Estrogen may dictate what problem-solving strategy brain uses

May 15, 2002

CHAMPAIGN, Ill. -- Deciding on hormone-replacement therapy - weighing the far-reaching benefits and risks - can give a woman a headache. Now researchers say estrogen may dictate what problem-solving strategies the brain uses to solve problems.

According to a study of rats published in the June issue of Behavioral Neuroscience, activation of different parts of the brain may depend on the presence or absence of estrogen. Rats treated with the hormone learned a place-oriented task faster than rats not getting it, but those not on estrogen were faster completing a response-driven task. These tasks are believed to be controlled by different neural or memory systems.

"What we found is that given these analogous tasks that require different cognitive strategies, estrogen biased the rats to use a place, or spatial, strategy," said Donna L. Korol, a psychology professor at the University of Illinois at Urbana-Champaign. "Those not given estrogen are better using a response, or non-spatial, strategy. This suggests that estrogen isn't just good for all kinds of memory. Rather, it is very specific in dictating what strategy one takes. Estrogen may enhance some and impair other forms of learning."

In the National Science Foundation-funded study, Korol and Lacy L. Kolo (St. Louis University School of Medicine) used young rats whose ovaries had been removed to decrease circulating estrogen levels. Three weeks later, some of them received injections of estrogen, while others got a placebo, before learning to find food in two similar four-arm mazes.

In the place-training test, food always was at the same place, but the required turn changed, depending on the rats' starting point. Rats on estrogen learned the task faster than the untreated group. For the response-training test, the rats always found food by turning right (or left) at the first opportunity regardless of where they had started. Rats without estrogen learned this task quicker than the estrogen-treated ones.

"If estrogen was simply enhancing learning, the results should have been the same for each task, but that was not the case," Korol said. "It appears that estrogen is enhancing place learning at the expense of response learning. Both these task scenarios are important, because they reveal that estrogen isn't just up- or down-regulating something. It is shifting what individuals are good at solving - without estrogen, they still are good at something."

A postmenopausal woman not on HRT may believe that her ability to solve a problem as she always had is slipping. In reality, the brain may be shifting gears into a different strategy that the woman is not used to harnessing, Korol said.

In a chapter for a book published last year, "Animal Research and Human Health," Korol and Carol A. Manning of the University of Virginia noted that when an aging woman's hormone level declines, her brain might actually shift into a problem-solving mode more common to men. "Women may actually get better at performing a task from a different approach, but they are not used to doing it that way, so they view the change as an impairment," Korol said. "Theoretically, this may be true, but we don't know this for sure yet. The question is, Can you tap into the other strength?"

Korol is among a growing body of researchers studying the cognitive impacts of estrogen. Researchers so far have found that estrogen increases nerve-cell communications and brain excitability, in general, but findings related to memory and learning have often conflicted as to whether cognition was impaired or enhanced.

Many previous studies involved water-escape tests, in which rats are stressed as they begin to learn new tasks. The stress, Korol said, "seems to impair cognition in the presence of estrogen, but when there is no stress estrogen helps the capacity to learn."

The positive-reward, food-based tests used in Korol's lab remove stress from the equation. "Now we are going in and looking at the specific brain structures," she said. "Having estrogen at high physiological levels will shift the strategy that you use to solve a task. It might be doing so by changing the functioning or activity of certain brain areas."
-end-


University of Illinois at Urbana-Champaign

Related Stress Articles from Brightsurf:

Stress-free gel
Researchers at The University of Tokyo studied a new mechanism of gelation using colloidal particles.

Early life stress is associated with youth-onset depression for some types of stress but not others
Examining the association between eight different types of early life stress (ELS) and youth-onset depression, a study in JAACAP, published by Elsevier, reports that individuals exposed to ELS were more likely to develop a major depressive disorder (MDD) in childhood or adolescence than individuals who had not been exposed to ELS.

Red light for stress
Researchers from the Institute of Industrial Science at The University of Tokyo have created a biphasic luminescent material that changes color when exposed to mechanical stress.

How do our cells respond to stress?
Molecular biologists reverse-engineer a complex cellular structure that is associated with neurodegenerative diseases such as ALS

How stress remodels the brain
Stress restructures the brain by halting the production of crucial ion channel proteins, according to research in mice recently published in JNeurosci.

Why stress doesn't always cause depression
Rats susceptible to anhedonia, a core symptom of depression, possess more serotonin neurons after being exposed to chronic stress, but the effect can be reversed through amygdala activation, according to new research in JNeurosci.

How plants handle stress
Plants get stressed too. Drought or too much salt disrupt their physiology.

Stress in the powerhouse of the cell
University of Freiburg researchers discover a new principle -- how cells protect themselves from mitochondrial defects.

Measuring stress around cells
Tissues and organs in the human body are shaped through forces generated by cells, that push and pull, to ''sculpt'' biological structures.

Cellular stress at the movies
For the first time, biological imaging experts have used a custom fluorescence microscope and a novel antibody tagging tool to watch living cells undergoing stress.

Read More: Stress News and Stress Current Events
Brightsurf.com is a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for sites to earn advertising fees by advertising and linking to Amazon.com.