The Silver Spring monkeys were 17 wild-born macaque monkeys from the Philippines who were kept in the Institute of 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—regarded as one of the most exciting discoveries of the 20th century.