Published on 17.06.2024

Refined methods for conducting cognitive tests on laboratory monkeys

Researchers at the Swiss Non-Human Primate Competence Center for Research at the University of Fribourg have developed a method that significantly improves the well-being of the macaques used in experiments. Instead of having an anchoring system implanted into the surface of the skull to stabilize and hold the head during a visual task, in future experiments the primates can place their head in a chin rest and take breaks independently as they please. In the two series of tests carried out, the monkeys even showed a greater willingness to participate. This new method not only improves animal welfare but also expands the scientific knowledge gained.

The research group led by Prof. Dr. Michael Schmid at the University of Fribourg examines brain circuits in the visual system to understand how we see and how vision can be improved when it is affected by disease. For their research, the group also works with non-human primates; it tracks and precisely measures their eye movements. The use of rhesus macaques in visual research is crucial due to the similarity of their visual system to that of humans.

Chin rests instead of an anchoring system
Until now, the standard method used was to surgically insert an anchoring system into the surface of the skull of the primates, which allowed their heads to be stabilized and held, thus ensuring the precision of the measurements taken. Although these operations were performed in such a way that they did not cause the monkeys a great amount of pain, this method was nevertheless invasive, altered the monkeys’ appearance considerably and posed the constant risk of postoperative infection.

While invasive techniques have been the norm up until now, the trend has shifted to non-invasive methods such as face masks or head rests to improve animal welfare and address ethical concerns.

The team at Prof. Schmid’s research laboratory is now presenting a new method for biomedical research on macaques that involves a 3D-printed chin rest; this approach is also used for research carried out on dogs and humans. It improves the precision of the results as well as the length of time the macaques are willing to participate and increases their welfare.

The chin rest ensures accurate eye movement measurements for cognitive function studies and allows macaques to participate in or withdraw from experiments on their own accord. This method thus promotes more ethical research practices and improves training efficiency by aligning the need for scientific precision with advances in animal welfare.

Progress using the 3R principle
In accordance with its policy statement on animal experiments, the University of Fribourg is committed to the ethical treatment of animals and is implementing this policy in accordance with the 3R principle (replace, reduce, refine). The chin-rest method for non-human primates, which has now been tested, is a good example of refinement, i.e. an improvement in animal welfare.

“We were very positively surprised not only by the how the new method increased the animals’ willingness to participate but also by how it improved the precision of the eye-movement measurements,” stated Michael Schmid as he described the experiment. “We hope our results will encourage other research groups to explore similar new methods as well.”

Since this method is more cost-effective and less invasive, it is also likely to be used by experimental laboratories at other research institutions. For the University of Freiburg, the results have been quite a success – one which proves that cutting-edge research and research to improve animal welfare are not mutually exclusive, but, on the contrary, actually complement one other.


Published in the Journal of Neuroscience Methods

Link to an explanatory video

Link to the SPCCR

Link to the policy statement on animal experiments at the University of Fribourg