Socially Isolated Mice Have Difficulty Forming Relationships

Researchers in Japan have found that social proximity in mice is not only influenced by individual behavioral traits, but also those of surrounding individuals.

AsianScientist (Feb. 6, 2019) – A video-based behavioral analysis system, researchers in Japan have shown that social isolation in adolescence impacts the ability of adult mice to form new social relationships. They published their findings in Communications Biology.

Mice, like humans, are social animals that start to develop social relationships with individuals and groups from birth. Social relationships are a key determinant of social behavior and numerous studies have shown that when mice experience maternal separation or social isolation during development, their socio-emotional and cognitive behaviors are affected. However, long-term behavioral analyses of multiple animals in a natural group setting are rarely performed.

In the present study, a research team led by Professor Masaki Kakeyama of Waseda University, Japan, developed a video-based behavioral analysis system for long-term behavioral tracking of multiple mice. This software, referred to as the Multiple-Animal Positioning System (MAPS), can automatically and separately analyze the social behavior of multiple mice in group housing.

“Each mouse is individually identified by an ID tag on its back,” said Kakeyama. “MAPS can then automatically acquire their individual positions based on a pattern-matching technique and save this information to a hard disk drive along with video images. This approach allows MAPS to perform an automated, long-term video tracking of each mouse under social housing conditions.”

Using MAPS, the researchers first examined how the social experience of mice in adolescence affects adult social proximity with unfamiliar mice. First, male mice were either housed in groups or reared in social isolation during adolescence. The researchers observed that mice housed in groups began to huddle in one location within two hours.

On the contrary, the mice reared in social isolation stayed as far away from each other as possible and took two days for all four of them to finally huddle together. These findings indicate that adolescent social isolation results in deficient social relationship formation in adulthood.

The researchers then carried out a separate experiment wherein two isolated and two group-housed mice were placed in the same experimental chamber to examine their behavior under a mixed-housing condition. They discovered that isolated mice took less time to form relationships with unfamiliar mice under the mixed-housing than in the isolated-mice-only housing condition, indicating that social proximity is not only influenced by individual behavioral traits, but also those of surrounding individuals.

“Additionally, visual observation of video images revealed that the group-housed mice reduced their activity or even became immobile when approached by others,” said Kakeyama. “This suggests that low activity [upon approach], or being ‘composed,’ might be an important factor for establishing social relationships.”

The results of this study may not be directly applicable to humans, but Kakeyama hopes that the newly-developed software will contribute to research in understanding how our minds develop through socialization, as well as advance the treatment of psychiatric disorders, such as autism spectrum disorder and social anxiety disorder.

The article can be found at: Endo et al. (2018) Multiple Animal Positioning System Shows That Socially-reared Mice Influence the Social Proximity of Isolation-reared Cagemates.


Source: Waseda University; Photo: Shutterstock.
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