(But Not To Form New Memories).
There remains clear evidence from multiple studies that high levels of anxiety can impair memory function. However, this impairment appears to only impact recall and has either neutral or beneficial impact on memory encoding (the process by which new information is stored).
One reason why anxiety impairs the ability to recall information relates to a hormone involved in the stress response called cortisol.
Cortisol serves a number of different functions but is most often thought of as the hormone involved in the stress response (often referred to as fight or flight).
When we encounter a perceived threat, the hypothalamus prompts the adrenal glands to release a surge of adrenaline and cortisol.
The surge of adrenaline increases the heart rate, elevates blood pressure and boosts energy supplies. Cortisol increases the levels of sugars (glucose) in the bloodstream, enhances the brains use of glucose and increases the availability of substances designed to repair tissue. In addition, cortisol also curbs all non-essential functions or those functions that could be detrimental to the fight or flight response, as well as altering our immune system responses and suppressing our digestive system. It also communicates with regions of the brain that control motivation and fear (see fig.1. Adapted from Kim, Pellman and Kim, 2015)
As part of this process, cortisol binds to receptors in the hippocampus and the amygdala, both of which are important for learning and memory. The greater the stress, the greater the impact on the function of the hippocampus (see fig.2 taken from Kim, Pellman and Kim, 2015)
The impact of cortisol on memory is complex. Research has discovered that inducing stress in participants by raising their cortisol levels benefits memory consolidation, that is, the formation of new memories. However, increasing cortisol levels during retrieval impairs recall.
Examining the role of naturally occurring cortisol levels.
In a study published in 2013, researchers decided to investigate the role of naturally occurring levels of cortisol (as opposed to inducing higher levels) to see how these natural levels impacted memory. They accomplished this by taking saliva samples from more than one thousand volunteers and subjecting them to a memory test at three data collection points: before memory encoding (the point at which we form new memories), between encoding and recall and after recall.
The memory test included a number of pictures that were either emotionally positive, negative or neutral. Volunteers viewed the pictures and classified them in relation to emotional arousal (or valence) and were then asked to recall the pictures after 10 minutes and 20 hours.
It was discovered that volunteers with a greater decrease in cortisol levels during memory retrieval had better recall of the pictures regardless of valence and time duration.
The study found no association between cortisol level and memory encoding.
These results would suggest that increased levels of cortisol help in the formation of memories but inhibit the recall of memories.
Implications for teaching and learning.
This and other studies have wide implications for teaching and learning and for the need to embed coping strategies within pupils engaged in high stakes testing. They also suggest that such strategies are best directed towards the process of exam-taking rather than stress reduction in general (which can be beneficial). Obviously there remains the need to identify chronic levels of stress in all pupils and in all circumstances, however, this should not include the elimination or all stressful events.