Rat moms’ behavior reflected in their babies’ brains

rat mother and her pups

Mother rats have a big influence on their pups’ brains, a new study finds.

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In their first year, babies grow and change in all sorts of obvious and astonishing ways. As their bodies become longer, heavier and stronger, so do their brains. Between birth and a child’s first birthday, her brain nearly triples in size as torrents of newborn nerve cells create neural pathways.

This incredible growth can be influenced by a baby’s early life environment, scientists have found. Tragic cases of severe neglect or abuse can throw brain development off course, resulting in lifelong impairments. But in happier circumstances, warm caregivers influence a baby’s brain, too.

A new study in rats provides a glimpse of how motherly actions influence a pup’s brain. Scientists recorded electrical activity in the brains of rat pups as their mamas nursed, licked and cared for their offspring. The results, published in the July 21 Current Biology, offer a fascinating minute-to-minute look at the effects of parenting.

Researchers led by Emma Sarro of New York University’s medical school implanted electrodes near six pups’ brains to record neural activity. Video cameras captured mother-pup interactions, allowing the scientists to link specific maternal behaviors to certain sorts of brain activity.

Two types of brain patterns emerged: a highly alert state and a sleepier, zoned-out state, Sarro and colleagues found. Pups’ brains were alert while they were drinking milk and getting groomed by mom. Pups’ brains’ were similarly aroused when the pups were separated from their mom and siblings.  Some scientists think that these bursts of brain activity help young brains form the right connections between regions.

Pups’ brains showed more Zen-like activity when they were attached to their mothers’ nipple but not getting any milk. Nursing for comfort — not for food — lulled the pups’ brains into a state similar to that observed in sleeping or meditating people. This sort of neuronal action might help the brain solidify connections made during those earlier bursts of action.

Without more experiments, it’s hard to say exactly what these particular types of brain waves do for the growing brain. The active periods might be providing brief windows during which nerve cells can easily connect to other cells, and the slower, more relaxed periods might allow the brain to then cement those new connections in place.

No matter what sorts of mysterious machinations are happening in a developing brain, one thing is clear: The actions of moms (and probably dads too) help sculpt the process.

Laura Sanders is the neuroscience writer. She holds a Ph.D. in molecular biology from the University of Southern California.

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