(photo credit: INGIMAGE)
It’s obvious that if you don’t get enough sleep – at least seven hours of shuteye per night – you’ll feel very irritable and oversensitive, but now, researchers at Tel Aviv Sourasky Medical Center and Tel Aviv University have discovered the brain mechanism responsible for this behavior in people.
Without enough sleep, even the simplest of tasks feel like a heavy burden, and we feel we are emotionally unbalanced.
While it has been known for some time that lack of sleep causes over-activation of the “emotional centers” in the brain, it was not clear whether sufferers are still able to regulate their emotions.
According to the study by Prof. Talma Hendler, director of the Functional Brain Center at TAU’s Wohl Institute for Advanced Imaging, and her doctoral student Etti Ben-Simon, published in the Journal of Neuroscience in an article is titled “Losing Neutrality: The Neural Basis of Impaired Emotional Control without Sleep,” functional magnetic resonance imaging (fMRI) and electroencephalograms (EEGs) were used to record the brain activity of 18 volunteers before and after they were prevented from sleeping for 24 hours.
Participants in the research were asked to carry out two different cognitive-emotional tasks – recalling a series of numbers and identifying patterns of rapid movement when neutral photos (such as of colleagues at work) or emotional photos (such as of a crying baby) were presented. They were asked to ignore the photos so they could carry out the assignment while constantly overcoming their emotional reactions.
The researchers focused on the activity of the amygdala, the brain’s central region for processing emotions, as well as the activity of the frontal regions responsible for regulating emotional reactions.
As expected, the reaction of the amygdala was stronger in response to emotional photographs when the participants were alert (after a night’s sleep of seven to nine hours). But after 24 hours of the sleeplessness, the researchers were surprised to discover that in addition to emotional pictures affecting the amygdala, the effect was identical also for neutral pictures, hinting at an undiagnosed emotional reaction. In addition, the activity in the frontal regions that regulate emotional activity was significantly reduced.
Examining the sleep habits of the participants showed that emotional over-activity was connected to the small amount of REM (rapid eye movement) sleep, which occurs when people dream and sleep deeply; this discovery supported the importance of this phase in sleep for emotional processing, the researchers said.
The study showed that nights without sleep cause a decline in the “emotional activation threshold” of the brain, which creates an exaggerated emotional reaction even to neutral stimulation and profound decline in cognitive control of emotion.
Notably, such a decline was associated with lower REM sleep amounts, supporting a role for REM sleep in overnight emotional processing.
“Altogether, our findings suggest that losing sleep alters emotional reactivity by lowering the threshold for emotional activation, leading to a maladaptive loss of emotional neutrality,” the researchers said.
Although participants showed enhanced limbic and electro-physiological reactions to emotional distractors regardless of their sleep state, they were specifically unable to ignore neutral distracting information after sleep deprivation; even if stimulation is completely neutral, it becomes emotional and carries much more weight than it ordinarily would if the person had enough sleep, they stated.
The brain mechanism, they discovered, also succeeds in explaining the connection between sleeplessness and anxiety.
Studies show that loss of emotional neutrality is one of the main signs of anxiety attacks, so the research results explain how people become more and more anxious when they get too little sleep.
The research also raises important questions, such as how this exaggerated sensitivity affects daily life and our ability to make decisions.
“Most of us have sleep deficits,” said Hendler. “What do they do to our brains? Our findings are very worrisome when we take into account the continually declining amount of sleep in the Western world and the emotional price we are paying for it.”