Stress – getting the balance right

Trouble sleeping, excessive snacking, heart palpitations? Oh yes - it’s revision time! Although all these negative symptoms can be attributed to the release of stress hormones – you’ll be relieved to know that stress can also help you remember. Just last month, scientists finally cracked the cellular mechanism by which stress hormones boost long-term memory.

The main hormone released during stress is called cortisol, which is a naturally occurring steroid just like testosterone and estrogen. At times of excessive stress, the rise in cortisol levels is accompanied by the release of noradrenaline, a signalling molecule related to the more familiar fight-or-flight hormone, adrenaline. This explains the racing heart and elevated blood pressure that you may experience at peak revision time. But how does a stress hormone affect memory?
We know from animal studies in birds and mammals that stress hormones have dual effects on learning and memory. Short-term stress enhances learning. This is why you can recall traumatic events in detail, but wouldn’t be able to remember what you had on your toast yesterday morning. Thus, a slightly elevated cortisol level is good for strengthening memories.

Exactly how stress enhances long-term memory formation has now been revealed by a study conducted in the Netherlands and The University of California. The study involved mimicking stressful conditions by injecting glucocorticoids, which is the rodent version of cortisol. Results showed that the injection caused an increase in production of proteins needed for long-term memory in the hippocampus, a key brain structure required for memory formation. Interestingly, this effect was mediated by switching on gene production, through direct chemical modification of DNA. In fact, the hippocampus contains the highest density of glucocorticoid receptors in the central nervous system – meaning its activity is easily modulated by stress hormones.

However, as we all know, too much of the good stuff is always bad for you. This is the case for cortisol also, as long-term stress can be detrimental for memory formation. Again, neuroscientists have dutifully provided us with an explanation. Learning and memory deteriorates when elevated glucocorticoids trigger cell death and inhibition of brain cells in the hippocampus. As mentioned above, these cells are vital for forming new memories, explaining why their inhibition leads to disrupted learning.

As a final note of warning, long-term exposure to stress hormones has been shown to cause damage to your body beyond just brain cells. Studies in various species have shown that over time, elevated glucocorticoids ultimately lead to premature death. The reason for this has been related to the fact that these hormones activate severe inflammatory cascades in the body.

So, remember, even though the exams are stressful, they are not worth risking your health and sanity! And in moderation, a healthy amount of exam fear can even be your memory-boosting friend.

This article was also published in Student Direct: Mancunion on the 3rd of May 2010. It can be accessed here.