Rhesus monkeys can sense their own heartbeat

Interoception refers to the ability of sensing the internal state of one’s body, such as observing when the heart starts racing or breathing quickens. Since impaired interoceptive awareness is linked to decreased capacity to regulate emotions and increased susceptibility to mental health conditions such as anxiety and depression, or even to neurodegenerative diseases like Alzheimer’s, understanding its ontogenetic and phylogenetic origins is crucial for future psychologic and neuropsychiatric research. 

Now, a study led by the California National Primate Research Center at the University of California, Davis has found the first clear evidence of interoception in the animal kingdom: rhesus monkeys seem to be able to perceive and monitor their own heartbeats.

“Interoception is hugely important for emotion regulation and mental health in adults, and yet we know very little about how it develops in early infancy or comes to be across evolutionary time,” said study co-author Manos Tsakiris, a professor of Psychology at the Royal Holloway, University of London. “The work we present here represents a first successful attempt to fill these gaps.” 

Professor Tsakiris and his colleagues monitored four rhesus monkeys which were placed in front of an infrared eye tracker that bounced and generated a sound either synchronous or asynchronous with the monkeys’ heartbeats. All the monkeys spent more time observing the stimuli presented out of rhythm with their heartbeat, suggesting that they were conscious of their own heartbeats and were thus surprised by the out-of-sync stimuli. These results match those from similar experiments performed on human infants, and provide the first behavioral evidence that rhesus monkeys have a well-developed interoceptive sense.

“This model will be used in future translational studies of neurodegenerative diseases, including Alzheimer’s,” said study lead author Eliza Bliss-Moreau, an associate professor of Psychology at UC Davis. “If we can measure interoception, we can track it as a behavioral biomarker of disease progression.” 

Further research is needed to study the mechanisms of interoception in other animals and clarify the extent to which disruption in animals’ ability to sense their internal states could also be linked to neurological and psychiatric disorders. 

The study is published in the journal Proceedings of the National Academy of Sciences.

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By Andrei Ionescu, Earth.com Staff Writer