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Memory Loss Before Your Time May Be Due to Stress as
Infant
Oct. 13, 2005 Baby boomers and young senior
citizens that are experiencing memory loss and cognitive decline before
their time, may have stress experienced as babies to blame.
Psychological stress during infancy has been found
to cause early impaired memory and a decline in related cognitive
abilities, according to a UC Irvine School of Medicine study. The study
suggests that the emotional stress associated with parental loss, abuse
or neglect may contribute to the type of memory loss during middle-age
years that is normally seen in the elderly.
The study, conducted in rats, is believed to be the
first to show that early life emotional stress initiates a slow
deterioration of brain-cell communication in adulthood. These
cell-signaling deficits occur in the hippocampus, a brain region
involved in learning, storage and recall of learned memories. Study
results appear in the Oct. 12 issue of The Journal of Neuroscience.
The loss of cognitive function later in life is
probably a result of both genetic and environmental factors, said study
leader Dr. Tallie Z. Baram, the Danette Shepard Chair in Neurological
Sciences. While it is not yet possible to change a persons genetic
background, it may be feasible to block the environmental effects,
particularly of early life stress, on learning and memory later in life.
These studies point to the development of new, more effective ways to
prevent cognitive impairment later in life.
In their study, Baram, post-graduate researcher
Kristen Brunson and colleagues found that limiting the nesting material
in cages where neonatal 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.
Starting in middle age, however, these graduates
of early life stress began to exhibit deficits in their ability to
remember the location of objects they had seen before, as well as to
recognize objects that they had encountered on the previous day.
Strikingly, these difficulties worsened as the rats grew older, much
more rapidly than in rats that were raised for their first week of life
under typical nurturing environment.
The researchers teamed up with Gary Lynch, a UCI
professor of psychiatry and human behavior and a world leader in the
study of the mechanisms of learning and memory, to understand the
effects early life stress had on the brain-cell activity in the rats.
The normal increase in brain communication through synapses, considered
to be the cellular basis for learning and memory, was found to be faulty
in the middle-aged rats exposed to early life stress.
In testing these cellular abnormalities, the
researchers recorded the electrical activity of brain cells, which
appeared normal in young adult rats exposed to early life stress, but
became very disturbed as they reached middle age. These changes in
brain-cell activity were consistent with the rats behavioral changes.
More than 50 percent of the worlds children are
raised under stressful conditions, as revealed by UNESCO last year.
While it has been suspected that early life stress can lead to later
cognitive impairment, it is not yet possible to affirm this suspicion in
human studies, because childrens genetic background or other
confounders make these analyses too complex.
The current study allows investigators to show that
the early stress itself is responsible for the cognitive decline. In
addition, now that concrete deficits in brain-cell communication have
been found, the new understanding of the cellular basis for how this
occurs will permit the researchers to find the specific molecules
involved and to design medicines to prevent the deficits.
Eniko Kramar, Bin Lin, Yuncai Chen, Laura Lee
Colgin and Theodore K. Yanagihara of UCI contributed to the study, which
was supported by the National Institutes of Health.
About the University of California, Irvine:
Celebrating 40 years of innovation, the University of California, Irvine
is a top-ranked university dedicated to research, scholarship and
community service. Founded in 1965, UCI is among the fastest-growing
University of California campuses, with more than 24,000 undergraduate
and graduate students and about 1,400 faculty members. The
second-largest employer in dynamic Orange County, UCI contributes an
annual economic impact of $3 billion. For more UCI news, visit
www.today.uci.edu.
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