Infant brains have powerful reactions to fear

SAN DIEGO — Babies as young as 5 months old possess networks of brain cell activity that react to facial emotions, especially fear, a new study finds.

“Networks for recognizing facial expressions are in place shortly after birth,” Catherine Stamoulis of Harvard Medical School said November 13 during a news conference at the annual meeting of the Society for Neuroscience. “This work … is the first evidence that networks that are involved in a function that is critical to survival, such as the recognition of facial expressions, come online very early in life.”

Stamoulis and colleagues at Harvard and Boston Children’s Hospital analyzed a database of brain electrical activity collected from 58 infants as they aged from 5 months to 3 years. Brain activity was measured as the infants viewed pictures of female faces expressing happiness, anger or fear. Computer models of the brain activity showed that networks responding to fear were activated much more dramatically than those for happy or angry faces, even in the youngest infants.

As babies grew older, their brain networks responding to facial emotions became less complex as redundant nerve cell connections were pruned. But the fear network remained more complex than the others, and response to fearful faces remained elevated over time. Understanding the brain circuitry involved in responding to emotional facial expressions could have implications for research on developmental disorders, Stamoulis said.