What is going on in my own body? According to an experimental study, rhesus monkeys also have the ability for so-called interoception. Accordingly, the animals are able to recognize their own heartbeat by the frequency. The scientists explain that the monkeys could therefore be used as a model animal for neuropsychiatric research. Interoceptive disorders are associated with anxiety, depression and Alzheimer’s disease in humans.
Your stomach is rumbling, your heart is racing or it’s out of rhythm… “Something’s wrong with me”. The ability to recognize our internal state and certain processes can indicate problems in the body that require our attention. “Interoception, the self-monitoring of our physiological systems, plays a role in many areas of human life,” says Eliza Bliss-Moreau of the California National Primate Research Center in Davis. She and her colleagues are also interested in this perceptual system for a specific reason: Studies show that impaired interoceptive perception is associated with a reduced ability to regulate emotions and an increased susceptibility to psychological problems. Certain procedures have therefore long been aimed at increasing one’s own body awareness. Among other things, people are encouraged to specifically perceive their own heartbeat.
Do animals have a sense of their bodies too?
However, there are still many unanswered questions about the background to the apparently complex significance of interoception. It is unclear, for example, which evolutionary origins self-awareness has and to what extent animals are also capable of it. In order to obtain new information, Bliss-Moreau and her colleagues have now carried out experiments with rhesus monkeys: They investigated the extent to which the animals can intuitively distinguish their own heartbeat from frequencies that are clocked differently.
The test animals sat in front of a screen that displayed a visual representation of heartbeats and also generated matching sounds. In some runs, the animals were presented with a display of their own heart rate, which was recorded via electrodes on the arm. In the other case, an asynchronous heart rate was displayed – a heartbeat that was either faster or slower than the animal’s. In all runs, an eye tracker recorded the eye movements of the respective monkey.
The evaluations revealed that all of the monkeys in the test spent more time looking at stimuli that were not presented in rhythm with their own heartbeat than with those that corresponded to their own. As the scientists explain, this is a sign that they were able to connect their own heartbeat with the audiovisual information. Because it is already known from many studies that people – including babies – as well as monkeys look longer at things that they find surprising or unexpected. The scientists therefore interpret the results as the first experimental evidence that rhesus monkeys have a human-like ability to perceive their heartbeat and thus also have an interoceptive sense.
Potential for neuropsychiatric research
“The work we present here is a first successful step in filling an important research gap,” says co-author Manos Tsakiris from Royal Holloway University of London. “Interoception is enormously important for emotion regulation and human mental health, and yet we know very little about how it develops in early childhood or evolves over the course of evolution,” says the scientist. In this context, the results now show that rhesus monkeys, which are often used in research as a model animal for humans, could also be used in the study of interoception. “The study provides indications of the extent to which the rhesus monkey model can be used to improve our understanding of brain and body functions,” say the scientists.
As they emphasize in conclusion, this affects research fields of enormous importance. Interoceptive disorders are associated with anxiety, depression and Alzheimer’s disease. “The rhesus monkey model could be used in future translational studies of neurodegenerative diseases, including Alzheimer’s,” said Bliss-Moreau. “If we can measure interoception, we can track it as a behavioral biomarker of disease progression,” explains the researcher. “A next step will now be to investigate the mechanism by which interoception might be involved in various psychiatric and neuropsychiatric diseases,” says Tsakiris.
Source: University of California – Davis, professional article: PNAS, doi: 10.1073/pnas.2119868119