The Silver Spring monkeys were 17 wild-born macaque monkeys from the Philippines who were kept in the Institute for Behavioral Research in Silver Spring, Maryland. From 1981 until 1991, they became what one writer called the most famous lab animals in history, as a result of a battle between animal researchers, animal advocates, politicians, and the courts over whether to use them in research or release them to a sanctuary. Within the scientific community, the monkeys became known for their use in experiments into neuroplasticity—the ability of the adult primate brain to reorganize itself.
The monkeys had been used as research subjects by Edward Taub, a psychologist, who had cut afferent ganglia that supplied sensation to the brain from their arms, then used arm slings to restrain either the good or deafferented arm to train them to use the limbs they could not feel. In May 1981, Alex Pacheco of the animal-rights group People for the Ethical Treatment of Animals (PETA) began working undercover in the lab, and alerted police to what PETA viewed as unacceptable living conditions for the monkeys. In what was the first police raid in the U.S. against an animal researcher, police entered the Institute and removed the monkeys, charging Taub with 17 counts of animal cruelty and failing to provide adequate veterinary care. He was convicted on six counts; five were overturned during a second trial, and the final conviction was overturned on appeal in 1983, when the court ruled that Maryland's animal cruelty legislation did not apply to federally funded laboratories.
The ensuing battle over the monkeys' custody saw celebrities and politicians campaign for the monkeys' release, an amendment in 1985 to the Animal Welfare Act, the transformation of PETA from a group of friends into a national movement, the creation of the first North American Animal Liberation Front cell, and the first animal research case to reach the United States Supreme Court. In July 1991, PETA's application to the Supreme Court for custody was rejected. Days later, the last two monkeys were killed after veterinarians determined they were suffering and should be euthanized.
During the subsequent dissection of the monkeys, it was discovered that significant cortical remapping had occurred, suggesting that being forced to use limbs with no sensory input had triggered changes in their brains' organization. This evidence of the brain's plasticity helped overturn the widely held view that the adult brain cannot reorganize itself in response to its environment.
Background
Edward Taub
Edward Taub (born 1931) is a behavioral neuroscientist currently based at the University of Alabama at Birmingham. He became interested in behaviorism while studying philosophy at Columbia University, and went on to study under Fred Keller and Wiliam N. Schoenfeld, the experimental psychologists. He took a job as a research assistant in a neurology lab to gain more understanding of the nervous system, and became involved in deafferentation experiments with monkeys.
An afferent nerve is a sensory nerve that conveys impulses from the skin and other sensory organs to the spine and the brain. Deafferentation is a surgical procedure in which the spinal cord is opened up and the sensory nerves cut so that these impulses do not reach the brain. A monkey whose limbs have been deafferented will not feel them, or even be able to sense where they are in space. At his trial in 1981, Taub told the court that deafferented monkeys are notoriously difficult to look after, because they regard their deafferented limbs as foreign objects, mutilating them and trying to chew them off. Taub continued working with deafferented monkeys at New York University, where he obtained his Ph.D. in 1970. Engaged in what he saw at first as pure research, he conducted several kinds of deafferentation experiments. He deafferented monkeys' entire bodies, so that they could feel no part of themselves. He deafferented them at birth. He removed monkey fetuses from the uterus, deafferented them, then returned them to be born with no sense of their own bodies.