Whole-body transplant

A brain transplant or whole-body transplant is a procedure in which the brain of one organism is transplanted into the body of another. It is a procedure distinct from head transplantation, which involves transferring the entire head to a new body, as opposed to the brain only. Theoretically, a person with advanced organ failure could be given a new and functional body while keeping their own personality, memories, and consciousness through such a procedure.

No human brain transplant has ever been conducted. Neurosurgeon Robert J. White, has grafted the head of a monkey onto the headless body of another monkey. EEG readings showed the brain was later functioning normally. It was thought to prove that the brain was an immunologically privileged organ, as the host's immune system did not attack it at first, but immunorejection caused the monkey to die after nine days. Brain transplants and similar concepts have also been explored in various forms of science fiction.

One of the most significant barriers to the procedure is the inability of nerve tissue to heal properly; scarred nerve tissue does not transmit signals well (this is why a spinal cord injury is so devastating). However, recent research at the Wistar Institute of the University of Pennsylvania involving tissue-regenerating mice (known as MRL mice) may provide pointers for further research as to how to regenerate nerves without scarring. It is possible that a completely clean cut will not generate scarred tissue.

Alternatively a brain–computer interface can be used connecting the subject to their own body. A study 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 sufficient: an adult brain cannot fit into a skull that has not reached its full growth, which occurs at age 9–12 years.

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