By HELEN GAVAGHAN in WASHINGTON DC Controversy surrounding the now notorious ‘Silver Springs monkeys’ in the US erupted again last week. The monkeys have been at the centre of a tug-of-war between researchers and animal rights activists for almost a decade. This week the scientific journal Science published results from neurological experiments performed shortly before the animals were killed. Scientists familiar with the field say that the results are important . Animal rights activists claim that the experiments were unnecessary. In January 1990 several activists, led by an animal rights group, the Physicians Committee for Responsible Medicine (PCRM), tried to stop the work by bringing a lawsuit against Louis Sullivan, the secretary of the department of Health and Human Services, alleging scientific misconduct. The National Institutes of Health, which has custody of the monkeys, falls under the aegis of Sullivan’s department. Although the experiments are now complete, Neal Barnard, head of the PCRM, says he intends to go ahead with the case. The Silver Springs monkeys (16 macaques and one rhesus monkey) first hit the headlines in 1981. Since then they have served as a focus for a debate about research on animals which has generated bad publicity for the NIH and resulted in complex legal proceedings. The animals were subjects in experiments at the laboratory of Edward Taub in the NIH’s Institute of Behavioural Research at Silver Springs, near Washington DC. Nine of them had undergone a surgical procedure known as deafferentation, in which nerves carrying signals from a particular part of the body to the brain are cut. In eight of the macaques, nerves from one arm were cut. In a ninth, the nerves from both were severed. Taub found that the macaques could be trained to use their crippled arm because although nerves carrying signals to the brain were severed, those carrying signals from the brain to the limb remained intact. In 1981, he wanted to determine how much fine control the animals had over their de-afferented limbs. That work stopped not long after Taub employed Alex Pacheco as a technician. Pacheco, who is now head of an animal rights group called People for the Ethical Treatment of Animals (PETA), gathered enough evidence to convince local police that the animals were badly treated and should be removed from Taub’s laboratory. Taub was prosecuted for animal cruelty and found guilty on six counts. Over the next four years, other courts overturned those verdicts. Of the animals that have survived, five of those not surgically crippled are now at San Diego Zoo. The NIH, which took custody of the animals, sent the rest to the Tulane Primate Center in Louisiana in 1986. Since their arrival at Tulane, the legal battle to determine their fate has intensified. Animal rights activists wanted the macaques to go to a centre where they could be rehabilitated. They also argued that the de-afferented limbs should be amputated to prevent the animals damaging them. In 1988 vets examining the animals for the NIH thought the animals should be destroyed. The NIH then argued that if the animals had to be destroyed, it should be possible to carry out more neurological experiments before killing them. The NIH sent a document to Congress outlining their proposed experiments. The research published in Science is the result of those experiments. And the document sent to Congress is at the centre of the suit that the PCRM has brought against Sullivan. Whatever the outcome, the macaques, dead or alive, are potent symbols in a highly emotional debate about the use of animals in experiments. At one extreme are the animal activists threatening scientists and their families and on the other side are scientists who espouse the domino theory, that if they admit any fault, all their research will be stopped. One British neurologist, who asked to remain anonymous, said: ‘In a climate of fear, it’s very difficult to go about putting your house in order, except in absolute privacy.’ Tim Pons, from the Laboratory of Neuropsychology at the National Institute for Mental Health, is the main author of the paper in Science. He says: ‘Yes, some scientists break the rules, but does that mean you stop all research on animals? We have some corrupt congressmen, does that mean you abolish Congress?’ At a more mundane level, Bill Cottrell, from the Animal Welfare Institute, says the polarisation of the debate makes it difficult for the people in the middle to make progress. ‘In reality research on animals is going to happen. Given that reality, how can research be made least painful?