In 1981, a group of 17 macaques known as the Silver Spring Monkeys became the most famous research animals in the USA when Alex Pacheco, an undercover college student and animal rights activist, infiltrated the laboratory of psychologist Edward Taub to expose the experiments that took place inside. In his research on neuroplasticity, Taub severed the afferent ganglia to certain limbs while immobilising the limbs that were neurologically intact in an attempt to train the macaques to use the appendages that lacked neural feedback.