Many organs can be transplanted nowadays, including the liver, lungs and kidneys.
Can the brain be transplanted?
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Yes, brain transplantation is technically possible, but only for short periods of time, and only in experimental settings.
In terms of a full-brain transplant there has been only one group that have made serious attempts in doing this (according to wikipedia and a literature search on my end). In the 1960's White and colleagues transplanted canine brains from one animal to another (White et al., 1965). In total 6 brains were transplanted. However, the recipients' brains were not removed and the brains were merely surgically transplanted into the neck region of the recipient animal, and connected to the recipient's cervical vasculature (carotide arteries and jugular vein). Hence, the recipient canines ended up with two brains. The authors, however showed with these experiments that the transplantation of brains was feasible, and that the transplants survived and remained functional, which was evidenced by EEG activity. The brains survived from 6 hours up to two days.
Later, White and colleagues worked out a way to keep an isolated (but blood-perfused) monkey brain alive outside the skull, potentially allowing for a primate brain to be transplanted (White et al, 1975). The procedure could include longer-term 'storage' of the brain by cooling it, making the possibility of transplantation more feasible. However, White realized the difficulties with this approach, since, and I quote:
[...] by definition the brain must be isolated before the transplantation, and thus requiring all nervous tissue connections to be severed (e.g. cranial nerves and spinal cord), the isolated transplanted monkey brain is without a mechanism to receive or transmit information.
To address this issue White et al. set out to transfer the entire cephalon (head) of a monkey to the body of a recipient whose own cephalon had been removed at a mid-cervical level. Under these circumstances the brain, being within its own cephalon, still connects to the cranial nerves:
White et al. succeeded in transplanting a head, but the preparation rarely survived longer than three days due to haemorrhagic shock (White et al, 1975). Basically the recipient was quadriplegic, as the face was fully functional and White comments, and I quote:
Observe the wakeful appearance of the cephalon and the obvious movement of the facial musculature with open mouth and eyes. This preparation gives every evidence of being in intelligent contact with its environment. [...] Cortical [EEG] activity in this preparation demonstrates awake recordings.
Hence, with the current available technology it does not make much sense to perform a brain transplant, as the transplanted brain cannot be functionally (neurally) connected to recipient body. However, strides are being made in re-connecting a severed spinal cord (Canavero, 2013), endeavors that could bring head transplants a little closer.
Quadriplegic people obviously face extreme psychological challenges (Sane Australia). However, even when they have become quadriplegic due to an event later in life, they are not mentally changed, in that they are still 'themselves'. Therefore, although human transplants never have been done, I dare to say that the transplanted head will determine the psychological 'self' of the recipient body, which includes memory and personal traits. At least, assuming the brain can be transplanted without inflicting neuronal damage.
- White et al. Science 1965;150:779-81
- White et al. Resuscitation 1975;4,197-210
- Canavero et al. Surg Neurol Int 2013;4:S335–S42
- CBS News