应激时激素释放会导致记忆力丧失

    Have you ever forgotten something during a stressful situation that you should have remembered? New research demonstrates that a hormone called cortisol, which is elevated during stress, interferes with memory functioning.

    According to James McGaugh, a coauthor on the new report, the results of this new study correlate well with previous animal studies, which have shown that high levels of the same stress hormone can prevent rats from remembering old memories.

    Cortisol "depressed the memory for a short period of time. So this would imply why it is that you go in for a job interview and you can‘t remember a lot of things you should remember quite well," explained McGaugh, director of the center for the neurobiology of learning and memory at the University of California, Irvine. The same would apply to conditions like examinations, combat and courtroom testimony, he added.

    Results from the animal studies prompted the researchers, led by Dominique J.F. de Quervain, of the department of psychiatry at the University of Zurich in Switzerland, to study the same effect in humans. The report appears in the April edition of the journal Nature Neuroscience

    To study cortisol‘s effect on memory in humans, the investigators gave 36 people a list of 60 unrelated nouns to learn. Each word appeared for four seconds on a computer screen. Study participants were instructed to remember the words for tests that would be given immediately after they learned the list and then again, one day later.

    The subjects also received pills (either cortisone-a precursor of cortisol-or a placebo) at one of three times: one hour before the initial word presentation; just after the word presentation; or one hour before the retention test.

    The cortisone pills provided a dose that produced cortisol levels (as measured by salvia concentrations) that are similar to the levels achieved during stress. However, none of the subjects reported feeling stressed, most likely because elevated cortisol is a result of stress, not a cause of it.

    The investigators then tested the subjects‘ abilities to remember the word lists immediately after learning the list and a day later. Compared to the placebo, the cortisone pills impaired memory but only when they were given an hour before a free recall test one full day after learning the original list. Therefore, just like in rats, high levels of this stress hormone impaired memory only when people tried to recall old, but not recent, memories.

    "It was surprising that the results matched so beautifully with the results we obtained with laboratory rats," McGaugh explained. "This is a rare occasion in which we jumped from a laboratory rat experiment to a human experiment and found the same results with memory."

    McGaugh said that high cortisol levels during a learning situation, as opposed to during testing, usually cause a person or animal to learn better. "This would explain why we remember important events," he said, "because important events release stress hormones, and they act on the brain to imprint a stronger memory."

    Cortisol is secreted by the adrenal cortex, part of the adrenal gland, which is adjacent to the kidneys. In a condition called hypercortisolemia, the adrenal cortex is hyperactive, secreting too much cortisol. "It‘ll be important now to find out what memory effects there are in subjects with this particular disease," McGaugh said.