depth perception). they were awarded a nobel prize for their work. deep-brain stimulation in 1983, designer drug users took mptp, which created a parkinsonian syndrome. later that same year, researchers reproduced the effect in non-human primates. over the next seven years, the brain areas that were over- and under-active in parkinson's were mapped out in normal and mptp-treated macaque monkeys using metabolic labelling and microelectrode studies. in 1990, deep brain lesions were shown to treat parkinsonian symptoms in macaque monkeys treated with mptp, and these were followed by pallidotomy operations in humans with similar efficacy. by 1993, it was shown that deep brain stimulation could effect the same treatment without causing a permanent lesion of the same magnitude. deep brain stimulation has largely replaced pallidotomy for treatment of parkinson's patients that require neurosurgical intervention. current estimates are that 20,000 parkinson's patients have received this treatment. aids the non-human primate models of aids, using hiv-2, shiv, and siv in macaques, have been used as a complement to ongoing research efforts against the virus. the drug tenofovir has had its efficacy and toxicology evaluated in macaques, and found longterm-highdose treatments had adverse effects not found using short term-high dose treatment followed by long term-low dose treatment. this finding in macaques was translated into human dosing regimens. prophylactic treatment with anti-virals has been evaluated in macaques, because introduction of the virus can only be controlled in an animal model. the finding that prophylaxis can be effective at blocking infection has altered the treatment for occupational exposures, such as needle exposures. such exposures are now followed rapidly with anti-hiv drugs, and this practice has resulted in measurable transient virus infection similar to the nhp model. similarly, the mother-to-fetus transmission, and its fetal prophylaxis with antivirals such as tenofovir and azt, has been evaluated in controlled testing in macaques not possible in humans, and this knowledge has guided antiviral treatment in pregnant mothers with hiv. "the comparison and correlation of results obtained in monkey and human studies is leading to a growing validation and recognition of the relevance of the animal model. although each animal model has its limitations, carefully designed drug studies in nonhuman primates can continue to advance our scientific knowledge and guide future clinical trials." treatment of anxiety and depression the reason for studying primates is due to the similar complexity of the cerebral processes in the human brain which controls emotional responses and can be beneficial for testing new pharmacological treatments. an experiment published in the neuroscience & biobehavioral reviews describes habituation of the black-tufted marmoset in a figure eight maze model. they were presented with a taxidermized wild-cat, rattlesnake, a hawk as well as a stuffed toy bear on one side of the maze. two cameras and a two way mirror was used to observe the difference between the monkeys natural behaviors versus the behaviors expressed by the diazepam induced monkeys in thirteen different locations inside the maze. scientist barros and his colleagues created this model to allow the monkeys to roam a less confined environment and slightly eliminate outside factors that may induce stress. allegations many of the best-known allegations of abuse made by animal protection or animal rights groups against animal-testing facilities involve non-human primates. university of wisconsin–madison the so-called "pit of despair" was used in experiments conducted on rhesus macaque monkeys during the 1970s by american comparative psychologist harry harlow at the university of wisconsin–madison. the aim of the research was to produce clinical depression. the vertical chamber was a stainless-steel bin with slippery sides that sloped to a rounded bottom. a 3/8 in. wire mesh floor 1 in. above the bottom of the chamber allowed waste material to drop out of holes. the chamber had a food box and a water-bottle holder, and was covered with a pyramid top so that the monkeys were unable to escape. harlow placed baby monkeys in the chamber alone for up to six weeks. within a few days, they stopped moving about and remained huddled in a corner. the monkeys generally exhibited marked social impairment and peer hostility when removed from the chamber; most did not recover. university of california, riverside on april 21, 1985, activists of the animal liberation front (alf) broke into the uc riverside laboratories and removed hundreds of animals. according to vicky miller of peta, who reported the raid to newswire services, uc-riverside "has been using animals in experiments on sight deprivation and isolation for the last two years and has recently received a grant, paid for with our tax dollars, to continue torturing and killing animals." according to ucr officials, the alf claims of animal mistreatment were "absolutely false," and the raid would result in long-term damage to some of the research projects, including those aimed at developing devices and treatment for blindness. ucr officials also reported the raid also included smashing equipment and resulted in several hundred thousand dollars of damage. covance in germany in 2004, journalist friedrich mülln took undercover footage of staff in covance in münster, europe's largest primate-testing center. staff were filmed handling monkeys roughly, screaming at them, and making them dance to blaring music. the monkeys were shown isolated in small wire cages with little or no natural light, no environmental enrichment, and subjected to high noise levels from staff shouting and playing the radio. primatologist jane goodall described their living conditions as "horrendous." a veterinary toxicologist employed as a study director at covance in vienna, virginia, from 2002 to 2004, told city officials in chandler, arizona, that covance was dissecting monkeys while the animals were still alive and able to feel pain. the