Social (or physical) distancing has been one of the main focal points during the coronavirus pandemic. Some people engage in this process almost naturally, sensing that another person could be infected and keeping them at bay. For others, a large social nudge has been required.
Humans are not the only mammals to engaged in social distancing in response to a perceived illness in another. Mice too have been observed engaging in this form of behavior, as a new study finds.
Undertaken at MIT’s Picower Institute for Learning and Memory, animal scientists ran studies that showed what happens when male mice encounter a female mouse who is displaying observable signs of illness. When this situation occurs, the males forgo their normal inquisitive nature which typically veers towards seeking to mate with the female. Instead, the males interact very little with females.
The females were rendered ‘sick’ by an injection of a component of the Gram-negative bacterium cell wall called lipopolysaccharide (or endotoxin). This component can trigger fever.
What is important about this form of behavior is that to engage in it requires the mouse to override a natural inclination to be close to a fellow rodent. This requires a rewiring of brain circuit.
This means that not only have mice been recorded undertaking social distancing in a laboratory study, but the researchers have also additionally pinpointed the area of the brain they believe is responsible for this activity.
As to where in the brain this is happening, the area identified is the amygdala. This region of the brain is located within the temporal lobes of the brain’s cerebrum in complex vertebrates. This brain area plays a key role in the processing of memory, decision-making and emotional responses. The region also enables the detection of distinctive odors.
In the case of this experiment, the male mice detected an aroma from the sick female rodents, and this elicited a response in the form of a warning signal: Stay away or else you may become sick too. Involved in this process is a hormone called thyrotropin releasing hormone which plays a part in suppressing mating behavior
This is sufficiently powerful as to overcome the desire to mate, something that has always been assumed to be naturally programmed into the mouse in response to appropriate stimuli (in this case a female).
The research is groundbreaking in that it is the first to show the way illness alters a healthy individuals’ interactions with those who are sick. It also connects to wider research that considers the extent to which pathogens can influence biological and social behavior.
The research has been published in the journal Nature. The study is titled “An amygdala circuit that suppresses social engagement.”
