Mothers Teach Babies What to Fear Based on Smell

The bond between a mother and her newborn is further cemented by specific fears that are subconsciously passed on through smell.

Recent findings published Monday in the Proceedings of the National Academy of Sciences may help explain how some mothers' previously experienced traumas--including post-traumatic stress disorder (PTSD) and certain phobias--could affect their children later in life.

"During the early days of an infant rat's life, they are immune to learning information about environmental dangers. But if their mother is the source of threat information, we have shown they can learn from her and produce lasting memories," said lead study author Jacek Debiec, M.D., Ph.D., the U-M psychiatrist and neuroscientist, in a news release. "Before they can even make their own experiences, they basically acquire their mothers' experiences. Most importantly, these maternally-transmitted memories are long-lived, whereas other types of infant learning, if not repeated, rapidly perish."

For the study, researchers taught rats to fear the smell of peppermint by giving the rodents electric shocks whenever they were exposed to the candy. However, a control group in the experiment did not experience anything when given the scent.

With the use of brain imaging techniques, researchers were able to examine genetic patterns in the minds of the rat models. Findings revealed that the newborn rats could learn their mother's fear even when they weren't present; researchers tested this by exposing the newborns to the smell of peppermint.

However, when researchers blocked amygdala activity the newborns' brains, they did not learn to fear the smell--suggesting potential treatments could disrupt learning patterns that involve irrational thoughts and fears.

In the future, researchers said they hope to conduct human studies.