August 30, 2004
Estrogen Benefits For Cognitive Performance Depend On Stress Level

In female rats running through water mazes higher estrogen estrogen levels helped boost performance only when the conditions were not stressful.

"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."

What is the evolutionary adaptation that is causing this difference in performance under different conditions?

We already have fairly limited abilities to regulate the extent of our stress response. We can take drugs that make us more relaxed and also other drugs that suppress inflammation response. We will of course eventually achieve much more control over the body's stress response. One future use of the ability to regulate stress response will be to create levels of stress that have the effect of optimally tuning the mind to reach peak performance for specific types of cognitive tasks.

Of course hormones will be manipulated to produce differences in cognitive function as well. But what we really need with hormones is the ability to make different target tissue types see different hormone levels. Rather than the whole body seeing, for instance, pharmaceutically boosted levels of testosterone expect to see the development of means to target only muscles or only the brain to produce only a subset of all the effects that testosterone produces. Ditto for estrogen, progesterone, and other hormones. Lots of effects of these hormones go together in nature. But you can bet people will want to, say, enhance their physical appearance without changing their cognitive function and vice versa.

Share |      Randall Parker, 2004 August 30 03:00 AM  Brain Enhancement


Comments
nectarflowed said at August 30, 2004 2:55 PM:

Regarding the issue of controlling the body's stress response, there is evidence that the brain already has very significant controlling ability that is generally not used to it's potential. The neurofeedback center the Biocybernaut Institute (I assume cybernaut used as in "a computer user or programmer" (OED)) appears to have had interesting success with training individuals, including professional athletes, how to use their brains more effectively in this area.

As a side note, they've also been involved with anti-aging work: "'Anxiety and Aging: Intervention with EEG Alpha Feedback' was a quarter million dollar US Government Federal Grant conducted at UCSF ... using Biocybernaut Institute neurofeedback technology ... [which proved to be] effective behavioral medicine for restoring youthfulness."

(The institutes' publications section on their website (www.biocybernaut.com) has lots of information.)

Fly said at August 30, 2004 6:19 PM:

Randall: “What is the evolutionary adaptation that is causing this difference in performance under different conditions?”

A specific trait or behavior response is likely due to a complex interplay of many genes. So unless the trait is important for reproductive fitness it may not be the result of selection for that trait. Instead the trait could be a chance phenotype arising from a combination of genes that are selected for other traits.

Example: Gene A strongly affects IQ. Gene B strongly affects muscle strength. Gene A and gene B together cause an unusual stress response to cold. Gene A is strongly selected because of its IQ affect. Gene B is strongly selected because of its muscle strength affect. The unusual response to cold stress is a trait that is not directly selected.

I’m guessing that there are a relatively small number of physical traits and behaviors (numbering in the thousands) that are sufficiently important that the genes primarily responsible for the traits are under selective pressure. I expect that a much larger number of traits and behaviors result from complex interactions of genes that are not under selective pressure for those traits.

Who knows whether this applies to estrogen and cold stress?

Will we be able to tune our stress response? Genetically we might not be able to do so because tinkering with the genes might cause an unwanted affect elsewhere. But as Randall says we should be able to target a medicine to specific tissues and thereby modify the desired traits or behaviors without causing unwanted side effects.

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