Even before their eyes open and their fur grows out, young mice can distinguish a mother figure from a stranger.
Baby mice recognize their mamas, just like human infants do. And researchers have found that mouse pups form memories of their mothers that last into adulthood.
Elizabeth Gould and her colleagues at Princeton University in New Jersey gave newborn house mice (Mus musculus) to foster mothers for rearing. Within a few days, pups given the choice of approaching their foster mum or a female mouse they had never met tended to turn their noses towards their caregiver. They also ‘whistled’ more for her than for the unknown mouse, another sign that baby mice recognize and prefer their mums. Once weaned, however, mice sought to make the stranger’s acquaintance instead.
After spending time with their foster mothers, young mice experienced a rise in the activity of neurons in a brain region involved in social memory — an animal’s ability to recognize and remember members of its own species. In adult mice, the activity of these neurons was higher after the animals hung out with the stranger.
Turning off these ‘social’ neurons reduced the rodents’ ability to distinguish their mums from unknown females, which suggests that these brain cells contribute to the formation of the earliest social memories.