Experiencing chronic stress day after day can produce physical and mental wear and tear and retard learning. However, acute stress -- a short stressful incident -- may energise learning and memory, according to a recent study.

Researchers at the University of Buffalo (U-B) have shown that in mice acute stress can produce a beneficial effect on learning and memory, through the effect of the stress hormone corticosterone (cortisol in humans) on the brain's prefrontal cortex, a key region that controls learning and emotion.

Specifically, they demonstrated that acute stress increases transmission of the neurotransmitter glutamate and improves working memory.'Stress hormones have both protective and damaging effects on the body,' said Zhen Yan, senior study author at UB.

'This paper and others we have in the pipeline explain why we need stress to perform better, but don't want to be stressed out.' To test the effect of acute stress on working memory, Yan and colleagues trained rats in a maze until they could complete it correctly 60-70 percent of the time.

When the rodents reached this level of accuracy for two consecutive days, half were put through a 20-minute forced swim, which served as acute stress, and then were put through the maze again.

Results showed that the stressed rats made significantly fewer mistakes as they went through the maze both four hours after the stressful experience and one day post-stress, compared to the non-stressed rats. These findings appeared in the July online edition of Proceedings of the National Academy of Sciences.