It has long been thought that the stress of a mother during her pregnancy may imprint on the brain of her developing child. 

There is a growing body of research to better understand how the human brain develops across its lifespan, from fetus to old age. "We are interested in how a human brain constructs over time to become the adult brain," says Nim Tottenham of Columbia University, whose work focuses on identifying sensitive periods of brain development from childhood into adolescence.

Research in newborns and older children to understand prenatal influences has been confounded by the postnatal environment.  But recent advancements in fetal imaging allowed researchers to gain insight into a critical time period in brain development.

Using fetal resting-state fMRI, they examined functional connectivity in 47 human fetuses scanned between the 30th and 37th week of gestation. The researchers recruited the participating mothers from a low-resource and high-stress urban setting, with many reporting high levels of depression, anxiety, worry, and stress.

They found that mothers reporting high stress had fetuses with a reduced efficiency in how their neural functional systems are organized. It is the first time, imaging has shown a direct influence of maternal stress on fetal brain development, independent of influences of the postnatal environment.

 The data suggest that the brain does not develop in a sequence from simplest systems (e.g., vision, motor) to more complex high-order systems, but perhaps instead first develops the areas that will be most critical in bridging across systems.

The researchers found that the cerebellum played a central role in the observed effects, suggesting it may be especially vulnerable to the effects of prenatal or early life stress. The cerebellum has the highest density of glucocorticoid receptors. Glucocorticoids are the hormones released by the body as a response to Stress.  

Making connections into adulthood

Cognitive neuroscientists are especially interested in understanding sensitive periods of time when the environment has the largest influence on future brain functions. 

"A majority of developmental change during childhood and adolescence are the changes in connections.  Researchers observe that most connections happen between the amygdala and prefrontal cortex because of the very large changes they observed there across childhood and adolescence and their central role in emotional behaviors.

The connections develop very slowly over childhood, with a dramatic shift toward the end of childhood when the transition to adolescence brings about more adult-like characteristics. Looking at coincidental environmental events in childhood, the researchers also found data to suggest that amygdala-medial PFC connections are highly impressionable to external forces.

We must consider the developing brain in context, thinking about the role of the environment in shaping the brain.