employee approached the city with her concerns when she learned that covance planned to build a new laboratory in chandler. she alleged that three monkeys in the vienna laboratory had pushed themselves up on their elbows and had gasped for breath after their eyes had been removed, and while their intestines were being removed during necropsies (autopsy). when she expressed concern at the next study directors' meeting, she says she was told that it was just a reflex. she told city officials that she believed such movements were not reflexes but suggested "botched euthanasia performed by inadequately trained personnel." she alleged that she was ridiculed and subjected to thinly veiled threats when she contacted her supervisors about the issue. university of cambridge buav alleges that monkeys were left unattended for up to 15 hours after having parts of their brains removed to induce strokes. in the uk, after an undercover investigation in 1998, the british union for the abolition of vivisection (buav), a lobby group, reported that researchers in cambridge university's primate-testing labs were sawing the tops off marmosets' heads, inducing strokes, then leaving them overnight without veterinarian care, because staff worked only nine to five. the experiments used marmosets that were first trained to perform certain behavioral and cognitive tasks, then re-tested after brain damage to determine how the damage had affected their skills. the monkeys were deprived of food and water to encourage them to perform the tasks, with water being withheld for 22 out of every 24 hours. the research defence society defended cambridge's research. the rds wrote that the monkeys were fully anaesthetised, and appropriate pain killers were given after the surgery. "on recovery from the anaesthesia, the monkeys were kept in an incubator, offered food and water and monitored at regular intervals until the early evening. they were then allowed to sleep in the incubators until the next morning. no monkeys died unattended during the night after stroke surgery." a court rejected buav's application for a judicial review. buav appealed. columbia university in 2003, cnn reported that a post-doctoral veterinarian at columbia university complained to the university's institutional animal care and use committee about experiments being conducted on baboons by e. sander connolly, an assistant professor of neurosurgery. the experiment involved a left transorbital craniectomy to expose the left internal carotid artery to occlude the blood supply to the brain. a clamp was placed on this blood vessel until the stroke was induced, after which connolly would test a potential neuroprotective drug which if effective, would be used to treat humans suffering from stroke. connolly developed this methodology to make more consistent stroke infarcts in primates, which would improve the detection of differences in stroke treatment groups, and "provide important information not obtainable in rodent models." the baboons were kept alive after the surgery for observation for three to ten days in a state of "profound disability" which would have been "terrifying," according to neurologist robert hoffman. connolly's published animal model states that animals were kept alive for three days, and that animals that were successfully self-caring were kept alive for 10 days. people for the ethical treatment of animals has expressed strong opposition to this experiment and has written multiple letters to the nih and other federal agencies to halt further mistreatment of baboons and other animals at columbia. an investigation by the u.s. department of agriculture found "no indication that the experiments...violated federal guidelines." the dean of research at columbia's school of medicine said that connolly had stopped the experiments because of threats from animal rights activists, but still believed his work was humane and potentially valuable. attacks on researchers in 2006, activists forced a primate researcher at ucla to shut down the experiments in his lab. his name, phone number, and address were posted on the website of the ucla primate freedom project, along with a description of his research, which stated that he had "received a grant to kill 30 macaque monkeys for vision experiments. each monkey is first paralyzed, then used for a single session that lasts up to 120 hours, and finally killed." demonstrations were held outside his home. a molotov cocktail was placed on the porch of what was believed to be the home of another ucla primate researcher. instead, it was accidentally left on the porch of an elderly woman unrelated to the university. the animal liberation front claimed responsibility for the attack. as a result of the campaign, the researcher sent an email to the primate freedom project stating "you win", and "please don't bother my family anymore." in another incident at ucla in june 2007, the animal liberation brigade placed a bomb under the car of a ucla children's ophthalmologist, who performs experiments on cats and rhesus monkeys; the bomb had a faulty fuse and did not detonate. ucla is now refusing freedom of information act requests for animal medical records. the house of ucla researcher edythe london was intentionally flooded on october 20, 2007, in an attack claimed by the animal liberation front. london conducts research on addiction using non-human primates, and no claims were made by the alf of any violation of any rules or regulations regarding the use of animals in research. london responded by writing an op-ed column in the la times titled "why i use laboratory animals." in 2009, a ucla neurobiologist known for using animals to research drug addiction and other psychiatric disorders had his car burned for the second time. china in infectious disease research, china invests more than the u.s. does in conducting research on non-human primates. "select agents and toxins" refers to a list of over 60 substances that pose the greatest risk to public health, and china uses non-human primates to test treatment of these select agents and toxins more than the u.s. does.