From Our New Delhi Bureau
Scientists understand that stress in early childhood can create lifelong psychological troubles, but have only begun to explain how they emerge in the brain.
For example, they have observed that stress incurred early in life attenuates neural growth. Now a new study with male mice exposed to stress shows that the hippocampus reaches some developmental milestones early —essentially maturing faster in response to stress.
The findings, the first to track and report signs of stress-related early maturation in a brain region as mice develop, may lend some credence to the expression that children facing early adversity have to “grow up too fast.”
Kevin Bath, assistant professor of cognitive, linguistic, and psychological sciences at Brown University, became curious about whether some brain regions were maturing faster when he observed that certain traits in humans and rodents — such as fear-driven learning and memory, sexual development, and neural connectivity among some brain regions — were accelerated, rather than stunted, after early life stress. Some of these qualities, particularly memory and emotion regulation, involve the hippocampus.
“There were a number of different indicators that (early maturation) might be happening,” he says. “We wanted to carefully assess this and look at a number of different markers of not only growth, but also maturation of these animals, and to measure it not only at the behavioural level but also at the neuro-molecular level.”
For the study, published in the journal Hormones and Behavior, researchers exposed the mice to a period of fragmented maternal care — a condition comparable to one that might affect a child growing up in an economically challenged, single-parent household, for example.
At four days of age, pups and their mothers were moved from standard cages to ones where the materials available to the mother for nest building were inadequate. Food and water remained plentiful, but the mother responded anxiously and would frequently depart to search for anything that might work as nesting material.
Pups therefore received less consistent and attentive care from their harried and distracted mothers than experimental controls that were never moved from standard cages. After just a week of exposure to this manipulation (a significant span of time for mice who mature from birth to adulthood in just eight weeks), the mice returned to cages with everything they needed.
By then, however, the effects of the stress were already well underway. Researchers made several measurements in mice at 4 days and at 50 days (when mice reach young adulthood) to track how development in the hippocampus varied between mice exposed to stress and the unstressed controls.
In other words, rather than invest for the long run in optimally refined systems in the cortex for learning rules and suppressing emotional responses, mice may instead invest in accelerating the maturation of more primal systems, such as the hippocampus, to support short-term priorities, like racing to survive long enough to reproduce at least once.
