The kind of experiments on monkeys’ brains that we describe here, fall into the category of fundamental or academic research, animal experiments to gather information or data, but with no direct or specified application for human health.
Case study: Brain research on monkeys – decades of suffering with no human application
The kind of experiments on monkeys’ brains that we describe here, fall into the category of fundamental or academic research, animal experiments to gather information or data, but with no intended application for human health. Such projects can continue for decades, with no end in sight. For example:
At the Institute of Neurology in London a series of experiments has been funded by The Wellcome Trust, the National Centre for the 3Rs (Refinement, Reduction & Replacement of Animals in Research), and the Biotechnology & Biological Sciences Research Council.
A report describes an experiment where the heads of three macaque monkeys, two male and one female, were cut open to fix a head piece to restrain their heads and implant a recording chamber and electrodes into their brains. Electrical current was delivered to the brain. The monkeys had to grasp different objects for food reward while their brain activity was recorded both with and without electricity being applied to the brain. Two of the animals were killed at the end of the experiment.
The team received funding for this research, despite that they themselves cite a number of similar experiments on primates, and similar work using humans. The researchers don’t specify how this research might be helpful for humans and there is no discussion in the published paper, of the known differences between human and monkey brains.
The same group of researchers published a similar paper where two monkeys also received repeated surgeries and implants in the brains and their arms, again to monitor brain activity.
There are fundamental differences between human and monkey brains. A study comparing the processing of motion in the human and macaque brains commented that “a complete homology between cortical areas of humans and monkeys is highly unlikely”considering anatomical and behavioural differences and the 30 million year evolutionary gap between the two species. It also highlights how the specific areas of the brain involved in these cruel experiments differs between humans and monkeys.
There is no doubt that these monkeys will have suffered extreme fear and distress, as well as the pain of surgery, and yet these researchers acknowledge that non-invasive studies using human subjects are already carried out.
Case study: French dental study on monkeys
At the National Veterinary School of Lyon, France, researchers simulated human periodontal disease in 8 healthy long-tailed macaque monkeys, in a study funded by Dental manufacturing company, Dentsply.
A report describes how researchers performed multiple surgeries on the roots of monkeys’ teeth to study the effect of dental cavity material on healing. Monkeys’ gums were cut to expose roots of the teeth and jaw bones. A 3mm cavity was drilled into the tooth base and the outer layers were removed with a hand scaler. Inflammation was induced in the gums. During a second surgery various substances, including one derived from brains, were used to fill in the damaged teeth. A total of 8 cavities were created in each monkey. The monkeys underwent numerous CT scans until they were killed 12 weeks later by anaesthetic overdose and draining of the blood, and their jaws cut in to pieces for further analysis.
There is no question that these monkeys would have suffered extreme fear and pain during this study. As well as the direct impact of the invasive dental treatments, the monkeys would have suffered from the associated effects of recovering from the numerous surgeries and scans. At one point the monkeys were only fed soft food, so that food would not interfere with the surgical sites; this gives an indication of how delicate these sites were – and no indication is given as to whether pain killers were administered.
The research was carried out despite a number of previous studies which investigated the healing effects of the same dental materials, including studies in dogs. In addition, studies in humans have already been carried and treatments for halting the progression of periodontal disease in humans are already successful.
The authors also note that “the induced inflammation referred to in the current study is different from the inflammation caused by periodontal diseases”. Human studies of regeneration in periodontal disease have highlighted that researchers need to take into account the effect of systemic factors in patients, such as metabolic disorder, and risk factors such as smoking, medication and genetic susceptibility. Such consideration cannot be made in an animal model that has been artificially created in the laboratory.
Overall, this study does not add any new information apart from testing in another non-human species; it reports the same findings and just adds to this existing data.
