally altered because they are still "themselves". Although human transplants have never been performed, I dare to say that the transplanted head determines the psychological “self” of the recipient body, which includes memory and personal characteristics. At least under the assumption that the brain can be transplanted without causing neural damage.


References
-White et al.science 1965;150 : 779- 81
-White et al.revival 1975;4 , 197 - 210
-Canavero et al.Surg Neurol Int 2013; 4: S335 - S42

further reading
-CBS news

A face

Impressive! That's great. Although I am sad about the animals that were used in experiments.

AliceD ♦

@CRags - When I first read about these (terrible) experiments, I couldn't help but feel a certain amount of thrill. Obviously, and fortunately, from now on such experiments would no longer exist. At least not until a possible functional reconnection to the peripheral nervous system can be established.