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Your co-worker sluggishly walks into the office and tells you they were up all night working on their client pitch. Do you marvel at their dedication and commitment, or do you shrug it off and think, “Yeah, I’ve had plenty of those nights?

Odds are, your response would be the latter. After all, sleep is for the weak.

It is not uncommon for us to push our bodies to an unhealthy point in hopes of reaching our goals, whether it’s being a good parent and taking care of your newborn, or pulling an all-nighter to cram for the bar exam.

Being sleep deprived has become such a norm in today’s society that we often brush it off as an unavoidable part of our lives. Studies show that 31 percent of the Canadian and American population is sleep deprived. In fact the World Health Organization has claimed we are in the midst of a catastrophic sleep-loss epidemic.  

Now perhaps you may be thinking, I’ve gotten through many nights with little sleep and managed to surviveWhat’s all this fuss about “sleep deprivation?” Well, although you may have physically ended the day in one piece (and perhaps felt accomplished for completing more work), unbeknownst to you, your brain took a much bigger hit.

The link between sleep deprivation and brain pathways

Research on sleep — or rather, lack of sleep — has revealed there are major side effects when you don’t get enough of it. This includes, among many other deleterious outcomes, increased negative emotionality and an inability to distinguish between threatening and non-threatening stimuli.

This failed detection is often regarded as the basis for many anxiety disorders including generalized anxiety disorder (GAD) and post-traumatic stress disorder (PTSD). In these cases, a neuro-related hyperarousal and amplified negativity bias leads to a distorted perception of ambiguous stimuli that get perceived as threatening. Resolving this bias is crucial for managing our anxiety.

In other words, a sleepy brain is particularly susceptible to negative emotion states and heightened anxiety.

This poses the question: How can a few lost hours of sleep have such a drastic effect on our brains and emotional (dis)functioning? To answer this, a team of neuroscientists at the Southwest University — led by Dr. Pan Feng — investigated the relationship between sleep and fear consolidation. They hypothesized that sleep deprivation is linked to increased sensitization of a particular brain region, the amygdala, which leads to increased reactivity towards negatively perceived stimuli and generates an amplified fear response.

The amygdala has long been known to play a pivotal role in the development and acquisition of fear. Of particular interest to the current investigation, the amygdala’s connections to two other brain regions called the ventromedial prefrontal cortex (vmPFC) and the insula, have been shown to affect this fear-based process.

Much of the clinical research on the vmPFC has pointed to the critical role it plays in emotional regulation. In the presence of a stimulus, the amygdala begins to orchestrate a response. This response, however, cannot be put into action without the approval of the vmPFC. The connection to the vmPFC ultimately results in amygdala activity being reduced.

The insula also takes part in the processing of emotions but unlike the vmPFC, the insula’s connection to the amygdala increases firing of the amygdala. This results in habituation to a negative stimulus. This habituation acts as a driving force for fear acquisition.

These two connections led the team to make two related predictions: Sleep deprivation would be associated with decreased amygdala-vmPFC connectivity; and increased amygdala-insula connectivity.

The experiment: shocking effects of an “all-nighter”

To test their hypothesis, the research team recruited seventy college students from the Southwest University. Once the participants in the sleep deprivation group had gone 24 hours without sleeping, they underwent a fear conditioning task.

The task consisted of a neutral conditioned stimulus in the form of three squares with different colors (blue, yellow or green) and an unconditioned stimulus involving a mild electric shock to the wrist. The goal was to associate the two stimuli so that if the participants were shown the three squares, they would react to a mild electric shock, even if the shock did not occur (think, Pavlovian classical conditioning).

Following the task, a resting state Functional Magnetic Resonance Imaging (fMRI) tracked changes in amygdala activity. The test was performed while participants were asked to rest and think of nothing in particular. Skin conductance responses were also measured through electrodes on participants’ fingertips. This technique provided information about the participants physiological arousal state.

As the research team hypothesized, the fMRI revealed an increase in the amygdala-insula connection for the sleep deprived participants, while the amygdala-vmPFC connectivity was increased for the control group (who received 8+ hours of sleep).

The sleep deprived group also experienced an increase in skin conductance response, indicating greater emotional arousal (i.e., more skin sweating). As suspected, the sleep-deprived group reported higher fear ratings than the control group. Together, these results provide clear evidence that sleep deprivation plays a fundamental role in the acquisition of fear via selective alterations in amygdaloid brain pattern activations.

Why does this a matter?

To return to our initial point, one third of the human population suffers from sleep deprivation. This means that 1 in 3 people you meet, experience increased negative emotionality and hyperarousal on any given day.

These factors can have a huge effect on the way we live our lives. It may cause us to give up on our dream job after one poor interview, or decide to drop out of business school because of a few botched presentations.

Being sleep-deprived will force us to always play it safe — to avoid potential losses and never take any risks. In other words, it may cause us to miss out on all the amazing opportunities that we’re presented with. All because of some falsely generated sense of fear; a fear that is, quite literally, “in our heads”.

The findings from the study will hopefully bring awareness to the unhealthy effects of sleep deprivation. With a few extra hours of sleep a week, we can obtain more control over our thoughts, emotions, and behaviors. We can live a life with less fear and more self-assurance.

Primary Reference

Feng, P., Becker, B., Zheng, Y., Feng, T. (2017). Sleep deprivation affects fear memory consolidation: bi-stable amygdala connectivity with insula and ventromedial prefrontal cortex. Social Cognitive and Affective Neuroscience, 13(2), 145-155.