Results of new research at Cornell University indicate that female mice show a strong impulse to socialize with other females during periods of acute isolation, dramatically increasing their production of social calls that are similar to human emotional sounds.
The researchers, whose study is published in PLOS ONE, said their behavior points to a promising path to understanding the brain mechanisms by which isolation affects people’s social motivation and Psychological health Growing concern during the COVID-19 pandemic.
“This kind of social interaction among female mice is more equivalent to our daily interactions with others,” said Catherine Chida, assistant professor of psychology in the College of Arts and Sciences.
“Intuitively, we know that social isolation has this effect on our behavior: We want to see and interact with people.”
The researchers set out to investigate whether exposure to acute isolation – just three days in their home cage – would cause mice to increase so-called ultrasonic vocalizations (USVs), as well as non-vocal social behaviors such as sniffing and following when another mouse was introduced to the the cage. Inaudible to humans, Tschida said USVs are neither speech nor language but sounds like laughter, crying, and sighing that help signal and communicate emotional states.
“It’s the kind of innate, emotional vocal communication that we produce in addition to the acquired speech sounds,” Chida said.
“By studying it in a mouse, we think we’ll gain insight into how this process is controlled in people as well.”
Female–female interactions demonstrated a ‘profound effect’ of acute isolation: a fourfold increase in USVs compared to a control group of mice kept in group housing and more non-vocal social behaviors.
“They interact a lot more, they talk a lot more, and the behavior of the animal in question — the lone mouse, basically — seems to have changed,” Tshida said.
Scientists believe that acute isolation may not be enough to significantly affect a male’s sex drive with females or an aggressive drive with other males. But it appears to have a strong influence on the desire for affiliative social contact that is believed to stimulate female social interaction. With one complicated caveat: After coming out of seclusion, female rats rode on other females more often, perhaps an expression of low-level aggression aimed at establishing social hierarchy.
Tschida’s lab is now moving from behavioral studies to neurological studies of interactions between female mice. Researchers hope to identify the neurons that encode social context and emotional states to determine how isolation affects circuits that control social impulses, including sounds. In the long term, this knowledge could contribute to understanding and treating disorders such as anxiety and depression, as well as factors that contribute In individual differences in susceptibility to social isolation.
“You feel lonely, and you want to seek out social interaction – what actually causes that at the level of brain circuits?” Chida said.
“As we flatten the end of the behavioral output, this becomes a much more traceable question.”