Whether such stress occurs in the womb or in the early years of life, it can change a person’s behavior for the worse and diminish his learning and memory ability. It can also push a person over the edge into substance abuse and psychiatric disorders.
“Prenatal stress can change the brain forever,” said Tallie Baram, a neurologist at the University of California at Irvine. “Stress changes how genes are expressed throughout life.”
Stress can disrupt beneficial behaviors, and can even change the size of areas in the brain, causing disturbances of various brain functions. For example, Baram told of an experiment of hers in which stress was induced in laboratory mice by preventing them from moving about for five hours and subjecting them to loud rock music. MRI brain scans showed that, just from this one experience, the mice’s fibers that carry signals between neurons were diminished in number.
The study, Baram said, provided “insights into why some people are forgetful or have difficulty retaining information during stressful situations.” She raised the prospect that one day scientists would be able to “design drugs to prevent the damage due to stress.”
In another experiment, University of Wisconsin at Milwaukee researcher Fred Helmstetter created stress in laboratory rats by immobilizing them for six hours a day, without food or water during that time, for 21 days. He discovered that the rats’ hippocampus, a part of the brain involved in learning and memory, shrank by 3 percent.
In another illustration of stress-related brain change, Nim Tottenham, a neuroscientist at the Weill Cornell Medical School, in New York, studied children adopted from foreign orphanages who experienced anxiety and found it hard to control their emotions.
Brain scans showed that these children showed abnormally high activity in the amygdala, a region involved in emotion. “Adverse rearing environments can produce long-lasting changes in the ability to regulate emotion,” Tottenham said.