Cognitive testing refinement: a computerized platform for self-paced auditory cognitive testing in common marmosets

April 4th 2022

In a recent publication1, a team of researchers led by Marcus Jeschke at the German Primate Center – Leibniz Institute for Primate Research (DPZ) and at the Institute for Auditory Neuroscience led by Tobias Moser at the University Medical Center described a new computerized platform that allowed marmosets to learn and perform auditory tasks at their own pace, undisturbed in their home-cage. The research aims at developing a new type of optical cochlear implants, which converts sound waves into light instead of electricity, to improve the technology currently available for the treatment of hearing loss. 

Common marmosets are of critical importance for the improvement of electric cochlear implants and the development of novel types of cochlear implants. The monkeys have a larger cochlea than most rodents, which makes a comparison and extrapolation of frequency resolution to humans much more direct. The animals communicate using a variety of sounds and rely on vocal communication for social behavior. Further, the non-human primate immune system is much closer related to the human immune system allowing more adequate conclusions about gene therapeutic manipulation in humans.

Marmosets have a sophisticated communication system and vocal repertoire that make them an ideal animal model for studying the auditory system and testing the efficacy and safety of the optical cochlear implant before application to humans. To test the animals’ ability to detect and discriminate sounds, the researchers designed a computerized platform called the Marmoset Experimental Behavioral Instrument (MXBI), which optimized animal welfare by allowing the monkeys to complete auditory tasks in their familiar home cage environment completely undisturbed. The MXBI consists of a touchscreen system inserted into the home cage, with which monkeys can interact at will, without dietary restriction or separation from their partner. The device displayed training protocols that were tailored to each monkey’s performance, so that animals could progressively learn and ultimately complete a series of auditory and psychoacoustic tasks. The monkeys interacted with the device with a consistent level of engagement and for sustained periods of time, even when they were not proficient enough to obtain a reward, showing that the MXBI functioned as an environmental enrichment tool.

Attached to the cage this training device allows automatic unsupervised auditory training and testing of common marmosets directly in their own cage. The mesh tunnel allows testing one animal at a time. Photo: Karin Tilch

 Similar automated touchscreen systems have been available for nonhuman primate visual cognitive testing, but it is the first time that they are successfully applied to the auditory modality. Such systems pave the way for cognitive experiments that not only provide enhanced phenotypic characterization of nonhuman primates in captivity, but also contribute to their improved well-being.

1Calapai, A., Cabrera-Moreno, J., Moser, T. et al. Flexible auditory training, psychophysics, and enrichment of common marmosets with an automated, touchscreen-based system. Nat Commun 13, 1648 (2022).