TedEd-18

The Surprising Link Between
Stress and Memory

You spend weeks studying for an important test. On the big day, you wait nervously as your teacher
hands it out. You’re working your way through, when you’re asked to define ‘ataraxia.’You know
you’ve seen it before, but your mind goes blank. What just happened? The answer lies in thecomplex relationship between stress and memory. There are many types and degrees of stress anddifferent kinds of memory, but we’re going to focus on how short-term stress impacts your memory
for facts.
To start, it helps to understand how this kind of memory works. Facts you read, hear, or study
become memories through a process with three main steps. First comes acquisition: the moment
you encounter a new piece of information. Each sensory experience activates a unique set of brain
areas. In order to become lasting memories, these sensory experiences have to be consolidated by
the hippocampus, influenced by the amygdala, which emphasizes experiences associated with

TedEd-18

The Surprising Link Between
Stress and Memorystrong emotions. The hippocampus then encodes memories, probably by strengthening the synaptic
connections stimulated during the original sensory experience. Once a memory has been encoded,
it can be remembered, or retrieved, later. Memories are stored all over the brain, and it’s likely theprefrontal cortex that signals for their retrieval.
So how does stress affect each of these stages? In the first two stages, moderate stress canactually help experiences enter your memory. Your brain responds to stressful stimuli by releasing
hormones known as corticosteroids, which activate a process of threat-detection and threatresponse in the amygdala. The amygdala prompts your hippocampus to consolidate the stressinducing experience into a memory. Meanwhile, the flood of corticosteroids from stress stimulates
your hippocampus, also prompting memory consolidation. But even though some stress can be
helpful, extreme and chronic stress can have the opposite effect. Researchers have tested this byinjecting rats directly with stress hormones. As they gradually increased the dose of corticosteroids,
the rats’ performance on memory tests increased at first, but dropped off at higher doses. Inhumans, we see a similar positive effect with moderate stress. But that only appears when thestress is related to the memory task — so while time pressure might help you memorize a list,having
a friend scare you will not. And the weeks, months, or even years of sustained corticosteroids that
result from chronic stress can damage the hippocampus and decrease your ability to form newmemories. It would be nice if some stress also helped us remember facts, but unfortunately, theopposite is true. The act of remembering relies on the prefrontal cortex, which governs thought,attention, and reasoning. When corticosteroids stimulate the amygdala, the amygdala inhibits, orlessens the activity of the prefrontal cortex. The reason for this inhibition is so the fight/flight/freeze
response can overrule slower, more reasoned thought in a dangerous situation. But that can also
have the unfortunate effect of making your mind go blank during a test. And then the act of trying toremember can itself be a stressor, leading to a vicious cycle of more corticosteroid release and anTedEd-18

The Surprising Link Between
Stress and Memory

even smaller chance of remembering.
So what can you do to turn stress to your advantage and stay calm and collected when it mattersthe most? First, if you know a stressful situation like a test is coming, try preparing in conditions
similar to the stressful environment. Novelty can be a stressor. Completing practice questions undertime pressure, or seated at a desk rather than on a couch, can make your stress response to thesecircumstances less sensitive during the test itself. Exercise is another useful tool. Increasing yourheart and breathing rate is linked to chemical changes in your brain that help reduce anxiety andincrease your sense of well-being. Regular exercise is also widely thought to improve sleeping
patterns, which comes in handy the night before a test. And on the actual test day,try taking deep
breaths to counteract your body’s flight/fight/freeze response. Deep breathing exercises have shown
measurable reduction in test anxiety in groups ranging from third graders to nursing students.
So the next time you find your mind going blank at a critical moment, take a few deep breaths until
you remember ataraxia: a state of calmness, free from anxiety.