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Memory Can Get Stressed Out

August 19, 1998

A team of researchers has come up with an explanation for something many test takers, public speakers and performers already know: Memory can fail under pressure.

The scientists at the University of California at Irvine showed that an elevated level of a stress hormone hinders the ability of rats to find their way back to a hidden target. The study was to be published Thursday in the journal Nature.

``This is the science of, `Oh, I’ve been so stressed lately, I have trouble remembering,‴ said Robert Sapolsky, a Stanford University neuroscientist who has also studied how stress hormones impair memory.

The UC researchers first taught rats to swim to a plastic platform hidden just beneath the water’s surface in a steel tank. Then, they gave the rats a small electric shock and tested how well they were able to swim back to the platform after two minutes, 30 minutes and four hours.

The rats were equally able after two minutes and four hours, but at least 50 percent less successful after 30 minutes. The 30-minute trial corresponded to a peak level of the stress hormone corticosterone, which was secreted in response to the electric shock.

The scientists also chemically blocked production of the hormone and found that the rats had no memory trouble. Conversely, injections of the hormone impeded memory just like an electric shock.

The rat hormone corticosterone is similar to cortisol, which is secreted under stress by the human adrenal gland, near the kidneys. James L. McGaugh, who directs UC’s Center for the Neurobiology of Learning and Memory, said his research team is studying whether its findings also apply to humans, and is confident they do.

He said the findings suggest that people should relax before taking tests or performing other activities dependent on memory.

James W. Lane, a psychologist at a St. Louis drug rehabilitation center who has researched memory trouble, said such studies may ultimately help determine whether repressed memory actually exists.

He said that stress hormone floods a person’s system during a frightening experience, such as physical abuse, and maybe later clouds recollection.

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