Case study: Spinal experiments at University of Newcastle
At the University of Newcastle, two female macaques suffered restriction of food to motivate them to perform in experiments where they were trained to grasp and pull a handle for a food reward. Monkeys underwent three surgeries implanting various devices into their hand muscles, brain and spine. They had recording chambers fixed to their heads, which allowed electrodes to be inserted into their brains during experiments. Parts of the spinal bone were removed and a recording chamber screwed onto the back so that electrodes could be inserted into the spinal cord.
A chemical was injected in multiple areas of the brain to temporarily paralyse the areas that controlled hand movements. The researchers then sent currents down the spinal electrodes to see the effect on the arm and hand muscles in the paralysed monkeys. They assessed the ability of the monkeys to be able to perform reach and grasp movements by presenting pieces of food in front of them when their hand and arm muscles were paralysed. Then they measured their ability to pull a lever in order to get a food reward. The effects of the paralyzing chemical lasted several hours.
In a different experiment, the same research team surgically exposed the spines of four female rhesus monkeys for electrical stimulation. They inserted pairs of steel wires into 14 muscles of the arm and hand. Two of the monkeys had sections of their spine removed to expose the spinal cord, and two had a cut made in their throat, with the oesophagus, trachea and veins moved to one side and muscles cut away for access to the spine which they bore through with a dental drill. Electrodes were placed in different sites of the spine and head, through which an electric current was sent, to record the response in the arm and hands.
This research was a repetition of previous experiments by the same researchers, which they cite as finding the same results as the current study. It is also outlined how electrical stimulation of the spinal cord in patients for chronic pain is an established therapy, so this technique is already being used in humans. Furthermore, a study in patients with chronic spinal cord injury has been carried out, finding that electrical spinal stimulation can improve the hand motor function.
Case study: Cruel gravity experiment on monkeys, Baylor College of Medicine, Texas
Researchers wanted to investigate which cells in the brain respond to gravity. Two macaque monkeys had implants attached to their heads for immobilisation, electrodes inserted into their brain to make recordings, and coils attached to their eyes to measure movements. Monkeys were restrained in chairs inside a motorised spherical enclosed simulator which researchers used to create “sensory conflict”. The monkeys were rotated in different directions 24 times while restrained in the simulator. As well as suffering from the implants in their heads and eyes, monkeys would have experienced stress from being restrained in the chair, placed in the simulator and rotated.
Studies on brain areas associated with the perception of gravity are carried out in humans using non-invasive methods such as fMRI scanning. These include studies which identified the areas of the brain involved, as was the aim of the primate research. The processing of gravity direction in the human brain has been studied extensively in brain damaged patients making invasive experiments on monkeys entirely unjustifiable.
Case study: Social isolation for monkeys
Monkeys were used in experiments to find out if they had the same susceptibility to sex and social status in advertising campaigns, as humans. Monkeys suffered social isolation for the duration of the tests. Animals underwent water restriction and performed around 100 repetitive trials a day on a touch screen computer. Research on brand advertising and the association with sex and social status has been extensively researched in human volunteers making this research was entirely unnecessary and pointless. This research presents no benefit to humans or animals.
Case study: Chemical eye burning experiments in dogs, College of Veterinary Medicine, Missouri
Seven healthy beagle dogs were sedated and physically manually restrained to obtain scans of the eyes. All of the dogs were sedated and subjected to alkali burns (faster acting than acid burns) on their right eye using a chemical applied for 15-30 seconds, which causes damage and ulceration to the cornea. They were examined daily for 14 days. Once the ulcers had healed on their right eye, dogs received alkali burns to their left eye, but this time the chemical was applied for 30 seconds. After 14 days of examination they were killed so that their corneas could be removed and dissected to examine the scars. The researchers discuss how this experiment has already been carried out in numerous other species, and how it is a frequent injury that humans experience.
The researchers discuss how this experiment has already been carried out in numerous other species, and how it is a frequent injury that humans experience. The researchers claim that in vitro models using cell cultures “fail to replicate the complicated process of wound healing” however, models using human corneal tissue have included a 3D in vitro model which can be used to examine wound healing.