When Recall Fails the Stress Test

If you’ve ever assiduously crammed for a Shakespeare final and yet blanked out as you stared at an empty blue book, there’s a physiological explanation that won’t help your grade but may ease your mind.

In a new study, neuroscientists at UC Irvine say it is true that stress can temporarily rob you of memory.

A hormone released during acute stress seems to block the retrieval of long-term memory, according to a study published last month in the scientific journal Nature by UC Irvine postdoctoral scientists Benno Roozendaal and Dominique de Quervain.

“It’s so common,” Roozendaal said. “Everybody has been in a situation when they were so stressed, like a job interview, that they feel they did terrible.”

The initial research at UC Irvine’s Center for the Neurobiology of Learning and Memory was done on rats; studies have now begun on humans, Roozendaal said. He said rats produce the hormone corticosterone, which is similar to the human hormone cortisol, released by the adrenal glands.

Roozendaal said the rats were placed in a tank of water and trained to swim to a platform. Then the rodents’ feet were shocked, and they were placed intermittently back in the tank. The rats that were placed back in the water about half an hour after the shock swam around randomly, too stressed to remember the platform. Researchers also tested the rats’ blood.

“The block peaks 30 minutes after a stressful incident,” Roozendaal said. “Four hours after the stress, the hormone is back to base levels.”

In the human trials, a pill is given that jump-starts the production of cortisol in the brain. People then are asked to recall a series of words.

Roozendaal said the findings show stress can impair the retrieval of stored information; this somewhat contradicts other studies showing that acute stress can actually enhance the storage of memory.

He used his own dissertation defense as an example: “There was nobody on the committee who knew the material better than I did. Yet when they asked me questions, I wasn’t able to think clearly enough to give the answers that I would have given in a situation when I would not be stressed.”

But he never forgot the experience.