Social ties may preserve memory, slow brain ageing

A strong social network of friends and family may help preserve memory and protect it from the ill effects of ageing, a study in mice suggests.
Scientists from the Ohio State University in the US found that mice housed in groups had better memories and healthier brains than animals that lived in pairs.
The discovery bolsters a body of research in humans and animals that supports the role of social connections in preserving the mind and improving quality of life, said Elizabeth Kirby, an assistant professor at Ohio State.
“Our research suggests that merely having a larger social network can positively influence the ageing brain,” said Kirby, lead researcher of the study published in the journal Frontiers in Aging Neuroscience.
“We know that in humans there’s a strong correlation between cognitive health and social connections, but we don’t know if it is having a group of friends that’s protecting people or if it’s that people with declining brain health withdraw from their human connections,” Kirby said.
This study was designed to answer that hard-to-crack question with an animal model.
Some mice lived in pairs, which Kirby refers to as the “old-couple model.” Others were housed for three months with six other roommates, a scenario that allows for “pretty complex interactions.”
The mice were 15 months to 18 months old during the experiment – a time of significant natural memory decline in the rodent lifespan.
In tests of memory, the group-housed mice fared better. One test challenged the mice to recognise that a toy, such as a plastic car, had moved to a new location.
A mouse with good brain health will gravitate toward the novelty of something that has been relocated.
“With the pair-housed mice, they had no idea that the object had moved. The group-housed mice were much better at remembering what they’d seen before and went to the toy in a new location, ignoring another toy that had not moved,” Kirby said.
In another common maze-based memory test, mice are placed on a well-lit round table with holes, some of which lead to escape hatches. Their natural tendency is to look for the dark, unexposed and “safe” escape routes.
Both groups of mice improved their escape-route search strategies with practice – but the research team was struck by the differences in the groups’ response to repeated tests, Kirby said.
The “couples” mice didn’t get faster at the test when it was repeated over the course of a day.
“But over the course of many days, they developed a serial-searching strategy where they checked every hole as quickly as possible. It’d be like walking as quickly as possible through each row of a parking lot to look for your car rather than trying to remember where your car actually is and walk to that spot,” Kirby said.
The group-housed mice improved with each trial, though.
“They seemed to try to memorize where the escape hatches are and walk to them directly, which is the behavior we see in healthy young mice,” Kirby said.
“And that tells us that they’re using the hippocampus, an area of the brain that is really important for good memory function,” she said.
In humans, mice and many other animals, brain function in the hippocampus markedly declines with age, even in the absence of dementia. Exercise and social ties are known to preserve memory in this region in people, Kirby said. (PTI