Rat study ties baby stress to middle-aged mental decline

NEW YORK (Reuters Health) – A short period of psychological
stress in infancy can lead to impaired learning and memory and
a decline in cognitive abilities in middle-age, according to
research conducted in rats.

The study is believed to be the first to show that early
life emotional stress may initiate a slow decline of brain-cell
communication in adulthood. These cell-signaling deficits occur
in the hippocampus — a region of the brain involved in
learning, storage and recall of learned memories.

In their study, Dr. Tallie Z. Baram of the University of
California, Irvine, and colleagues found that limiting the
nesting material in cages where newborn rats lived with their
mothers led to emotional stress for both mothers and pups. All
evidence of this stress disappeared by the time the pups
reached adulthood, the researchers report in the Journal of
Neuroscience.

However, starting in middle age, the rats that endured
early-life stress began to exhibit deficits in their ability to
remember the location of objects they had seen before. They
also had trouble recognizing objects that they had encountered
on the previous day. These difficulties worsened as the rats
grew older, and developed much more rapidly than in rats that
were raised from the first week of life in a typical nurturing
environment.

“The cellular bases for the cognitive difficulties were a
result of change in the fine structure of brain cells, which
impaired their ability to enhance their communication, as
normally happens during the process of learning,” Baram said in
an interview with Reuters Health.

Baram noted that over 50 percent of the world’s children
are raised under stressful conditions. “While it has been
suspected that early life stresses can lead to later cognitive
impairment, it is not possible to affirm this suspicion in
human studies, because the genetic background of children or
other confounders make these analyses too complex,” the
researcher said.

“Over the last decade we have learned a tremendous amount
how our genes shape our brain,” Baram explained. “Now we need
to also enhance our understanding of how experience and
environmental signals, particularly early in life, influence
our cognitive function and our behavior for life.”

SOURCE: Journal of Neuroscience October 12, 2005.