Baby's Smile a Natural High for Mom

July 7, 2008 -- Seeing her baby smile may provide a natural high for mom.

A new study shows seeing her baby's smile lights up the reward center in a mother's brain. Researchers say understanding that reaction may help explain that special mother-child bond and determine why it sometimes goes wrong.

"The relationship between mothers and infants is critical for child development," says researcher Lane Strathearn, MBBS, FRACP, assistant professor of pediatrics at Baylor College of Medicine, in a news release. "For whatever reason, in some cases, that relationship doesn't develop normally. Neglect and abuse can result, with devastating effects on a child's development."

Baby's Smile a Natural High

In the study, published in Pediatrics, researchers had 28 first-time mothers view images of their own child and other infants while hooked up to a functional magnetic resonance imaging (MRI) scanner.

The functional MRI provided information on activation of different regions of the brains as the women viewed the images of the babies smiling or portraying neutral or sad emotions.

Researchers found that when the mothers saw happy images of their own baby, activation increased in areas of the brain associated with reward and the neurotransmitter dopamine compared with seeing images of other babies.

"These are areas that have been activated in other experiments associated with drug addiction," says Strathearn. "It may be that seeing your own baby's smiling face is like a 'natural high.'"

Overall, the mothers' brains responded much more strongly to their own infants than to others, but researchers found the strength of that natural-high reaction depended on the baby's facial expression.

"The strongest activation was with smiling faces," says Strathearn. "We were expecting a different reaction with sad faces."

Instead, they found little difference in the reaction of the mothers' brains to their own baby's crying face compared to that of an unknown child.

"Understanding how a mother responds uniquely to her own infant, when smiling or crying, may be the first step in understanding the neural basis of mother-infant attachment," says Strathearn.