Life is grace. Sleep is forgiveness. The night absolves. Darkness wipes the slate clean, not spotless to be sure, but clean enough for another day’s chalking.
Frederick Buechner, The Alphabet of Grace
How did you feel when you woke up today? Did you get up slowly, felt refreshed and had enough time to eat breakfast and plan your day? Or did you throw your alarm against the wall, curse at everything in your path until you felt alive enough to make a cup of coffee? If you are like the 1 in 5 Americans that get less than 6 hours of sleep, you might have trouble remembering simple things, be ill-prepared to deal with everyday stressors and be on edge - leading to unnecessary arguments with friends and family. Although the exact function of sleep is still unknown, lack thereof has been studied extensively. The results are striking - memory encoding problems, emotional disturbances and trouble adjusting to stressful situations are all linked to sleep deprivation. So what happens to us when we don't sleep?
We become negative.
Restful sleep happens in the REM (Rapid eye movement) stage of sleep.
“REM sleep typically occupies 20-25% of total sleep, about 90-120 min of a night’s sleep. REM sleep normally occurs close to morning. During a night of sleep, one usually experiences about four or five periods of REM sleep; short at the beginning of the night and longer towards the end. REM sleep is called paradoxical sleep because it has the same brain wave patterns as waking, hence why dreams occur in this stage.”
Researchers in Amsterdam had participants watch a scary movie and uncovered that stress causes higher overall fragmentation of sleep, an increase in awakenings and even alterations in manifest content of the dreams. When dealing with everyday problems, REM disturbance is related to adopting an avoidance coping strategy such as denial or suppression instead of an approach-oriented coping strategy such as the unfolding of stress and talking about it. In other words, stress affects your sleep and sleep affects your daily stress.
We become less empathetic.
A worse mood is probably the hallmark of sleep deprivation. In this altered mindset, daily stressors are perceived as worse. Poor sleep quality is related to a decreased ability in cognitive reappraisal (i.e. the ability to cognitively reframe an event in order to lessen its impact). After a night of restless sleep,
We no longer have the capability to think logically about our emotions.
Indeed, connectivity between the medial prefrontal cortex (mPFC), which exerts inhibitory control over the amygdala (governs emotions) was decreased in participants who did not sleep. Interestingly, sleep debt alters the processing of negative stimuli but total sleep deprivation acts as an anti-depressant and amplifies reactivity to positive emotional stimuli. That is to say, all-nighters might give you a short-lived blithe attitude. Another nasty effect of sleep deprivation is a failure at recognizing facial emotional expression, such as anger or happiness. Participants reported feeling themselves less able to understand their emotions and those of others.
We forget things.
Without adequate sleep, it is difficult to retrieve emotional memories. Sterpenich et al. found that the brain networks of those who were not allowed to sleep were disturbed for 6 months following the testing episode. Why do we need REM sleep to remember? Although there are no concrete answers, the theory is that amygdala and hippocampus (responsible for memory encoding) are two regions well known to play a pivotal role in consolidation of emotional memories. During REM sleep, the emotional features of sleep trigger release of hormones (such as cortisol) which in turn increases activation of the amygdala. The amygdala promotes memory consolidation by extending projections to the hippocampus.
We repeat mistakes.
In 2009, van der Helm and Walker supposed the “sleep to forget and sleep to remember (SFSR)” hypothesis. In sum,
They proposed that REM sleep helps unload the emotional weight from the actual memory.
After being shown a series of disturbing pictures, participants who slept were less reactive to the same pictures the next day as participants who were not allowed to sleep. While awake, “increased concentrations of aminergic neurotransmitters and amygdala activation during wakefulness promote encoding of emotional memories.”
So, this cocktail makes memories stick, and during REM sleep the release of these same neurotransmitters in a smaller quantity strengthens the connection between the emotion and the event. In essence, serving an adaptive quality to avoid said disturbing event in the future. Indeed, this supports the “threat simulation theory” which suggests that dreaming is
“a defense mechanism, which repeatedly simulates threatening events, leading to the rehearsal of cognitive mechanisms which lead to efficient threat perception and avoidance.”
The dopaminergic (reward) pathway also lights up when we dream, contributing to the color, sight, sound touch and smell of our dreams. Indeed, in individuals with post-traumatic stress disorders who are plagued by nightmares, drugs suppressing the dopaminergic reward pathway offers some solace.
We don’t know why we sleep. But we do know, that when we don’t get enough sleep we become moody, forgetful and most importantly - less able to manage our daily stressors. So get your beauty sleep – because a rested brain is a happy brain.
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