Neuroscientists, child development specialists, and pretty much all the rest of us understand that a baby’s brain is vastly different in some ways from that of a mature adult. However, scientists who research the infant brain are just beginning to learn the impact of these contrasts. A mother’s care of her hurt baby, one new study suggests, impacts early brain development by altering gene activity in a part of the brain involved in emotions.

"Our study shows that a mother comforting her infant in pain does not just elicit a behavioral response, but also the comforting itself modifies — for better or worse — critical neural circuitry during early brain development," said Dr. Regina Sullivan, the senior study investigator and a neurobiologist at NYU School of Medicine. Her research will be presented Tuesday at a meeting of the American Society for Neuroscience.

Sullivan’s latest research began with a careful analysis of the genes in infant rat brains. In particular, she and her co-researchers studied what happened when baby rats experienced pain. Delivering mild electric shocks to the babies, they discovered that, in comparison to rats not in pain, several hundred genes within their brains became active. However, fewer than 100 genes lit up in the brains of rat pups who were shocked while their mothers were present.

Going further, the researchers removed and performed genetic analyses on the amygdala, the almond-sized region of the brain responsible for processing emotions, such as fear and pleasure. (Humans share this same brain feature.) Here, the researchers discovered that while the electric shock altered some genes, the presence of the infant’s mother also modified genes and so changed brain development. Specifically, the mother’s presence changed a number of genes associated with cAMP and GPCR signaling, which have been linked to communication between cells, as well as genes linked to the release of hormones.

While this research may be fascinating in and of itself, it also illuminates the complexity of treating pain in newborns.

"Nobody wants to see an infant suffer, in rats or any other species," Sullivan said. "But if opiate drugs are too dangerous to use in human infants because of their addictive properties, then the challenge remains for researchers to find alternative environmental stimuli, including maternal presence, coddling, or other cues, such as a mother's scent, that could relieve the pain."

Source: Sullivan R, Barr GA. The presence of the mother alters the valence of cues associated with painful stimuli and regulates changes in the amygdala of infant rats. American Society for Neuroscience. 2014.