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 brain transplant has ever been conducted. The only known head transplant was conducted by neurosurgeon Robert J. White, in which Dr. White 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.
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.
There was at first thought to be an advantage, however, with respect to the immune response. The brain was thought to be an immunologically privileged organ, so rejection would not be a problem. (When other organs are transplanted, aggressive rejection can occur; this is a major difficulty with kidney and liver transplants. However, immune cells of the CNS contribute to the maintenance of neurogenesis and spatial learning abilities in adulthood, so the transplanted brain would not be unhindered from the transplant.)
In 1982, Dr. Dorothy T. Krieger, chief of endocrinology at Mount Sinai Medical Center in New York City, achieved success with a partial brain transplant in mice.
In 1998, a team of surgeons from the University of Pittsburgh Medical Center attempted to transplant a group of brain cells to Alma Cerasini, who had suffered a severe stroke that caused the loss of mobility in her right limbs as well as limited speech. The team's hope was that the cells would correct the listed damage.
The whole-body transplant is just one of several means of putting a consciousness into a new body that have been explored by both scientists and writers.
Edgar Rice Burroughs' The Mastermind of Mars involves a surgeon who does this as his main operation, and a man from Earth, the narrator and main character, who is trained to do it as well.
In Neil R. Jones Professeur Jameson stories (1931), the main character is the last earthman, whose brain is saved by some alien cyborgs called the Zoromes, and is inserted into a robotic body, making him immortal.
Robert Heinlein's 1970 science fiction novel, I Will Fear No Evil, features a main character named Johann Sebastian Bach Smith whose entire brain is transplanted into his deceased secretary's skull.
A similar procedure often found in science fiction is the transfer of one consciousness to another without moving the brain. This is found in many sources, most often a body swap between two characters of an ongoing television series; it occurs in the original Star Trek series twice, in the X-Files episode Dreamland, in the Doctor Who serial "Mindwarp", and in Freaky Friday, Farscape, Stargate SG-1, Buffy the Vampire Slayer, Dollhouse, Red Dwarf, Avatar, Dark Shadows; even in Archie comics. Since there is no movement of the brain(s), however, this is not quite the same as a whole-body transplant.
In the horror film The Skeleton Key, the protagonist, Caroline, discovers that the old couple she is looking after are poor Voodoo witch doctors who stole the bodies of two young, privileged children in their care using a ritual which allows a soul to swap bodies. Unfortunately the evil old couple also trick Caroline and their lawyer into the same procedure, and both end up stuck in old dying bodies unable to speak while the witch doctors walk off with their young bodies.
In Anne Rice's The Tale of the Body Thief, the vampire Lestat discovers a man, Raglan James, who can will himself into another person's body. Lestat demands that the procedure be used on him to allow him to be human once again, but soon finds that he has made an error and is forced to recapture James in his vampiric form so he can take his body back.
Similar in many ways to this is the idea of mind uploading, promoted by Marvin Minsky and others with a mechanistic view of natural intelligence and an optimistic outlook regarding artificial intelligence. It is also a goal of Raëlism, a small cult based in Florida, France, and Quebec. While the ultimate goal of transplanting is transfer of the brain to a new body optimized for it by genetics, proteomics, and/or other medical procedures, in uploading the brain itself moves nowhere and may even be physically destroyed or discarded; the goal is rather to duplicate the information patterns contained within the brain.
Another similar literary theme, though different from either procedure described above, is the transplanting of a human brain into an artificial, usually robotic, body. Examples of this include: Caprica; Fullmetal Alchemist; Ghost in the Shell; RoboCop; the DC Comics superhero Robotman; the Cybermen from the Doctor Who television series; the cymeks in the Legends of Dune series; or full-body cyborgs in many manga or works in the cyberpunk genre. In one episode of Star Trek, Spock's Brain is stolen and installed in a large computer-like structure; and in "I, Mudd" Uhura is offered immortality in an android body. The novel Harvest of Stars by Poul Anderson features many central characters who undergo such transplants, and deals with the difficult decisions facing a human contemplating such a procedure. In the Star Wars expanded universe the shadow droids were created by taking the brains of grievously wounded TIE fighter pilot aces. After surgically transplanting them into a protective cocoon filled with nutrient fluids. they were surgically connected to cybernetic hardware that gave them external sensors, flight control and tactical computers that augmented their reflexes beyond the biological limit; at the cost of their humanity. Emperor Palpatine also imbued them with the dark side giving them a sixth sense, and making them into extensions of his own will.