An isolated brain is a brain kept alive in vitro, either by perfusion by a blood substitute, often an oxygenated solution of various salts, or by submerging the brain in oxygenated artificial cerebrospinal fluid (CSF). It is the biological counterpart of brain in a vat. A related concept, attaching the brain or head to the circulatory system of another organism, is called a head transplant. An isolated brain however is more typically attached to an artificial perfusion device rather than a biological body.
The brains of many different organisms have been kept alive in-vitro for hours, or in some cases days. The central nervous system of invertebrate animals is often easily maintained as they need less oxygen and to a larger extent get their oxygen from CSF; for this reason their brains are more easily maintained without perfusion. Mammalian brains on the other hand have a much lesser degree of survival without perfusion and an artificial blood perfusate is usually used.
For methodological reasons, most research on isolated mammalian brains has been done with guinea pigs. These animals have a significantly larger basilar artery (a major artery of the brain) compared to rats and mice, which makes cannulation (to supply CSF) much easier.
- 1812 – Julien Jean César Le Gallois (a.k.a. Legallois) put forth the original idea for resuscitating severed heads through the use of blood transfusion.
- 1818 – Mary Shelley published Frankenstein; or, the Modern Prometheus.
- 1836 – Astley Cooper showed in rabbits that compression of the carotid and vertebral arteries leads to death of an animal; such deaths can be prevented if the circulation of oxygenated blood to the brain is rapidly restored.
- 1857 – Charles Brown-Sequard decapitated a dog, waited ten minutes, attached four rubber tubes to the arterial trunks of the head, and injected blood containing oxygen by means of a syringe. Two or three minutes later voluntary movements of the eyes and muscles of the muzzle resumed. After cessation of oxygenated blood transfusion movements stopped.
- 1887 – Jean Baptiste Vincent Laborde made what appears to be first recorded attempt to revive the heads of executed criminals by connecting the carotid artery of the severed human head to the carotid artery of a large dog. According to Laborde's account, in isolated experiments a partial restoration of brain function was attained.
- 1912 – Corneille Heymans maintained life in an isolated dog's head by connecting the carotid artery and jugular vein of the severed head to the carotid artery and jugular vein of another dog. Partial functioning in the severed head was maintained for a few hours.
- 1928 – Sergey Bryukhonenko showed life could be maintained in the severed head of a dog by connecting the carotid artery and jugular vein to an artificial circulation machine.
- 1963 – Robert J. White isolated the brain from one monkey and attached it to the circulatory system of another animal.
In philosophy, the brain in a vat is any of a variety of thought experiments intended to draw out certain features of our ideas about knowledge, reality, truth, mind, and meaning. A contemporary version of the argument originally given by Descartes in Meditations on First Philosophy (i.e., that he could not trust his perceptions on the grounds that an evil demon might, conceivably, be controlling his every experience), the brain in a vat is the idea that a brain can be fooled into anything when fed appropriate stimuli.
The inherently philosophical idea has also become a staple of many science fiction stories, with many such stories involving a mad scientist who might remove a person's brain from the body, suspend it in a vat of life-sustaining liquid, and connect its neurons by wires to a supercomputer which would provide it with electrical impulses identical to those the brain normally receives. According to such science fiction stories, the computer would then be simulating a virtual reality (including appropriate responses to the brain's own output) and the person with the "disembodied" brain would continue to have perfectly normal conscious experiences without these being related to objects or events in the real world.
No such procedure in humans has ever been reported by a research paper in a scholarly journal, or other reliable source. Also, the ability to send external electric signals to the brain of a sort that the brain can interpret, and the ability to communicate thoughts or perceptions to any external entity by wire, is, except for very basic commands, well beyond current (2016) technology.
Growing an isolated brain
Isolated biological "brains", grown from cultured neurons which were originally separated, have been developed. These are not the same thing as the brains of organisms, but they have been used to control some simple robotic systems.
Teams at the Georgia Institute of Technology and the University of Reading have created neurological entities integrated with a robot body. The brain receives input from sensors on the robot body and the resultant output from the brain provides the robot's only motor signals.
Isolated brains in fiction
The concept of a brain in a jar (or brain in a vat) is a common theme in science fiction:
- More Fun #62 ( Dec. 1940) had the Spectre battle a human brain in a vat that had developed enormous powers and become mobile and sprouted an arm.
- The final novel in C.S. Lewis's "Space Trilogy," That Hideous Strength, uses the isolated brain of Francois Alcasan, an Algerian radiologist guillotined for murder, as a plot device. At some point in the novel, it is revealed that Alcasan's artificially-perfused head is used to allow evil intelligence to communicate with humans directly.
- Many people in the Ghost in the Shell manga and anime franchise possess cyberbrains, which can sustain a modified human brain within a cybernetic body indefinitely.
- In Alexander Beliaev's novel Head of Prof. Dowell (1925), Professor Dowell discovers a way of keeping heads of dead people alive and even to give them new bodies. After his death Dowell himself becomes a subject of such an experiment
- In Donovan's Brain (see term), the 1942 science fiction novel by Curt Siodmak (filmed three times in different versions: 1942, 1953 and 1962), the brain of a ruthless millionaire is kept alive in a tank where it grows to monstrous proportions and powers.
- In Madeleine L'Engle's novel A Wrinkle in Time (1963), the character IT is a disembodied telepathic brain that dominates the planet of Camazotz.
- A brainship is a fictional concept of an interstellar starship. A brainship is made by inserting the disembodied brain and nervous system or malformed body of a human being into a life-support system, and connecting it surgically to a series of computers via delicate synaptic connections (a Brain–computer interface.) The brain "feels" the ship (or any other connected peripherals) as part of its own body. An example, The Ship Who Sang (1969) short story collection by science fiction author Anne McCaffrey is about the brainship Helva.
- The 2011 web series The Mercury Men features a brain in a jar ("The Battery") that can communicate telepathically and over a walkie-talkie-like devices and is revealed to control the "mercury men" for a catastrophic plan to destroy Earth.
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