Stress in pregnancy hits offspring's emotional brain
By Helen Philips
July 12, 2006 / Newscientist
Stress experienced by a pregnant female can alter the structure of her offspring's brain, particularly regions vital for emotional development, scientists have discovered. Furthermore, in rodents at least, the effects differ in male and female offspring. That might help explain the different susceptibilities of men and women to emotional and psychiatric disorders, says Katharina Braun, from the University of Magdeburg,Germany. Braun presented the work at the Federation of European Neuroscience Societies' annual meeting in Vienna, Austria, on Tuesday. Braun and colleagues at the University of Jerusalem in Israel studied the effects of stress on pregnant rats. If they become stressed in last trimester of pregnancy, their offspring developed fewer nerve connections in two brain regions that control emotions - the cingulate cortex and orbitofrontal cortex. In addition, the nerve cells in several other regions show different branching patterns to normal, with different effects on males and females. In the hippocampus, an important region that controls memory and emotion, males show an increase in branching while females show a decrease. In the prefrontal cortex, the males develop shorter nerve branches, while the females do not. Braun has not yet tested the behavioural effects of these changes on adult rats, but the results could reveal a possible mechanism for the development of emotional disorders seen in humans.
"Early experiences, especially emotional experiences, shape brain circuits for later life," says Braun. The susceptibility to stress continues after birth, with different types of stress and trauma leading to different brain effects, she adds.
For example, daily painful stimuli given to young rodent pups, separation from their mother, each led to changes in the prefrontal cortex. But while separation led to more nerve connections, stimuli led to fewer.
Further experiments on brush tail rats - which are unusual in that the father helps care for the offspring - showed that removal of the father early in the pups' life also leads to fewer neuron connections in the brain's emotion centres.
The pups grow up underactive and do not respond to the voices of their mothers. Animals that were emotionally deprived seem to develop emotional and social deficits.
Braun compared the results to the sad experiences of Romanian orphans. "Like the animal brain, the human brain needs to learn the grammar of emotions," she says. "Children after they are adopted catch up nicely on cognitive level, but the emotional side looks like it has been somehow frozen." (See Orphaned boys and girls react differently to care.)
"We are now collaborating with psychiatrists, asking questions such as 'Can these effects be reversed?'," says Braun. Knowing when the adult brain loses the flexibility of the young brain will be important.
Some evidence for hope came from work by Igor Branchi, at the University of Rome in Italy. He reported that when rodents were allowed extra social stimulation - the mouse equivalent of kindergarten - a lot of early emotional deficits could be improved.
Boys and Girls
Boys are more likely to develop attention deficit hyperactivity disorder (ADHD) than girls - a disorder that seems to be related to the brain's prefrontal attention systems, while women are more likely to develop depression, which is known to be related to shrinkage in the hippocampus.
12:02 12 July 2006
NewScientist.com news service
Helen Philips, Vienna
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25 March 2006
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Federation of Neurosciences Annual Meeting
University of Magdeburg
From issue of New Scientist magazine, 12 July 2006, page