Email to a friend
Study suggests stress of task determines
if estrogen helps cognition
Barlow, Life Sciences Editor
photo to enlarge
by Kwame Ross
Juraska, right, professor of psychology and of neuroscience,
led a new study at the University of Illinois suggesting that
the stress of any given task at least partially determines
if hormones will help the mind. Psychology doctoral student
Marisa J. Rubinow, left, was a co-author of the new study,
Ill. — Does estrogen help cognition? Many women ponder that question
as a quality-of-life issue while deciding on estrogen therapy since
it has been linked to potential disease complications. Now, a new study
at the University of Illinois at Urbana-Champaign suggests that the
stress of any given task at least partially determines if hormones will
help the mind.
Reporting in the August issue of Behavioral Neuroscience, four researchers
show the introduction of a single stressor – water temperature
– into a water maze prompted opposite responses among female rats
with either high or low levels of estrogen and progesterone.
“Water temperature totally reversed who did better,” said
Janice M. Juraska, a professor of psychology and of neuroscience.
“Proestrous rats, which have high hormone levels, did better when
the water was warm, presumably because they were less stressed. Estrous
rats did better when the water was cold, presumably because they are
not as prone to get stressed during this time.”
Proestrous rats are fertile and ready to mate, while estrous rats have
low hormone levels and won’t mate. For the study – funded
by a grant to Juraska from the National Science Foundation – 44
female rats were divided into four groups. The two groups of rats in
proestrus and the two groups in estrus had to learn the route and swim
to a submerged platform in either warm (91 degrees Fahrenheit; 33 Celsius)
or cold water (66.2 degrees Fahrenheit; 19 Celsius).
Many scientists have tried to answer the hormones-cognition question,
but the various findings, measuring different tasks, have been inconsistent
and often contradictory.
“These discrepancies of sometimes opposite results have been very
difficult to resolve,” Juraska said. “Even for simple tests
of spatial behavior, high hormones can either help or hinder, and nobody
has understood why.”
Juraska’s lab previously had shown in studies using the water
maze that rats with high levels of hormones, either naturally occurring
in the estrous cycle or with high doses administered into rats whose
ovaries had been removed, do less well finding the platform.
Psychology doctoral student Marisa J. Rubinow, a co-author of the new
study, wondered if stress during a task might be a factor in the varied
results showing up in the literature. Now, after the new results, Rubinow
and Juraska suggest that the timing and duration of stress, as well
as the memory systems involved in a task, all may be factors that determine
the effects of ovarian hormones on performance.
“Will hormones help how your brain works – how you think,
your cognition?” Juraska said. “I wish I had a simple answer.
It depends on many things about the task, and one of them is how stressful
the task is. There is no simple translation to behavior.”
Other co-authors on the paper were Linda M. Arseneau, formerly in the
department of animal sciences and now with the U. of I. Division
of Research Safety, and J. Lee Beverly, a professor of animal sciences
and of neuroscience.