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So exactly, how does a lack of sleep impact our emotional brain?
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Why does that lack of sleep make us
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so emotionally irrational and hyperreactive?
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[Sleeping with Science]
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Well, several years ago, we conducted a brain imaging study.
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And we took a group of healthy adults.
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And we either gave them a full night of sleep
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or we sleep-deprived them.
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And then the next day, we placed them inside an MRI scanner,
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and we looked at how their emotional brain was reacting.
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And we focused on one structure in particular,
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it's called the amygdala.
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And the amygdala is one of the centerpiece regions
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for the generation of strong emotional reactions,
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including negative emotional reactions.
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Now when we looked at those people who had had a full night of sleep,
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what we saw was a nice, appropriate moderate degree
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of reactivity from the amygdala.
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It wasn't as though there was no response at all,
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but it was an appropriate response.
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Yet in those people who were sleep-deprived,
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that deep emotional brain center was in fact, hyperactive.
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Indeed, the amygdala was almost 60 percent more responsive
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under conditions of a lack of sleep.
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But why was that the case?
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And what we went on to discover,
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is that there's another brain region that's involved.
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This brain region is called the prefrontal cortex,
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and it sits directly above your eyes.
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And you can think of the prefrontal cortex
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almost like the CEO of your brain.
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It's very good at making high-level, executive, top-down
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control decisions and reactions.
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In fact, it's one of the most evolved regions of our brain.
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And one of the parts of the brain that it controls
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is this deep emotional center, the amygdala.
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Now in those people who had had a full night of sleep,
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there was a nice, strong communication and connection
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between the prefrontal cortex,
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regulating that deep emotional brain center.
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But in those people who were sleep-deprived,
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that communication, that connection between the prefrontal cortex
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and that deep amygdala emotional brain center
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had essentially been severed.
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And as a consequence,
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the amygdala was responding far more reactively
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due to a lack of sleep.
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It's almost as though without sleep
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we become all emotional accelerator pedal,
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and too little regulatory control brake.
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And that seems to be the reason that we become so unbuckled
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in terms of our emotional integrity
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when we haven't been sleeping well.
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So that's the bad that can happen
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if I take sleep away from you.
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But it turns out
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that there's something good that happens
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when you get your sleep back.
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And sleep, particularly rapid eye movement sleep,
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actually offers a form of emotional first aid.
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Because it's during sleep at night
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that we take these difficult emotional experiences
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that we've been having during the day,
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and that sleep acts almost like a nocturnal soothing balm,
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taking the sharp edges off those difficult experiences.
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And so perhaps it's not time that heals all wounds,
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it's time during sleep that provides that form of emotional convalescence.
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So that when we come back the next day,
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we're able to cope with those emotional memories.