Short stressful events can enhance working memory

Washington, July 24 (ANI): Acute stress resulting from short stressful incidents can actually enhance learning and memory, says researchers at the University at Buffalo.

In trials on rodents, the researchers have shown that 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.

The researchers specifically 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. 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," said Zhen Yan, a professor of physiology and biophysics at UB and senior author on the study.

In order to test the effect of acute stress on working memory, the researchers 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.

According to the results, 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.

To determine whether the corticosterone neuropathway was responsible for the improved memory, as they proposed, the researchers injected one group of rats before the stressful forced-swim with a medicinal compound that blocks the pathway, and injected another group with saline.

The research team observed that the saline group, in which the corticosterone neuropathway was not blocked, performed better in the maze than the blocked group.

They also determined that the stressful experience did not increase depression or anxiety-related behaviour in the animals.

"It is known that stress has both positive and negative actions in the brain, but the underlying mechanism is elusive. Several key brain regions involved in cognition and emotions, including the prefrontal cortex, have been identified as the primary target of corticosteroid, the major stress hormone," said Yan.

He added: "Our current study identifies a novel mechanism that underlies the impact of acute stress on working memory, a cognitive process depending on glutamate receptor-mediated excitatory signals in prefrontal cortex circuits."

The study has been published in the online edition of Proceedings of the National Academy of Sciences. (ANI)