Does stress affect your memory? - Elizabeth Cox

941,507 views ・ 2018-09-04

TED-Ed


Please double-click on the English subtitles below to play the video.

00:08
You spend weeks studying for an important test.
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On the big day, you wait nervously as your teacher hands it out.
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You’re working your way through, when you’re asked to define ‘ataraxia.’
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You know you’ve seen it before, but your mind goes blank.
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What just happened?
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The answer lies in the complex relationship
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between stress and memory.
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There are many types and degrees of stress
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and different kinds of memory,
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but we’re going to focus on how short-term stress
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impacts your memory for facts.
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To start, it helps to understand how this kind of memory works.
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Facts you read, hear, or study
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become memories through a process with three main steps.
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First comes acquisition:
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the moment you encounter a new piece of information.
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Each sensory experience activates a unique set of brain areas.
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In order to become lasting memories,
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these sensory experiences
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have to be consolidated by the hippocampus,
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influenced by the amygdala,
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which emphasizes experiences associated with strong emotions.
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The hippocampus then encodes memories,
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probably by strengthening the synaptic connections
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stimulated during the original sensory experience.
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Once a memory has been encoded,
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it can be remembered, or retrieved, later.
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Memories are stored all over the brain,
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and it’s likely the prefrontal cortex that signals for their retrieval.
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So how does stress affect each of these stages?
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In the first two stages,
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moderate stress can actually help experiences enter your memory.
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Your brain responds to stressful stimuli
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by releasing hormones known as corticosteroids,
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which activate a process of threat-detection
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and threat-response in the amygdala.
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The amygdala prompts your hippocampus
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to consolidate the stress-inducing experience into a memory.
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Meanwhile, the flood of corticosteroids from stress
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stimulates your hippocampus,
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also prompting memory consolidation.
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But even though some stress can be helpful,
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extreme and chronic stress can have the opposite effect.
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Researchers have tested this by injecting rats directly with stress hormones.
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As they gradually increased the dose of corticosteroids,
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the rats’ performance on memory tests increased at first,
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but dropped off at higher doses.
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In humans, we see a similar positive effect with moderate stress.
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But that only appears when the stress is related to the memory task—
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so while time pressure might help you memorize a list,
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having a friend scare you will not.
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And the weeks, months, or even years
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of sustained corticosteroids that result from chronic stress
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can damage the hippocampus
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and decrease your ability to form new memories.
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It would be nice if some stress also helped us remember facts,
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but unfortunately, the opposite is true.
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The act of remembering relies on the prefrontal cortex,
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which governs thought, attention, and reasoning.
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When corticosteroids stimulate the amygdala,
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the amygdala inhibits, or lessens the activity of,
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the prefrontal cortex.
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The reason for this inhibition is so the fight/flight/freeze response
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can overrule slower, more reasoned thought in a dangerous situation.
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But that can also have the unfortunate effect
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of making your mind go blank during a test.
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And then the act of trying to remember can itself be a stressor,
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leading to a vicious cycle of more corticosteroid release
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and an even smaller chance of remembering.
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So what can you do to turn stress to your advantage
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and stay calm and collected when it matters the most?
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First, if you know a stressful situation like a test is coming,
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try preparing in conditions similar to the stressful environment.
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Novelty can be a stressor.
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Completing practice questions under time pressure,
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or seated at a desk rather than on a couch,
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can make your stress response to these circumstances
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less sensitive during the test itself.
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Exercise is another useful tool.
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Increasing your heart and breathing rate
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is linked to chemical changes in your brain
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that help reduce anxiety and increase your sense of well-being.
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Regular exercise is also widely thought to improve sleeping patterns,
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which comes in handy the night before a test.
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And on the actual test day,
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try taking deep breaths to counteract your body’s flight/fight/freeze response.
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Deep breathing exercises have shown measurable reduction in test anxiety
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in groups ranging from third graders to nursing students.
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So the next time you find your mind going blank at a critical moment,
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take a few deep breaths until you remember ataraxia:
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a state of calmness, free from anxiety.
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