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  the complex relationship between stress and memory. There are many types  and degrees of stress and different 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 strong 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 the prefrontal cortex  that signals for their retrieval. So how does stress  affect each of these stages? In the first two stages, moderate stress can actually  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 threat-response in the amygdala. The amygdala prompts your hippocampus to consolidate the stress-inducing  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 by injecting 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. In humans, we see a similar  positive effect with moderate stress. But that only appears when  the stress 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 new memories. It would be nice if some stress  also helped us remember facts, but unfortunately, the opposite 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,  or lessens 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 to remember can itself be a stressor, leading to a vicious cycle  of more corticosteroid release and an even smaller chance of remembering. So what can you do to turn stress  to your advantage and stay calm and collected  when it matters the 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  under time pressure, or seated at a desk  rather than on a couch, can make your stress response to these circumstances less sensitive during the test itself. Exercise is another useful tool. Increasing your heart  and breathing rate is linked to chemical changes  in your brain that help reduce anxiety  and increase 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.